1. బీజకణోత్పత్తి గురించి వ్యాసం వ్రాయుము
జ. శుక్ర జననం, అండజననాలను కలిపి బీజకణోత్పత్తి అంటారు. పురుషజీవులలో శుక్రజననం, స్త్రీ జీవులలో అండజననం జరుగుతుంది.
బీజకోశములలో ఉండే జనన కణాలు విభజన చెంది, స్త్రీలలో అండములు పురుషులలో శుక్రకణములను ఏర్పరచును. ద్వయస్థితిక క్రోమోజోముల సంఖ్యను (2X) కలిగిఉన్న జనన కణాలు క్షయకరణ విభజన ద్వారా ఏక స్థితిక (X) క్రోమోజోముల సంఖ్యను కలిగిన బీజకణాలను ఏర్పరచును.
I శుక్ర జననం
పురుషబీజకణాలు లేదా శుక్రకణాలు ఏర్పడే విధానాన్ని శుక్రజననం అంటారు. ఇది ముష్కంలో జరుగును. ముష్కం నిర్మాణంలో పొడవైన శుక్రోత్పాదక నాళికలు మెలికలు తిరిగి ఉంటాయి. వీటిమధ్య కల ఖాళీలలో రక్తకేశనాళికలు, సంయోజకకణజాలము, నాడులు, లీడిగ్ కణములు ఉంటాయి. ఈ లీడిగ్ కణములు పురుష లైంగిక హార్మోనులను (టెస్టోష్టిరాన్) ఉత్పత్తి చేసి, ద్వితీయలైంగిక లక్షణములు ఏర్పడటానికి దోహదపడును. శుక్రోత్పాదక నాళికల గోడలలో కల జనన కణములు విభజనలు జరుపుకొని శుక్రకణములను ఉత్పత్తి చేయును. ఈ జనన కణముల మధ్య కల ప్రత్యేకమైన కణములైన సెర్టోలి కణములు శుక్రకణముల ఉత్పత్తి అవసరమైన పోషకములను అందించును.
శుక్రకణ జననాన్ని రెండు దశలుగా విభజించవచ్చును. అవి. ఎ. శుక్రకణోత్పాదన కణము ఏర్పడుట బి. శుక్రకణోత్పాదక కణము శుక్రకణముగా ఏర్పడుట
ఎ. శుక్రకణోత్పాదన కణము ఏర్పడుట:
శుక్రకణోత్పాదన కణము మూడు దశలుగా జరుగును. అవి ఎ. కణ విభజన దశ బి. పెరుగుదల దశ సి. పరిణిత దశ
విభజన దశ: శుక్రోత్పాదనాళికల బాహ్య ఉపరితలముపై జననకణాలు ఉంటాయి. ఈ కణాలను ప్రాధమిక బీజకణాలు లేదా శుక్రమాతృకణాలు అంటారు. ఇవి అనేక విభజనలు జరుపుకొని శుక్రకణ మాతృకణాలుగా మార్పు చెందుతాయి. ప్రతి శుక్రకణ మాతృ కణాలు ధ్వయస్థితిక క్రోమోజోములను కలిగి ఉంటాయి. ఈ దశ శిశువు పిండదశలో మొదలయి మరల యుక్తవయసు వచ్చే వరకూ సాగుతుంది.
పెరుగుదల దశ: జీవి యుక్తవయసుకు చేరాకా ప్రతి శుక్రకణ మాతృకణములు తన చుట్టూ ఉన్న సెర్టోలి కణములనుండి ఆహార పదార్ధములను గ్రహించి పెద్దవవుతాయి. వీటిలోని క్రోమోజోములు నాలుగు జతల క్రొమాటిడ్ లను ఏర్పరుచుకొని తదుపరి దశ అయిన క్షయకరణ విభజనకు తయారుగా ఉంటాయి.
పరిణిత దశ: ఈ దశలో ఒక్కొక్క కణం క్షయకరణ విభజన జరుపుకొని నాలుగు ఏకస్థితిక చలన రహిత శుక్రకణాలను ఏర్పరుస్తుంది. మొదటి క్షయకరణ విభజన వలన రెండు ఏకస్థితిక ద్వితీయ శుక్రమాతృకణాలు ఏర్పడును. క్షయకరణ విభజన II వలన ఒక్కో ద్వితీయ శుక్రమాతృకణము రెండు ఏకస్థితిక శుక్రకణాలను ఏర్పరచును. ఇవి తదుపరి విభజనలు జరుపుకొనక, విభేధీకరణ చెంది చలించగలిగే స్పెర్మ్ లేదా శుక్రకణముగా మారును
బి. శుక్రకణోత్పాదకము - చలించే శుక్రకణము ఏర్పడుట
చలన రహిత శుక్రకణాలు (స్పెర్మాటిడ్ లు) చలన సహితంగా, క్రియాశీలకంగా మారటాన్ని శుక్రకణోత్పాదకము లేదా స్పెర్మియోజెనిసిస్ అంటారు.
ఫలదీకరణ సమయములో అండమును చేరి దానితో సంయోగము చెందుట శుక్రకణము యొక్క ప్రాధమిక విధి. ఆ విధిని నిర్వర్తించుటకొరకై శుక్రకణము యొక్క నిర్మాణములో ఈ క్రింది మార్పులు జరుగును.
ఎ. కేంద్రకములో జరుగు మార్పులు: ఈ దశలో శుక్రకణోత్పాదక కేంద్రకం ద్రవాన్ని పోగొట్టుకొని చిన్నదవుతుంది. క్రోమోజోములు కూడా సూక్ష్మ రూపంలోకి వస్తాయి.
బి. ఎక్రోసోము ఏర్పడుట: శుక్రకణ పూర్వాంతమున ఒక టోపీ ఆకారపు నిర్మాణము ఏర్పడుతుంది. దీనిని ఎక్రోసోము అంటారు. ఇది గాల్జి దేహమునుండి ఏర్పడుతుంది. గాల్జి పదార్ధము కళికగా మారి, తనలోని ద్రవమును పోగొట్టుకొని కేంద్రకము యొక్క పైభాగాన్ని కప్పుతుంది. దీనినే కేంద్రక పూర్వఛత్రకము లేక ఎక్రోసోము అంటారు. ఎక్రోసోమునందుకల ఎంజైములు, అండము యొక్క పై త్వచ మును కరిగించి, శుక్రకణ కేంద్రకము అండములోకి ప్రవేశించటంలో తోడ్పడును
సి. తారావత్కేంద్రాలు (సెంట్రియోల్స్): సెంట్రోజోములోని రెండు తారావత్కేంద్రాలో మొదటిది శుక్రకణ మెడ మరియు మధ్య తునకలను ఏర్పరచును. దీనిని సమీపాగ్ర తారావత్కేంద్రము అంటారు. రెండవ తారావత్కేంద్రము అక్షీయ తంతువును కలిగ్ ఇది శుక్రకణిం తోకను ఏర్పరచును. ఇది 9+2 అమరికను కలిగి ఉండును.
డి. మధ్యభాగము: శుక్రకణము మధ్య భాగములో మైటోఖాండ్రియాలన్నీ కేంద్రీకృతమై ఫలదీకరణ సమయములో శుక్రకణము చలించటానికి అవసరమైన శక్తిని అందచేస్తాయి.
ఇ. పరిణితి చెందిన శుక్రకణము: పరిణితి చెందిన శుక్రకణము లో శీర్షము (హెడ్) భాగములో అక్రోజోమ్, కేంద్రకము - మధ్యభాగము(మిడిల్ పీస్) లో రెండు సెంట్రియోల్ లు మరియు తోక లేద కశాభము అను భాగములతో ఉండును
II అండజననం
స్త్రీబీజకోశములోని జననస్థరపు కణాలు అండములుగా అభివృద్ధి చెందటాన్ని అండజననము అంటారు.
సకశేరుకములలో ఒక జత స్త్రీ బీజకోశములు ఉంటాయి. స్త్రీబీజకోశపు ఉపరితలం పై ఉపకళా కణజాలంతో ఒక పొర ఏర్పడును దీనిని జననోపకళ అంటారు. ఈ జనన ఉపకళా కణాలు సమవిభజనలు చెంది చిన్న చిన్న గుంపులు గుంపులుగా కణముల సముదాయములను ఏర్పరచును. ఒక్కొక్క గుంపును గ్రాఫియన్ పుటిక అంటారు. ఒక గ్రాఫియన్ పుటికలో బాగా అభివృధ్ది చెందిన ఒక కణము “అండ మాతృకణముగా” ఏర్పడును. మిగిలిన కణాలు ఈ అభివృద్ది చెందే అండానికి పోషకపదార్ధములను అందించును. ఇలా పరిణితిచెందిన గ్రాఫియన్ పుతిక అండాశయం ఉపరితలానికి చేరి పగిలిపోవటం ద్వారా అండం విడుదల జరుగును. ఈ రకంగా అండాశయం నుండి నుండి అండం విడుదల కావటాన్ని అండోత్సర్గము/అండోత్పత్తి అంటారు.
ఈ ప్రక్రియ మూడు దశలలో జరుగును అవి. ఎ. విభజన దశ బి. పెరుగుదల దశ సి. పరిణిత దశ
విభజన దశ; ఇందులో స్త్రీబీజకోశంలోని జననోపకళ కణాలు అనేక సమవిభజనలు జరుపుకొని ఎక్కువ కణాలను ఏర్పరచును. ఈ కణాలను అండమాతృకణాలు అంటారు. ఇవి కూడా అనేక విభజనలు జరుపుకొని ప్రాధమిక అండమాతృకణం ఏర్పడుతుంది. ఈ దశ వరకూ గల కణాలు అన్నీ ద్వయస్థితిలో ఉంటాయి.
వృద్ధి/పెరుగుదల దశ: ప్రతి అండమాతృకణం ప్రొటీన్ క్రొవ్వులను సొనపదార్ధ రూపం లో ఎక్కువగా సేకరించుకొంటుంది. ఈ సొనపదార్ధం అండంలోని క్రిందిభాగంలో ఎక్కువగా కేంద్రీకృతమౌతుంది, కనుక ఈ భాగాన్ని భృహుత్కంఢ దృవం అనీ దానికి వ్యతిరేకంగా దిశలో ఉన్న భాగాన్ని జాంతవ దృవమనీ అంటారు. సొనపదార్ధాన్ని పూర్తిగా ఏర్పరచుకొన్న అండమాతృకణాన్ని, ప్రాధమిక అండమాతృకణం అంటారు.
పరిపక్వ దశ: ప్రాధమిక అండమాతృకణం మొదటి క్షయకరణ విభజన రెండు అసమాన కణాలుగా ఏర్పడుతుంది. పెద్దకణాన్ని ద్వితీయ అండమాతృకణం అనీ, చిన్నకణాన్ని దృవకణం అని అంటారు. ఇవి ఏకస్థితికాలు. ఇది మరల విభజన జరుపుకోగా ఏర్పడే పెద్దకణాన్ని పరిపక్వ అండము లేదా గుడ్డు అంటారు. మొదటి మరియు రెండవ దృవదేహాలు అదృశ్యమవుతాయి.
అలా ఉత్పత్తి అయిన అండాలు అండోత్పత్తి అనే ప్రక్రియ ద్వారా అండాశయము వెలుపలకు విడుదల చేయబడును.
Zoology in the Classroom - is a blog for teachers and students of zoology. I have been teaching as Zoology teacher for the last 30 years. I post the notes or handouts that I supply to my students in my classroom. Hope this will benefit Zoology fraternity
Tuesday, October 4, 2016
Friday, September 23, 2016
Canal system in Scypha
Canal system in Scypha
Body of Scypha consists of a complex system of pores and canals. This system is generally referred to as canal system or aquiferous system. Bodywall has cellular layers, outer pinacoderm and inner choanoderm. In between these two layers, there is a non-cellular gelatinous mesenchyme in between. But the bodywall is so folded as to form regularly arranged alternating invaginations and evaginations, establishing the sycon type of canal system. The various components of canal system of Scypha are:
1) Ostia or dermal pores
2) Incurrent canals
3) Prosopyles
4) Radial canals
5) Apopyles
6) Spongocoel
7) Osculum
8) Current of water
1) Ostia or dermal pores:
The external grooves of body surface are stretched over by a thin pore membrane. It bears two or more openings for the ingress of outside water into the body of sponge. These pores are known as Ostia (Latin, Ostium=door) or dermal pores. Because of the presence of contractile cells or myocytes around them, the ostia can reduce in diameter and thus regulate the amount of ingressing (incoming) water.
2) Incurrent canals:
These are the invaginated folds of bodywall and are also called inhalent canals. These communicate with outside through ostia but end blindly at their inner ends. Pinacocytes line these canals throughout.
3) Prosopyles:
Incurrent canals communicate with radial canals through intercellular spaces called prosopyles (Greek. Pros=near, pyle=gate)
4) Radial canals:
Evaginations of bodywall form thimble-shaped chambers lined by flagellated choanocytes. These chambers are called flagellated or radial canals.
Incurrent and radial canals are parallel and alternate with each other, both vertically and radially. The arrangement is such that, in a vertical or tangential section through the wall of a cylinder, each radial canal is surrounded on four sides by incurrent canals, and each incurrent canal is surrounded likewise by four radial canals.
Radial canals end blindly at their outer ends but lead at their inner ends into spongocoel.
5) Apopyles:
Openings of radial canals into spongocoel are called apopyles (Greek apo=away from, pyle=gate) or internal ostia. These are surrounded by contractile myocytes serving as a sphincter.
6) Spongocoel:
It is the large central cavity of the body forming the vertical axis of the cylinder (Greek sponges=sponge+koilos=hollow). In Leucosolenia, spongocoel is lined by flagellated collar cells or choanocytes. In Scypha, the choanocytes line the radial canals, whereas the spongocoel is lined with the epidermal pinacocytes.
7) Osculum:
Spongocoel leads to outside through a terminal opening, the osculum. The oscula are provided with sphincters to regulate the rate of water flow in the body. Sphincters are lined by special contractile pinacocytes.
Sphincters are lined by special contractile pinacocytes, called myocytes (Greek. Myos, muscle+kytos=cell)
8) Current of water
Flow of water in canal system is maintained by continuous beating of flagella of collar cells lining the radial canals. Every beat of a flagellum consists of a normal active stroke and a recovery stroke. Electron microscopy revealed that there is no coordination between the beating of flagella of adjacent cells. The course taken by water current into the canal system is as follows.
Water from outside through dermal ostia Incurrent canals through prosopyles
Radial canals
Through apopyles
to outside Spongocoel Radial canals
Body of Scypha consists of a complex system of pores and canals. This system is generally referred to as canal system or aquiferous system. Bodywall has cellular layers, outer pinacoderm and inner choanoderm. In between these two layers, there is a non-cellular gelatinous mesenchyme in between. But the bodywall is so folded as to form regularly arranged alternating invaginations and evaginations, establishing the sycon type of canal system. The various components of canal system of Scypha are:
1) Ostia or dermal pores
2) Incurrent canals
3) Prosopyles
4) Radial canals
5) Apopyles
6) Spongocoel
7) Osculum
8) Current of water
1) Ostia or dermal pores:
The external grooves of body surface are stretched over by a thin pore membrane. It bears two or more openings for the ingress of outside water into the body of sponge. These pores are known as Ostia (Latin, Ostium=door) or dermal pores. Because of the presence of contractile cells or myocytes around them, the ostia can reduce in diameter and thus regulate the amount of ingressing (incoming) water.
2) Incurrent canals:
These are the invaginated folds of bodywall and are also called inhalent canals. These communicate with outside through ostia but end blindly at their inner ends. Pinacocytes line these canals throughout.
3) Prosopyles:
Incurrent canals communicate with radial canals through intercellular spaces called prosopyles (Greek. Pros=near, pyle=gate)
4) Radial canals:
Evaginations of bodywall form thimble-shaped chambers lined by flagellated choanocytes. These chambers are called flagellated or radial canals.
Incurrent and radial canals are parallel and alternate with each other, both vertically and radially. The arrangement is such that, in a vertical or tangential section through the wall of a cylinder, each radial canal is surrounded on four sides by incurrent canals, and each incurrent canal is surrounded likewise by four radial canals.
Radial canals end blindly at their outer ends but lead at their inner ends into spongocoel.
5) Apopyles:
Openings of radial canals into spongocoel are called apopyles (Greek apo=away from, pyle=gate) or internal ostia. These are surrounded by contractile myocytes serving as a sphincter.
6) Spongocoel:
It is the large central cavity of the body forming the vertical axis of the cylinder (Greek sponges=sponge+koilos=hollow). In Leucosolenia, spongocoel is lined by flagellated collar cells or choanocytes. In Scypha, the choanocytes line the radial canals, whereas the spongocoel is lined with the epidermal pinacocytes.
7) Osculum:
Spongocoel leads to outside through a terminal opening, the osculum. The oscula are provided with sphincters to regulate the rate of water flow in the body. Sphincters are lined by special contractile pinacocytes.
Sphincters are lined by special contractile pinacocytes, called myocytes (Greek. Myos, muscle+kytos=cell)
8) Current of water
Flow of water in canal system is maintained by continuous beating of flagella of collar cells lining the radial canals. Every beat of a flagellum consists of a normal active stroke and a recovery stroke. Electron microscopy revealed that there is no coordination between the beating of flagella of adjacent cells. The course taken by water current into the canal system is as follows.
Water from outside through dermal ostia Incurrent canals through prosopyles
Radial canals
Through apopyles
to outside Spongocoel Radial canals
Thursday, September 22, 2016
HERDMANIA TYPE STUDY
Affinities of Urochordates .
The typical tunicate looks like a non-chordate animal. If the life history of such animal is studied, the larval form reveals the chordate chara’4ters of that animal.
In 1816, Lamarck and Cuvier placed these animals in one class ‘Tunicata’. Allis described a compound Ascidian “Botryllus’ in 1756.KowalevskSi. Worked on the development ofthe Ascidian and placd them’in tunicates after observing the chordate features
.
Urochordates-Resemblance. With Chordate. :- .
1. Presence of dorsal tubular nerve cord,
2. Presence of Notochord,
3. Well developed pharynx with gill-slits.
4. Presence of endostyle on the ventral side of the pharynx
.5. Presence of atrium around pharynx.
.6. Presence of post - anal tail, with tail fin.
, Because of these chordate features tunicates are included in chordates group.
Urochordates-Resemblance with Amphioxus:
1. Presence of notochord.
2. Presence of dorsal tubular nerve cord.
3. Presence of large pharynx with gill slits.
4. Presence of atrium and atriopore.
5. Presence of muscle band.
Thus, the Urochordates show close relation with Cephalochordates. But the
Urochordates differ with other Chordates because of the following peculiar characters.
1 .Presence of retrogressive metamorphosis.
2. Absence of segmentation.
Because of these characters zoologists included these animals in a
Separate sub-phylum Urochordates.
During recent years many zoologists regarded the tunicates as primitive and ancestral forms to chordates as a whole.
previous topic urochordata classification
Urochordata Classification
Classification of Urochordata
Subphylum Urochordata is divided into three classes.
CLASS 1. ASCIDIACEA CLASS 2. THALIACEA CLASS : 3 . LARVACEA (APPENDICULARIA)
CLASS 1. ASCIDIACEA:
1. These are sedentary tunicates.
2. The body is covered by a test.
3. Pharynx is large and contains gill-slits.
4. Notochord, nerve-cord and tail are absent
5. These are Bisexual animals.
6. Life-history includes a typicalTadpole larva. The class Ascidiacea is divided into two orders.
Order 1. Enterogona
These ascidians bear one gonad in the intestinal loop. Neural gland is ventral to the ganglion. Tadpole larva is seen:
Ex: Ascidia and Ciona.
Order: 1. Pleurogona:
In these ascidians,gonads are paired and are present in the atrial wall. Neural gland is dorsal to the ganglion:
Ex : Herdmania, Botryllus.
CLASS 2. THALIACEA :-
1. These Urochordates are free-swimming and pelagic forms.
2. They are covered by transparent test.
3. The brachial and atrial apertures are placed at anterior and posterior ends.
4. Pharynx is small.
5. Gill-slits number is less.
6. Notochord, nerve-cord and tail are absent in the adult.
7. Asexual reproduction is by budding.
‘8. These are bisexual animals.
9. Tailed larva may be present or absent.
10. Alternation of generations can be seen in the life history.
The class thaliacea is divided into three orders.
1. Doliolida, 2. Pyrosomida and 3. Salpida.
Order 1. Doliolida (Cyclomyarla)
1. Barrel shaped body is completely covered by Muscle bands,
2. Pharynx is small
3. Number of gill slits will be small.
4. Tailed larva is seen
5. Sexual Blasto-zooid and asexual oozooid stages will alternate in the life cycle.
Ex :Doliolum.
Order 2. Pyrosomlda :
1. This order includes colonial forms.
2. Muscle bands are small and present at the ends.
3. Gill-slits are many.
4. Tailed larval stage is absent.
Ex : Pyrosoma (Luminescent colonial form).
Order 3. Salplda (Hemimyaria) :-
1. This order includes organisms whose body is prism like.
2. Muscle bands are complete dorsally and incomplete ventrally.
3. Only one pair of lateral gill slits are present.
4. Tailed larval stage is absent.
5. Life history includes alternation of generations.
Ex: Salpa.
CLASS : 3 . LARVACEA (APPENDICULARIA)
1. These are free - swimming, pelagic tunicates.
2. True’ test covering is lacking
3. They show loose gelatinous house.
4. This house is useful for filter feeding.
5. Two gill slits re present.
6. Atrium is absent. ..
7. Notochord and nerve cord are Persistent
8. They show tail throughout their life.
9. Neotenic forms are included.
Ex: Oikopleura. ‘
Urochordata Characters
Urochordata General Characters
The tunicates were first regarded as sponges. Lamark in 1816 placed Tunicata in between the Radiata and Vermes in his system of classification. Later, they were included in Mollusca. In 1866 Kowalevsky kept them in chordates.
Their chordate features are clearly seen in the larval stages. All Urochordates are marine and occur in all the seas. Majority of them are sedentary and some are pelagic.
1. Body shows variation in size and form.
2,. The body is un segmented and has no tail
3. The body is covered by a test. It is formed by tunicine which is
rallied to cellulose. Hence the name Tunicata.
4. Body wall shows one-layered epidermis, dermis is made by connective tissue and muscles, and atrial epithehum.
5.Celome is absent.
6. Atrial cavity surrounds the pharynx, into this cavity the gill slits,anus and genital ducts will open. It opens through atrial aperture.
7. Larva has notochord in the tail. It disappears during metamorphosis.
8. Respiratory system contains gills in the pharyngeal wall.
9. Ciliary mode of feeding is common.
10. Open type of Circulatory system is seen.
11. The heart is ventral and it periodically reverses its function.
12. Nervous system is represented by a single dorsal ganglion in the adult.
13. Excretion is carried on by nephrocytes.
14. Asexual reproduction is by budding.
15. Bisexual animal and cross fertilisation is favored.
16. Fertilization is external.
17. Development includes a minute, free swimming tadpole larva with a tail, a dorsal nerve cord, and a notochord in the tail. In some urochordates retrogressive metamorphosis is seen in the life history.
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Herdmania Excretory Organ:
Excretory Organ Of Herdmania:
A neural gland is present above the brain in herdmaina. it Is brown in colour. It is present In the mantle. 1t is 4mm in diameter. It show branching tibuIes. At one end it leads into a short duct which opens by ciliated funnel above the dorsal tubercle. In the blood nephrocytes cell are present. They coiled waste matter. They come to the neural gland from there, they are sent out The neural gland secretes a hormone. It help in metamorphosis. Neural gland is considered homologous to pituitary glands of vertebrates.
Herdmania- Spicules
Herdmania- Spicules in the test:
In the test of Herdmania two types of calcareous spicules are Present. They are:
1) Microscieres : These are 40 to 80 microns in length. They are minute.
2) Megascleres : These are long spicules. They show different shapes. They are 1.5 to 3.5 mm in length. They are two types.
a) Spindle shaped Megascleres. They are 1.5 to 2.5 mm in length.
b) Pipette shaped Megascleres. They are 3.5 mm. in length.
The rnicroscleres are present only in the test. But the megascleres occur in the test, body wall, and viscera.
Herdmania-Spicules Function:
1) They give support to the test
2) They protect the animal from predators.
3) They fix mantle with test.
Herdmania- Nervous System
NERVOUS SYSTEM OF HERDMANIA:
Herdmania shows brain or nerve ganglion. It is 4 mm long. It is present in the mantle in between the two siphons. A neural gland is present above the brain. From the brain three nerves arise, one goes to the bronchial siphon, and two will go to the atrial siphon. The brain represents the degenerated nervous system of the larva.
Receptors:
1. Red pigmented spots on the test are photoreceptors. They are sensitive to light.
2. Sensory cells of the margins of siphons and tentacles are tango receptors. They are sensitive to touch.
3. The cells on the margins of siphons are rheo receptors. They are sensitive to water currents.
4. Cells lining the siphons are thermo receptors. They are sensitive to changes of temperature.
Herdmania Gonads
Gonads of Herdmanla :
Ans: Herdmania is a bisexual animal. It is a protogynous animal. Ovary matures’ first. Hence cross fertilization takes place.
Herdmania contains a pair of gonads. The left gonad lies in the intestinal loop above the heart. Each gonad shows 10 to 25 lobes arranged in two rows. The median lobe is single and large. Other lobes are oval in shape.
Each lobe shows outer large testicular part and inner small ovarian part. The testicular part is brick red in colour and produces sperms. The ovarian part is pink in colour and produce ova. From each testicular part sperm ductule will arise. They open into spermduct. From each ovarian part ovarian ductule will come. They open into the oviduct. Each gonad has an oviduct and spermduct. They run parallelly and open separately into cloaca behind anus.
Herdmania -Retrogressive Metamorphosis
Retrogressive Metmorphosis in herdmania
During metamorphosis the larva will loose all the chordate characters and attains an invertebrate like form. This type of metamorphosis, where highly advanced larval form ends in a lowly organised adult is called retrogressive metamorphosis.
Fixation of the larva: The larva swims for some time without feeding. It is fixed to a sub- stratum with the help of the adhesive papillae. It stands erect with the tail upwards. Then it undergoes retrogressive metamorphosis.
Changes during metamorphosis:
1.Notochord, nerve cord muscles and tail will be reduced. All the above structures will help the larva to swim freely in the water. But they are not useful to the sedentary adult
2.. The alimentary canal becomes complicated. The pharynx en larges ln size. The number of gill slits will increase by divisions. The stomach and intestine will grow.
3. The nervous system is reduced and the anterior part of nervous system is developed into a small neuralganglion attached to it neural gland is present. ;:
4. The atrial cavity enlarges into a sac like structure.
5. The eyespot and statocyst will completely disappear.
6. Gonads develop from mesencyme.
When these changes are taking place, the region between the adhesive papillae and mouth grows very rapidly. At the same time the growth of the dorsal region is stopped. Because of this, the body rotates through 1800 angle and mouth is brought to the top
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HERDMANIA TADPOLE LARVA
ORGANISATION OF HERDMANIA TADPOLE LARVA:
Herdmania is a hermaphrodite animal. The fertilised eggs undergo holoblastic unequal clevage and it develops into blastula. it shows upper micromeres and lower macromeres. By invagination of the macromeres gastrulation takes place and gastrula is formed. This gastrula develops into a tailed larva called Ascidian Tadpole larva. (Herdmanis life history, is not clearly known. Clavilina’s life history is known. It is followed here.
The larva is 3 mm in length. It has short oval body and a long tail.
This larva shows all the chordate features.
1) The body is covered by thin test.
2) The tail is long and shows a tail fin or caudal fin.
3) The tail is supported by notochord. Hence it comes under urochordata.
4) On the dorsal side above the notochord hollow nerve cord is present. This nerve cord is enlarged at the anterior end as a cerebral vesicle. In the cerebral vesicle pigmented eye spot is present. Statocyst is also present. They work as sense organs.
5) On either side of the notochord in the tail region muscles are Present which are helpful in the locomotion.
6) On the trunk region digestive system is present. It shows large pharynx with few gills slits. They open into atrium. On the mid ventral floor of the pharynx an endostyle is present.
7) Atrium opens out through atriopore.
8) Below the pharynx on the ventral side a muscular heart is present.
9) On the anterior end of the trunk three adhesive papillae are present These are very much useful to attach the larva to the substratum
This Herdmania tadpole larva shows all chordate characters. This larvae ‘undergoes retrogressive’ metamorphosis and develops into adult Herdmania.
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Herdmanla -External characters
External characters of Herdmania
Herdmania is a simple ascidian, In Indian ocean this genus Is represented by 4 species. ,
1. Herdmania pallida, 2. H.ennurensis, 3. H.mauritiana 4. H. ceylonica.
Herdmania belongs to,
Phylum: Chordata,
Sub-phylum: Urochordata,
Class: Ascidiacea,
Order: Pleurogona.
Herdmania is a marine and sedentary animal. It is fixed to rocky substratum by a flat base. When it is disturbed, it suddenly contracts its body, and emits inner contents with force through its apertures. Hence it is called Sea squirt.
External Features :-
It is potato like in shape. It is pink in colour. On the free side, body shows two projections, the brançhial and atrial siphons. The branchial siphon is short. The branchial siphon shows a branchial aperture or the mouth. The atrial siphon is longer. It bears the atrial aperture. Both the openings are bounded by four lips.
Herdmania - external characters.
Test of Herdmania:The body of this animal is covered and protected by test. It Ls a thick, leathery covering of the body.It is secreted by the epidermis of the body wall. It has matrix, corpuscles, fibrils, blood vessels and spicules.
The matrix is composed of tunicin, which is cellulose. The cells in the test are of six types, large eosinophilous cells, amoeboid cells, small eosinophilous cells, vacuolated cells, receptor cells and nerve cells.
Fine fibrils present in the matrix. In the test blood vessels are present. In the test the spicules are calcareous spicules. They are microscleres, and megascleres.
The test protects the body. Anchors the animals to substratum. Its spicules form a supporting frame work.
Herdmania Body wall :
The body-wall of Herdmania is called Mantle. It is thick, and muscular in the antero-dorsal region of the body. It is thin, non-muscular and transparent in the postero ventral region. It shows epidermis, mesenchyme, and inner epidermis.
1.Epidermis : It Is single layer of cells. It covers the bronchial and atrial apertures and siphons. The epidermis is interrupted at places where spicules and blood-vessels pass from the mantle into the test.
. 2. Mesènchyme: It develops from the mesoderm. It has connective tissue containing blood-sinuses, muscle-fibers, nerve fibers and cells. The muscle fibers are long and flat. They contain large nuclei.
3. Inner Epidermis: It is single layer of flat cells. It forms the lining of the atrial cavity. .
‘1.The body-wall protects visceral organs.
2. The outer epidermis secretes the test.
3. The musculature brings contraction of the body and the siphons.
Herdmania Atrium:
In Herdmania coelome is not developed. Atrium is a spacious ectoderm lined cavity. it is covered by the mantle A part of the atrium surrounds the pharynx. The stigmata of the pharynx open into this cavity. Part of the atrium is dorsal to the pharynx. It is very wide and is called cloaca. The rectum and gonoducts open into this. The cloaca opens to the exterior through atrial siphon and trial aperture. The atrial siphon shows a ring of processes called atrial tentacles at its base.
The typical tunicate looks like a non-chordate animal. If the life history of such animal is studied, the larval form reveals the chordate chara’4ters of that animal.
In 1816, Lamarck and Cuvier placed these animals in one class ‘Tunicata’. Allis described a compound Ascidian “Botryllus’ in 1756.KowalevskSi. Worked on the development ofthe Ascidian and placd them’in tunicates after observing the chordate features
.
Urochordates-Resemblance. With Chordate. :- .
1. Presence of dorsal tubular nerve cord,
2. Presence of Notochord,
3. Well developed pharynx with gill-slits.
4. Presence of endostyle on the ventral side of the pharynx
.5. Presence of atrium around pharynx.
.6. Presence of post - anal tail, with tail fin.
, Because of these chordate features tunicates are included in chordates group.
Urochordates-Resemblance with Amphioxus:
1. Presence of notochord.
2. Presence of dorsal tubular nerve cord.
3. Presence of large pharynx with gill slits.
4. Presence of atrium and atriopore.
5. Presence of muscle band.
Thus, the Urochordates show close relation with Cephalochordates. But the
Urochordates differ with other Chordates because of the following peculiar characters.
1 .Presence of retrogressive metamorphosis.
2. Absence of segmentation.
Because of these characters zoologists included these animals in a
Separate sub-phylum Urochordates.
During recent years many zoologists regarded the tunicates as primitive and ancestral forms to chordates as a whole.
previous topic urochordata classification
Urochordata Classification
Classification of Urochordata
Subphylum Urochordata is divided into three classes.
CLASS 1. ASCIDIACEA CLASS 2. THALIACEA CLASS : 3 . LARVACEA (APPENDICULARIA)
CLASS 1. ASCIDIACEA:
1. These are sedentary tunicates.
2. The body is covered by a test.
3. Pharynx is large and contains gill-slits.
4. Notochord, nerve-cord and tail are absent
5. These are Bisexual animals.
6. Life-history includes a typicalTadpole larva. The class Ascidiacea is divided into two orders.
Order 1. Enterogona
These ascidians bear one gonad in the intestinal loop. Neural gland is ventral to the ganglion. Tadpole larva is seen:
Ex: Ascidia and Ciona.
Order: 1. Pleurogona:
In these ascidians,gonads are paired and are present in the atrial wall. Neural gland is dorsal to the ganglion:
Ex : Herdmania, Botryllus.
CLASS 2. THALIACEA :-
1. These Urochordates are free-swimming and pelagic forms.
2. They are covered by transparent test.
3. The brachial and atrial apertures are placed at anterior and posterior ends.
4. Pharynx is small.
5. Gill-slits number is less.
6. Notochord, nerve-cord and tail are absent in the adult.
7. Asexual reproduction is by budding.
‘8. These are bisexual animals.
9. Tailed larva may be present or absent.
10. Alternation of generations can be seen in the life history.
The class thaliacea is divided into three orders.
1. Doliolida, 2. Pyrosomida and 3. Salpida.
Order 1. Doliolida (Cyclomyarla)
1. Barrel shaped body is completely covered by Muscle bands,
2. Pharynx is small
3. Number of gill slits will be small.
4. Tailed larva is seen
5. Sexual Blasto-zooid and asexual oozooid stages will alternate in the life cycle.
Ex :Doliolum.
Order 2. Pyrosomlda :
1. This order includes colonial forms.
2. Muscle bands are small and present at the ends.
3. Gill-slits are many.
4. Tailed larval stage is absent.
Ex : Pyrosoma (Luminescent colonial form).
Order 3. Salplda (Hemimyaria) :-
1. This order includes organisms whose body is prism like.
2. Muscle bands are complete dorsally and incomplete ventrally.
3. Only one pair of lateral gill slits are present.
4. Tailed larval stage is absent.
5. Life history includes alternation of generations.
Ex: Salpa.
CLASS : 3 . LARVACEA (APPENDICULARIA)
1. These are free - swimming, pelagic tunicates.
2. True’ test covering is lacking
3. They show loose gelatinous house.
4. This house is useful for filter feeding.
5. Two gill slits re present.
6. Atrium is absent. ..
7. Notochord and nerve cord are Persistent
8. They show tail throughout their life.
9. Neotenic forms are included.
Ex: Oikopleura. ‘
Urochordata Characters
Urochordata General Characters
The tunicates were first regarded as sponges. Lamark in 1816 placed Tunicata in between the Radiata and Vermes in his system of classification. Later, they were included in Mollusca. In 1866 Kowalevsky kept them in chordates.
Their chordate features are clearly seen in the larval stages. All Urochordates are marine and occur in all the seas. Majority of them are sedentary and some are pelagic.
1. Body shows variation in size and form.
2,. The body is un segmented and has no tail
3. The body is covered by a test. It is formed by tunicine which is
rallied to cellulose. Hence the name Tunicata.
4. Body wall shows one-layered epidermis, dermis is made by connective tissue and muscles, and atrial epithehum.
5.Celome is absent.
6. Atrial cavity surrounds the pharynx, into this cavity the gill slits,anus and genital ducts will open. It opens through atrial aperture.
7. Larva has notochord in the tail. It disappears during metamorphosis.
8. Respiratory system contains gills in the pharyngeal wall.
9. Ciliary mode of feeding is common.
10. Open type of Circulatory system is seen.
11. The heart is ventral and it periodically reverses its function.
12. Nervous system is represented by a single dorsal ganglion in the adult.
13. Excretion is carried on by nephrocytes.
14. Asexual reproduction is by budding.
15. Bisexual animal and cross fertilisation is favored.
16. Fertilization is external.
17. Development includes a minute, free swimming tadpole larva with a tail, a dorsal nerve cord, and a notochord in the tail. In some urochordates retrogressive metamorphosis is seen in the life history.
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Herdmania Excretory Organ:
Excretory Organ Of Herdmania:
A neural gland is present above the brain in herdmaina. it Is brown in colour. It is present In the mantle. 1t is 4mm in diameter. It show branching tibuIes. At one end it leads into a short duct which opens by ciliated funnel above the dorsal tubercle. In the blood nephrocytes cell are present. They coiled waste matter. They come to the neural gland from there, they are sent out The neural gland secretes a hormone. It help in metamorphosis. Neural gland is considered homologous to pituitary glands of vertebrates.
Herdmania- Spicules
Herdmania- Spicules in the test:
In the test of Herdmania two types of calcareous spicules are Present. They are:
1) Microscieres : These are 40 to 80 microns in length. They are minute.
2) Megascleres : These are long spicules. They show different shapes. They are 1.5 to 3.5 mm in length. They are two types.
a) Spindle shaped Megascleres. They are 1.5 to 2.5 mm in length.
b) Pipette shaped Megascleres. They are 3.5 mm. in length.
The rnicroscleres are present only in the test. But the megascleres occur in the test, body wall, and viscera.
Herdmania-Spicules Function:
1) They give support to the test
2) They protect the animal from predators.
3) They fix mantle with test.
Herdmania- Nervous System
NERVOUS SYSTEM OF HERDMANIA:
Herdmania shows brain or nerve ganglion. It is 4 mm long. It is present in the mantle in between the two siphons. A neural gland is present above the brain. From the brain three nerves arise, one goes to the bronchial siphon, and two will go to the atrial siphon. The brain represents the degenerated nervous system of the larva.
Receptors:
1. Red pigmented spots on the test are photoreceptors. They are sensitive to light.
2. Sensory cells of the margins of siphons and tentacles are tango receptors. They are sensitive to touch.
3. The cells on the margins of siphons are rheo receptors. They are sensitive to water currents.
4. Cells lining the siphons are thermo receptors. They are sensitive to changes of temperature.
Herdmania Gonads
Gonads of Herdmanla :
Ans: Herdmania is a bisexual animal. It is a protogynous animal. Ovary matures’ first. Hence cross fertilization takes place.
Herdmania contains a pair of gonads. The left gonad lies in the intestinal loop above the heart. Each gonad shows 10 to 25 lobes arranged in two rows. The median lobe is single and large. Other lobes are oval in shape.
Each lobe shows outer large testicular part and inner small ovarian part. The testicular part is brick red in colour and produces sperms. The ovarian part is pink in colour and produce ova. From each testicular part sperm ductule will arise. They open into spermduct. From each ovarian part ovarian ductule will come. They open into the oviduct. Each gonad has an oviduct and spermduct. They run parallelly and open separately into cloaca behind anus.
Herdmania -Retrogressive Metamorphosis
Retrogressive Metmorphosis in herdmania
During metamorphosis the larva will loose all the chordate characters and attains an invertebrate like form. This type of metamorphosis, where highly advanced larval form ends in a lowly organised adult is called retrogressive metamorphosis.
Fixation of the larva: The larva swims for some time without feeding. It is fixed to a sub- stratum with the help of the adhesive papillae. It stands erect with the tail upwards. Then it undergoes retrogressive metamorphosis.
Changes during metamorphosis:
1.Notochord, nerve cord muscles and tail will be reduced. All the above structures will help the larva to swim freely in the water. But they are not useful to the sedentary adult
2.. The alimentary canal becomes complicated. The pharynx en larges ln size. The number of gill slits will increase by divisions. The stomach and intestine will grow.
3. The nervous system is reduced and the anterior part of nervous system is developed into a small neuralganglion attached to it neural gland is present. ;:
4. The atrial cavity enlarges into a sac like structure.
5. The eyespot and statocyst will completely disappear.
6. Gonads develop from mesencyme.
When these changes are taking place, the region between the adhesive papillae and mouth grows very rapidly. At the same time the growth of the dorsal region is stopped. Because of this, the body rotates through 1800 angle and mouth is brought to the top
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HERDMANIA TADPOLE LARVA
ORGANISATION OF HERDMANIA TADPOLE LARVA:
Herdmania is a hermaphrodite animal. The fertilised eggs undergo holoblastic unequal clevage and it develops into blastula. it shows upper micromeres and lower macromeres. By invagination of the macromeres gastrulation takes place and gastrula is formed. This gastrula develops into a tailed larva called Ascidian Tadpole larva. (Herdmanis life history, is not clearly known. Clavilina’s life history is known. It is followed here.
The larva is 3 mm in length. It has short oval body and a long tail.
This larva shows all the chordate features.
1) The body is covered by thin test.
2) The tail is long and shows a tail fin or caudal fin.
3) The tail is supported by notochord. Hence it comes under urochordata.
4) On the dorsal side above the notochord hollow nerve cord is present. This nerve cord is enlarged at the anterior end as a cerebral vesicle. In the cerebral vesicle pigmented eye spot is present. Statocyst is also present. They work as sense organs.
5) On either side of the notochord in the tail region muscles are Present which are helpful in the locomotion.
6) On the trunk region digestive system is present. It shows large pharynx with few gills slits. They open into atrium. On the mid ventral floor of the pharynx an endostyle is present.
7) Atrium opens out through atriopore.
8) Below the pharynx on the ventral side a muscular heart is present.
9) On the anterior end of the trunk three adhesive papillae are present These are very much useful to attach the larva to the substratum
This Herdmania tadpole larva shows all chordate characters. This larvae ‘undergoes retrogressive’ metamorphosis and develops into adult Herdmania.
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Herdmanla -External characters
External characters of Herdmania
Herdmania is a simple ascidian, In Indian ocean this genus Is represented by 4 species. ,
1. Herdmania pallida, 2. H.ennurensis, 3. H.mauritiana 4. H. ceylonica.
Herdmania belongs to,
Phylum: Chordata,
Sub-phylum: Urochordata,
Class: Ascidiacea,
Order: Pleurogona.
Herdmania is a marine and sedentary animal. It is fixed to rocky substratum by a flat base. When it is disturbed, it suddenly contracts its body, and emits inner contents with force through its apertures. Hence it is called Sea squirt.
External Features :-
It is potato like in shape. It is pink in colour. On the free side, body shows two projections, the brançhial and atrial siphons. The branchial siphon is short. The branchial siphon shows a branchial aperture or the mouth. The atrial siphon is longer. It bears the atrial aperture. Both the openings are bounded by four lips.
Herdmania - external characters.
Test of Herdmania:The body of this animal is covered and protected by test. It Ls a thick, leathery covering of the body.It is secreted by the epidermis of the body wall. It has matrix, corpuscles, fibrils, blood vessels and spicules.
The matrix is composed of tunicin, which is cellulose. The cells in the test are of six types, large eosinophilous cells, amoeboid cells, small eosinophilous cells, vacuolated cells, receptor cells and nerve cells.
Fine fibrils present in the matrix. In the test blood vessels are present. In the test the spicules are calcareous spicules. They are microscleres, and megascleres.
The test protects the body. Anchors the animals to substratum. Its spicules form a supporting frame work.
Herdmania Body wall :
The body-wall of Herdmania is called Mantle. It is thick, and muscular in the antero-dorsal region of the body. It is thin, non-muscular and transparent in the postero ventral region. It shows epidermis, mesenchyme, and inner epidermis.
1.Epidermis : It Is single layer of cells. It covers the bronchial and atrial apertures and siphons. The epidermis is interrupted at places where spicules and blood-vessels pass from the mantle into the test.
. 2. Mesènchyme: It develops from the mesoderm. It has connective tissue containing blood-sinuses, muscle-fibers, nerve fibers and cells. The muscle fibers are long and flat. They contain large nuclei.
3. Inner Epidermis: It is single layer of flat cells. It forms the lining of the atrial cavity. .
‘1.The body-wall protects visceral organs.
2. The outer epidermis secretes the test.
3. The musculature brings contraction of the body and the siphons.
Herdmania Atrium:
In Herdmania coelome is not developed. Atrium is a spacious ectoderm lined cavity. it is covered by the mantle A part of the atrium surrounds the pharynx. The stigmata of the pharynx open into this cavity. Part of the atrium is dorsal to the pharynx. It is very wide and is called cloaca. The rectum and gonoducts open into this. The cloaca opens to the exterior through atrial siphon and trial aperture. The atrial siphon shows a ring of processes called atrial tentacles at its base.
Thursday, September 15, 2016
Practical Manual B.Voc
Etroplus surantensis
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Genus: Etroplus
Etroplus suratensis is a euryhaline species that inhabits mainly brackish water and river mouths. It is an oval-shaped cichlid with a short snout, small mouth not extending past the front margin of the eye with a greyish-green colouration on the flanks, with 6 to 8 dark bars and a dark spot at base of the pectoral fin. Most scales on the sides are with a pearly spot (Costa 2007). Macrophytic fragments form the most important component of its diet along with molluscs, although detritus, diatoms, and animal matter are also ingested (De Silva et al. 1984). Many aspects of this species was studies in order to assess it's suitability for culture in ponds and tanks by Jayaprakash et al. (1990).Adults engage in altruistic multiple parental care where several adults care for a single brood that presumably were spawned by only two of the adults (Ward and Wyman 1977).
Mugil cephalus
Phylum: Chordata
Class: Actinopterygii
Order: Mugiliformes
Family: Mugilidae
Genus: Mugil
Mugil cephalus is cosmopolitan in the coastal waters of most tropical and subtropical zones. In the western Atlantic Ocean, it is found from Nova Scotia, Canada south to Brazil, including the Gulf of Mexico. It is absent in the Bahamas and the Caribbean Sea. In the eastern Atlantic Ocean, the striped mullet occurs from the Bay of Biscay (France) to South Africa, including the Mediterranean Sea and the Black Sea. The eastern Pacific Ocean range includes southern California south to Chile.
The flathead grey mullet is catadromous, frequently found coastally in estuaries and freshwater environments. Adult mullet have been found in waters ranging from zero salinity to 75‰, while juveniles can only tolerate such wide salinity ranges after they reach lengths of 4–7 cm. Adults form huge schools near the surface over sandy or muddy bottoms and dense vegetation and migrate offshore to spawn in large aggregations. The larvae move inshore to extremely shallow water, which provides cover from predators as well as a rich feeding ground. After reaching 5 cm in length, these young mullet move into slightly deeper waters.
Flathead grey mullet is a diurnal feeder, consuming mainly zooplankton, dead plant matter, and detritus. Mullet have thick-walled gizzard-like segments in their stomach along with a long gastrointestinal tract that enables them to feed on detritus. They are an ecologically important link in the energy flow within estuarine communities. Feeding by sucking up the top layer of sediments, flathead grey mullet remove detritus and microalgae. They also pick up some sediment which functions to grind food in the gizzard-like portion of the stomach. Mullet also graze on epiphytes and epifauna from seagrasses as well as ingest surface scum containing microalgae at the air-water interface. Larval flathead grey mullet feed primarily on microcrustaceans. Copepods, mosquito larvae, and plant debris have been found in the stomach contents of larvae under 35 mm in length. The amount of sand and detritus in the stomach contents increases with length, indicating that more food is ingested from the bottom substrate as the fish matures.
Eleutheronema tetradachylum
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Polynemidae
Genus: Eleutheronema
Dorsal spines (total): 9; Dorsal soft rays (total): 13-15; Anal spines: 3; Anal soft rays: 14 - 16. Pectoral filaments 4; fin membranes vivid yellow in life, except in large specimens, > ca 35 cm SL. Vomer with deciduous tooth plates on both sides, except in juveniles. Posterior part of maxilla deep, 3-4% of SL. Short tooth plate extension onto lateral surface of lower jaw. 7-9% SL (Ref. 41639).
Adults occur mainly over shallow muddy bottoms in coastal waters. Also enter rivers (Ref. 3479, 6390, 11230). Juveniles found in estuaries. During winter, adults ascend the rivers. They usually form loose schools, although larger fish are more often observed in pairs or singly (Ref. 6390). Feed on prawns and fish (largely members of Mugilidae, Engraulidae, and Sciaenidae) with occasional polychaetes. Frequency of crustaceans to fish in the diet varies seasonally. Larvae (7-30 mm TL) feed mainly on copepods and mysids but also take shrimps and prawn larvae (Ref. 57343). Juveniles (31-60 TL) feed on prawns shrimps and mysids (Ref. 57343). Protandrous hermaphrodites. Marketed fresh, frozen, and dried or salted.
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Genus: Etroplus
Etroplus suratensis is a euryhaline species that inhabits mainly brackish water and river mouths. It is an oval-shaped cichlid with a short snout, small mouth not extending past the front margin of the eye with a greyish-green colouration on the flanks, with 6 to 8 dark bars and a dark spot at base of the pectoral fin. Most scales on the sides are with a pearly spot (Costa 2007). Macrophytic fragments form the most important component of its diet along with molluscs, although detritus, diatoms, and animal matter are also ingested (De Silva et al. 1984). Many aspects of this species was studies in order to assess it's suitability for culture in ponds and tanks by Jayaprakash et al. (1990).Adults engage in altruistic multiple parental care where several adults care for a single brood that presumably were spawned by only two of the adults (Ward and Wyman 1977).
Mugil cephalus
Phylum: Chordata
Class: Actinopterygii
Order: Mugiliformes
Family: Mugilidae
Genus: Mugil
Mugil cephalus is cosmopolitan in the coastal waters of most tropical and subtropical zones. In the western Atlantic Ocean, it is found from Nova Scotia, Canada south to Brazil, including the Gulf of Mexico. It is absent in the Bahamas and the Caribbean Sea. In the eastern Atlantic Ocean, the striped mullet occurs from the Bay of Biscay (France) to South Africa, including the Mediterranean Sea and the Black Sea. The eastern Pacific Ocean range includes southern California south to Chile.
The flathead grey mullet is catadromous, frequently found coastally in estuaries and freshwater environments. Adult mullet have been found in waters ranging from zero salinity to 75‰, while juveniles can only tolerate such wide salinity ranges after they reach lengths of 4–7 cm. Adults form huge schools near the surface over sandy or muddy bottoms and dense vegetation and migrate offshore to spawn in large aggregations. The larvae move inshore to extremely shallow water, which provides cover from predators as well as a rich feeding ground. After reaching 5 cm in length, these young mullet move into slightly deeper waters.
Flathead grey mullet is a diurnal feeder, consuming mainly zooplankton, dead plant matter, and detritus. Mullet have thick-walled gizzard-like segments in their stomach along with a long gastrointestinal tract that enables them to feed on detritus. They are an ecologically important link in the energy flow within estuarine communities. Feeding by sucking up the top layer of sediments, flathead grey mullet remove detritus and microalgae. They also pick up some sediment which functions to grind food in the gizzard-like portion of the stomach. Mullet also graze on epiphytes and epifauna from seagrasses as well as ingest surface scum containing microalgae at the air-water interface. Larval flathead grey mullet feed primarily on microcrustaceans. Copepods, mosquito larvae, and plant debris have been found in the stomach contents of larvae under 35 mm in length. The amount of sand and detritus in the stomach contents increases with length, indicating that more food is ingested from the bottom substrate as the fish matures.
Eleutheronema tetradachylum
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Polynemidae
Genus: Eleutheronema
Dorsal spines (total): 9; Dorsal soft rays (total): 13-15; Anal spines: 3; Anal soft rays: 14 - 16. Pectoral filaments 4; fin membranes vivid yellow in life, except in large specimens, > ca 35 cm SL. Vomer with deciduous tooth plates on both sides, except in juveniles. Posterior part of maxilla deep, 3-4% of SL. Short tooth plate extension onto lateral surface of lower jaw. 7-9% SL (Ref. 41639).
Adults occur mainly over shallow muddy bottoms in coastal waters. Also enter rivers (Ref. 3479, 6390, 11230). Juveniles found in estuaries. During winter, adults ascend the rivers. They usually form loose schools, although larger fish are more often observed in pairs or singly (Ref. 6390). Feed on prawns and fish (largely members of Mugilidae, Engraulidae, and Sciaenidae) with occasional polychaetes. Frequency of crustaceans to fish in the diet varies seasonally. Larvae (7-30 mm TL) feed mainly on copepods and mysids but also take shrimps and prawn larvae (Ref. 57343). Juveniles (31-60 TL) feed on prawns shrimps and mysids (Ref. 57343). Protandrous hermaphrodites. Marketed fresh, frozen, and dried or salted.
Thursday, September 8, 2016
Gene Cloning
Gene Cloning – Enzymatic cleavage of DNA, Restriction enzymes (Endonucleases) and Ligation.
Gene Cloning
To clone means to make identical copies. Gene cloning means production of a number of similar copies of a required gene. DNA cloning involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copies of the selected gene.
This technology has made it possible to isolate, clone and produce DNA for all the genes in appropriate quantity so that they can be sequenced and characterized. Similarly, some of the genes which are expressed at very low level, can be cloned and desired amount of recombinant proteins can be produced.
Gene cloning involves the following steps
1. Cutting the DNA to be cloned from the chromosomal using sequence specific Restriction Endonuclease.
2. Selecting a cloning vector (a small molecule capable of self-replicating inside host cells), and cutting the cloning vector with the same restriction endonuclease to produce sticky ends.
3. Incubating the vector and subject DNA to join together DNA ligase. The resultant DNA is called recombinant DNA.
4. Transferring the reconbinant DNA to an appropriate host such as bacteria, virus or yeast which will provide necessory biomachinary for DNA replication.
5. Identifying the host cells that contain the recombinant DNA.
Enzymatic Cleavage of DNA
To cut the DNA at specific sites Restriction endonucleases are used. (RENs).
Restrictions Endonucleases:
A Restriction Endonuclease is an enzyme that cuts DNA at specific recognition points known as Restriction sites. These are most important groups of enzymes for manipulation of DNA. These enzymes were discovered in Escherichia coli. In bacteriophages these enzymes restrict the replication of viral DNA. Many types of restriction endonucleases were isolated. RENs were named based on the bacterial from which they were isolated.
The first letter of the enzyme indicates the genus name and next two letters the species name, followed by strain name and finally a number indicating the order of discovery. Eg. EcoRI: here E represents Escherichia, co represents coli, R represents the strain and I represents the first endonuclease.
Types of Endonucleases: over 3000 RENs have been studied in detail and more than 600 are available commercially. Naturally occurring Endonucleases are categorized in to four groups namely type I, II, III and IV based on their nature of their restriction sites. All types of enzymes recognize a specific DNA sequence and cleave that DNA at that point. They differ in their recognition sequence and cofactor requirements.
Type I RENs cuts DNA at random location as far as 1000 or more Basepairs from the recognition site. Type II cuts approximately 25 base pairs from the site. Type I and Type III require ATP. They are large enzymes with multiple subunits.
Type II RENs cut the DNA with in the recognized sequence without the need of ATP. They are smaller and simpler. Hence they are predominantly used in biotechnology.
Most of the Type II RENs generate Sticky ends. The open ends of the DNA molecule after the cut are called as Sticky ends.
The Length of restriction recognition sites varies. The Enzyme EcoRI, SacI etc recognize 6 basepair sequence of DNA. Most of the recognition sequences are palindromes – they read the same forward and backward.
Some of the important RENS and their restriction sites.
Enzyme Source Recognition Sequence Cut
EcoRI
Escherichia coli
5'GAATTC
3'CTTAAG 5'---G AATTC---3'
3'---CTTAA G---5'
EcoRII
Escherichia coli
5'CCWGG
3'GGWCC 5'--- CCWGG---3'
3'---GGWCC ---5'
BamHI
Bacillus amyloliquefaciens
5'GGATCC
3'CCTAGG 5'---G GATCC---3'
3'---CCTAG G---5'
HindIII
Haemophilus influenzae
5'AAGCTT
3'TTCGAA 5'---A AGCTT---3'
3'---TTCGA A---5'
TaqI
Thermus aquaticus
5'TCGA
3'AGCT 5'---T CGA---3'
3'---AGC T---5'
For convenience it is usual practice to simplifly the description of recognition sequences by showing only one strand of DNA, which runs in the 5’ to 3’ direction. Thus the EcoRI recognition sequence would be shown as G\AATTC.
Restriction enzymes with same sequence specificity and cut site are known as isochizomers. Enzymes that recognize the same sequences but cleave at different points are known as Neochizomers. Under extreme conditions like rise in pH, Low ionic strength) RENs are capable of cleaving sequences which are similar but not identical to their definied recognition sequences.
Applications of Restriction Endonucleases:
1. RENs formed in different bacteria can be used to break the DNA of any organism and the required DNA segment can be introduced in the DNA of another organism to produce Recombinant DNA
2. Restriction enzymes are highly useful to get desirable DNA segments. This is because these enzymes break the DNA at specific sites.
3. The DNAsegment isolated with the help of restriction enzymes can be used in DNA probe, genomic libraries and cDNA libraries.
4. With the isolated DNA segments, mRNA can be transcribed with which required proteins can be synthesized.
5. In restriction Fragment Length Polymorphism (RFLP) also restriction enzymes are very useful.
Enzymatic ligation of DNA
To hybridize (attach) the DNA fragments formed by the RENs to a plasmid DNA, the ends of both DNA are to be attached by forming hydrogen bonds and diester bonds. This process of attachment of the DNA fragments is known as Ligation. It is done by certain specialized enzymes called Ligases.
Ligase: (ligare = to glue together) is a special type of enzyme that can link together two DNA strands that have double strand break.
Mertz and Davis, 1972 first succeeded in producing rDNA in Escherichia coli by ligation of the sticky ends of DNA with ligase.
The mechanism of DNA ligase is to form two covalent phosphodiester bonds between 3’hydroxyl ends of one nucleotide with the 5’ phosphate end of another. ATP is required for ligation. Ligase will also work with blunt ends, but neets high concentrations of enzymes.
In mammals there are four specific types of ligases.ie. DNA ligases, I, II, III and IV. LIgases can be classified into two groups on their requirement for ATP and NAD+ as co factors. All eukaryotic enzymes are ATP dependent, whereas most prokaryotic enzymes require NAD+ for their activity.
Most experiments use T4 DNA ligase (isolated from bacteriophase T4) which is most active at 25oC. High temperatures disrupts hydrogen bonding. The commonly available DNA ligases were originally discovered in bacteriophase T4, E.coli and other bacteria.
Applications of Ligases
DNA ligases are essential tools in modern molecular biology for generating rDNA sequences such as
1. Joining double stranded DNA with cohesive or blunt ends
2. Joining of oligonucleotide linkers or adaptors to blunt ended DNA
3. Repairing in duplex DNA, RNA or DNA-RNA hybrids
4. DNA ligases are used with restriction enzyes to insert DNA fragments often genes into plasmids.
Transgenesis and Production of transgenic animals (Fish and Goat).
Transgenesis is the process of introducing an exogenous gene – called transgene- into a living organism so that the organism will exhibit a new property and transmit that property to its offspring. A transgene is the name given to the introduced DNA. The term transgenesis was coined by Gordon and Ruddle in 1981.
Animals produced through transgenesis are called Transgenic animals. Transgenic animals are genetically modified organisms with a new hereditary character.
Transgenic animals can be used to produce valuable products. Many proteins produced by transgenic animals are important for medical applications. For example, a transgenic pig has been produced with the ability to synthesize human hemoglobin for use as a blood substitute. Transgenic goat has been developed to produce a protein needed by the patients suffering from cystic fibrosis. Transgenisis is essential for improving the quality and quantity of the eggs, meat, milk etc, in addition to drug resistant animals.
The Mouse is the first animal used for transgenesis. RD Palmiter and RL Brinter (1982) isolated gene for growth hormone in human being. This gene was ligated with plasmid pBR322 to produce rDNA. It was transferred to the zygote of a mouse invitro. The embryo was implanted in the uterus of a foster mouse. Then the new born mouse was found to be transgenic which contained a gene from humans.
Methods of creation of transgenic Animals
There are three methods used for creations of transgenic animals are DNA micro injection, Embryonic stemcell-mediated gene transfer and Retrovirus mediated gene transfer.
DNA micro injection
Introduction of transgene by microinjection involves the following procedure. A young female mouse is given the FSH (follicle stimulating hormone) and HCG (human chorionic gonadotropin). Thus the mouse produces 30-35 ova. It was allowed to mate with a male. Then the fertilized ova are collected from the fallopian tubes. The transgene is introduced into the male pronucleus by using
micro injection needle. After amphimixis the embryo is allowed to devide. Then the embryo was implanted into the uterus of a foster mother. The new borns are called transgenic mice.
Hence DNA micro injection method is a random method. Success rate is very poor. This method has many disadvantages. The introduced DNA may not insert into the genome of the host. The foster mother may not accept the introduced fertilized ovum for further development. The introduced DNA may not express the desired trait. . A major advantage of this method is its applicability to a wide variety of species..
Embryonic stemcell-mediated gene transfer
The Recombinant DNA is transferred into embryo stem cells (ES). The cells are then cultured in the laboratory and those expressing the desired protein are selected. These modified ES cells are incorporated into the cavity of the embryo. This embryo is raised in a foster mother. The resulting transgenic animal will be a mosaic, because only a small proportion of the cells in its body will be expressing the protein.
Through this method transgenic goats and cows can now be designed to produce human proteins like blood clotting factors intheir milk.
Retroviral vector method:
Small fragments of DNA (8kb) can be effectively transferred by retrovirus. This method is not suitable for the transfer of large fragments of DNA. The main drawback in this method is the risk of retroviral contamination in products (such as human food) produced by transgenic animals. Hence this method is not popular in transgenesis.
Gene Cloning
To clone means to make identical copies. Gene cloning means production of a number of similar copies of a required gene. DNA cloning involves separating a specific gene or DNA segment from a larger chromosome, attaching it to a small carrier DNA. The resultant hybrid DNA is called recombinant DNA, which is transferred to a proper host (bacteria, virus or yeast) and replicated to make multiple copies of the selected gene.
This technology has made it possible to isolate, clone and produce DNA for all the genes in appropriate quantity so that they can be sequenced and characterized. Similarly, some of the genes which are expressed at very low level, can be cloned and desired amount of recombinant proteins can be produced.
Gene cloning involves the following steps
1. Cutting the DNA to be cloned from the chromosomal using sequence specific Restriction Endonuclease.
2. Selecting a cloning vector (a small molecule capable of self-replicating inside host cells), and cutting the cloning vector with the same restriction endonuclease to produce sticky ends.
3. Incubating the vector and subject DNA to join together DNA ligase. The resultant DNA is called recombinant DNA.
4. Transferring the reconbinant DNA to an appropriate host such as bacteria, virus or yeast which will provide necessory biomachinary for DNA replication.
5. Identifying the host cells that contain the recombinant DNA.
Enzymatic Cleavage of DNA
To cut the DNA at specific sites Restriction endonucleases are used. (RENs).
Restrictions Endonucleases:
A Restriction Endonuclease is an enzyme that cuts DNA at specific recognition points known as Restriction sites. These are most important groups of enzymes for manipulation of DNA. These enzymes were discovered in Escherichia coli. In bacteriophages these enzymes restrict the replication of viral DNA. Many types of restriction endonucleases were isolated. RENs were named based on the bacterial from which they were isolated.
The first letter of the enzyme indicates the genus name and next two letters the species name, followed by strain name and finally a number indicating the order of discovery. Eg. EcoRI: here E represents Escherichia, co represents coli, R represents the strain and I represents the first endonuclease.
Types of Endonucleases: over 3000 RENs have been studied in detail and more than 600 are available commercially. Naturally occurring Endonucleases are categorized in to four groups namely type I, II, III and IV based on their nature of their restriction sites. All types of enzymes recognize a specific DNA sequence and cleave that DNA at that point. They differ in their recognition sequence and cofactor requirements.
Type I RENs cuts DNA at random location as far as 1000 or more Basepairs from the recognition site. Type II cuts approximately 25 base pairs from the site. Type I and Type III require ATP. They are large enzymes with multiple subunits.
Type II RENs cut the DNA with in the recognized sequence without the need of ATP. They are smaller and simpler. Hence they are predominantly used in biotechnology.
Most of the Type II RENs generate Sticky ends. The open ends of the DNA molecule after the cut are called as Sticky ends.
The Length of restriction recognition sites varies. The Enzyme EcoRI, SacI etc recognize 6 basepair sequence of DNA. Most of the recognition sequences are palindromes – they read the same forward and backward.
Some of the important RENS and their restriction sites.
Enzyme Source Recognition Sequence Cut
EcoRI
Escherichia coli
5'GAATTC
3'CTTAAG 5'---G AATTC---3'
3'---CTTAA G---5'
EcoRII
Escherichia coli
5'CCWGG
3'GGWCC 5'--- CCWGG---3'
3'---GGWCC ---5'
BamHI
Bacillus amyloliquefaciens
5'GGATCC
3'CCTAGG 5'---G GATCC---3'
3'---CCTAG G---5'
HindIII
Haemophilus influenzae
5'AAGCTT
3'TTCGAA 5'---A AGCTT---3'
3'---TTCGA A---5'
TaqI
Thermus aquaticus
5'TCGA
3'AGCT 5'---T CGA---3'
3'---AGC T---5'
For convenience it is usual practice to simplifly the description of recognition sequences by showing only one strand of DNA, which runs in the 5’ to 3’ direction. Thus the EcoRI recognition sequence would be shown as G\AATTC.
Restriction enzymes with same sequence specificity and cut site are known as isochizomers. Enzymes that recognize the same sequences but cleave at different points are known as Neochizomers. Under extreme conditions like rise in pH, Low ionic strength) RENs are capable of cleaving sequences which are similar but not identical to their definied recognition sequences.
Applications of Restriction Endonucleases:
1. RENs formed in different bacteria can be used to break the DNA of any organism and the required DNA segment can be introduced in the DNA of another organism to produce Recombinant DNA
2. Restriction enzymes are highly useful to get desirable DNA segments. This is because these enzymes break the DNA at specific sites.
3. The DNAsegment isolated with the help of restriction enzymes can be used in DNA probe, genomic libraries and cDNA libraries.
4. With the isolated DNA segments, mRNA can be transcribed with which required proteins can be synthesized.
5. In restriction Fragment Length Polymorphism (RFLP) also restriction enzymes are very useful.
Enzymatic ligation of DNA
To hybridize (attach) the DNA fragments formed by the RENs to a plasmid DNA, the ends of both DNA are to be attached by forming hydrogen bonds and diester bonds. This process of attachment of the DNA fragments is known as Ligation. It is done by certain specialized enzymes called Ligases.
Ligase: (ligare = to glue together) is a special type of enzyme that can link together two DNA strands that have double strand break.
Mertz and Davis, 1972 first succeeded in producing rDNA in Escherichia coli by ligation of the sticky ends of DNA with ligase.
The mechanism of DNA ligase is to form two covalent phosphodiester bonds between 3’hydroxyl ends of one nucleotide with the 5’ phosphate end of another. ATP is required for ligation. Ligase will also work with blunt ends, but neets high concentrations of enzymes.
In mammals there are four specific types of ligases.ie. DNA ligases, I, II, III and IV. LIgases can be classified into two groups on their requirement for ATP and NAD+ as co factors. All eukaryotic enzymes are ATP dependent, whereas most prokaryotic enzymes require NAD+ for their activity.
Most experiments use T4 DNA ligase (isolated from bacteriophase T4) which is most active at 25oC. High temperatures disrupts hydrogen bonding. The commonly available DNA ligases were originally discovered in bacteriophase T4, E.coli and other bacteria.
Applications of Ligases
DNA ligases are essential tools in modern molecular biology for generating rDNA sequences such as
1. Joining double stranded DNA with cohesive or blunt ends
2. Joining of oligonucleotide linkers or adaptors to blunt ended DNA
3. Repairing in duplex DNA, RNA or DNA-RNA hybrids
4. DNA ligases are used with restriction enzyes to insert DNA fragments often genes into plasmids.
Transgenesis and Production of transgenic animals (Fish and Goat).
Transgenesis is the process of introducing an exogenous gene – called transgene- into a living organism so that the organism will exhibit a new property and transmit that property to its offspring. A transgene is the name given to the introduced DNA. The term transgenesis was coined by Gordon and Ruddle in 1981.
Animals produced through transgenesis are called Transgenic animals. Transgenic animals are genetically modified organisms with a new hereditary character.
Transgenic animals can be used to produce valuable products. Many proteins produced by transgenic animals are important for medical applications. For example, a transgenic pig has been produced with the ability to synthesize human hemoglobin for use as a blood substitute. Transgenic goat has been developed to produce a protein needed by the patients suffering from cystic fibrosis. Transgenisis is essential for improving the quality and quantity of the eggs, meat, milk etc, in addition to drug resistant animals.
The Mouse is the first animal used for transgenesis. RD Palmiter and RL Brinter (1982) isolated gene for growth hormone in human being. This gene was ligated with plasmid pBR322 to produce rDNA. It was transferred to the zygote of a mouse invitro. The embryo was implanted in the uterus of a foster mouse. Then the new born mouse was found to be transgenic which contained a gene from humans.
Methods of creation of transgenic Animals
There are three methods used for creations of transgenic animals are DNA micro injection, Embryonic stemcell-mediated gene transfer and Retrovirus mediated gene transfer.
DNA micro injection
Introduction of transgene by microinjection involves the following procedure. A young female mouse is given the FSH (follicle stimulating hormone) and HCG (human chorionic gonadotropin). Thus the mouse produces 30-35 ova. It was allowed to mate with a male. Then the fertilized ova are collected from the fallopian tubes. The transgene is introduced into the male pronucleus by using
micro injection needle. After amphimixis the embryo is allowed to devide. Then the embryo was implanted into the uterus of a foster mother. The new borns are called transgenic mice.
Hence DNA micro injection method is a random method. Success rate is very poor. This method has many disadvantages. The introduced DNA may not insert into the genome of the host. The foster mother may not accept the introduced fertilized ovum for further development. The introduced DNA may not express the desired trait. . A major advantage of this method is its applicability to a wide variety of species..
Embryonic stemcell-mediated gene transfer
The Recombinant DNA is transferred into embryo stem cells (ES). The cells are then cultured in the laboratory and those expressing the desired protein are selected. These modified ES cells are incorporated into the cavity of the embryo. This embryo is raised in a foster mother. The resulting transgenic animal will be a mosaic, because only a small proportion of the cells in its body will be expressing the protein.
Through this method transgenic goats and cows can now be designed to produce human proteins like blood clotting factors intheir milk.
Retroviral vector method:
Small fragments of DNA (8kb) can be effectively transferred by retrovirus. This method is not suitable for the transfer of large fragments of DNA. The main drawback in this method is the risk of retroviral contamination in products (such as human food) produced by transgenic animals. Hence this method is not popular in transgenesis.
Sunday, August 21, 2016
DISASTER MANAGEMENT MATERIAL
4. Discuss the disaster management in environment.
Geological processes like earthquakes, volcanoes, floods and landslides are normal natural events which have resulted in the formation of the earth that we have today. They are, however, disastrous in their impacts when they affect human settlements. Human societies have witnessed a large number of such natural hazards in different parts of the world and have tried to learn to control these processes, to some extent.
Earthquakes: Earthquakes occur due to sudden movements of earth.s crust. The earth.s crust has several tectonic plates of solid rock which slowly move along their boundaries. When friction prevents these plates from slipping, stress builds up and results in sudden fractures which can occur along the boundaries of the plates or fault lines (planes of weakness) within the plates. This causes earthquakes, the violent, short-term vibrations in the earth. The point on a fault at which the first movement occurs during an earthquake is called the epicenter.
The severity of an earthquake is generally measured by its magnitude on Richter Scale, as shown below:
The largest earthquake ever recorded occurred on May 22, 1960 in Chile with the estimated magnitude of 9.5 on Richter Scale, affecting 90,000 square miles and killing 6,000 people. The devastating earthquake which hit Bhuj Town in Gujarat had caused massive damage, killing 20,000-30,000 people and leaving many injured. It had an energy equivalent to a 5.3 megaton hydrogen bomb.
Earthquake-generated water waves called tsunamis can severely affect coastal areas. These giant sea swells can move at a speed upto 1000 Km/hr or even faster. While approaching the sea shore they may often reach 15 m or sometimes upto 65 m in height and cause massive devastation in coastal areas. In China such waves killed 8,30,000 people in 1556 and 50,000 in 1976. Anthropogenic activities can also cause or enhance the frequency of earthquakes. Three such activities identified are:
(a) Impoundment of huge quantities of water in the lake behind a big dam.
(b) Under ground nuclear testing.
(c) Deep well disposal of liquid waste.
Damage to property and life can be prevented by constructing earthquake-resistant buildings in the earthquake prone zones or seismic areas. For this, the structures are heavily reinforced, weak spots are strategically placed in the building that can absorb vibrations from the rest of the building, pads or floats are placed beneath the building
on which it can shift harmlessly during ground motion. Wooden houses are preferred in earthquake prone areas as in Japan.
Floods
Generally the stream channels accommodate some maximum stream flow. However, due to heavy rains or sudden snow melt the quantity of water in streams exceeds their capacity and water overflows the banks and causes inundation of the surrounding land. This situation is called flood.
A flood generally doesn.t damage property or cause casualities to an extent as done by other natural disasters. However, it causes a great economic loss and health related problems due to widespread contamination. Virtually anything the flood water touches gets contaminated, posing serious threat to health due to outbreak of epidemics.
Human activities have been the main causes for increasing the severity and frequency of floods. Construction of roads, parking space and buildings that cover the earths surface hardly allows infiltration of water into the soil and speeds up the runoff. Clearing of forests for agriculture has also increased the severity of floods. In India, Uttar Pradesh is considered to be amongst the worst flood hit states of the country. It has nearly 20% of the total 40 million hectares of flood prone zone of the country.
Flood plains, the low lying areas which get inundated during floods help to reduce floods. Building up of flood control structures like flood walls or deepening of river channels have only transferred the problems downstream. Building walls prevents spilling out the flood water over flood plains, but it increases the velocity of water to affect the areas downstream with greater force. Table 5.4 shows the occurrence of natural hazards in our country.
On an average, every year one major disaster hits India, causing huge economic losses and loss of human life. There is a need for systematic studies and strategies to evolve a Disaster Management Plan for our country.
To check the floods, efforts need to be made to restore wetlands, replace ground cover on water-courses, build check-dams on small streams, move buildings off the flood plains etc. Instead of raising buildings on flood plains, it is suggested that floodplains should be used for wildlife habitat, parks, recreational areas and other uses, which are not susceptible to flood damage. River-networking in the country is also being proposed to deal with the flood problem.
Landslides
Landslide occurs when coherent rock of soil masses move downslope due to gravitational pull. Slow landslips don.t cause much worry but sudden rockslides and mudslides are dangerous. Water and vegetation influence landslides. Chemical action of water gradually cause chemical weathering of rocks making them prone to landslides. Vegetation consolidates the slope material, provides cohesion by its root system and also retards the flow of water and its erosion capacity.
However, this can be masked by many other exerting factors like:
(i) Earthquakes, vibrations etc.
(ii) Disturbances in resistant rock overlying rock of low resistance. (iii) Saturation of the unconsolidated sediments with water.
(iv) Unconsolidated sediments exposed due to logging, road or house building.
Landslides are governed by the forces which tend to pull the earth material down slope (move in case of slopes with steeper slip plane) and resisting forces which tend to resist such movements.
It is difficult to control landslides. However, these can be minimized by stabilizing the slope by:
(i) Draining the surface and subsurface water.
(ii) Providing slope support like gabions (wired stone blocks)
(iii) Concrete support at the base of a slope.
Cyclones
Cyclones are recurring phenomena in the tropical coastal regions. Tropical cyclones in the warm oceans are formed because of heat and moisture. One of the requirements for formation of tropical cyclones is that the sea surface temperature (SST) should be above 26°C.
Tropical cyclones move like a spinning top at the speed of 10-30 Km per hour. They can last for a week or so and have a diameter varying between 100 to 1500 Km. Since in the western parts of the main ocean no cold currents exist, tropical cyclones originate there.
Tropical cyclones are called hurricanes in the Atlantic, Caribbean and north eastern Pacific,. ‘typhoons’ in the western Pacific; and ‘cyclones’ in the Indian Ocean and ‘willy willies’ in the sea around Australia. More storms occur in the Bay of Bengal than in the Arabian Sea. Of 5-6 storms that form in the year about half of them are severe.
Hurricane winds (74 miles per hour or more), rains and storm surge (often 50-100 miles wide dome of water) often devastate the area where it strikes on land. The devastation is more when storm surge and normal astronomical tide coincide. Sea water with combined force rushes inlands and inundates the low lying areas.
Management: It is difficult to stop the recurrence of cyclones. Some long term defence measures can help to protect us from devastation. Such measures include, planting more trees on the coastal belt, construction of dams, dykes, embankments, storm shelter, wind breaks, proper drainage and wide roads for quick evacuation.
Explain the solid waste management.
Higher standards of living of ever increasing population has resulted in
an increase in the quantity and variety of waste generated. It is now
realized that if waste generation continues indiscriminately then very
soon it would be beyond rectification. Management of solid waste has,
therefore, become very important in order to minimize the adverse
effects of solid wastes. Solid waste (waste other than liquid or gaseous)
can be classified as municipal, industrial, agricultural, medical, mining
waste and sewage sludge.
Sources of Urban and Industrial Wastes
Urban waste consists of medical waste from hospitals; municipal solid
wastes from homes, offices, markets (commercial waste) small cottage
units, and horticulture waste from parks, gardens, orchards etc.
l Waste from homes (Domestic waste) contains a variety of
discarded materials like polyethylene bags, empty metal and
aluminium cans, scrap metals, glass bottles, waste paper,
diapers, cloth/rags, food waste etc.
l Waste from shops mainly consists of waste paper, packaging
material, cans, bottles, polyethylene bags, peanut shells,
eggshells, tea leaves etc.
l Biomedical waste includes anatomical wastes, pathological
wastes, infectious wastes etc.
l Construction/demolition waste includes debris and rubbles,
wood, concrete etc.
l Horticulture waste and waste from slaughter houses include
vegetable parts, residues and remains of slaughtered animals,
respectively.
The urban solid waste materials that can be degraded by microorganisms
are called biodegradable wastes. Examples of this type of
waste are vegetable wastes, stale food, tea leaves, egg shells, peanut
shells, dry leaves etc. Wastes that cannot be degraded by microorganisms
are called non-biodegradable wastes. For example,
polyethylene bags, scrap metal, glass bottles etc.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.
Geological processes like earthquakes, volcanoes, floods and landslides are normal natural events which have resulted in the formation of the earth that we have today. They are, however, disastrous in their impacts when they affect human settlements. Human societies have witnessed a large number of such natural hazards in different parts of the world and have tried to learn to control these processes, to some extent.
Earthquakes: Earthquakes occur due to sudden movements of earth.s crust. The earth.s crust has several tectonic plates of solid rock which slowly move along their boundaries. When friction prevents these plates from slipping, stress builds up and results in sudden fractures which can occur along the boundaries of the plates or fault lines (planes of weakness) within the plates. This causes earthquakes, the violent, short-term vibrations in the earth. The point on a fault at which the first movement occurs during an earthquake is called the epicenter.
The severity of an earthquake is generally measured by its magnitude on Richter Scale, as shown below:
The largest earthquake ever recorded occurred on May 22, 1960 in Chile with the estimated magnitude of 9.5 on Richter Scale, affecting 90,000 square miles and killing 6,000 people. The devastating earthquake which hit Bhuj Town in Gujarat had caused massive damage, killing 20,000-30,000 people and leaving many injured. It had an energy equivalent to a 5.3 megaton hydrogen bomb.
Earthquake-generated water waves called tsunamis can severely affect coastal areas. These giant sea swells can move at a speed upto 1000 Km/hr or even faster. While approaching the sea shore they may often reach 15 m or sometimes upto 65 m in height and cause massive devastation in coastal areas. In China such waves killed 8,30,000 people in 1556 and 50,000 in 1976. Anthropogenic activities can also cause or enhance the frequency of earthquakes. Three such activities identified are:
(a) Impoundment of huge quantities of water in the lake behind a big dam.
(b) Under ground nuclear testing.
(c) Deep well disposal of liquid waste.
Damage to property and life can be prevented by constructing earthquake-resistant buildings in the earthquake prone zones or seismic areas. For this, the structures are heavily reinforced, weak spots are strategically placed in the building that can absorb vibrations from the rest of the building, pads or floats are placed beneath the building
on which it can shift harmlessly during ground motion. Wooden houses are preferred in earthquake prone areas as in Japan.
Floods
Generally the stream channels accommodate some maximum stream flow. However, due to heavy rains or sudden snow melt the quantity of water in streams exceeds their capacity and water overflows the banks and causes inundation of the surrounding land. This situation is called flood.
A flood generally doesn.t damage property or cause casualities to an extent as done by other natural disasters. However, it causes a great economic loss and health related problems due to widespread contamination. Virtually anything the flood water touches gets contaminated, posing serious threat to health due to outbreak of epidemics.
Human activities have been the main causes for increasing the severity and frequency of floods. Construction of roads, parking space and buildings that cover the earths surface hardly allows infiltration of water into the soil and speeds up the runoff. Clearing of forests for agriculture has also increased the severity of floods. In India, Uttar Pradesh is considered to be amongst the worst flood hit states of the country. It has nearly 20% of the total 40 million hectares of flood prone zone of the country.
Flood plains, the low lying areas which get inundated during floods help to reduce floods. Building up of flood control structures like flood walls or deepening of river channels have only transferred the problems downstream. Building walls prevents spilling out the flood water over flood plains, but it increases the velocity of water to affect the areas downstream with greater force. Table 5.4 shows the occurrence of natural hazards in our country.
On an average, every year one major disaster hits India, causing huge economic losses and loss of human life. There is a need for systematic studies and strategies to evolve a Disaster Management Plan for our country.
To check the floods, efforts need to be made to restore wetlands, replace ground cover on water-courses, build check-dams on small streams, move buildings off the flood plains etc. Instead of raising buildings on flood plains, it is suggested that floodplains should be used for wildlife habitat, parks, recreational areas and other uses, which are not susceptible to flood damage. River-networking in the country is also being proposed to deal with the flood problem.
Landslides
Landslide occurs when coherent rock of soil masses move downslope due to gravitational pull. Slow landslips don.t cause much worry but sudden rockslides and mudslides are dangerous. Water and vegetation influence landslides. Chemical action of water gradually cause chemical weathering of rocks making them prone to landslides. Vegetation consolidates the slope material, provides cohesion by its root system and also retards the flow of water and its erosion capacity.
However, this can be masked by many other exerting factors like:
(i) Earthquakes, vibrations etc.
(ii) Disturbances in resistant rock overlying rock of low resistance. (iii) Saturation of the unconsolidated sediments with water.
(iv) Unconsolidated sediments exposed due to logging, road or house building.
Landslides are governed by the forces which tend to pull the earth material down slope (move in case of slopes with steeper slip plane) and resisting forces which tend to resist such movements.
It is difficult to control landslides. However, these can be minimized by stabilizing the slope by:
(i) Draining the surface and subsurface water.
(ii) Providing slope support like gabions (wired stone blocks)
(iii) Concrete support at the base of a slope.
Cyclones
Cyclones are recurring phenomena in the tropical coastal regions. Tropical cyclones in the warm oceans are formed because of heat and moisture. One of the requirements for formation of tropical cyclones is that the sea surface temperature (SST) should be above 26°C.
Tropical cyclones move like a spinning top at the speed of 10-30 Km per hour. They can last for a week or so and have a diameter varying between 100 to 1500 Km. Since in the western parts of the main ocean no cold currents exist, tropical cyclones originate there.
Tropical cyclones are called hurricanes in the Atlantic, Caribbean and north eastern Pacific,. ‘typhoons’ in the western Pacific; and ‘cyclones’ in the Indian Ocean and ‘willy willies’ in the sea around Australia. More storms occur in the Bay of Bengal than in the Arabian Sea. Of 5-6 storms that form in the year about half of them are severe.
Hurricane winds (74 miles per hour or more), rains and storm surge (often 50-100 miles wide dome of water) often devastate the area where it strikes on land. The devastation is more when storm surge and normal astronomical tide coincide. Sea water with combined force rushes inlands and inundates the low lying areas.
Management: It is difficult to stop the recurrence of cyclones. Some long term defence measures can help to protect us from devastation. Such measures include, planting more trees on the coastal belt, construction of dams, dykes, embankments, storm shelter, wind breaks, proper drainage and wide roads for quick evacuation.
Explain the solid waste management.
Higher standards of living of ever increasing population has resulted in
an increase in the quantity and variety of waste generated. It is now
realized that if waste generation continues indiscriminately then very
soon it would be beyond rectification. Management of solid waste has,
therefore, become very important in order to minimize the adverse
effects of solid wastes. Solid waste (waste other than liquid or gaseous)
can be classified as municipal, industrial, agricultural, medical, mining
waste and sewage sludge.
Sources of Urban and Industrial Wastes
Urban waste consists of medical waste from hospitals; municipal solid
wastes from homes, offices, markets (commercial waste) small cottage
units, and horticulture waste from parks, gardens, orchards etc.
l Waste from homes (Domestic waste) contains a variety of
discarded materials like polyethylene bags, empty metal and
aluminium cans, scrap metals, glass bottles, waste paper,
diapers, cloth/rags, food waste etc.
l Waste from shops mainly consists of waste paper, packaging
material, cans, bottles, polyethylene bags, peanut shells,
eggshells, tea leaves etc.
l Biomedical waste includes anatomical wastes, pathological
wastes, infectious wastes etc.
l Construction/demolition waste includes debris and rubbles,
wood, concrete etc.
l Horticulture waste and waste from slaughter houses include
vegetable parts, residues and remains of slaughtered animals,
respectively.
The urban solid waste materials that can be degraded by microorganisms
are called biodegradable wastes. Examples of this type of
waste are vegetable wastes, stale food, tea leaves, egg shells, peanut
shells, dry leaves etc. Wastes that cannot be degraded by microorganisms
are called non-biodegradable wastes. For example,
polyethylene bags, scrap metal, glass bottles etc.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.
Industrial waste: Industrial waste consists of a large number
of materials including factory rubbish, packaging material,
organic wastes, acids, alkalis and metals etc. During some
industrial processing large quantities of hazardous and toxic
materials are also produced. The main sources of industrial
wastes are chemical industries, metal and mineral processing
industries. Radioactive wastes are generated by nuclear power
plants. Thermal power plants produce fly ash in large
quantities. Solid wastes from other types of industries include
scrap metal, rubber, plastic, paper, glass, wood, oils, paints,
asphalt, tars, dyes, scrap leather, ceramics, abrasives, slag,
heavy metals, asbestos, batteries. In Europe and North
America the environmental laws and safety laws are becoming
more stringent due to which disposal of hazardous wastes is
becoming a problem. Cost of disposal of such wastes is
increasing. Therefore, these wastes are being exported to
developing countries which do not even have sufficient
knowledge or technique for their disposal.
Effects of Solid Wastes
Municipal solid wastes heap up on the roads due to improper disposal
system. People clean their own houses and litter their immediate
surroundings which affects the community including themselves. This
type of dumping allows biodegradable materials to decompose under
uncontrolled and unhygienic conditions. This produces foul smell and
breeds various types of insects and infectious organisms besides spoiling
the aesthetics of the site.
Industrial solid wastes are sources of toxic metals and hazardous
wastes, which may spread on land and can cause changes in physico-
chemical and biological characteristics thereby affecting productivity
of soils. Toxic substances may leach or percolate to contaminate the
ground water.
In refuse mixing the hazardous wastes are mixed with garbage
and other combustible waste. This makes segregation and disposal all
the more difficult and risky. Various types of wastes like cans, pesticides,
cleaning solvents, batteries (zinc, lead or mercury) radioactive materials,
plastics are mixed up with paper, scraps and other non-toxic materials
which could be recycled. Burning of some of these materials produce
dioxins, furans and polychlorinated biphenyls, which have the potential
to cause various types of ailments including cancer.
Wednesday, August 17, 2016
Practical Manual B.Voc
Megalops cyprinoides
Phylum: Chordata
Class: Actinopterygii
Order: Elopiformes
Family: Megalopidae
Genus: Megalops
In appearance, it is like the Atlantic tarpon, Megalops atlanticus: olive-green on top, and silver on the sides. The large mouth is turned upwards; the lower jaw contains an elongated, bony plate. The last ray of the dorsal fin is much longer than the others, reaching nearly to the tail. It is capable of filling its swim bladder with air and absorbing oxygen from it. Species in fresh water tend to be smaller than the saltwater species, growing just over 50 cm (20 in), while saltwater species grow over a 1 m (3.3 ft). They live an upwards of 44 years and mature within two. They complete their metamorphosis from their larvae stage in 10 days.[2]
Lates calcarifer
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Latidae
Genus: Lates
This species has an elongated body form with a large, slightly oblique mouth and an upper jaw extending behind the eye. The lower edge of the preoperculum is serrated with a strong spine at its angle; the operculum has a small spine and a serrated flap above the origin of the lateral line. Its scales are ctenoid. In cross section, the fish is compressed and the dorsal head profile clearly concave. The single dorsal and ventral fins have spines and soft rays; the paired pectoral andpelvic fins have soft rays only; and the caudal fin has soft rays and is truncate and rounded. Barramundi are salt and freshwater sportfish, targeted by many. They have large, silver scales, which may become darker or lighter, depending on their environments. Their bodies can reach up to 1.8 m (5.9 ft) long, though evidence of them being caught at this size is scarce. The maximum weight is about 60 kg (130 lb). The average length is about 0.6–1.2 m (2.0–3.9 ft). Its genome size is about 700 Mb, which was sequenced and published in Animal Genetics (2015, in press) by James Cook University.
Barramundi are demersal, inhabiting coastal waters, estuaries, lagoons, and rivers; they are found in clear to turbid water, usually within a temperature range of 26−30 °C. This species does not undertake extensive migrations within or between river systems, which has presumably influenced establishment of genetically distinct stocks in Northern Australia.
Phylum: Chordata
Class: Actinopterygii
Order: Elopiformes
Family: Megalopidae
Genus: Megalops
In appearance, it is like the Atlantic tarpon, Megalops atlanticus: olive-green on top, and silver on the sides. The large mouth is turned upwards; the lower jaw contains an elongated, bony plate. The last ray of the dorsal fin is much longer than the others, reaching nearly to the tail. It is capable of filling its swim bladder with air and absorbing oxygen from it. Species in fresh water tend to be smaller than the saltwater species, growing just over 50 cm (20 in), while saltwater species grow over a 1 m (3.3 ft). They live an upwards of 44 years and mature within two. They complete their metamorphosis from their larvae stage in 10 days.[2]
Lates calcarifer
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Latidae
Genus: Lates
This species has an elongated body form with a large, slightly oblique mouth and an upper jaw extending behind the eye. The lower edge of the preoperculum is serrated with a strong spine at its angle; the operculum has a small spine and a serrated flap above the origin of the lateral line. Its scales are ctenoid. In cross section, the fish is compressed and the dorsal head profile clearly concave. The single dorsal and ventral fins have spines and soft rays; the paired pectoral andpelvic fins have soft rays only; and the caudal fin has soft rays and is truncate and rounded. Barramundi are salt and freshwater sportfish, targeted by many. They have large, silver scales, which may become darker or lighter, depending on their environments. Their bodies can reach up to 1.8 m (5.9 ft) long, though evidence of them being caught at this size is scarce. The maximum weight is about 60 kg (130 lb). The average length is about 0.6–1.2 m (2.0–3.9 ft). Its genome size is about 700 Mb, which was sequenced and published in Animal Genetics (2015, in press) by James Cook University.
Barramundi are demersal, inhabiting coastal waters, estuaries, lagoons, and rivers; they are found in clear to turbid water, usually within a temperature range of 26−30 °C. This species does not undertake extensive migrations within or between river systems, which has presumably influenced establishment of genetically distinct stocks in Northern Australia.
Friday, July 15, 2016
ఫలదీకరణం
2. ఫలదీకరణం ను విశదీకరింపుము
జ. స్త్రీ బీజకణం మరియు పురుష బీజకణముల కలయికను ఫలదీకరణం అంటారు. లైంగిక ప్రత్యుత్పత్తి జరిపే జీవులలో ఫలదీకరణ ముఖ్యమైన క్రియ. ఇందులో రెందు ఏకస్థితిక కణాలైన అండము మరియు శుక్రకణములు కలయిక వల్ల ద్వయస్థితిక సంయుక్త బీజము ఏర్పడుతుంది. సంయుక్తబీజం పిండంగా మారి పిల్ల జీవిగా వృద్ధి చెందుతుంది.
ఫలదీకరణ జంతువుల శరీరం వెలుపల జరిగితే బాహ్యఫలదీకరణం (కప్ప) అని, శరీరం లోపల జరిగితే అంతరఫలదీకరణ అని (మానవుడు) అంటారు. బాహ్య ఫలదీకరణంలో శుక్రకణాలు మరియు అండాలను పరిసరాల మాధ్యమం లోకి విడుదల చేయ బడతాయి. శుక్రకణం అండమును చేరి ఫలదీకరణ జరుపుతుంది. అంతర ఫలదీకరణలో పురుష జీవి తన శుక్రకణాలను స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ లోనికి ప్రవేశపెడుతుంది. తరువాత శుక్రకణము చురుకుగా కదులుతూ అండమును చేరుకొని ఫలదీకరణ జరుపును.
కొన్ని సందర్భములలో శుక్రకణాలు కొన్ని రసాయినిక పదార్ధముల ప్రభావముచేత అండముల వద్దకు చేర్చబడతాయి
ఫెర్టిలైజిన్ మరియు యాంటి ఫెర్టిలైజిన్
శుక్రకణములను ఆకర్షించు పదార్ధమును ఫెర్టిలైజిన్ అంటారు. ఇది పక్వము పొందిన అండములనుండి ఎక్కువమొత్తాలలో విడుదల చేయబడుతుంది. ఇది అండముల పరిసర మాధ్యమము లోకి (నీరు లేదా కణబాహ్య ద్రవాలు) స్రవింపబడి, సమీపములో నున్న శుక్రకణములను తనవైపునకు ఆకర్శించును.
శుక్రకణము ఉపరితలముపై యాంటి ఫెర్టిలైజిన్ అను పదార్ధమును కలిగిఉంటుంది. ఫెర్టిలైజిన్ – యాంటిఫెర్టిలైజిన్ అణువులు ఒకదానితొ ఒకటి బంధనము ఏర్పరచు కొనటం ద్వారా శుక్రకణము అండముల ప్రాధమిక కలయిక జరుగుతుంది.
కెపాసిటేషన్: శుక్రకణం స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ మార్గములో ప్రవేసించిన తరువాత, దాని ఉపరితల త్వచములో కల ప్రొటీన్ల నిర్మాణంలో మార్పు వస్తుంది. అప్పుడు మాత్రమే ఇది, అండము యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడా ను చొచ్చుకు పోగలిగే సామర్ధ్యాన్ని పొందుతుంది. ఈ ప్రక్రియను కెపాసిటేషన్ అంటారు.
శుక్రకణము అండములో ప్రవేశించుట: శుక్రకణం అండాన్ని చేరగానే దాని లోని ఎక్రోసోము లైసిన్ అనే ఎంజైమును స్రవించి అండం యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడాను కరిగించును. తరువాత ఎక్రోసోము సాగి సన్నని పొడవైన నాళిక వలె ఏర్పడును. దీనిని ఎక్రోసోమల్ తంతువు అంటారు. ఇది అండములోనికి చొచ్చుకొని పోవును.
అండము ఉత్తేజమును పొంది ప్రతిచర్యను చూపుట: ఎక్రోసోమల్ తంతువు అండమును తాకగానే అండము యొక్క ఉపరితలము ముందుకు సాగి శంకువు వంటి ఫలదీకరణ కొన ను ఏర్పరచును. ఇది హయలిన్ అనబడు పదార్ధముతో ఏర్పడును. ఈ ఫలదీకరణ కొన ముందుకు విస్తరించి శుక్రకణమును తనలోనికి లాక్కొనును. తరువాత నెమ్మది నెమ్మదిగా ఫలదీకరణ కొన లోనికి ముడుచుకు పోవును.
పాలిస్పెర్మీ నిరోధము: సాధారణంగా అండములోనికి ఒక శుక్రకణము మాత్రమే ప్రవేశిస్తుంది. కానీ కొన్ని సందర్భాలలో ఒకటి కంటే ఎక్కువ శుక్రకణాలు ప్రవేసించటాన్ని పాలిస్పెర్మ్య్ అంటారు. అలాంటి పరిస్థితులలో అట్టి అండములోని పిండము అభివృద్ది చెందక నశించిపోవును. కనుక ఒక శుక్రకణము ప్రవేశించిన తరువాత అండత్వచాలలో అనేక బౌతిక రసాయినిక చర్యలు జరిగి, మరొక శుక్రకణము లోనికి ప్రవేశించకుండా నిరోధిస్తాయి.
ప్రాక్కేంద్రకాల కలయిక: అండంలో ప్రవేశించిన వెంటనే శుక్రకణం తల లావెక్కి పురుష ప్రాక్కేంద్రకం గా మారుతుంది. అదే సమయంలో అండంలోని కేంద్రకం చివరి పరిపక్వ విభజన జరుపుకొని ఫలదీకరణకు సిద్దమౌతుంది. అండకేంద్రకాన్ని స్త్రీ ప్రాక్కేంద్రకం అంటారు. ఈ రెండు కేంద్రకాలు క్షయకరణ విభజన ద్వారా ఏర్పడినవి కనుక వీటిలో ఏకస్థితిక క్రోమోజోములు ఉంటాయి. ఈ రెండుక్రోమోజోముల కలయిక వలన ఏర్పడే సంయుక్తబీజం ద్వయస్థితిక స్థితిని పొందుతుంది.
శుక్రకణ కేంద్రకం (పురుషకేంద్రకం) స్త్రీ కేంద్రకాన్ని చేరుకొనే మార్గాన్నిశుక్రకణ మార్గం అంటారు. స్త్రీ ప్రాక్కేంద్రకం కూడా పురుషకేంద్రకాన్ని చేరటానికి కొంతదూరం ప్రయాణిస్తుంది. ఇవి రెండు తమ కేంద్రక త్వచాలను కరిగిపోయి, పిత్రు మరియు మాతృ క్రోమోజోములు రెండు పక్కపక్కకు చేరి సమవిభజనకు (అండం విభజనలు జరుపుకొని పిండాన్ని ఏర్పరచును) సిద్దమవుతాయి. ఫలదీకరణ సమయంలో జరిగే కేంద్రక పదార్ధముల కలయిక వలన పితృ మరియు మాతృ లక్షణాలు కలిసిపోతాయి. స్త్రీ మరియు పురుష ప్రాక్కేంద్రకాల కలయిక అనంతరం అండాన్ని సంయుక్త బీజం అంటారు.
సంయుక్త బీజములో క్రోమోజోముల నిడివి పెరుగుతుంది, మైటోఖాండ్రియాల సంఖ్య పెరుగును, కేంద్రకాంశము పెద్దదగును. ఎండోప్లాస్మిక్ రెటిక్యులం, గాల్జి, సెంట్రోజోములు అదృశ్యం అవుతాయి. ప్రొటీన్లు, కొవ్వులు, గ్లైకోజెన్ వంటి ఆహారపదార్ధలతో తయారయ్యే సొనపదార్ధం అండములో నిక్షిప్తం చేయబడుతుంది. ఫలదీకరణమ్ జరిగిన వెంటనే విదళనం మొదలౌతుంది.
జ. స్త్రీ బీజకణం మరియు పురుష బీజకణముల కలయికను ఫలదీకరణం అంటారు. లైంగిక ప్రత్యుత్పత్తి జరిపే జీవులలో ఫలదీకరణ ముఖ్యమైన క్రియ. ఇందులో రెందు ఏకస్థితిక కణాలైన అండము మరియు శుక్రకణములు కలయిక వల్ల ద్వయస్థితిక సంయుక్త బీజము ఏర్పడుతుంది. సంయుక్తబీజం పిండంగా మారి పిల్ల జీవిగా వృద్ధి చెందుతుంది.
ఫలదీకరణ జంతువుల శరీరం వెలుపల జరిగితే బాహ్యఫలదీకరణం (కప్ప) అని, శరీరం లోపల జరిగితే అంతరఫలదీకరణ అని (మానవుడు) అంటారు. బాహ్య ఫలదీకరణంలో శుక్రకణాలు మరియు అండాలను పరిసరాల మాధ్యమం లోకి విడుదల చేయ బడతాయి. శుక్రకణం అండమును చేరి ఫలదీకరణ జరుపుతుంది. అంతర ఫలదీకరణలో పురుష జీవి తన శుక్రకణాలను స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ లోనికి ప్రవేశపెడుతుంది. తరువాత శుక్రకణము చురుకుగా కదులుతూ అండమును చేరుకొని ఫలదీకరణ జరుపును.
కొన్ని సందర్భములలో శుక్రకణాలు కొన్ని రసాయినిక పదార్ధముల ప్రభావముచేత అండముల వద్దకు చేర్చబడతాయి
ఫెర్టిలైజిన్ మరియు యాంటి ఫెర్టిలైజిన్
శుక్రకణములను ఆకర్షించు పదార్ధమును ఫెర్టిలైజిన్ అంటారు. ఇది పక్వము పొందిన అండములనుండి ఎక్కువమొత్తాలలో విడుదల చేయబడుతుంది. ఇది అండముల పరిసర మాధ్యమము లోకి (నీరు లేదా కణబాహ్య ద్రవాలు) స్రవింపబడి, సమీపములో నున్న శుక్రకణములను తనవైపునకు ఆకర్శించును.
శుక్రకణము ఉపరితలముపై యాంటి ఫెర్టిలైజిన్ అను పదార్ధమును కలిగిఉంటుంది. ఫెర్టిలైజిన్ – యాంటిఫెర్టిలైజిన్ అణువులు ఒకదానితొ ఒకటి బంధనము ఏర్పరచు కొనటం ద్వారా శుక్రకణము అండముల ప్రాధమిక కలయిక జరుగుతుంది.
కెపాసిటేషన్: శుక్రకణం స్త్రీ ప్రత్యుత్పత్తి వ్యవస్థ మార్గములో ప్రవేసించిన తరువాత, దాని ఉపరితల త్వచములో కల ప్రొటీన్ల నిర్మాణంలో మార్పు వస్తుంది. అప్పుడు మాత్రమే ఇది, అండము యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడా ను చొచ్చుకు పోగలిగే సామర్ధ్యాన్ని పొందుతుంది. ఈ ప్రక్రియను కెపాసిటేషన్ అంటారు.
శుక్రకణము అండములో ప్రవేశించుట: శుక్రకణం అండాన్ని చేరగానే దాని లోని ఎక్రోసోము లైసిన్ అనే ఎంజైమును స్రవించి అండం యొక్క వెలుపలి పొర అయిన జోనా పెల్లుసిడాను కరిగించును. తరువాత ఎక్రోసోము సాగి సన్నని పొడవైన నాళిక వలె ఏర్పడును. దీనిని ఎక్రోసోమల్ తంతువు అంటారు. ఇది అండములోనికి చొచ్చుకొని పోవును.
అండము ఉత్తేజమును పొంది ప్రతిచర్యను చూపుట: ఎక్రోసోమల్ తంతువు అండమును తాకగానే అండము యొక్క ఉపరితలము ముందుకు సాగి శంకువు వంటి ఫలదీకరణ కొన ను ఏర్పరచును. ఇది హయలిన్ అనబడు పదార్ధముతో ఏర్పడును. ఈ ఫలదీకరణ కొన ముందుకు విస్తరించి శుక్రకణమును తనలోనికి లాక్కొనును. తరువాత నెమ్మది నెమ్మదిగా ఫలదీకరణ కొన లోనికి ముడుచుకు పోవును.
పాలిస్పెర్మీ నిరోధము: సాధారణంగా అండములోనికి ఒక శుక్రకణము మాత్రమే ప్రవేశిస్తుంది. కానీ కొన్ని సందర్భాలలో ఒకటి కంటే ఎక్కువ శుక్రకణాలు ప్రవేసించటాన్ని పాలిస్పెర్మ్య్ అంటారు. అలాంటి పరిస్థితులలో అట్టి అండములోని పిండము అభివృద్ది చెందక నశించిపోవును. కనుక ఒక శుక్రకణము ప్రవేశించిన తరువాత అండత్వచాలలో అనేక బౌతిక రసాయినిక చర్యలు జరిగి, మరొక శుక్రకణము లోనికి ప్రవేశించకుండా నిరోధిస్తాయి.
ప్రాక్కేంద్రకాల కలయిక: అండంలో ప్రవేశించిన వెంటనే శుక్రకణం తల లావెక్కి పురుష ప్రాక్కేంద్రకం గా మారుతుంది. అదే సమయంలో అండంలోని కేంద్రకం చివరి పరిపక్వ విభజన జరుపుకొని ఫలదీకరణకు సిద్దమౌతుంది. అండకేంద్రకాన్ని స్త్రీ ప్రాక్కేంద్రకం అంటారు. ఈ రెండు కేంద్రకాలు క్షయకరణ విభజన ద్వారా ఏర్పడినవి కనుక వీటిలో ఏకస్థితిక క్రోమోజోములు ఉంటాయి. ఈ రెండుక్రోమోజోముల కలయిక వలన ఏర్పడే సంయుక్తబీజం ద్వయస్థితిక స్థితిని పొందుతుంది.
శుక్రకణ కేంద్రకం (పురుషకేంద్రకం) స్త్రీ కేంద్రకాన్ని చేరుకొనే మార్గాన్నిశుక్రకణ మార్గం అంటారు. స్త్రీ ప్రాక్కేంద్రకం కూడా పురుషకేంద్రకాన్ని చేరటానికి కొంతదూరం ప్రయాణిస్తుంది. ఇవి రెండు తమ కేంద్రక త్వచాలను కరిగిపోయి, పిత్రు మరియు మాతృ క్రోమోజోములు రెండు పక్కపక్కకు చేరి సమవిభజనకు (అండం విభజనలు జరుపుకొని పిండాన్ని ఏర్పరచును) సిద్దమవుతాయి. ఫలదీకరణ సమయంలో జరిగే కేంద్రక పదార్ధముల కలయిక వలన పితృ మరియు మాతృ లక్షణాలు కలిసిపోతాయి. స్త్రీ మరియు పురుష ప్రాక్కేంద్రకాల కలయిక అనంతరం అండాన్ని సంయుక్త బీజం అంటారు.
సంయుక్త బీజములో క్రోమోజోముల నిడివి పెరుగుతుంది, మైటోఖాండ్రియాల సంఖ్య పెరుగును, కేంద్రకాంశము పెద్దదగును. ఎండోప్లాస్మిక్ రెటిక్యులం, గాల్జి, సెంట్రోజోములు అదృశ్యం అవుతాయి. ప్రొటీన్లు, కొవ్వులు, గ్లైకోజెన్ వంటి ఆహారపదార్ధలతో తయారయ్యే సొనపదార్ధం అండములో నిక్షిప్తం చేయబడుతుంది. ఫలదీకరణమ్ జరిగిన వెంటనే విదళనం మొదలౌతుంది.
Wednesday, June 8, 2016
Practical Manual B.Voc
Tilapia mossambica
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Subfamily: Pseudocrenilabrinae
Tribe: Tilapiini
Genus: Oreochromis
The native Mozambique tilapia is laterally compressed, and has a deep body with long dorsal fins, the front part of which have spines. Native coloration is a dull greenish or yellowish, and there may be weak banding. Adults reach approximately 35 centimetres (14 in) in length and up to 1.13 kilograms (2.5 lb). Size and coloration may vary in captive and naturalized populations due to environmental and breeding pressures. It lives for up to 11 years.
It is a remarkably robust and fecund fish, readily adapting to available food sources and breeding under suboptimal conditions. It also tolerates brackish water and survives temperatures below 50 °F (10 °C) and above 100 °F (38 °C). Sustained water temperatures of 55 degrees are lethal to Mozambique tilapia.
Body compressed; caudal peduncle longer than deep. Scales cycloid. A knob-like protuberance present behind upper jaw on dorsal surface of snout. Upper jaw length shows sexual dimorphism, and mouth of male larger than that of female. First gill arch with 20 to 22 gillrakers. Lateral line interrupted. Spinous and soft ray parts of dorsal fin continuous. Dorsal fin with 15 to 18 spines and 10 to 13 soft rays. Anal fin with 3 spines and 9-10 rays. Caudal fin truncated. Colour in spawning season, pectoral, dorsal and caudal fins becoming reddish; colour male shows much brighter orange tail than female.
Hypophthalmichthys molitrix
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Hypophthalmichthys
Species: H. molitrix
Identification: The silver carp is a deep-bodied fish that is laterally compressed. They are a very silvery in color when young and when they get older they fade from a greenish color on the back to silver on the belly. They have very tiny scales on their body but the head and the opercles are scaleless. They have a large mouth without any teeth in the jaw, but they have pharyngeal teeth. Its eyes are situated far forward on the midline of the body and are slightly turned down.
Silver carp are unlikely to be confused with native cyprinids due to size and unusual position of the eye. They are most similar to bighead carp (H. nobilis) but have a smaller head, and upturned mouth without teeth, a keel that extends forward past pelvic fin base, lack the dark blotches characteristic of bighead carp and have highly branched gill rakers.
Juvenile fish lack spines in fins. Metalarvae and early juvenile are similar to bighead carp (Hypophthalmichthys nobilis) but pectoral fin extends only to base of pelvic fin (as opposed to beyond in the pelvic fin in bighead)
The species is known for leaping out of the water when startled (e.g., by noises such as a boat motor).
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Subfamily: Pseudocrenilabrinae
Tribe: Tilapiini
Genus: Oreochromis
The native Mozambique tilapia is laterally compressed, and has a deep body with long dorsal fins, the front part of which have spines. Native coloration is a dull greenish or yellowish, and there may be weak banding. Adults reach approximately 35 centimetres (14 in) in length and up to 1.13 kilograms (2.5 lb). Size and coloration may vary in captive and naturalized populations due to environmental and breeding pressures. It lives for up to 11 years.
It is a remarkably robust and fecund fish, readily adapting to available food sources and breeding under suboptimal conditions. It also tolerates brackish water and survives temperatures below 50 °F (10 °C) and above 100 °F (38 °C). Sustained water temperatures of 55 degrees are lethal to Mozambique tilapia.
Body compressed; caudal peduncle longer than deep. Scales cycloid. A knob-like protuberance present behind upper jaw on dorsal surface of snout. Upper jaw length shows sexual dimorphism, and mouth of male larger than that of female. First gill arch with 20 to 22 gillrakers. Lateral line interrupted. Spinous and soft ray parts of dorsal fin continuous. Dorsal fin with 15 to 18 spines and 10 to 13 soft rays. Anal fin with 3 spines and 9-10 rays. Caudal fin truncated. Colour in spawning season, pectoral, dorsal and caudal fins becoming reddish; colour male shows much brighter orange tail than female.
Hypophthalmichthys molitrix
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Hypophthalmichthys
Species: H. molitrix
Identification: The silver carp is a deep-bodied fish that is laterally compressed. They are a very silvery in color when young and when they get older they fade from a greenish color on the back to silver on the belly. They have very tiny scales on their body but the head and the opercles are scaleless. They have a large mouth without any teeth in the jaw, but they have pharyngeal teeth. Its eyes are situated far forward on the midline of the body and are slightly turned down.
Silver carp are unlikely to be confused with native cyprinids due to size and unusual position of the eye. They are most similar to bighead carp (H. nobilis) but have a smaller head, and upturned mouth without teeth, a keel that extends forward past pelvic fin base, lack the dark blotches characteristic of bighead carp and have highly branched gill rakers.
Juvenile fish lack spines in fins. Metalarvae and early juvenile are similar to bighead carp (Hypophthalmichthys nobilis) but pectoral fin extends only to base of pelvic fin (as opposed to beyond in the pelvic fin in bighead)
The species is known for leaping out of the water when startled (e.g., by noises such as a boat motor).
Friday, May 6, 2016
DIGESTIVE SYSTEM OF PILA NOTES
DIGESTIVE SYSTEM OF PILA
It consists of
I) Alimentary canal
II) Digestive glands
Alimentary canal of Pila is a coiled tube extending from the mouth and ending at the anus.
Entire canal may be divided into three regions
A) Foregut - buccal cavity and oesophagus
B) Midgut - stomach and intestine
C) Hind gut – rectum
A) Foregut
1) Buccal cavity:
This is a chamber into which mouth opens
It is lined by cuticle and surrounded by a large, thick-walled, highly muscular and pear shaped structure, the buccal mass.
Its wall is provided with several sets of muscles for its movement and the movement of radula
a) Buccal musculature: Out of several sets of muscles, the protractors are well developed. They include
i) a median dorsal-three pairs of anterior dorso-laterals and two pairs of posterior dorso-laterals on the dorsal surface and
ii) three anterior muscles and
iii) a pair of long and strong latero-ventral forward muscles on the ventral surface.
These muscles are mainly concerned with the protrusion and depression of the buccal mass.
b) Vestibule and jaws: Buccal cavity is regionated into an anterior tubular part called vestibule, and a posterior part.
The posterior limit of the short vestibule is marked by a pair of thickened jaws, placed dorso-laterally one on each side and connected together by a thin cuticular membrane.
Anterior cutting edge of each jaw is truncated and serrated, bearing numerous small and two or three large tooth-like processes.
Wall of the vestibule is beset with longitudinal muscle fibres that form the mouth sphincter.
Sphincter regulates the opening of the mouth and operates the jaws at the time of feeding.
c) Odontophore: In the posterior part of the buccal cavity the floor is raised into a thick muscular structure called tongue mass or odontophore.
Structure is supported by two sets of cartilages
i) a pair of more or less triangular superior cartilages lying below the epithelium at the top of the odontophore
ii) a pair of S-shaped lateral cartilages, with thick ventral edges and thin dorsal edges, lying on the sides.
Anteriorly the odontophore forms a small process, the sub-radular organ, roofing a narrow space called the sub-lingual cavity.
d)Radula: Buccal cavity contains a brownish, chitinous, curved, ribbon-like structure, called the radula or lingual ribbon.
Its anterior end bearing a pair of wing-like flaps, runs longitudinally over the summit of the odontophore.
Its posterior end is lodged in a band-like, 2mm wide radular sac flexed behind and below the buccal mass.
Radula itself is formed by secretion of the epithelial lining of the radular sac.
Below the radula lies a delicate and elastic, sub-radular membrane.
Dorsal surface of the radula bears teeth arranged in numerous transverse rows.
Each row contains seven teeth, one central rachidian, and one lateral and two marginals on its either side, giving the formula 2, 1, 1, 1, 2.
Radula is moved forward and backward on the odontophore for rasping food particles.
Movements, called chain-saw movements (Huxley), are brought about by protractor and retractor muscles; the radula can even be protruded from the mouth.
Regular use causes the radula to wear off at the anterior end, but the loss is made good by regular addition of radular material at the posterior end
2) Oesophagus: This is a narrow and long tube emerging dorsally from the buccal mass.
Running posteriorly for a short distance, it turns to left and enters the visceral mass to open into the stomach
3) stomach: It lies on the left side of the visceral mass, below the pericardium.
Its cavity is U-shaped which is regionated into a broad posterior cardiac chamber that receives the oesophagus and a narrow anterior pyloric chamber from which the intestine starts.
Lining of the stomach is folded; folds of the cardiac stomach are low and run from right to left, while those of the pyloric stomach are somewhat prominent and run transversely.
A short rounded and blind pouch, the caecum, arises from the lower outer wall of the pyloric chamber.
At the junction of two chambers of the stomach opens a duct from the digestive gland.
4) Intestine: Pyloric stomach is followed by a long and coiled intestine. It runs backward into the visceral mass where it makes 2.5 or 3 coils, between the gonad in front and the digestive gland behind, before joining the rectum.
5) Rectum: It comprises of a thick-walled tube which extends into the branchial chamber of the mantle cavity between the ctenidium and genital duct.
Its external opening, the anus, lies about 6 mm away from the edge of the right nuchal lobe.
II) Digestive glands
1. Salivary glands. These are two in number and lie on either side of the posterior part of the buccal mass.
Each gland looks like a branching white mass.
A duct from each gland enters the muscles of the buccal mass and then opens into the buccal cavity in the area of the dorsal buccal glands.
Salivary secretion contains mucin-like substance and a carbohydrase enzyme.
2. Digestive gland. A somewhat triangular plate or cone with a convex outer and more or less flattened inner surface occupies the greater part of the coiled visceral mass.
This structure is a digestive gland (often referred to as the liver or hepatopancreas), which is also coiled and is brownish to dirty green in colour.
It has two main lobes, smaller in contact with the stomach and larger extending to the apex of the spiral.
Two separate ducts arise from two lobes which unite together to form a common duct before opening into the stomach.
These ducts, open into the digestive gland, branch repeatedly and end blindly in a very large number of small tubes the alveoli.
Alveoli are lined with a digestive epithelium made up of three types of cells
i) secretory cells- secrete a cellulose digesting enzyme
ii) resorptive cells- digest proteins intracellularly
iii) lime cells- store calcium phosphate.
Semi-digested food enters into these alveoli, where digestion of cellulose and proteins takes place.
3. Oesophageal pouches: A pair of simple, rounded, cream-coloured oesophageal pouches lies below the salivary glands.
Each pouch opens by a narrow duct at the junction of the buccal cavity and oesophagus.
These pouches probably secrete digestive enzymes.
4. Buccal glands: These are a pair of glandular areas in the roof of the buccal cavity, a little in front of its junction with the oesophagus.
Each glandular area consists of two pads, separated by an oblique longitudinal furrow; each pad bears a row of transverse grooves.
Exact function of these glands is not known. They are probably of the nature of accessory digestive glands.
It consists of
I) Alimentary canal
II) Digestive glands
Alimentary canal of Pila is a coiled tube extending from the mouth and ending at the anus.
Entire canal may be divided into three regions
A) Foregut - buccal cavity and oesophagus
B) Midgut - stomach and intestine
C) Hind gut – rectum
A) Foregut
1) Buccal cavity:
This is a chamber into which mouth opens
It is lined by cuticle and surrounded by a large, thick-walled, highly muscular and pear shaped structure, the buccal mass.
Its wall is provided with several sets of muscles for its movement and the movement of radula
a) Buccal musculature: Out of several sets of muscles, the protractors are well developed. They include
i) a median dorsal-three pairs of anterior dorso-laterals and two pairs of posterior dorso-laterals on the dorsal surface and
ii) three anterior muscles and
iii) a pair of long and strong latero-ventral forward muscles on the ventral surface.
These muscles are mainly concerned with the protrusion and depression of the buccal mass.
b) Vestibule and jaws: Buccal cavity is regionated into an anterior tubular part called vestibule, and a posterior part.
The posterior limit of the short vestibule is marked by a pair of thickened jaws, placed dorso-laterally one on each side and connected together by a thin cuticular membrane.
Anterior cutting edge of each jaw is truncated and serrated, bearing numerous small and two or three large tooth-like processes.
Wall of the vestibule is beset with longitudinal muscle fibres that form the mouth sphincter.
Sphincter regulates the opening of the mouth and operates the jaws at the time of feeding.
c) Odontophore: In the posterior part of the buccal cavity the floor is raised into a thick muscular structure called tongue mass or odontophore.
Structure is supported by two sets of cartilages
i) a pair of more or less triangular superior cartilages lying below the epithelium at the top of the odontophore
ii) a pair of S-shaped lateral cartilages, with thick ventral edges and thin dorsal edges, lying on the sides.
Anteriorly the odontophore forms a small process, the sub-radular organ, roofing a narrow space called the sub-lingual cavity.
d)Radula: Buccal cavity contains a brownish, chitinous, curved, ribbon-like structure, called the radula or lingual ribbon.
Its anterior end bearing a pair of wing-like flaps, runs longitudinally over the summit of the odontophore.
Its posterior end is lodged in a band-like, 2mm wide radular sac flexed behind and below the buccal mass.
Radula itself is formed by secretion of the epithelial lining of the radular sac.
Below the radula lies a delicate and elastic, sub-radular membrane.
Dorsal surface of the radula bears teeth arranged in numerous transverse rows.
Each row contains seven teeth, one central rachidian, and one lateral and two marginals on its either side, giving the formula 2, 1, 1, 1, 2.
Radula is moved forward and backward on the odontophore for rasping food particles.
Movements, called chain-saw movements (Huxley), are brought about by protractor and retractor muscles; the radula can even be protruded from the mouth.
Regular use causes the radula to wear off at the anterior end, but the loss is made good by regular addition of radular material at the posterior end
2) Oesophagus: This is a narrow and long tube emerging dorsally from the buccal mass.
Running posteriorly for a short distance, it turns to left and enters the visceral mass to open into the stomach
3) stomach: It lies on the left side of the visceral mass, below the pericardium.
Its cavity is U-shaped which is regionated into a broad posterior cardiac chamber that receives the oesophagus and a narrow anterior pyloric chamber from which the intestine starts.
Lining of the stomach is folded; folds of the cardiac stomach are low and run from right to left, while those of the pyloric stomach are somewhat prominent and run transversely.
A short rounded and blind pouch, the caecum, arises from the lower outer wall of the pyloric chamber.
At the junction of two chambers of the stomach opens a duct from the digestive gland.
4) Intestine: Pyloric stomach is followed by a long and coiled intestine. It runs backward into the visceral mass where it makes 2.5 or 3 coils, between the gonad in front and the digestive gland behind, before joining the rectum.
5) Rectum: It comprises of a thick-walled tube which extends into the branchial chamber of the mantle cavity between the ctenidium and genital duct.
Its external opening, the anus, lies about 6 mm away from the edge of the right nuchal lobe.
II) Digestive glands
1. Salivary glands. These are two in number and lie on either side of the posterior part of the buccal mass.
Each gland looks like a branching white mass.
A duct from each gland enters the muscles of the buccal mass and then opens into the buccal cavity in the area of the dorsal buccal glands.
Salivary secretion contains mucin-like substance and a carbohydrase enzyme.
2. Digestive gland. A somewhat triangular plate or cone with a convex outer and more or less flattened inner surface occupies the greater part of the coiled visceral mass.
This structure is a digestive gland (often referred to as the liver or hepatopancreas), which is also coiled and is brownish to dirty green in colour.
It has two main lobes, smaller in contact with the stomach and larger extending to the apex of the spiral.
Two separate ducts arise from two lobes which unite together to form a common duct before opening into the stomach.
These ducts, open into the digestive gland, branch repeatedly and end blindly in a very large number of small tubes the alveoli.
Alveoli are lined with a digestive epithelium made up of three types of cells
i) secretory cells- secrete a cellulose digesting enzyme
ii) resorptive cells- digest proteins intracellularly
iii) lime cells- store calcium phosphate.
Semi-digested food enters into these alveoli, where digestion of cellulose and proteins takes place.
3. Oesophageal pouches: A pair of simple, rounded, cream-coloured oesophageal pouches lies below the salivary glands.
Each pouch opens by a narrow duct at the junction of the buccal cavity and oesophagus.
These pouches probably secrete digestive enzymes.
4. Buccal glands: These are a pair of glandular areas in the roof of the buccal cavity, a little in front of its junction with the oesophagus.
Each glandular area consists of two pads, separated by an oblique longitudinal furrow; each pad bears a row of transverse grooves.
Exact function of these glands is not known. They are probably of the nature of accessory digestive glands.
Tuesday, April 5, 2016
విదళనం
విదళన లక్షణాలు
ఎ. విదళనంలో సంయుక్త బీజం సైజు పెరగదు, కాని వాని లోని కణముల సంఖ్య విపరీతంగా పెరుగును.
బి. విదళనంలో జరిగే కణవిభజన వేగం, ఒక జీవి జీవిత చరిత్రలో మరెక్కడా జరగదు.
సి. కణముల సంఖ్య పెరగటం వలన DNA పరిమాణము పెరుగును
డి. విదళన సమయంలో కణవిభజనకు అవసరమైన శక్తిని ఇవ్వటానికి ఆక్సిజన్ వినిమయనం అధికమౌతుంది.
విదళన రేఖలు/అక్షాలు
విదళనం సంయుక్తబీజం పై ఒక నిర్ధిష్ట ప్రాంతంలో ప్రారంభమౌతుంది. ఈ ప్రాంతంలో ఒక చీలిక ఏర్పడుతుంది. ఈ చీలికను విదళన చీలిక అంటారు. ఈ విదళన చీలిక లోతుగా విస్తరించటం వల్ల సంయుక్త బీజం రెండుకణాలుగా విడిపోతుంది. ఈ విదళన చీలిక ప్రధానంగా నాలుగు మార్గాలద్వారా విస్తరించవచ్చును. అవి.....
ఎ. ఆయత లేదా నిలువురేఖ: విదళన రేఖ అండం యొక్క రెండు దృవాల వైపు విస్తరించి మధ్య అక్షం గుండా ప్రయాణించి రెండు సమాన అర్ధభాగాలను ఏర్పరచును.
ఉదా: కప్ప, కోడి అండాలలో మొదటి రెండు విదళన చీలికలు
బి. ఆయత సమాంతర రేఖ: విదళన రేఖ ఆయత విదళనరేఖ కు సమాంతరంగా జరుగును. ఉదా: కప్ప, కోడి అండంలో మూడు, నాలుగు విదళనాలు
సి. అడ్డు రేఖ: అండం మధ్య భాగం నుంచి అడ్డుగా విస్తరించును. దీని ఫలితంగా అండం పైన క్రింద ఖండాలుగా విభజన జరుగును. ఉదా: ఉన్నత క్షీరదాలలో మొదటి విదళన రేఖ
డి. అడ్డు సమాంతర రేఖ: ఈ రకం విదళన రేఖ అడ్డు రేఖకు సమాంతరంగా జరుగును. ఉదా. కప్పలలో అయిదవ విదళన రేఖ
విదళనంలో రకాలు
అండంలో పీతకపదార్ధం అధికంగా ఉన్నప్పుడు, సొనపదార్ధం అధికంగా ఉన్న దృవమును బృహత్కంఢ దృవం అని, సొనపదార్ధం తక్కువగా ఉన్న దృవాన్ని జాంతవదృవమనీ అంటారు.
అండాల రకాలను బట్టి జంతువులలో ప్రధానంగా రెండురకాల విదలనాలు జరుగుతాయి
ఎ. పూర్ణభంజిత/సంపూర్ణ విదళనం: ఈ పద్దతిలో దాదాపు అండంలోని మొత్తం కణపదార్ధం, సొనపదార్ధం తో సహా విభజించబడుతుంది. ఇట్టి విభజన సమపీతక, మధ్యస్థ పీతక అండాలలో జరుగును. ఉదా: ఉభయచరాలు, ఆంఫియాక్సస్.
పూర్ణ భంజిత విదళనంలో ఏర్పడే బ్లాస్టోమియర్ల సైజుల ఆధారంగా ఇది మరల మూడు రకాలు.
• సమాన పూర్ణభంజిత విదళనం: ఈ విధానంలో విదళన చీలిక అండం మొత్తం విస్తరించి రెండు సమానమైన బ్లాస్టోమియర్లను ఏర్పరచును. ఉదా. అరేలియా, ఎఖైనోడెర్మేటా
• అసమాన పూర్ణభంజిత విదళనం: ఈ విధానంలో విదళనం ఫలితంగా ఏర్పడే బ్లాస్టోమియర్లు అసమానంగా ఉంటాయి. సూక్ష్మ ఖంఢాలు జాంతవదృవం వైపు, స్థూల ఖంఢాలు బృహత్కంఢ దృవంవైపు ఉంటాయి. ఉదా. ఆంఫియాక్సస్, ఉభయచరాలు
పూర్ణ భంజిత విదళనంలో ఏర్పడే బ్లాస్టోమియర్ల అమరిక ఆధారంగా ఇది మరల రెండు రకాలు.
• వలయ పూర్ణభంజిత విదళనం: ఈ విధానంలో ఏర్పడిన బ్లాస్టోమియర్ ల అమరిక వలయసౌష్టవాన్ని చూపును. ఉదా. కప్పలో మొదటి విదళనం ఆయతంగా జరిగి, అండం రెండు సమాన అర్ధభాగాలుగా ఏర్పడును. తరువాత రెండవ విదళనం ఆయతంగా మొదటిదానికి లంబకోణంలో (రైట్ ఏంగిల్) జరిగి నాలుగు సమాన బ్లాస్టోమియర్లు ఏర్పడును. మూడవ విదళనం అండం అడ్డంగా జరగటం వల్ల ఎనిమిది అసమాన బ్లాస్టోమియర్లు ఏర్పడును. వీటిలో జాంతవదృవంవైపు నాలుగు చిన్న సూక్ష్మఖండాలు, సొనపదార్ధం కల బృహత్కండదృవంలో నాలుగు స్థూల ఖండాలు ఉంటాయి. ఇవి ఒకదానిపై ఒక అమరి ఉండటం ద్వారా వలయసౌష్టవాన్ని చూపును
• సర్పిల పూర్ణ భంజిత విదళనం: ఈ విదళనం వలన ఏర్పడే బ్లాస్టోమియర్లు, దృవాలను కలిపే అక్షం వెంబడి సర్పిల ఆకారంలో అమరి ఉంటాయి. బ్లాస్టోమియర్లు కుడివైపు సర్పిలంగా అమరితే – డెక్స్ ట్రల్ సర్పిల విదళనం అని, ఎడమవైపుకు సర్పిలంగా అమరితే సినిస్ట్రల్ సర్పిల విదళనం అని అంటారు.
• ద్విపార్శ్వ పూర్ణభంజిత విదళనం: ఈ రకమైన విదళనంలో ఏర్పడే బ్లాస్టోమియర్లు అక్షానికి కుడి ఎడమవైపుల సమానంగా బింబప్రతి బింబాలు గా అమరుతాయి. ఆవిధంగా బ్లాష్టులా ద్విపార్శ్వసౌష్టవాన్ని ప్రదర్శించును.
బి. అసంపూర్ణ/అంతర్ భంజిత విదళనం: ఈ విధానంలో పీతకపదార్ధం ఉపరితలంపై జీవకణాల సముదాయం ఒక చిన్న్జ బిళ్ళ వలె తేలి ఉంటుంది. దీనిని బ్లాస్టో డిస్క్ అంటారు. విదళనం సొనపదార్ధాని వదిలి, ఈ బ్లాస్టో డిస్క్ ను చిన్న చిన్న కణాలుగా విభజించి పిండాన్ని ఏర్పరచును. ఇట్టి విదళనం సొనపదార్ధం అధికంగా ఉండే అండాలలో జరుగును ఉదా: చేపలు, సరీసృపాలు, పక్షులు. ఇది మరలా రెండు రకాలు
• చక్రాభ విదళనం: పీతక పదార్థంపై, కణపదార్ధం చిన్న బిళ్ళలాగ ఉండి (బ్లాస్టోడిస్క్) ఉంటుంది. విదళనం ఈ బ్లాస్టోడిస్క్ కు మాత్రమే పరిమితమై ఉండును. పీతకపదార్ధం విదళనం చెందదు. ఉదా: చేపలు, పక్షులు
• ఉపరితల అంతర్ భంజిత విదళనం : ఈ విదళనం కేంద్ర పీతక అండాలకు ప్రత్యేకము. ఇట్టి అండాలలో కణపదార్థం ఉపరితలానికే పరిమితమై ఉంటుంది. అందుచే విదళనం కూడా ఉపరితలానికే పరిమితమౌతుంది. మధ్య ప్రాంతంలో కల పీతకపదార్థం విదళనం చెందదు. ఉదా: కీటకాలు
బ్లాస్టోమియర్ ల భవిష్యత్తును బట్టి విదళనాలను రెండురకాలుగా విభజించారు
• నిర్ధారిత విదళనం: ఈ విదళనం ద్వారా ఏర్పడిన బ్లాస్టోమియర్ ల భవిష్యత్తు ముందుగానే నిర్ణయించబడి ఉంటుంది. అంటే అండము 4 లేక 8 కణముల దశలొ ఉన్నప్పుడే ఆ యా కణములు భవిష్యత్తులో ఏ యే అవయవాలను ఏర్పరగలవో నిర్ధారణ జరిగిపోతుంది. ఈ కణాలలో ఏ ఒక్క కణమైన నశించినట్లయితె, ఆ అవయవము ఏర్పడదు. ఉదా: అన్నిలిడా, మొలస్కా
• అనిర్ధారిత విదళనం: విదళనం ద్వారా ఏర్పడే బ్లాస్టోమియర్ ల భవిష్యత్తు ముందుగానే నిర్ణయించబడక పోయినట్లయితే అట్టి విదళనాన్ని అనిర్ధారిత విదళనం అంటారు. అండము 4 లేక 8 కణముల దశలొ ఉన్నప్పుడు ఏ ఒక్క కణమైనా నశించినట్లయితే, అవితిరగి ఏర్పడతాయి. అవయవోత్పత్తి సమస్య రాదు. ఉదా: సకశేరుకాలు
విదళనం ద్వారా కణజాలము, అవయవాలు ఏర్పడటానికి అవసరమైన స్థాయిలో కణాలు ఏర్పడటం జరుగుతుంది. విదళనం అనేది పిండ స్వరూపం ఏర్పడే వరకూ జరుగుతుంది. తదనంతరం అలా ఏర్పడిన కణాలు అవయవాలుగా ఏర్పడి, పరిమాణాన్ని పెంచుకొని పూర్తి పిండాన్ని ఏర్పరచును.
ఎ. విదళనంలో సంయుక్త బీజం సైజు పెరగదు, కాని వాని లోని కణముల సంఖ్య విపరీతంగా పెరుగును.
బి. విదళనంలో జరిగే కణవిభజన వేగం, ఒక జీవి జీవిత చరిత్రలో మరెక్కడా జరగదు.
సి. కణముల సంఖ్య పెరగటం వలన DNA పరిమాణము పెరుగును
డి. విదళన సమయంలో కణవిభజనకు అవసరమైన శక్తిని ఇవ్వటానికి ఆక్సిజన్ వినిమయనం అధికమౌతుంది.
విదళన రేఖలు/అక్షాలు
విదళనం సంయుక్తబీజం పై ఒక నిర్ధిష్ట ప్రాంతంలో ప్రారంభమౌతుంది. ఈ ప్రాంతంలో ఒక చీలిక ఏర్పడుతుంది. ఈ చీలికను విదళన చీలిక అంటారు. ఈ విదళన చీలిక లోతుగా విస్తరించటం వల్ల సంయుక్త బీజం రెండుకణాలుగా విడిపోతుంది. ఈ విదళన చీలిక ప్రధానంగా నాలుగు మార్గాలద్వారా విస్తరించవచ్చును. అవి.....
ఎ. ఆయత లేదా నిలువురేఖ: విదళన రేఖ అండం యొక్క రెండు దృవాల వైపు విస్తరించి మధ్య అక్షం గుండా ప్రయాణించి రెండు సమాన అర్ధభాగాలను ఏర్పరచును.
ఉదా: కప్ప, కోడి అండాలలో మొదటి రెండు విదళన చీలికలు
బి. ఆయత సమాంతర రేఖ: విదళన రేఖ ఆయత విదళనరేఖ కు సమాంతరంగా జరుగును. ఉదా: కప్ప, కోడి అండంలో మూడు, నాలుగు విదళనాలు
సి. అడ్డు రేఖ: అండం మధ్య భాగం నుంచి అడ్డుగా విస్తరించును. దీని ఫలితంగా అండం పైన క్రింద ఖండాలుగా విభజన జరుగును. ఉదా: ఉన్నత క్షీరదాలలో మొదటి విదళన రేఖ
డి. అడ్డు సమాంతర రేఖ: ఈ రకం విదళన రేఖ అడ్డు రేఖకు సమాంతరంగా జరుగును. ఉదా. కప్పలలో అయిదవ విదళన రేఖ
విదళనంలో రకాలు
అండంలో పీతకపదార్ధం అధికంగా ఉన్నప్పుడు, సొనపదార్ధం అధికంగా ఉన్న దృవమును బృహత్కంఢ దృవం అని, సొనపదార్ధం తక్కువగా ఉన్న దృవాన్ని జాంతవదృవమనీ అంటారు.
అండాల రకాలను బట్టి జంతువులలో ప్రధానంగా రెండురకాల విదలనాలు జరుగుతాయి
ఎ. పూర్ణభంజిత/సంపూర్ణ విదళనం: ఈ పద్దతిలో దాదాపు అండంలోని మొత్తం కణపదార్ధం, సొనపదార్ధం తో సహా విభజించబడుతుంది. ఇట్టి విభజన సమపీతక, మధ్యస్థ పీతక అండాలలో జరుగును. ఉదా: ఉభయచరాలు, ఆంఫియాక్సస్.
పూర్ణ భంజిత విదళనంలో ఏర్పడే బ్లాస్టోమియర్ల సైజుల ఆధారంగా ఇది మరల మూడు రకాలు.
• సమాన పూర్ణభంజిత విదళనం: ఈ విధానంలో విదళన చీలిక అండం మొత్తం విస్తరించి రెండు సమానమైన బ్లాస్టోమియర్లను ఏర్పరచును. ఉదా. అరేలియా, ఎఖైనోడెర్మేటా
• అసమాన పూర్ణభంజిత విదళనం: ఈ విధానంలో విదళనం ఫలితంగా ఏర్పడే బ్లాస్టోమియర్లు అసమానంగా ఉంటాయి. సూక్ష్మ ఖంఢాలు జాంతవదృవం వైపు, స్థూల ఖంఢాలు బృహత్కంఢ దృవంవైపు ఉంటాయి. ఉదా. ఆంఫియాక్సస్, ఉభయచరాలు
పూర్ణ భంజిత విదళనంలో ఏర్పడే బ్లాస్టోమియర్ల అమరిక ఆధారంగా ఇది మరల రెండు రకాలు.
• వలయ పూర్ణభంజిత విదళనం: ఈ విధానంలో ఏర్పడిన బ్లాస్టోమియర్ ల అమరిక వలయసౌష్టవాన్ని చూపును. ఉదా. కప్పలో మొదటి విదళనం ఆయతంగా జరిగి, అండం రెండు సమాన అర్ధభాగాలుగా ఏర్పడును. తరువాత రెండవ విదళనం ఆయతంగా మొదటిదానికి లంబకోణంలో (రైట్ ఏంగిల్) జరిగి నాలుగు సమాన బ్లాస్టోమియర్లు ఏర్పడును. మూడవ విదళనం అండం అడ్డంగా జరగటం వల్ల ఎనిమిది అసమాన బ్లాస్టోమియర్లు ఏర్పడును. వీటిలో జాంతవదృవంవైపు నాలుగు చిన్న సూక్ష్మఖండాలు, సొనపదార్ధం కల బృహత్కండదృవంలో నాలుగు స్థూల ఖండాలు ఉంటాయి. ఇవి ఒకదానిపై ఒక అమరి ఉండటం ద్వారా వలయసౌష్టవాన్ని చూపును
• సర్పిల పూర్ణ భంజిత విదళనం: ఈ విదళనం వలన ఏర్పడే బ్లాస్టోమియర్లు, దృవాలను కలిపే అక్షం వెంబడి సర్పిల ఆకారంలో అమరి ఉంటాయి. బ్లాస్టోమియర్లు కుడివైపు సర్పిలంగా అమరితే – డెక్స్ ట్రల్ సర్పిల విదళనం అని, ఎడమవైపుకు సర్పిలంగా అమరితే సినిస్ట్రల్ సర్పిల విదళనం అని అంటారు.
• ద్విపార్శ్వ పూర్ణభంజిత విదళనం: ఈ రకమైన విదళనంలో ఏర్పడే బ్లాస్టోమియర్లు అక్షానికి కుడి ఎడమవైపుల సమానంగా బింబప్రతి బింబాలు గా అమరుతాయి. ఆవిధంగా బ్లాష్టులా ద్విపార్శ్వసౌష్టవాన్ని ప్రదర్శించును.
బి. అసంపూర్ణ/అంతర్ భంజిత విదళనం: ఈ విధానంలో పీతకపదార్ధం ఉపరితలంపై జీవకణాల సముదాయం ఒక చిన్న్జ బిళ్ళ వలె తేలి ఉంటుంది. దీనిని బ్లాస్టో డిస్క్ అంటారు. విదళనం సొనపదార్ధాని వదిలి, ఈ బ్లాస్టో డిస్క్ ను చిన్న చిన్న కణాలుగా విభజించి పిండాన్ని ఏర్పరచును. ఇట్టి విదళనం సొనపదార్ధం అధికంగా ఉండే అండాలలో జరుగును ఉదా: చేపలు, సరీసృపాలు, పక్షులు. ఇది మరలా రెండు రకాలు
• చక్రాభ విదళనం: పీతక పదార్థంపై, కణపదార్ధం చిన్న బిళ్ళలాగ ఉండి (బ్లాస్టోడిస్క్) ఉంటుంది. విదళనం ఈ బ్లాస్టోడిస్క్ కు మాత్రమే పరిమితమై ఉండును. పీతకపదార్ధం విదళనం చెందదు. ఉదా: చేపలు, పక్షులు
• ఉపరితల అంతర్ భంజిత విదళనం : ఈ విదళనం కేంద్ర పీతక అండాలకు ప్రత్యేకము. ఇట్టి అండాలలో కణపదార్థం ఉపరితలానికే పరిమితమై ఉంటుంది. అందుచే విదళనం కూడా ఉపరితలానికే పరిమితమౌతుంది. మధ్య ప్రాంతంలో కల పీతకపదార్థం విదళనం చెందదు. ఉదా: కీటకాలు
బ్లాస్టోమియర్ ల భవిష్యత్తును బట్టి విదళనాలను రెండురకాలుగా విభజించారు
• నిర్ధారిత విదళనం: ఈ విదళనం ద్వారా ఏర్పడిన బ్లాస్టోమియర్ ల భవిష్యత్తు ముందుగానే నిర్ణయించబడి ఉంటుంది. అంటే అండము 4 లేక 8 కణముల దశలొ ఉన్నప్పుడే ఆ యా కణములు భవిష్యత్తులో ఏ యే అవయవాలను ఏర్పరగలవో నిర్ధారణ జరిగిపోతుంది. ఈ కణాలలో ఏ ఒక్క కణమైన నశించినట్లయితె, ఆ అవయవము ఏర్పడదు. ఉదా: అన్నిలిడా, మొలస్కా
• అనిర్ధారిత విదళనం: విదళనం ద్వారా ఏర్పడే బ్లాస్టోమియర్ ల భవిష్యత్తు ముందుగానే నిర్ణయించబడక పోయినట్లయితే అట్టి విదళనాన్ని అనిర్ధారిత విదళనం అంటారు. అండము 4 లేక 8 కణముల దశలొ ఉన్నప్పుడు ఏ ఒక్క కణమైనా నశించినట్లయితే, అవితిరగి ఏర్పడతాయి. అవయవోత్పత్తి సమస్య రాదు. ఉదా: సకశేరుకాలు
విదళనం ద్వారా కణజాలము, అవయవాలు ఏర్పడటానికి అవసరమైన స్థాయిలో కణాలు ఏర్పడటం జరుగుతుంది. విదళనం అనేది పిండ స్వరూపం ఏర్పడే వరకూ జరుగుతుంది. తదనంతరం అలా ఏర్పడిన కణాలు అవయవాలుగా ఏర్పడి, పరిమాణాన్ని పెంచుకొని పూర్తి పిండాన్ని ఏర్పరచును.
Friday, April 1, 2016
CONCEPTS OF BIOSTATISTICS AND BIOINFORMATICS SYLLABUS
CONCEPTS OF BIOSTATISTICS AND BIOINFORMATICS 30hours
UNIT-III
3.1 Introdution of Biostatistics Concept of probability, basic laws and its application to Mendelian segregation. Concept of probability distribution. Binomial and Poisson distributions, Normal distribution and their application to biology
3.2 Concept of sampling and sampling distribution. Concept of test of hypothesis. Applications of t-test statistics to biological problems/data: Chi-square, statistic applications in biology.
UNIT-IV
4.1 Introduction to Bioinformatics
Biological Databases – Nucleotide sequence and Protein databases, their utilization in Biotechnology, Storage of biological data in databanks, data retrieval from databases and their utilization
4.2 Human Genome Project.
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UNIT-III
3.1 Introdution of Biostatistics Concept of probability, basic laws and its application to Mendelian segregation. Concept of probability distribution. Binomial and Poisson distributions, Normal distribution and their application to biology
3.2 Concept of sampling and sampling distribution. Concept of test of hypothesis. Applications of t-test statistics to biological problems/data: Chi-square, statistic applications in biology.
UNIT-IV
4.1 Introduction to Bioinformatics
Biological Databases – Nucleotide sequence and Protein databases, their utilization in Biotechnology, Storage of biological data in databanks, data retrieval from databases and their utilization
4.2 Human Genome Project.
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భారతదేశంలో వన్యప్రాణి సంరక్షణా చరిత్ర
భారతదేశంలో వన్యప్రాణి సంరక్షణా చరిత్ర
ప్రాచీన భారతదేశంలో మునుల ఆశ్రమాలసమీపంలో వన్యప్రాణులను వేటాడటం పట్ల నిషేదం ఉండేది. ఇది ఒకరకంగా పరోక్ష సంరక్షణ.
భారతదేశ ఇతిహాసాలు పురాణాలలో వివిధ జంతువులకు దైవత్వాన్ని ఇవ్వటం జరిగింది. ఉదాహరణకు అనేక వన్యజీవులు వివిధదేవతలకు వాహనాలుగా ఉన్నాయి. దుర్గాదేవికి సింహం, పార్వతీదేవికి పులి, వినాయకునికి మూషికము, కుమారస్వామికి నెమలి వంటివి. అంతేకాక కోతి ఆంజనేయ స్వరూపమని, పాము సుబ్రహ్మణ్యేశ్వరుని రూపమని, గోవు పవిత్రజంతువనీ పూజలందుకోవటం వంటి చర్యలు పరోక్షంగా ఆయా జీవుల సంరక్షణ కు దోహదపడేవి
కీ.పూ మూడవశతాబ్దంలో చంద్రగుప మౌర్యుని పరిపాలనలో అడవులను సంరక్షించటానికి “కూప్యాధ్యక్షుడు” అనే పేరుతో అధికారి ఉండేవాడని చరిత్ర చెపుతున్నది. ఈ అధికారి అడవులను సంరక్షించుట, వేటను నియంత్రించుట వంటి పనులు చేయటం ద్వారా వన్యప్రాణి సంరక్షణ జరిగేది.
కౌటిల్యుని అర్ధశాస్త్రం లో అడవులను, వన్యప్రాణులను సంరక్షించటానికి అనేక చట్టాలు, అతిక్రమించిన వారికి విధించాల్సిన శిక్షలు కనిపిస్తాయి.
అక్బర్ పరిపాలనలో వ్యన్యప్రాణులను వేటాడటం విచ్చలవిడిగా జరిగింది. ఈయనకాలంలోనే వన్యప్రాణుల సంఖ్యతగ్గిపోతే, అనేకమంది వ్యక్తులు వలయాకారంలో ఏర్పడు డప్పులు వాయిస్తూ వన్యప్రాణులను ఒకచోటికి కేంద్రీకృతం చేసి వేటాడటం అనే పద్దతి మొదలైంది. దీనికారణంగా కూడా వన్యప్రాణుల సంఖ్య తగ్గిపోయింది. అప్పటికి భారతదేశం అంతటావిస్తరించి ఉన్న సింహాలు, ఖడ్గమృగాలు అక్బర్ కాలంలో కొన్నిప్రాంతాలకే పరిమితమైనాయి. చీటాలు పూర్తిగా భారతదేశం నుంచి అంతరించి పోయాయి.
జహంగిర్ కాలంలోవన్యప్రాణి సంరక్షణకు ప్రత్యేక చట్టాలు చేయబడ్దాయి. వేట నిషేదించారు. ప్రత్యేక అనుమతితో మాత్రమే వేట జరిగేది.
బ్రిటిష్ పాలనప్రారంభంలో వన్యప్రాణుల వేట అవిచ్చిన్నంగా జరిగింది. అధికారులు, అతిధులకొరకు షికారీలు ఏర్పాటు చేసేవారు. వన్యప్రాణులను వేటాడటం ధైర్యసాహసాలకు, గొప్పతననానికి, ఉన్నతవర్గాలకు గౌరవచిహ్నంగా ఉండేది. వివిధ మహారాజులు, జమిందార్లు, నవాబులు కూడా అదెవిధంగా విచ్చలవిడి వేటను కొనసాగించారు. ఆకారణంగా పులులు, సింహాలు, ఖడ్గమృగాల సంఖ్య మరింత కుచించుకుపోయింది.
పంతొమ్మిదవశతాబ్దపు చివర్లో బ్రిటిష్ ప్రభుత్వం కళ్ళు తెరచి వివిధ చట్టాలు చేసింది. 1879 లో ఏనుగుల సంరక్షణ చట్టం, 1912 నాటి వన్య జీవులు పక్షుల చట్టం, 1927 నాటి భారతదేశ అటవీచట్టం వంటివి భారతవన్యజీవుల వైవిధ్యతను కాపాడటానికి దోహదపడ్డాయి
ప్రముఖ వేటగాడు అయిన Jim Corbett కృషితో, 1936 లో భారతదేశపు మొట్టమొదటి జాతీయపార్కు అయిన “హైలీ జాతీయపార్కును” Hailey National Park” (దీనినే తరువాత జిమ్ కోర్బెట్ జాతీయపార్కుగా పేరు మార్చారు) ఏర్పాటు చేయటం జరిగింది.
స్వాతంత్ర్యానంతరం వన్యప్రాణి సంరక్షణ అవసరం గుర్తించారు. వన్యప్రాణుల సంరక్షణ కొరకు చట్టాలు, మార్గదర్శకసూత్రాలు తయారుచేయటానికి, భారతప్రభుత్వం 1952 లో Indian Wildlife Board ను స్థాపించింది. ఈ బోర్డు ఆధ్వర్యంలో అనేక జాతీయపార్కులు, అభయారణ్యాలు, గేమ్ పార్కులు
1970 లలో వచ్చిన రెండు ప్రధానమైన చట్టాలు, భారతదేశవన్యప్రాణి సంరక్షణ రంగాన్ని సమూలంగా మార్చివేసాయి. ఒకటి 1972 నాటి Wild Life Protection Act, రెండు 1973 నాటి అప్పటికి అతిపెద్ద సంరక్షణా పధమైన Project Tiger లు.
1980 లో వచ్చిన చిప్కో ఉద్యమం కూడా వన్యజీవుల సంరక్షణలో ప్రపంచవ్యాప్త గుర్తింపు పొందింది. చెట్లు నరకటాన్ని వ్యతిరేకిస్తూ, ఆ చెట్లను కౌగిలించుకొని అహింసాయుత మార్గం ద్వారా ప్రతిఘటించటం ప్రజలలో ఎంతో చైతన్యాన్ని, పర్యావరణం పట్ల అవగాహనను కల్పించింది.
1990 నుండి వన్యప్రాణుల సంరక్షణలో బయోటెక్నాలజీ, వన్యప్రాణి ఫొరెన్సిక్స్, టెలిమెట్రీ, రిమోట్ సెన్సింగ్ టెక్నాలజీ, సాటిలైట్ మేపింగ్ వంటి అధునాతన పద్దతులు వచ్చి ఈ రంగాన్ని సమూలంగా మార్చివేసాయి.
ప్రాచీన భారతదేశంలో మునుల ఆశ్రమాలసమీపంలో వన్యప్రాణులను వేటాడటం పట్ల నిషేదం ఉండేది. ఇది ఒకరకంగా పరోక్ష సంరక్షణ.
భారతదేశ ఇతిహాసాలు పురాణాలలో వివిధ జంతువులకు దైవత్వాన్ని ఇవ్వటం జరిగింది. ఉదాహరణకు అనేక వన్యజీవులు వివిధదేవతలకు వాహనాలుగా ఉన్నాయి. దుర్గాదేవికి సింహం, పార్వతీదేవికి పులి, వినాయకునికి మూషికము, కుమారస్వామికి నెమలి వంటివి. అంతేకాక కోతి ఆంజనేయ స్వరూపమని, పాము సుబ్రహ్మణ్యేశ్వరుని రూపమని, గోవు పవిత్రజంతువనీ పూజలందుకోవటం వంటి చర్యలు పరోక్షంగా ఆయా జీవుల సంరక్షణ కు దోహదపడేవి
కీ.పూ మూడవశతాబ్దంలో చంద్రగుప మౌర్యుని పరిపాలనలో అడవులను సంరక్షించటానికి “కూప్యాధ్యక్షుడు” అనే పేరుతో అధికారి ఉండేవాడని చరిత్ర చెపుతున్నది. ఈ అధికారి అడవులను సంరక్షించుట, వేటను నియంత్రించుట వంటి పనులు చేయటం ద్వారా వన్యప్రాణి సంరక్షణ జరిగేది.
కౌటిల్యుని అర్ధశాస్త్రం లో అడవులను, వన్యప్రాణులను సంరక్షించటానికి అనేక చట్టాలు, అతిక్రమించిన వారికి విధించాల్సిన శిక్షలు కనిపిస్తాయి.
అక్బర్ పరిపాలనలో వ్యన్యప్రాణులను వేటాడటం విచ్చలవిడిగా జరిగింది. ఈయనకాలంలోనే వన్యప్రాణుల సంఖ్యతగ్గిపోతే, అనేకమంది వ్యక్తులు వలయాకారంలో ఏర్పడు డప్పులు వాయిస్తూ వన్యప్రాణులను ఒకచోటికి కేంద్రీకృతం చేసి వేటాడటం అనే పద్దతి మొదలైంది. దీనికారణంగా కూడా వన్యప్రాణుల సంఖ్య తగ్గిపోయింది. అప్పటికి భారతదేశం అంతటావిస్తరించి ఉన్న సింహాలు, ఖడ్గమృగాలు అక్బర్ కాలంలో కొన్నిప్రాంతాలకే పరిమితమైనాయి. చీటాలు పూర్తిగా భారతదేశం నుంచి అంతరించి పోయాయి.
జహంగిర్ కాలంలోవన్యప్రాణి సంరక్షణకు ప్రత్యేక చట్టాలు చేయబడ్దాయి. వేట నిషేదించారు. ప్రత్యేక అనుమతితో మాత్రమే వేట జరిగేది.
బ్రిటిష్ పాలనప్రారంభంలో వన్యప్రాణుల వేట అవిచ్చిన్నంగా జరిగింది. అధికారులు, అతిధులకొరకు షికారీలు ఏర్పాటు చేసేవారు. వన్యప్రాణులను వేటాడటం ధైర్యసాహసాలకు, గొప్పతననానికి, ఉన్నతవర్గాలకు గౌరవచిహ్నంగా ఉండేది. వివిధ మహారాజులు, జమిందార్లు, నవాబులు కూడా అదెవిధంగా విచ్చలవిడి వేటను కొనసాగించారు. ఆకారణంగా పులులు, సింహాలు, ఖడ్గమృగాల సంఖ్య మరింత కుచించుకుపోయింది.
పంతొమ్మిదవశతాబ్దపు చివర్లో బ్రిటిష్ ప్రభుత్వం కళ్ళు తెరచి వివిధ చట్టాలు చేసింది. 1879 లో ఏనుగుల సంరక్షణ చట్టం, 1912 నాటి వన్య జీవులు పక్షుల చట్టం, 1927 నాటి భారతదేశ అటవీచట్టం వంటివి భారతవన్యజీవుల వైవిధ్యతను కాపాడటానికి దోహదపడ్డాయి
ప్రముఖ వేటగాడు అయిన Jim Corbett కృషితో, 1936 లో భారతదేశపు మొట్టమొదటి జాతీయపార్కు అయిన “హైలీ జాతీయపార్కును” Hailey National Park” (దీనినే తరువాత జిమ్ కోర్బెట్ జాతీయపార్కుగా పేరు మార్చారు) ఏర్పాటు చేయటం జరిగింది.
స్వాతంత్ర్యానంతరం వన్యప్రాణి సంరక్షణ అవసరం గుర్తించారు. వన్యప్రాణుల సంరక్షణ కొరకు చట్టాలు, మార్గదర్శకసూత్రాలు తయారుచేయటానికి, భారతప్రభుత్వం 1952 లో Indian Wildlife Board ను స్థాపించింది. ఈ బోర్డు ఆధ్వర్యంలో అనేక జాతీయపార్కులు, అభయారణ్యాలు, గేమ్ పార్కులు
1970 లలో వచ్చిన రెండు ప్రధానమైన చట్టాలు, భారతదేశవన్యప్రాణి సంరక్షణ రంగాన్ని సమూలంగా మార్చివేసాయి. ఒకటి 1972 నాటి Wild Life Protection Act, రెండు 1973 నాటి అప్పటికి అతిపెద్ద సంరక్షణా పధమైన Project Tiger లు.
1980 లో వచ్చిన చిప్కో ఉద్యమం కూడా వన్యజీవుల సంరక్షణలో ప్రపంచవ్యాప్త గుర్తింపు పొందింది. చెట్లు నరకటాన్ని వ్యతిరేకిస్తూ, ఆ చెట్లను కౌగిలించుకొని అహింసాయుత మార్గం ద్వారా ప్రతిఘటించటం ప్రజలలో ఎంతో చైతన్యాన్ని, పర్యావరణం పట్ల అవగాహనను కల్పించింది.
1990 నుండి వన్యప్రాణుల సంరక్షణలో బయోటెక్నాలజీ, వన్యప్రాణి ఫొరెన్సిక్స్, టెలిమెట్రీ, రిమోట్ సెన్సింగ్ టెక్నాలజీ, సాటిలైట్ మేపింగ్ వంటి అధునాతన పద్దతులు వచ్చి ఈ రంగాన్ని సమూలంగా మార్చివేసాయి.
Wednesday, March 16, 2016
FLIGHT ADAPTATIONS
FLIGHT ADOPTATIONS
Flight -Main mode of locomotion used by most of the world's bird species.
Birds use flight
to obtain prey on the wing,
for foraging,
to commute to feeding grounds and
to migrate between the seasons.
Also used by some species to display during the breeding season and
to reach safe isolated places for nesting.
The most obvious adaptation for flight is the wing.
Forelimbs modified into the wings.
Attached high up on the thorax.
Equipped with special flight muscles and have been developed as instruments of propulsion through air.
The elongated flight- feathers of wings are called the remiges ;help in flight and also provide wing shape.
The expanded membranous part or vane of each remex forms a flexible and continuous surface for striking the air in flight.
The flight- feathers of a wing form a broad surface for supporting the bird in air.
The particular shape of the wing, with a thick strong leading edge, convex upper surface and concave lower surface, causes reduction in air pressure above and increase below, with minimum turbulence behind.
This helps in driving the bird forwards and upwards during flight.
Down feathers are soft and meant for insulation.
Tail feathers are called rectrices which stretch sideways so that tail can be used like a rudder for turning and balancing.
WEIGHT REDUCING ADAPTATIONS
Thin hollow bones
Extensive bone fusion especially in the pelvic and pectoral regions
Fusion of bones makes the skeleton light as well as strong.
Coracoid, furcula, and scapula form a sturdy tripod -supports the wings and broad surfaces for the attachment of large flight muscles.
The fusion of caudal bones into single pygostyle supports the tail feathers.
Most of the skull bones are firmly fused together.
The rigidity of the dorsal part of vertebral column due to fusion of vertebrae, provides a firm fuAdditional bony structures are fused into the pelvic girdle providing support to legs and rigidity.
Ribs are mostly fused with the vertebrae, pectoral girdle and sternum.
lcrum for the action of wings.
Except in flightless birds, the sternum bears a large keel for anchoring of flight muscles.
Bones in the forelimbs are highly modified for flight.
Some bones fused or reduced.
Fused clavicles form an elastic furcula that stores energy as it flexes during wing beats.
Extremely light feathers
Provide lightweight wing, tail and body contouring.
Elimination of teeth and jaws
Lack teeth or even a true jaw, instead having evolved a keratin beak - lightweight.
Elimination of tail vertebrae and some digits
To make it more efficient for flying
Elimination of most skin glands
A system of branching air sacs
They act as balloons providing lightness to the body and reduce the specific gravity of the body as they contain warm air
They act as accessory respiratory organs. They act as reservoir of air which is forced into lungs for ventilation during each expiration. Thus fresh air is available to lungs during inspiration as well as expiration.
Oviparous external egg reproduction
The expanded end of the oviduct receives the "naked" eggs.
Fertilization takes place in the upper oviduct before albumin and shell are added.
Special glands add albumin (white) to the egg as it passes down the oviduct.
Farther down, the shell membrane, shell, and pigments are secreted.
Eggs are laid outside the body- Less weight.
The atrophy of gonads between breeding season
Reproductive organs are small for the greater part of the year -decrease the birds’ weight for flight.
Only during mating season do reproductive organs (Ovaries and testes) reach functional size.
Only one ovary and oviduct
In most females, the left ovary and oviduct develop and the right ovary and oviduct degenerate or is greatly reduced -decrease the weight of body.
Female liver is displaced to the right to compensate for weight difference
Small testes
Males have small testes until the approach of the breeding season, when they may enlarge by 300 times.
Males of most species lack a penis; mating involves bringing cloacal surfaces in contact.
Rapid and efficient digestion minimizes weight of digesting food
The digestive system is extremely efficient in absorbing energy from small amounts of food at a rapid rate.
Because birds lack teeth they possess a gizzard.
Composed of four muscular bands that act to rotate and crush food by shifting the food from one area to the next within the gizzard.
Depending on the species, the gizzard may contain small pieces of grit or stone/pebbles that the bird Many birds possess a muscular pouch along the oesophagus called a crop.
The crop functions to both soften food and regulate its flow through the system by storing it temporarily.
The crop of pigeons, doves and some parrots, also produces a lipid / protein-rich "milk."
has swallowed to aid in the grinding process.
POWER INCREASING ADAPTATIONS
Heat conserving plumage
The light feathers hold a considerable blanket of enveloping air around the body and add much to its buoyancy.
The non-conducting covering of feathers insulates the body perfectly.
Prevents loss of heat. Enables the bird to endure intense cold at high altitudes and also to maintain a constant body temperature
Flight -Main mode of locomotion used by most of the world's bird species.
Birds use flight
to obtain prey on the wing,
for foraging,
to commute to feeding grounds and
to migrate between the seasons.
Also used by some species to display during the breeding season and
to reach safe isolated places for nesting.
The most obvious adaptation for flight is the wing.
Forelimbs modified into the wings.
Attached high up on the thorax.
Equipped with special flight muscles and have been developed as instruments of propulsion through air.
The elongated flight- feathers of wings are called the remiges ;help in flight and also provide wing shape.
The expanded membranous part or vane of each remex forms a flexible and continuous surface for striking the air in flight.
The flight- feathers of a wing form a broad surface for supporting the bird in air.
The particular shape of the wing, with a thick strong leading edge, convex upper surface and concave lower surface, causes reduction in air pressure above and increase below, with minimum turbulence behind.
This helps in driving the bird forwards and upwards during flight.
Down feathers are soft and meant for insulation.
Tail feathers are called rectrices which stretch sideways so that tail can be used like a rudder for turning and balancing.
WEIGHT REDUCING ADAPTATIONS
Thin hollow bones
Extensive bone fusion especially in the pelvic and pectoral regions
Fusion of bones makes the skeleton light as well as strong.
Coracoid, furcula, and scapula form a sturdy tripod -supports the wings and broad surfaces for the attachment of large flight muscles.
The fusion of caudal bones into single pygostyle supports the tail feathers.
Most of the skull bones are firmly fused together.
The rigidity of the dorsal part of vertebral column due to fusion of vertebrae, provides a firm fuAdditional bony structures are fused into the pelvic girdle providing support to legs and rigidity.
Ribs are mostly fused with the vertebrae, pectoral girdle and sternum.
lcrum for the action of wings.
Except in flightless birds, the sternum bears a large keel for anchoring of flight muscles.
Bones in the forelimbs are highly modified for flight.
Some bones fused or reduced.
Fused clavicles form an elastic furcula that stores energy as it flexes during wing beats.
Extremely light feathers
Provide lightweight wing, tail and body contouring.
Elimination of teeth and jaws
Lack teeth or even a true jaw, instead having evolved a keratin beak - lightweight.
Elimination of tail vertebrae and some digits
To make it more efficient for flying
Elimination of most skin glands
A system of branching air sacs
They act as balloons providing lightness to the body and reduce the specific gravity of the body as they contain warm air
They act as accessory respiratory organs. They act as reservoir of air which is forced into lungs for ventilation during each expiration. Thus fresh air is available to lungs during inspiration as well as expiration.
Oviparous external egg reproduction
The expanded end of the oviduct receives the "naked" eggs.
Fertilization takes place in the upper oviduct before albumin and shell are added.
Special glands add albumin (white) to the egg as it passes down the oviduct.
Farther down, the shell membrane, shell, and pigments are secreted.
Eggs are laid outside the body- Less weight.
The atrophy of gonads between breeding season
Reproductive organs are small for the greater part of the year -decrease the birds’ weight for flight.
Only during mating season do reproductive organs (Ovaries and testes) reach functional size.
Only one ovary and oviduct
In most females, the left ovary and oviduct develop and the right ovary and oviduct degenerate or is greatly reduced -decrease the weight of body.
Female liver is displaced to the right to compensate for weight difference
Small testes
Males have small testes until the approach of the breeding season, when they may enlarge by 300 times.
Males of most species lack a penis; mating involves bringing cloacal surfaces in contact.
Rapid and efficient digestion minimizes weight of digesting food
The digestive system is extremely efficient in absorbing energy from small amounts of food at a rapid rate.
Because birds lack teeth they possess a gizzard.
Composed of four muscular bands that act to rotate and crush food by shifting the food from one area to the next within the gizzard.
Depending on the species, the gizzard may contain small pieces of grit or stone/pebbles that the bird Many birds possess a muscular pouch along the oesophagus called a crop.
The crop functions to both soften food and regulate its flow through the system by storing it temporarily.
The crop of pigeons, doves and some parrots, also produces a lipid / protein-rich "milk."
has swallowed to aid in the grinding process.
POWER INCREASING ADAPTATIONS
Heat conserving plumage
The light feathers hold a considerable blanket of enveloping air around the body and add much to its buoyancy.
The non-conducting covering of feathers insulates the body perfectly.
Prevents loss of heat. Enables the bird to endure intense cold at high altitudes and also to maintain a constant body temperature
Tuesday, March 8, 2016
ENVIRONMENTAL STUDIES NOTES
1. Define Ecosystem? Explain the Structure and function of an ecosystem.
The term Ecology was coined by Earnst Haeckel in 1869. It is derived from the Greek words Oikos- home + logos- study. So ecology deals with the study of organisms in their natural home interacting with their surroundings. The surroundings or environment consists of other living organisms (biotic) and physical (abiotic) components. Modern ecologists believe that an adequate definition of ecology must
specify some unit of study and one such basic unit described by Tansley (1935) was ecosystem. An ecosystem is a group of biotic communities of species interacting with one another and with their non-living environment exchanging energy and matter. Now ecology is often defined as the study of ecosystems..
STRUCTURAL FEATURES
Composition and organization of biological communities and abiotic components constitute the structure of an ecosystem.
I. Biotic Structure
The plants, animals and microorganisms present in an ecosystem form the biotic component. These organisms have different nutritional be- haviour and status in the ecosystems and are accordingly known as Producers or Consumers, based on how do they get their food.
(a) Producers: They are mainly the green plants, which can synthesize their food themselves by making use of carbondioxide present in the air and water in the presence of sunlight by involving chlorophyll, the green pigment present in the leaves, through the process of photosynthesis. They are also known as photo autotrophs (auto=self; troph=food, photo=light). There are some microorganisms also which can produce organic matter to some extent through oxidation of certain chemicals in the
absence of sunlight. They are known as chemosynthetic organisms or chemo-autotrophs. For instance in the ocean depths, where there is no sunlight, chemoautotrophic sulphur bacteria make use of the heat generated by the decay of radioactive elements present in the earth.s core and released in ocean.s depths. They use this heat to convert dissolved hydrogen sulphide (H2S) and carbon dioxide (CO2) into organic compounds.
(b) Consumers: All organisms which get their organic food by feeding upon other organisms are called consumers, which are of the
following types:
(i) Herbivores (plant eaters): They feed directly on producers and hence also known as primary consumers. e.g. rabbit, insect, man.
(ii) Carnivores (meat eaters): They feed on other consumers. If they feed on herbivores they are called secondary consumers (e.g. frog) and if they feed on other carnivores (snake, big fish etc.) they are known as tertiary carnivores/consumers.
(iii) Omnivores: They feed on both plants and animals. e.g. humans, rat, fox, many birds.
(iv) Detritivores (Detritus feeders or Saprotrophs): They feed on the parts of dead organisms, wastes of living organisms, their castoffs and partially decomposed matter e.g. beetles, termites, ants, crabs, earthworms etc.
(c) Decomposers: They derive their nutrition by breaking down the complex organic molecules to simpler organic compounds and ultimately into inorganic nutrients. Various bacteria and fungi are decomposers.
In all the ecosystems, this biotic structure prevails. However, in some, it is the primary producers which predominate (e.g. in forests, agroecosystems) while in others the decomposers predominate (e.g. deep ocean).
II. Abiotic Structure
The physical and chemical components of an ecosystem constitute its abiotic structure. It includes climatic factors, edaphic (soil) factors, geographical factors, energy, nutrients and toxic substances. (a) Physical factors: The sunlight and shade, intensity of solar flux,
duration of sun hours, average temperature, maximum-minimum temperature, annual rainfall, wind, latitude and altitude, soil type, water availability, water currents etc. are some of the important physical features which have a strong influence on the ecosystem. We can clearly see the striking differences in solar flux, temperature and precipitation (rainfall, snow etc.) pattern in a desert ecosystem, in a tropical rainforest and in tundra ecosystem.
(b) Chemical factors: Availability of major essential nutrients like carbon, nitrogen, phosphorus, potassium, hydrogen, oxygen and sulphur, level of toxic substances, salts causing salinity and various organic substances present in the soil or water largely influence the functioning of the ecosystem. All the biotic components of an ecosystem are influenced by the abiotic components and vice versa, and they are linked together through energy flow and matter cycling as shown diagrammatically in Fig. 3.1.
The term Ecology was coined by Earnst Haeckel in 1869. It is derived from the Greek words Oikos- home + logos- study. So ecology deals with the study of organisms in their natural home interacting with their surroundings. The surroundings or environment consists of other living organisms (biotic) and physical (abiotic) components. Modern ecologists believe that an adequate definition of ecology must
specify some unit of study and one such basic unit described by Tansley (1935) was ecosystem. An ecosystem is a group of biotic communities of species interacting with one another and with their non-living environment exchanging energy and matter. Now ecology is often defined as the study of ecosystems..
STRUCTURAL FEATURES
Composition and organization of biological communities and abiotic components constitute the structure of an ecosystem.
I. Biotic Structure
The plants, animals and microorganisms present in an ecosystem form the biotic component. These organisms have different nutritional be- haviour and status in the ecosystems and are accordingly known as Producers or Consumers, based on how do they get their food.
(a) Producers: They are mainly the green plants, which can synthesize their food themselves by making use of carbondioxide present in the air and water in the presence of sunlight by involving chlorophyll, the green pigment present in the leaves, through the process of photosynthesis. They are also known as photo autotrophs (auto=self; troph=food, photo=light). There are some microorganisms also which can produce organic matter to some extent through oxidation of certain chemicals in the
absence of sunlight. They are known as chemosynthetic organisms or chemo-autotrophs. For instance in the ocean depths, where there is no sunlight, chemoautotrophic sulphur bacteria make use of the heat generated by the decay of radioactive elements present in the earth.s core and released in ocean.s depths. They use this heat to convert dissolved hydrogen sulphide (H2S) and carbon dioxide (CO2) into organic compounds.
(b) Consumers: All organisms which get their organic food by feeding upon other organisms are called consumers, which are of the
following types:
(i) Herbivores (plant eaters): They feed directly on producers and hence also known as primary consumers. e.g. rabbit, insect, man.
(ii) Carnivores (meat eaters): They feed on other consumers. If they feed on herbivores they are called secondary consumers (e.g. frog) and if they feed on other carnivores (snake, big fish etc.) they are known as tertiary carnivores/consumers.
(iii) Omnivores: They feed on both plants and animals. e.g. humans, rat, fox, many birds.
(iv) Detritivores (Detritus feeders or Saprotrophs): They feed on the parts of dead organisms, wastes of living organisms, their castoffs and partially decomposed matter e.g. beetles, termites, ants, crabs, earthworms etc.
(c) Decomposers: They derive their nutrition by breaking down the complex organic molecules to simpler organic compounds and ultimately into inorganic nutrients. Various bacteria and fungi are decomposers.
In all the ecosystems, this biotic structure prevails. However, in some, it is the primary producers which predominate (e.g. in forests, agroecosystems) while in others the decomposers predominate (e.g. deep ocean).
II. Abiotic Structure
The physical and chemical components of an ecosystem constitute its abiotic structure. It includes climatic factors, edaphic (soil) factors, geographical factors, energy, nutrients and toxic substances. (a) Physical factors: The sunlight and shade, intensity of solar flux,
duration of sun hours, average temperature, maximum-minimum temperature, annual rainfall, wind, latitude and altitude, soil type, water availability, water currents etc. are some of the important physical features which have a strong influence on the ecosystem. We can clearly see the striking differences in solar flux, temperature and precipitation (rainfall, snow etc.) pattern in a desert ecosystem, in a tropical rainforest and in tundra ecosystem.
(b) Chemical factors: Availability of major essential nutrients like carbon, nitrogen, phosphorus, potassium, hydrogen, oxygen and sulphur, level of toxic substances, salts causing salinity and various organic substances present in the soil or water largely influence the functioning of the ecosystem. All the biotic components of an ecosystem are influenced by the abiotic components and vice versa, and they are linked together through energy flow and matter cycling as shown diagrammatically in Fig. 3.1.
Thursday, February 4, 2016
ENVIRONMENTAL STUDIES NOTES
2. Define Bio-Geochemical cycles? Explain the Nitrogen cycle.
NUTRIENT CYCLING
Nutrients like carbon, nitrogen, sulphur, oxygen, hydrogen, phosphorus etc. move in circular paths through biotic and abiotic components and are therefore known as biogeochemical cycles.
Water also moves in a cycle, known as hydrological cycle. The nutrients too move through the food chain and ultimately reach the detritus compartment (containing dead organic matter) where various micro-organisms carry out decomposition.
Various organically bound nutrients of dead plants and animals are converted into inorganic substances by microbial decomposition that are readily used up by plants (primary producers) and the cycle starts afresh.
Nitrogen cycle
Cycling of one such important nutrient nitrogen is shown in Fig. Nitrogen is present in the atmosphere as N2 in large amount (78%) and it is fixed either by the physical process of lightening or biologically by some bacteria and/or cyanobacteria (blue green algae).
The nitrogen is taken up by plants and used in metabolism for biosynthesis of amino acids, proteins, vitamins etc. and passes through the food chain.
After death of the plants and animals, the organic nitrogen in dead tissues is decomposed by several groups of ammonifying and nitrifying bacteria which convert them into ammonia, nitrites and nitrates, which are again used by plants.
Some bacteria convert nitrates, into molecular nitrogen or N2 which is released back into the atmosphere and the cycle goes on.
3. Explain the ecological succession with suitable examples.
NUTRIENT CYCLING
Nutrients like carbon, nitrogen, sulphur, oxygen, hydrogen, phosphorus etc. move in circular paths through biotic and abiotic components and are therefore known as biogeochemical cycles.
Water also moves in a cycle, known as hydrological cycle. The nutrients too move through the food chain and ultimately reach the detritus compartment (containing dead organic matter) where various micro-organisms carry out decomposition.
Various organically bound nutrients of dead plants and animals are converted into inorganic substances by microbial decomposition that are readily used up by plants (primary producers) and the cycle starts afresh.
Nitrogen cycle
Cycling of one such important nutrient nitrogen is shown in Fig. Nitrogen is present in the atmosphere as N2 in large amount (78%) and it is fixed either by the physical process of lightening or biologically by some bacteria and/or cyanobacteria (blue green algae).
The nitrogen is taken up by plants and used in metabolism for biosynthesis of amino acids, proteins, vitamins etc. and passes through the food chain.
After death of the plants and animals, the organic nitrogen in dead tissues is decomposed by several groups of ammonifying and nitrifying bacteria which convert them into ammonia, nitrites and nitrates, which are again used by plants.
Some bacteria convert nitrates, into molecular nitrogen or N2 which is released back into the atmosphere and the cycle goes on.
3. Explain the ecological succession with suitable examples.
Wednesday, January 20, 2016
EXCRETORY SYSTEM OF LEECH
Excretory system of Leech
Excretory system consists of 17 pairs of small coiled tubes, the nephridia, arranged segmentally, one pair in each segment from 6th to22nd.
Nephridia are of two types
i ) testicular
ii) pre-testicular
i) Testicular nephridia
Posterior 11 pairs of nephridia lying one pair in each segment from 12 to 22nd, are termed testicular nephridia.
They are called testicular nephridia, due to the presence of a pair of testis sacs in each of these segments.
A typical testicular nephridium is a horseshoe-shaped structure traversed by a complicated system of canals
It consists of 6 parts:
1) main lobe
2) vesicle and vesicle duct
3) apical lobe
4) inner lobe
5) initial lobe
6) ciliated organ
1) Main lobe:
Forms the horseshoe proper
Lies in a ventro-lateral position between two adjacent caeca of crop
Forms the major part of nephridium
Consists of two unequal limbs
One limb is longer and anterior in position and the other shorter and posterior
Cells of main lobe are big and polyhedral in shape
2) Vesicle and the Vesicle duct.
A narrow vesicle duct arises from the inner ventral end of anterior limb of main lobe
Runs posteriorly to open into a large bladder or terminal vesicle, situated ventro-laterally behind the rest of nephridium
Vesicle is a large oval sac, with a non-contractile thin wall, internally lined by a ciliated epithelium
A short and narrow excretory duct, lined with a non-ciliated epithelium, leads from vesicle to open to the exterior through a rounded aperture, the nephridiopore
At its origin from vesicle, the excretory duct is provided with a sphincter muscle that controls the flow of excretory substances out of the vesicle.
M.L. Bhatia (1940)- bladder is lined by cilia
B. Dev- the so called cilia are in fact non-motile bacteria, the nephridial microflora, 2.8 to 7 microns in length
3) Apical lobe
Inner free end of posterior limb of main lobe is continued to form a stout apical lobe
Present antero-posteriorly beneath the crop
Its anterior end is slightly swollen and bent on itself like the handle of a walking stick
Its cells are big and traversed by regular intracellular canals.
4) Inner lobe or incurrent lobe
seen extending between the anterior and posterior limbs of main lobe
also runs forward along the outer side of apical lobe for about half of its length
5) Initial lobe
Long, narrow, transparent and cord-like structure
Formed of a single row of elongated tubular cells and closely coiled around the apical lobe.
Its posterior end joins the main lobe, while its anterior end runs inwards and reaches over the testis sac of its own side, where it ends blindly close to the perinephrostomial ampullae.
The intracellular canal of initial lobe gives off many diverticula in each cell.
6) Ciliated organ
Present inside peristomial ampullae
Suspended from the inner walls of ampullae by 4 to 5 strands or trabeculae.
It corresponds to the funnel or nephrostome of a typical annelid nephridium, but is a greatly modified and compound structure
Ciliated organ consists of a spongy central reservoir and ciliated funnels
The reservoir contains the central mass of connective tissue cells which manufacture the coelomic corpuscles
Outer wall of central mass, made of a single layer of cells, and bears numerous minute pores.
A ciliated funnel fits into each pore on the outside
Each funnel is like an ear lobe, with about one-fourth of its margin incomplete
Funnel covered with outwardly directed cilia on its outer margin and inner surface
In the embryo, ciliated organ has a distinct cellular connection with the nephridium.
But, in adult Hirudinaria, it loses the connection as well as excretory function and becomes a part of the haemocoelomic system.
It manufactures coelomic corpuscles for the haemocoelomic system.
II Pre-testicular nephridia
First six pairs of nephridia are termed pre-testicular nephridia because of their location in segments 6 to 11 without testis sacs themselves, but in front of those containing testis sacs.
These nephridia resemble testicular nephridia in all respects except that their initial lobes end loosely in general connective tissue on their side of ventral nerve cord.
There are no testis sacs, peri-nephrostomial ampullae and ciliated organs in their segments.
Excretory system consists of 17 pairs of small coiled tubes, the nephridia, arranged segmentally, one pair in each segment from 6th to22nd.
Nephridia are of two types
i ) testicular
ii) pre-testicular
i) Testicular nephridia
Posterior 11 pairs of nephridia lying one pair in each segment from 12 to 22nd, are termed testicular nephridia.
They are called testicular nephridia, due to the presence of a pair of testis sacs in each of these segments.
A typical testicular nephridium is a horseshoe-shaped structure traversed by a complicated system of canals
It consists of 6 parts:
1) main lobe
2) vesicle and vesicle duct
3) apical lobe
4) inner lobe
5) initial lobe
6) ciliated organ
1) Main lobe:
Forms the horseshoe proper
Lies in a ventro-lateral position between two adjacent caeca of crop
Forms the major part of nephridium
Consists of two unequal limbs
One limb is longer and anterior in position and the other shorter and posterior
Cells of main lobe are big and polyhedral in shape
2) Vesicle and the Vesicle duct.
A narrow vesicle duct arises from the inner ventral end of anterior limb of main lobe
Runs posteriorly to open into a large bladder or terminal vesicle, situated ventro-laterally behind the rest of nephridium
Vesicle is a large oval sac, with a non-contractile thin wall, internally lined by a ciliated epithelium
A short and narrow excretory duct, lined with a non-ciliated epithelium, leads from vesicle to open to the exterior through a rounded aperture, the nephridiopore
At its origin from vesicle, the excretory duct is provided with a sphincter muscle that controls the flow of excretory substances out of the vesicle.
M.L. Bhatia (1940)- bladder is lined by cilia
B. Dev- the so called cilia are in fact non-motile bacteria, the nephridial microflora, 2.8 to 7 microns in length
3) Apical lobe
Inner free end of posterior limb of main lobe is continued to form a stout apical lobe
Present antero-posteriorly beneath the crop
Its anterior end is slightly swollen and bent on itself like the handle of a walking stick
Its cells are big and traversed by regular intracellular canals.
4) Inner lobe or incurrent lobe
seen extending between the anterior and posterior limbs of main lobe
also runs forward along the outer side of apical lobe for about half of its length
5) Initial lobe
Long, narrow, transparent and cord-like structure
Formed of a single row of elongated tubular cells and closely coiled around the apical lobe.
Its posterior end joins the main lobe, while its anterior end runs inwards and reaches over the testis sac of its own side, where it ends blindly close to the perinephrostomial ampullae.
The intracellular canal of initial lobe gives off many diverticula in each cell.
6) Ciliated organ
Present inside peristomial ampullae
Suspended from the inner walls of ampullae by 4 to 5 strands or trabeculae.
It corresponds to the funnel or nephrostome of a typical annelid nephridium, but is a greatly modified and compound structure
Ciliated organ consists of a spongy central reservoir and ciliated funnels
The reservoir contains the central mass of connective tissue cells which manufacture the coelomic corpuscles
Outer wall of central mass, made of a single layer of cells, and bears numerous minute pores.
A ciliated funnel fits into each pore on the outside
Each funnel is like an ear lobe, with about one-fourth of its margin incomplete
Funnel covered with outwardly directed cilia on its outer margin and inner surface
In the embryo, ciliated organ has a distinct cellular connection with the nephridium.
But, in adult Hirudinaria, it loses the connection as well as excretory function and becomes a part of the haemocoelomic system.
It manufactures coelomic corpuscles for the haemocoelomic system.
II Pre-testicular nephridia
First six pairs of nephridia are termed pre-testicular nephridia because of their location in segments 6 to 11 without testis sacs themselves, but in front of those containing testis sacs.
These nephridia resemble testicular nephridia in all respects except that their initial lobes end loosely in general connective tissue on their side of ventral nerve cord.
There are no testis sacs, peri-nephrostomial ampullae and ciliated organs in their segments.
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