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.
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
Sunday, August 21, 2016
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.
Wednesday, January 6, 2016
ECOLOGICAL SUCCESSION
3. Explain the ecological succession with suitable examples.
Ecological succession is defined as an orderly process of changes in the community structure and function with time mediated through modifications in the physical environment and ultimately culminating in a stabilized ecosystem known as climax. The whole sequence of communities which are transitory are known as Seral stages or seres whereas the community establishing first of all in the area is called a pioneer community. Ecological successions starting on different types of areas or substrata are named differently as follows:
(i) Hydrarch or Hydrosere: Starting in watery area like pond, swamp, bog (ii) Mesarch: starting in an area of adequate moisture.
(iii) Xerarch or Xerosere: Starting in a dry area with little moisture. They can be of the following types:
Lithosere : starting on a bare rock
Psammosere : starting on sand
Halosere : starting on saline soil
Process of Succession
The process of succession takes place in a systematic order of sequential steps as follows:
(i) Nudation: It is the development of a bare area without any life form. The bare area may be caused due to landslides, volcanic eruption etc. (topographic factor), or due to drought, glaciers, frost etc. (Climatic factor), or due to overgrazing, disease outbreak, agricultural/ industrial activities (biotic factors).
(ii) Invasion: It is the successful establishment of one or more species on a bare area through dispersal or migration, followed by ecesis or establishment. Dispersal of the seeds, spores etc. is brought about by wind, water, insects or birds. Then the seeds germinate and grow on the land. As growth and reproduction start, these pioneer species increase in number and form groups or aggregations.
(iii) Competition and coaction: As the number of individuals grows there is competition, both inter-specific (between different species) and intra-specific (within the same species), for space, water and nutrition. They influence each other in a number of ways, known as coaction.
(iv) Reaction: The living organisms grow, use water and nutrients from the substratum, and in turn, they have a strong influence on the environment which is modified to a large extent and this is known as reaction. The modifications are very often such that they become unsuitable for the existing species and favour some new species, which replace them. Thus, reaction leads to several seral communities.
(v) Stabilization: The succession ultimately culminates in a more or less stable community called climax which is in equilibrium with the environment. The climax community is characterized by maximum biomass and symbiotic (mutually beneficial) linkages between organisms and are maintained quite efficiently per unit of available energy. Let us consider very briefly two types of succession. A. Hydrosere (Hydrarch): This type of succession starts in a water body like pond. A number of intermediate stages come and ultimately it culminates in a climax community which is a forest. The pioneer community consists of phytoplanktons, which are free floating algae, diatoms etc. Gradually these are replaced by rootedsubmerged plants followed by rooted-floating plants. Growth of these plants keep on adding organic matter to the substratum by death and decay and thus a layer of soil builds up and shallowing of water takes
place. Then Reed swamp (marshy) stage follows in which the plants are partly in water and partly on land. This is followed by a sedgemeadow stage of grasses then by a woodland consisting of shrubs and trees and finally by a forest acting as climax. (Fig. 3.15)
B. Xerosere (Xerarch): This type of succession originates on a bare rock, which lacks water and organic matter. Interestingly, here also the climax community is a forest, although the intermediate stages are very different.
The pioneer community here consists of crustose and foliose lichens. These lichens produce some weak acids and help in disintegrating the rock, a process known as weathering. Their growth helps in building up gradually some organic matter, humus and soil.
Then comes the community of mosses, followed by herbs, shrubs and finally the forest trees. Throughout this gradual process there is a slow build up of organic matter and water in the substratum.
Thus, succession tends to move towards mesic conditions (moderate condition), irrespective of the fact, whether it started from a dry (Xeric) condition or a moist (hydric) condition and it culminates in a stable climax community, which is usually a forest.
Ecological succession is defined as an orderly process of changes in the community structure and function with time mediated through modifications in the physical environment and ultimately culminating in a stabilized ecosystem known as climax. The whole sequence of communities which are transitory are known as Seral stages or seres whereas the community establishing first of all in the area is called a pioneer community. Ecological successions starting on different types of areas or substrata are named differently as follows:
(i) Hydrarch or Hydrosere: Starting in watery area like pond, swamp, bog (ii) Mesarch: starting in an area of adequate moisture.
(iii) Xerarch or Xerosere: Starting in a dry area with little moisture. They can be of the following types:
Lithosere : starting on a bare rock
Psammosere : starting on sand
Halosere : starting on saline soil
Process of Succession
The process of succession takes place in a systematic order of sequential steps as follows:
(i) Nudation: It is the development of a bare area without any life form. The bare area may be caused due to landslides, volcanic eruption etc. (topographic factor), or due to drought, glaciers, frost etc. (Climatic factor), or due to overgrazing, disease outbreak, agricultural/ industrial activities (biotic factors).
(ii) Invasion: It is the successful establishment of one or more species on a bare area through dispersal or migration, followed by ecesis or establishment. Dispersal of the seeds, spores etc. is brought about by wind, water, insects or birds. Then the seeds germinate and grow on the land. As growth and reproduction start, these pioneer species increase in number and form groups or aggregations.
(iii) Competition and coaction: As the number of individuals grows there is competition, both inter-specific (between different species) and intra-specific (within the same species), for space, water and nutrition. They influence each other in a number of ways, known as coaction.
(iv) Reaction: The living organisms grow, use water and nutrients from the substratum, and in turn, they have a strong influence on the environment which is modified to a large extent and this is known as reaction. The modifications are very often such that they become unsuitable for the existing species and favour some new species, which replace them. Thus, reaction leads to several seral communities.
(v) Stabilization: The succession ultimately culminates in a more or less stable community called climax which is in equilibrium with the environment. The climax community is characterized by maximum biomass and symbiotic (mutually beneficial) linkages between organisms and are maintained quite efficiently per unit of available energy. Let us consider very briefly two types of succession. A. Hydrosere (Hydrarch): This type of succession starts in a water body like pond. A number of intermediate stages come and ultimately it culminates in a climax community which is a forest. The pioneer community consists of phytoplanktons, which are free floating algae, diatoms etc. Gradually these are replaced by rootedsubmerged plants followed by rooted-floating plants. Growth of these plants keep on adding organic matter to the substratum by death and decay and thus a layer of soil builds up and shallowing of water takes
place. Then Reed swamp (marshy) stage follows in which the plants are partly in water and partly on land. This is followed by a sedgemeadow stage of grasses then by a woodland consisting of shrubs and trees and finally by a forest acting as climax. (Fig. 3.15)
B. Xerosere (Xerarch): This type of succession originates on a bare rock, which lacks water and organic matter. Interestingly, here also the climax community is a forest, although the intermediate stages are very different.
The pioneer community here consists of crustose and foliose lichens. These lichens produce some weak acids and help in disintegrating the rock, a process known as weathering. Their growth helps in building up gradually some organic matter, humus and soil.
Then comes the community of mosses, followed by herbs, shrubs and finally the forest trees. Throughout this gradual process there is a slow build up of organic matter and water in the substratum.
Thus, succession tends to move towards mesic conditions (moderate condition), irrespective of the fact, whether it started from a dry (Xeric) condition or a moist (hydric) condition and it culminates in a stable climax community, which is usually a forest.
Saturday, January 2, 2016
FASCIOLA NOTES
External morphology and life history of Fasciola hepatica
PHYLUM-PLATYHELMINTHES
CLASS-TREMATODA
ORDER-DIGENEA
1. Habit and Habitat of Fasciola Hepatica:
Fasciola hepatica (L., fasciola = small bandage; Gr., hepar = liver), the sheep liver fluke, lives as an endoparasite in the bile passages of sheep.
Fasciola hepatica, in addition to sheep, also infects other vertebrates like goat, deer, horse, dog, ass, ox and occasionally man. Fasciola hepatica is worldwide in distribution, particularly sheep and cattle raising areas are the primary zones where human beings are also infected.
Its other Indian species, F. gigantica (= indica) is found in the bile passages of buffaloes, cow, goats and pigs.
2. Shape, Size and Colour:
F. hepatica has a thin, dorsoventrally flattened, leaf-shaped, elongated and oval body. It measures about 25 to 30 mm in length and 4 to 12 mm in breadth.
The maximum width is at about anterior third of the body from where the body tapers anteriorly as well as posteriorly, however, the anterior end is somewhat rounded, while it is bluntly pointed posteriorly.
3. External Morphology:
Shape and size: body of F. hepatica is soft, oval in outline, dorso-ventrally flattened and leaf like. It is about 1.8 to 3cm, which is a little infront of the middle region of body. From this region body tapers away anteriorly as well as posteriorly. Anterior end is somewhat broad and rounded, while posterior end is bluntly pointed.
Colouration: Colour is usually pinkish, but the transparency of body wall enables the observer to see the blackish or brownish vitelline glands along the lateral margins, and the alimentary canal, which appears brownish due to ingested bile of the host.
Oral cone: anterior end of body is drawn out into a prominent conical projection, termed the oral cone or head lobe, bearing at its tip a somewhat triangular aperture, the mouth.
Suckers: there are two small suckers, anterior and ventral. Both are devoid of hooks and spines.
Anterior sucker: Mouth is situated at the centre and bottom of a cup-shaped muscular organ, known as the anterior or oral sucker. It has a diameter of about 1 mm. Muscles of oral sucker radiate from margin of mouth to the periphery of sucker. Oral sucker acts as an ideal suctorial organ serving for adhesion as well as ingestion.
Ventral sucker: About 3 to 4 mm. behind the oral sucker, situated mid-ventrally, is another bowl-like adhesive sucker, the ventral or posterior sucker, also known as acetabulum. It is without an aperture and has a diameter of about 1.6mm.
4. Life cycle and development:
Digenetic life cycle. Life cycle of F. hepatica is complex and completed in two hosts. Primary host, in which the adult fluke lives, is sheep. While the intermediate host, in which numerous larval stages are passed, is a snail (Lymnaea, Planorbis, etc.). This type of life cycle, involving two different kinds of hosts, is termed digenetic.
Copulation. Self-fertilization is of rare occurrence in liver flukes though they are hermaphrodite. In F. hepatica, copulation takes place in bile ducts of the host.
Two flukes in copulation bring their genital pores in opposition. Cirrus of one fluke, everted through its gonopore, penetrates the Laurer’s canal of the other through the latter’s temporary opening, and injects spermatozoa. Secretion of prostate glands, and perhaps also of the Mehlis’s glands, keep the sperm active for fertilization.
Fertilization. Fertilization is internal. In cross-fertilization, sperms received in Laurer’s canal during copulation, enter the distal end of oviduct where fertilization occurs. During self-fertilization, sperms enter the uterus of same fluke through female genital aperture and pass down to fertilize the egg.
Capsule formation. Each fertilized egg or zygote is surrounded by yolk cells, which provide yolk and shell material. Shell- globules of yolk cells contain proteins and a phenol.
According to Stephenson (1947), phenol is oxidized to a quinine in the proximal part of uterus. Quinine then tans the protein, producing a hard, resistant and lethary sclerotin like that of insects. This sclerotin forms the shell around fertilized eggs.
Capsules. Shelled eggs are termed capsules or simply eggs. A shell or capsule is yellow or brown, in colour and oval in shape. It is about 130 to 150µ long and 60 to 90µ wide.
It is operculate, i.e., provided with a lid or operculum. Situated immediately beneath the operculum, at the terminal end of egg is a viscous and granular cushion. About 3000or more such capsules may occur at a time in the uterus of a single fluke.
There may be as many as 200 flukes in the liver of one sheep. If each fluke produces 500,000 eggs, a single infected sheep may disperse 100 million fertile eggs. This vast capacity for egg production is necessary in view of the complicated life cycle and slim chances of survival.
Cleavage and embryonic development. Cleavage starts while eggs are still in uterus. Cleavage is holoblastic and unequal. First division of zygote results in two unequal cells, a larger somatic cell and a smaller propagatory cell. Subsequent divisions of somatic cell form larval ectoderm and tissues. Propagatory cell divides further into two daughter cells.
One daughter cell by its divisions finally produces the larval body. Other daughter cell divides several times to form a mass of smaller germ cells which cluster in the posterior part of larval body.
Encapsulated embryos or capsules or simply eggs do not develop further in fluke’s uterus.
A very large number of capsules leave fluke’s body through its gonopore into host’s intestine, and finally ejected out with its faeces.
Further development takes place when capsules come in contact with water (or Damp areas with at least 60% moisture content) which is slightly acidic (pH 6.5). Optimum temperature for development ranges from 220C to 250C.
Larval stages of Fasciola hepatica
Miracidium Larva. It is the first larval stage involved in life cycle. When suitable conditions become available, the encapsulated embryo, in 4-15 days, differentiates into a miracidium larva. It hatches out and swims in water. Hatching is initiated by a proteolytic hatching enzyme. It dissolves the cementing material by which operculum is attached, thus releasing the operculum.
Characters:
1) It is 150 microns in length. It is small. It is conical in shape.
2) It is covered by ciliated epidermal cells. ,
3) The body is covered by 21 ciliated cells which are arranged in five rows.
a) First row - six cells
b) Second row - six cells
c) Third row - three cells
d) Fourth row - four cells
e) Fifth row - two cells
4) With the help of cilia it swims in the water
5) At the apex of the larva an apical papilla or boring papilla is present.
6) An apical gland is present in the miracidium larva which opens into the apical papilla. On either side of it two penetration glands are present.
7) A brain is present. Above the brain two eye spots are present.
8) A pair of flame cells are present which open out laterally towards the posterior end. The larva shows a number of germ cells.
9) The miracidium larva lives only for 8 hours. During this time it will swim in search of the secondary host.
Transmission to secondary host:
The secondary host of liver fluke is Limnea truncatula or Planorbis (fresh water snailj.When the miracidium larva comes in contact with the snail it pierce into the soft body of snail. Apical papilla and secretions of penetration gland will help the larva to bore into the body of snail. In the body of snail miracidium develops into sporocyst stage.
Sporocyst:
In the body of snail miracidium enters into pulmonary sac. There miracidium will loose its ciliated epidermis. It becomes a bag like structure. It looses all the structures except flame cells and germ cells. The germ cells will undergo parthenogenesis and give rise to the next larvae called Redia. The sporocyst absorbs nourishment from the host tissues and often causes destruction to the host.
Redia:
In the sporocyst five to eight redia larvae are produced. They come out of the sporocyst by rupturing the wall of the sporocyst.
This larva is elongated in structure. It is covered by thin cuticle. It shows a collar which is muscular. It helps in locomotion.
Near the collar a birth pore is present. The next larval stage will go out through the birth pore. The larva shows a gut which opens out through mouth. Mouth opens into pharynx which leads into intestine.
Many flame cells are present. The flame cells of one side will open into a common excretory duct which opens out through a single nephridiopore. The mesenchyme of the larva shows germ cells.
The germ cells will undergo parthenogenesis and give rise to the next larval stage called cercaria in the winter season. These cercaria larvae will come out of the redia through birth pore.
Cercaria:
The redia larva will give 15 to 20 cercaria larvae. They are liberated from the redia larva through birth pore.
1) It is oval in shape with tail.
2) It is 0.25mm to 0.35mm in length.
3) The cuticle covering will show backwardly directed spines.
4) Two suckers are present, a) Oral sucker around mouth, b) ventral sucker.
5) The digestive system starts with mouth, opens into pharynx, oesophagus and intestine. Intestine divided into two branches.
6) More flame cells are present. All of them open into excretory tubules. The two excretory tubules will unite at the posterior end and become excretory bladder. It gives an excretory tube. It divides into two, which opens out through nephridiopore.
7) Germ cells are present.
The completely developed cercaria will enter into water from the body of snail. They swim for 2 or 3days in the water and settle on a water plant.
Metacercaria:
As many as a thousand metacercariae may be found attached to a single grass blade. They have a rounded form with a diameter of about 0.2mm.
Meta cercaria is in fact the juvenile fluke, also called marita. It differs from cercaria in that it has a rounded form, a thick hard cyst and large number of flame cells. It lacks a tail and cysogenous gland cells and its excretory bladder opens out directly through a single pore.
Germ cells or the genital rudiments are present as such. Cyst provides protection against short periods of desiccation.
Infection of primary host.
When the sheep eats the plants with metacercaria stages they enter into its digestive system. The cyst wall is digested in intestine, finally dissolves in proximal part of intestine and liberate the larva. It penetrates through the intestine wall and gets onto coelomic cavity.
Now it infect the liver, feeds on its tissue, and grows in size in five to six weeks. It then takes up its position in the bile duct, where it finally attains sexual maturity. In 11 to 13 weeks. After entering the body of host, it starts laying eggs.
PHYLUM-PLATYHELMINTHES
CLASS-TREMATODA
ORDER-DIGENEA
1. Habit and Habitat of Fasciola Hepatica:
Fasciola hepatica (L., fasciola = small bandage; Gr., hepar = liver), the sheep liver fluke, lives as an endoparasite in the bile passages of sheep.
Fasciola hepatica, in addition to sheep, also infects other vertebrates like goat, deer, horse, dog, ass, ox and occasionally man. Fasciola hepatica is worldwide in distribution, particularly sheep and cattle raising areas are the primary zones where human beings are also infected.
Its other Indian species, F. gigantica (= indica) is found in the bile passages of buffaloes, cow, goats and pigs.
2. Shape, Size and Colour:
F. hepatica has a thin, dorsoventrally flattened, leaf-shaped, elongated and oval body. It measures about 25 to 30 mm in length and 4 to 12 mm in breadth.
The maximum width is at about anterior third of the body from where the body tapers anteriorly as well as posteriorly, however, the anterior end is somewhat rounded, while it is bluntly pointed posteriorly.
3. External Morphology:
Shape and size: body of F. hepatica is soft, oval in outline, dorso-ventrally flattened and leaf like. It is about 1.8 to 3cm, which is a little infront of the middle region of body. From this region body tapers away anteriorly as well as posteriorly. Anterior end is somewhat broad and rounded, while posterior end is bluntly pointed.
Colouration: Colour is usually pinkish, but the transparency of body wall enables the observer to see the blackish or brownish vitelline glands along the lateral margins, and the alimentary canal, which appears brownish due to ingested bile of the host.
Oral cone: anterior end of body is drawn out into a prominent conical projection, termed the oral cone or head lobe, bearing at its tip a somewhat triangular aperture, the mouth.
Suckers: there are two small suckers, anterior and ventral. Both are devoid of hooks and spines.
Anterior sucker: Mouth is situated at the centre and bottom of a cup-shaped muscular organ, known as the anterior or oral sucker. It has a diameter of about 1 mm. Muscles of oral sucker radiate from margin of mouth to the periphery of sucker. Oral sucker acts as an ideal suctorial organ serving for adhesion as well as ingestion.
Ventral sucker: About 3 to 4 mm. behind the oral sucker, situated mid-ventrally, is another bowl-like adhesive sucker, the ventral or posterior sucker, also known as acetabulum. It is without an aperture and has a diameter of about 1.6mm.
4. Life cycle and development:
Digenetic life cycle. Life cycle of F. hepatica is complex and completed in two hosts. Primary host, in which the adult fluke lives, is sheep. While the intermediate host, in which numerous larval stages are passed, is a snail (Lymnaea, Planorbis, etc.). This type of life cycle, involving two different kinds of hosts, is termed digenetic.
Copulation. Self-fertilization is of rare occurrence in liver flukes though they are hermaphrodite. In F. hepatica, copulation takes place in bile ducts of the host.
Two flukes in copulation bring their genital pores in opposition. Cirrus of one fluke, everted through its gonopore, penetrates the Laurer’s canal of the other through the latter’s temporary opening, and injects spermatozoa. Secretion of prostate glands, and perhaps also of the Mehlis’s glands, keep the sperm active for fertilization.
Fertilization. Fertilization is internal. In cross-fertilization, sperms received in Laurer’s canal during copulation, enter the distal end of oviduct where fertilization occurs. During self-fertilization, sperms enter the uterus of same fluke through female genital aperture and pass down to fertilize the egg.
Capsule formation. Each fertilized egg or zygote is surrounded by yolk cells, which provide yolk and shell material. Shell- globules of yolk cells contain proteins and a phenol.
According to Stephenson (1947), phenol is oxidized to a quinine in the proximal part of uterus. Quinine then tans the protein, producing a hard, resistant and lethary sclerotin like that of insects. This sclerotin forms the shell around fertilized eggs.
Capsules. Shelled eggs are termed capsules or simply eggs. A shell or capsule is yellow or brown, in colour and oval in shape. It is about 130 to 150µ long and 60 to 90µ wide.
It is operculate, i.e., provided with a lid or operculum. Situated immediately beneath the operculum, at the terminal end of egg is a viscous and granular cushion. About 3000or more such capsules may occur at a time in the uterus of a single fluke.
There may be as many as 200 flukes in the liver of one sheep. If each fluke produces 500,000 eggs, a single infected sheep may disperse 100 million fertile eggs. This vast capacity for egg production is necessary in view of the complicated life cycle and slim chances of survival.
Cleavage and embryonic development. Cleavage starts while eggs are still in uterus. Cleavage is holoblastic and unequal. First division of zygote results in two unequal cells, a larger somatic cell and a smaller propagatory cell. Subsequent divisions of somatic cell form larval ectoderm and tissues. Propagatory cell divides further into two daughter cells.
One daughter cell by its divisions finally produces the larval body. Other daughter cell divides several times to form a mass of smaller germ cells which cluster in the posterior part of larval body.
Encapsulated embryos or capsules or simply eggs do not develop further in fluke’s uterus.
A very large number of capsules leave fluke’s body through its gonopore into host’s intestine, and finally ejected out with its faeces.
Further development takes place when capsules come in contact with water (or Damp areas with at least 60% moisture content) which is slightly acidic (pH 6.5). Optimum temperature for development ranges from 220C to 250C.
Larval stages of Fasciola hepatica
Miracidium Larva. It is the first larval stage involved in life cycle. When suitable conditions become available, the encapsulated embryo, in 4-15 days, differentiates into a miracidium larva. It hatches out and swims in water. Hatching is initiated by a proteolytic hatching enzyme. It dissolves the cementing material by which operculum is attached, thus releasing the operculum.
Characters:
1) It is 150 microns in length. It is small. It is conical in shape.
2) It is covered by ciliated epidermal cells. ,
3) The body is covered by 21 ciliated cells which are arranged in five rows.
a) First row - six cells
b) Second row - six cells
c) Third row - three cells
d) Fourth row - four cells
e) Fifth row - two cells
4) With the help of cilia it swims in the water
5) At the apex of the larva an apical papilla or boring papilla is present.
6) An apical gland is present in the miracidium larva which opens into the apical papilla. On either side of it two penetration glands are present.
7) A brain is present. Above the brain two eye spots are present.
8) A pair of flame cells are present which open out laterally towards the posterior end. The larva shows a number of germ cells.
9) The miracidium larva lives only for 8 hours. During this time it will swim in search of the secondary host.
Transmission to secondary host:
The secondary host of liver fluke is Limnea truncatula or Planorbis (fresh water snailj.When the miracidium larva comes in contact with the snail it pierce into the soft body of snail. Apical papilla and secretions of penetration gland will help the larva to bore into the body of snail. In the body of snail miracidium develops into sporocyst stage.
Sporocyst:
In the body of snail miracidium enters into pulmonary sac. There miracidium will loose its ciliated epidermis. It becomes a bag like structure. It looses all the structures except flame cells and germ cells. The germ cells will undergo parthenogenesis and give rise to the next larvae called Redia. The sporocyst absorbs nourishment from the host tissues and often causes destruction to the host.
Redia:
In the sporocyst five to eight redia larvae are produced. They come out of the sporocyst by rupturing the wall of the sporocyst.
This larva is elongated in structure. It is covered by thin cuticle. It shows a collar which is muscular. It helps in locomotion.
Near the collar a birth pore is present. The next larval stage will go out through the birth pore. The larva shows a gut which opens out through mouth. Mouth opens into pharynx which leads into intestine.
Many flame cells are present. The flame cells of one side will open into a common excretory duct which opens out through a single nephridiopore. The mesenchyme of the larva shows germ cells.
The germ cells will undergo parthenogenesis and give rise to the next larval stage called cercaria in the winter season. These cercaria larvae will come out of the redia through birth pore.
Cercaria:
The redia larva will give 15 to 20 cercaria larvae. They are liberated from the redia larva through birth pore.
1) It is oval in shape with tail.
2) It is 0.25mm to 0.35mm in length.
3) The cuticle covering will show backwardly directed spines.
4) Two suckers are present, a) Oral sucker around mouth, b) ventral sucker.
5) The digestive system starts with mouth, opens into pharynx, oesophagus and intestine. Intestine divided into two branches.
6) More flame cells are present. All of them open into excretory tubules. The two excretory tubules will unite at the posterior end and become excretory bladder. It gives an excretory tube. It divides into two, which opens out through nephridiopore.
7) Germ cells are present.
The completely developed cercaria will enter into water from the body of snail. They swim for 2 or 3days in the water and settle on a water plant.
Metacercaria:
As many as a thousand metacercariae may be found attached to a single grass blade. They have a rounded form with a diameter of about 0.2mm.
Meta cercaria is in fact the juvenile fluke, also called marita. It differs from cercaria in that it has a rounded form, a thick hard cyst and large number of flame cells. It lacks a tail and cysogenous gland cells and its excretory bladder opens out directly through a single pore.
Germ cells or the genital rudiments are present as such. Cyst provides protection against short periods of desiccation.
Infection of primary host.
When the sheep eats the plants with metacercaria stages they enter into its digestive system. The cyst wall is digested in intestine, finally dissolves in proximal part of intestine and liberate the larva. It penetrates through the intestine wall and gets onto coelomic cavity.
Now it infect the liver, feeds on its tissue, and grows in size in five to six weeks. It then takes up its position in the bile duct, where it finally attains sexual maturity. In 11 to 13 weeks. After entering the body of host, it starts laying eggs.
Wednesday, December 2, 2015
BIRDS LIST Afrotropical (African Tropics)
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