Class Amphibia amp Reptilia Animal Kingdom NEET Bio Part 18

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Class Amphibia: • 1. They are the first cold blooded vertebrates from evolution point of view which came to the land. Class Amphibian includes about 3,000 species. • 2. They are amphibious in nature, viz. they can live on land as well as in water. They are mostly found in warm countries. They are ectothermic (cold blooded). • 3. Body is divisible into head and trunk. Tail may be present in some amphibians. • 4. The skin is smooth or rough having glands which keep it moist. • 5. They are usually without scales, but if present they are hidden beneath the skin (e.g caecilians). • 6. Paired fins are absent. Unpaired fins may be present. Two pairs of limbs are used for locomotion except caecilions. • 7. The gills are present at least in the larval stage; some adult forms also carry external gills in addition to lungs (e.g., Necturus, Proteus). • 8. Skull is dicondylic, i.e., with two occipital condyles for articulation with vertebral column. • 9. The respiratory organs are lungs, buccopharyngeal cavity, skin and gills. • 10. The heart is three chambered, having two auricles and one ventricle. In the heart, there are present sinus venosus and truncus arteriosus. Both hepatic portal and renal portal systems are well developed. RBCs are biconvex, oval and nucleated. • 11. Kidneys are mesonephric. Urinary bladder is present in frog. Larvae and tailed amphibians (e.g., salamanders) are ammonotelic. Frogs and toads are ureotelic. • 12. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens outside through cloacal aperture. • 13. Ear consists of internal and middle ear. Tympanum (outer membrane) covers the middle ear. The eyes have eyelids. Nictitating membrane is well developed. • 14. Ten pairs of cranial nerves are present. • Class Reptilia: • 1. Reptiles are the creeping and burrowing cold blooded vertebrates bearing epidermal scales. They are ectothermic (cold-blooded) and are found mostly in the warmer parts of the world. They are few in colder parts. They are mostly terrestrial animals. There are about 6,000 living species of reptiles in the world. • 2. Skin is dry, rough and without glands, bearing epidermal scales or scutes. • 3. Snakes and lizards shed their scales as skin cast. • 4. They do not respire by means of gills. Respiration always takes place through lungs. Ribs help to expand and contract the body cavity, making the lung respiration more efficient than in amphibian. • 5. Skull is monocondylic, i.e., with single occipital condyle. • 6. Except in snakes, there are two pairs of pentadactyl limbs, each with 5 digits bearing claws— tetrapodus pentadactyl type. • 7. Heart consists of two auricles and a partially divided ventricle. In crocodilians, heart is four chambered (two auricles and two ventricles). Renal portal system is less developed. RBCs are nucleated. • 8. Kidneys are metanephric. Urinary bladder may be present. Crocodiles are ammonotelic. Turtles and alligators are ureotelic. Lizards and snakes are uricotelic. • 9. Twelve pairs of cranial nerves are present. • 10. Each ear consists of three parts; external, middle and internal. Snakes do not possess ears. • 11. The lateral line system is altogether absent. • 12. Tortoises feed almost entirely on vegetation. Some turtles are flesh eaters. All other reptiles are carnivorous/insectivorous. • 13. A typical cloaca is present. • 14. They are mostly oviparous. Reptiles lay macrolecithal eggs (= polylecithal eggs). Some forms are ovoviviparous or viviparous. Embryonic membranes (chorion, amnion, allantois and yolk sac) are formed during development. • ................................................................................. • Subscribe to NEET preparation channel: https://www.youtube.com/channel/UCVjG... • Like us on facebook: https://www.facebook.com/profile.php?... • Follow us our facebook page: / neetwithaks • Follow me on gmail ID: [email protected] • Category: Education • Being Human Charitable Trust (An NGO works on Education Health) • License: Standard YouTube License • #Being Human Charitable Trust

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