question_answer 59)

  Comment upon the habitats and external features of animals belonging to class-Amphibia and Reptilia.

Answer:

                  Amphibians (i) They possess dual life as they can live in aquatic as well as terrestrial habitat. They are ectothermic (cold blooded). (ii) They are tetrapods (4 limbs) which facilitate movement land. (iii) Their limbs are evolved from the pectoral and pelvic fins. (iv) Skin is thin, covered by mucus and mostly remain moist, also serves as an accessory source oxygen. (v) They are both gill and lung breathers; usually gills appear in the larval stage, replaced by lungs in the adults stage. (vi)They possess three chambered heart with two atria and one ventricle. (vii) The fertilization is mostly external, females are oviparous. (viii) Larva is a tadpole, which metamorphosis into adult thus shaving metamorphosis. e.g., Ranafrog, Nectureus (mud puppy), Salamandera (salamander). Reptiles (i) In reptiles, creeping and crawling mode of locomotion is found. (ii) They are mostly terrestrial animals and their body is covered by dry, and cornified skin, epidermal scales or scutes. (iii) Lungs are well developed and present in all stages of life. (iv) Toes possess claws. (v) Appendages are well adapted for the movement on land. (vi) Heart possesses a partially divided ventricle and 2 atria. (vii) They lay amniotic eggs which are incubate on land. (viii) They are poikilothermic or cold blooded animals. Temperature is regulated mechanically and not metabolically by moving in and out; heat source is usually the sun. (ix) fertilization is internal They are oviparous and development of young ones is direct. e.g., Chelone (turtle), Naja (cobra), Crocodicus (crocodile).