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

(N/A) Amphibia:
- As the name indicates (Gr.,Amphi: dual,bios: life),amphibians can live in aquatic as well as terrestrial habitats.
- Most of them have two pairs of limbs.
- Body is divisible into head and trunk.
- Tail may be present in some.
- The amphibian skin is moist (without scales).
- The eyes have eyelids.
- $A$ tympanum represents the ear.
- Alimentary canal,urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
- Respiration is by gills,lungs and through skin.
- The heart is three-chambered (two auricles and one ventricle).
- These are cold-blooded (poikilothermous) animals.
- Sexes are separate.
- Fertilisation is external.
- They are oviparous and development is direct or indirect.
- Examples: Bufo (Toad),Rana (Frog),Hyla (Tree frog),Salamandra (Salamander),Ichthyophis (Limbless amphibia).
Reptilia:
- The class name refers to their creeping or crawling mode of locomotion (Latin,repere or reptum: to creep or crawl).
- They are mostly terrestrial animals and their body is covered by dry and cornified skin,epidermal scales or scutes.
- They do not have external ear openings. Tympanum represents ear.
- Limbs,when present,are two pairs.
- Heart is usually three-chambered,but four-chambered in crocodiles.
- Reptiles are poikilotherms.
- Snakes and lizards shed their scales as skin cast.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
- Examples: Chelone (Turtle),Testudo (Tortoise),Chameleon (Tree lizard),Calotes (Garden lizard),Crocodilus (Crocodile),Alligator (Alligator),Hemidactylus (Wall lizard),Poisonous snakes - Naja (Cobra),Bangarus (Krait),Vipera (Viper).