Both snake and turtle have been placed by taxonomists in class Reptilia of phylum Chordata. This is done because of following features; (i) skin without glands; (ii) three-chambered (in-fact incompletely four chambered) heart; (iii) respiration through lungs; (iv) cold blooded; (v) hard shelled eggs; (vi) embryo protected by extra embryonic membranes.

Differentiate between flying lizard and Bird.
Flying lizard:-
1. It belongs to class Reptilia of phylum Chordata.
2. The animal is cold blooded.
3. Its heart is three chambered.
4. Feathers are absent.
5. Jaws have teeth.
6. It has normal fore limbs.
7. A patagium is present for helping in gliding (Patagium is a fold of skin extending between the forelimbs and hindlimbs of an arboreal animal).
8. Body is covered by scales.

Bird:- 1. It belongs to class Aves of phylum Chordata.
2. The animal is warm blooded.
3. Its heart is four-chambered.
4. Feathers are present.
5. jaws are modified into beak. Teeth are absent,
6. Its forelimbs are modified into wings.
7. A patagium is absent.
8. Scales are restricted to hindlimbs.

No (l) Leech and Nereis have metameric segmentation (i.e., external segmentation of body corresponding to internal segmentation), closed circulatory system and unjointed appendages. They belong to phylum Annelida.
(ii) Scolopendra (centipede), Prawn and Scorpion also have segmented body but they have open circulatory system, jointed appendages and chitinous exoskeleton. They belong to phylum Arthropoda.