Question

What are differences between the following:
(a) Cartilaginous fishes and bony fishes;
(b) Amphibia and Reptilia;
(c) Aves and mammals.

Answer 1

(a)
Cartilaginous fishes:
(i) They have a cartilaginous endoskeleton.
(ii) They contain five to seven pairs of gill slits.
(iii) Their mouth is ventral in position.
(iv) Swim bladder is absent in them.
Bony fishes:
(i) They have a bony endoskeleton.
(ii) They contain four pairs of gill slits.
(iii) Their mouth is terminal in position.
(iv) Air bladder is usually present in them
(b)
Amphibia:
(i) Their skin is glandular, smooth and moist.
(ii) Scales are not present in them.
(iii) They have a three chambered heart.
(iv) Fertilisation is external.
Reptilia:
(i) Their skin is non-glandular, dry and keratinized.
(ii) Horny scales are present over their body.
(iii) Their heart is incompletely four chambered.
(iv) Fertilisation is internal.
(c)
Aves
(i) Forelimbs are modified into wings.
(ii) The body is covered with feathers and scales
(iii) Mammary glands are absent.
(iv) A toothless beak is present.
Mammals:
(i) Wings are absent except in bats.
(ii) Feathers and scales are absent. Hair is present.
(iii) Females have mammary glands.
(iv) Teeth are present. Jaws do not form beak.