Question

What are differences between the following :

(a) Cartilaginous fishes and bony fishes ;

(b) Amphibia and Reptilia ;

(c) Aves and mammals.

Answer 1

What are differences between the following :

(a) Cartilaginous fishes and Bony fishes 

Cartilaginous fishes	Bony fishes
1. They have a cartilaginous endoskeleton.	1. They have a bony endoskeleton.
2. They contain 5-7 pairs of gill slits.	2. They contain four pairs of gill slits
3. An operculum is absent in them.	3. Their gill slits are covered with an operculum.
4. Their mouth is ventral in position	4. Their mouth is terminal in position.
5. Their caudal fin is heterocercal.	5. Their caudal fin is homocercal.
6. Swim bladder is absent in them.	6. Air bladder is usually present in them
Example. Indian shark, electric ray, etc.	Example. Carp, sea horse, etc.

(b) Amphibia and Reptilia 

Amphibia	Reptilia
1. Their skin is glandular, smooth and moist.	1. Their skin is non-glandular, dry and keratinised.
2. Scales are not present in them.	2. Horny scales are present over their body surface.
3. Their digits do not possess claws.	3. Their digits end in claws.
4. They have a three-chambered heart.	4. Their heart is incompletely four chambered.
Example. Frog, toad.	Example. Lizard, snake, tortoise, dinosaurs (extinct).

(c) Aves and mammals :

Aves	mammals
1. Forelimbs are modified into wings.	1. Wings are absent except in bats.
2. The body is covered with feathers and scales.	2. Feathers and scales are absent. Hair are present.
3. Skin is dry only a single preen gland is present.	3. Skin bears a number of sweat and oil glands.
4. Mammary glands are absent.	4. Mammary glands are absent.
5. A diaphragm is absent.	5. A muscular partition called diaphragm is present between thorax and abdomen.
6. A toothless beak is present.	6. Jaws do not form beak. Teeth are present