Answer to Question #151348 in Zoology for shadow

Question

anatomical modification observed among reptiles that was not present in fishes and amphibians?

Answer 1

Reptiles are ectothermic amniotes. They emerged as the dominant group during the Mesozoic era.

Most reptiles lay water-tight cleidoic eggs (covered by porous calcareous shell - to allow the passage of air to provide oxygen) on land with extraembryonic membranes namely amnion, allantois, chorion, and yolk sac which makes the egg an independent 'life support system'.

Thus, the 'amniotic egg helped the reptiles to abandon ties with their ancestral aquatic habitat. In addition to cleidoic eggs, the evolution of dry scaly skin to prevent water loss, two pairs of pentadactyl limbs with clawed digits for moving on land, pulmonary breathing, and internal fertilization are the key adaptations that led to the success of reptiles.

Skin is rough and dry. The exoskeleton occurs in the form of horny epidermal scales, shields, and claws.

Dentition is acrodont, homodont, and polyphyodont.

The exchange of respiratory gases takes place only through the lungs. They use ribs and intercostal muscles in ventilation. In turtles, gaseous exchange takes place through the vascular cloacal wall.

The reptiles are​​​​ uricotelic (uricotelism is an adaptation to conserve water).

The tympanic membrane is found at the inner border of the external auditory meatus. The middle ear has a single car ossicle called columella auris. Jacobson's organs, the specialized olfactory structures, are highly developed in lizards and snakes

Cleavage is meroblastic and Discoidal.

Fertilization is internal.

These modifications made the reptiles more successful.