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Which one of the following in birds, indicates their reptilian ancestry?
A
Two special chambers crop and gizzard in their digestive tract
B
Eggs with a calcareous shell
C
Scales on their hind limbs
D
Four-chambered heart
Detailed Solution
Birds have evolved from reptilian ancestors and are sometimes called glorified reptiles.
The skin of birds is dry and covered with feathers, but the hind limbs still bear epidermal scales, which are similar to the horny epidermal scales of reptiles.
This reptilian feature retained on the hind limbs indicates their reptilian ancestry.
The crop and gizzard are additional chambers of the digestive tract that are special adaptations of birds.
A four-chambered heart is an advanced feature of birds (shared with mammals and crocodiles) and is not typical of reptiles, most of which have a three-chambered heart.
Hard calcareous egg shells are characteristic of birds, while most reptiles lay eggs with leathery shells.
So the feature indicating reptilian ancestry is the scales on their hind limbs.
The skin of birds is dry and covered with feathers, but the hind limbs still bear epidermal scales, which are similar to the horny epidermal scales of reptiles.
This reptilian feature retained on the hind limbs indicates their reptilian ancestry.
The crop and gizzard are additional chambers of the digestive tract that are special adaptations of birds.
A four-chambered heart is an advanced feature of birds (shared with mammals and crocodiles) and is not typical of reptiles, most of which have a three-chambered heart.
Hard calcareous egg shells are characteristic of birds, while most reptiles lay eggs with leathery shells.
So the feature indicating reptilian ancestry is the scales on their hind limbs.