Question

Which one of the following in birds, indicates their reptilian ancestry?

• A. Scales on their hind limbs
• B. Four-chambered heart
• C. Two special chambers crop and gizzard in their digestive tract
• D. Eggs with a calcareous shell

Answer 1

Answer: (A)

Scales on their hind limbs

The dry skin of reptiles is covered with scales to prevent water loss as an adaptation to terrestrial life. The hind limbs of birds also have scales, which confirm their reptilian ancestry.

Crop is the enlarged part of oesophagus, which stores the food and is an avian adaptation to reduce their exposure to predators. Likewise, modern birds are toothless to trim the weight of head as a flight adaptation. Absence of tooth is compensated by presence of gizzard wherein food is chewed.

Reptilian heart is three chambered with two atria and one ventricle, while birds have four chambered heart with two atria and two ventricles.

So, the correct answer is option A.