Question

Which is not an aerial adaptation of birds?
(a) Single ovary
(b) Pneumatic bone
(c) Gizzard
(d) Keeled sternum

Answer 1

Hint: It is a specialized stomach found in most of the animals like crocodiles, alligators, earthworms used for grinding of food. This is also present in some fish, insects, molluscs and other invertebrates.

Complete step by step answer:
The single ovary helps aerial birds in flight by reducing its overall weight, whereas the pneumatic bone helps in flight and the keeled sternum is attached to the flight bone. Birds do not have gizzard.

The features of aerial birds are
- Aerial birds have the ability to fly.
- These birds can fly great distances to migrate in search of food and shelter with the change in the temperature.
- They have the ability to protect themselves from a predator in the air.
- They have a compact body- with heavier ventrally and strong dorsally to maintain balance in the air.
- Their loose skin modified for flight.
- Due to the presence of occipital condyle , they have a mobile neck and head.
- They have bipedal locomotion.
- Air sacs are present in a low position in the body.
- Body covering of feathers prevents heat loss and tail used for flight and counterbalance in perching.
- Their forelimbs modified are into wings – surface area is developed into elongated flight feathers called remiges
- Their bones are pneumatic, filled with air spaces which reduce weight while flight.
So, the correct answer is ‘gizzard’.

Note:
- The gizzard is found in some organisms and is known as the specialized stomach also known as ventriculus, gastric mill, and gigerium.
- When the food passes into their proventriculus also known as the glandular stomach or the true stomach then it passes through the secretory part of the stomach then lastly passes to gizzard for grinding the food.
- The gizzard is featured with chitinous plates or teeth lined with a tough layer made up of the carbohydrates protein complex kaolin.
- The gizzard helps in chewing the food, especially stone or hard food.