Birds have ___________ bones which helps them in flying.

Bat's wings are made up of ___________.

_______ is the seasonal movement of birds from one region to another.

An aquatic animal which inflates itself and displays spines on its body to scare away predators is the _____
 

The animal given in the image below gives us ___ to keep us warm in winters.

Sun $\to$ Plants $\to$ Mice $\to$ Snakes $\to$ Hawks

From the given food chain, which of the following best describes the hawk? 

Grass $\to$ Grasshopper $\to$ Frog $\to$ Snake

Animals who eat only plants are known as ______.

Which one of the following birds have webbed feet?

The evolution of modern humans started around  ___ years ago.