The voice box of birds is known as $..........$.

In which of the following are the $Syrinx$,$Furcula$,and $Pygostyle$ absent?

Identify the correct statements regarding class $Aves$.
$I$. Forelimbs are modified into wings and hindlimbs are modified for walking and swimming.
$II$. Heart is completely four-chambered.
$III$. They are homeotherms.
$IV$. They are oviparous and development is direct.

Out of the following,reptiles and birds differ in only one aspect. Which is it?

The flightless bird with forelimbs modified as paddle-like structures suited for swimming is known as:

Which one of the following organisms bears hollow and pneumatic long bones?