$A$ species that is produced by the loss or disappearance of a few characters found in its parents is termed as:

The number and kinds of organisms are not constant. How do you explain this statement?

Assertion $A$: Organisms show variations to adapt and utilize the environment to the maximum extent.
Reason $R$: Variations lead to the formation of new species.
Which option is correct for Assertion $A$ and Reason $R$?

The splint bone of the present-day horse is a vestige of which digit?

Neo-Darwinism or the synthetic theory of evolution is based upon:

From which ancestral groups did birds and mammals evolve?