Two or more species occupying identical or overlapping areas are known as

The niche of a population is defined as

Assertion : Biotic community has higher position than population in ecological hierarchy.
Reason : Population of similar individuals remains isolated in the community.

Some animals can change their body temperature according to the ambient temperature,then they are simply . . . . . . .

$A$: Antarctic fishes have blubber to withstand sub-zero temperatures.
$R$: Blubber are proteins which allow the freezing of body fluids.

Animals living in colder regions have shorter tails and ears compared to animals living in warmer regions. This phenomenon is called: