Nektons are

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

Given below are two statements.
Statement $I$: Habitat consists of numerous niches.
Statement $II$: Niche is an area where a species lives and prospers.
In the light of the above statements,choose the correct option.

Invertebrates living in the deep sea, at extreme depths, experience pressure how many times greater than the normal atmospheric pressure (in $times$)?

$I.$ Biochemical adaptations are seen in organisms living at great depths of the ocean to face crushing pressure.
$II.$ Allen's rule explains adaptations in mammals living in colder climates.
$III.$ Altitude sickness is caused because the body does not get enough oxygen due to low atmospheric pressure at high altitudes.
$IV.$ Desert lizards lack behavioural means to manage their body temperature.
Choose the correct option for the above statements.

Which of the following represents an organism and its ecological niche correctly?