What does $Allen's$ rule represent?

Many freshwater animals cannot live for long in sea water and vice-versa mainly because of the

Match the types of niche in Column-$I$ with their description in Column-$II$.

$i$. Habitat niche	$a$. In the absence of competition in the habitat
$ii$. Trophic niche	$b$. Position of organism in the environmental gradient
$iii$. Multidimensional niche	$c$. Physical space occupied by an organism
$iv$. Fundamental niche	$d$. Level of organism in the food chain

Read the following statements and select the option that represents the correct statements.
$(1)$ Kangaroo rats never drink water.
$(2)$ Birds undergo hibernation to escape adverse environmental conditions.
$(3)$ Thermal adaptation can be explained by Allen's Rule.
$(4)$ Opuntia possesses phylloclade for protection.

Temperature regulation is found in

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