The niche of a population is defined as

Consider the following four statements $(1-4)$ about certain desert animals such as kangaroo rat.
$(1)$ They have dark colour and high rate of reproduction and excrete solid urine.
$(2)$ They do not drink water,breathe at a slow rate to conserve water and have their body covered with thick hairs.
$(3)$ They feed on dry seeds and do not require drinking water.
$(4)$ They excrete very concentrated urine and do not use water to regulate body temperature.
Which two of the above statements for such animals are true?

Match the columns:

Column-$I$	Column-$II$
$(a)$ Bears	$(i)$ Diapause
$(b)$ Snails	$(ii)$ Hibernation
$(c)$ Zooplanktons	$(iii)$ Dormancy
$(d)$ Seeds	$(iv)$ Aestivation

What is a tree line?

Nektons are

Alpine forests of the Himalayas have: