The treeless biome of cold climates is:

Match the following in Column $I$ with the means adopted to tide over periods of unfavorable conditions in Column $II$.

$i$. Birds	$c$. Migration
$ii$. Seeds	$a$. Dormancy
$iii$. Snails	$d$. Aestivation
$iv$. Polar bear	$b$. Hibernation

$I.$ Many xerophytic plants have thick cuticle on leaf epidermis and sunken stomata.
$II.$ Some xerophytic plants have a special photosynthetic pathway $(CAM)$ that enables their stomata to close during the day.
$III.$ $Opuntia$ has spines (modified leaves) and a photosynthetic phylloclade (stem).
$IV.$ All adaptations are genetically fixed in all organisms.
Choose the combination of correct statements.

How many of the following pairs are correct regarding the thermal tolerance of organisms?
$(1)$ Aves - eurythermal
$(2)$ Mammals - stenothermal
$(3)$ Amphibia - stenothermal
$(4)$ Reptile - eurythermal

Give the differences between Hibernation and Aestivation.

Changes in the body form of some planktonic animals with seasonal changes in temperature are grouped under