Rainfall occurs in chaparral during

In most animals,the metabolic reactions proceed in a $A$ temperature range (in humans,it is $37^{\circ} C$). But there are microbes (archaebacteria) that flourish in hot springs and deep sea hydrothermal vents where temperatures far exceed $B$. Choose the correct option for $A$ and $B$.

$I.$ 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.

In the ecological hierarchy,the basic unit is . . . . . . .

What is adaptation? Explain with examples how various organisms show adaptations to cope with specific environmental conditions.

Life history traits of organisms have evolved in relation to the constraints imposed by which of the following?