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

$A$ regulators are able to maintain homeostasis by means which ensure constant body temperature,constant osmotic concentration,etc. All $B$ and $C$ and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation).
Evolutionary biologists believe that the 'success' of mammals is largely due to their ability to maintain a constant body $D$ and thrive whether they live in Antarctica or in the Sahara desert.
Choose the correct option for $A, B, C$ and $D$.

Consider the following four statements regarding certain desert animals like the kangaroo rat:
$(a)$ They have a dark color,a high rate of reproduction,and excrete solid urine.
$(b)$ They do not drink water,breathe slowly to conserve water,and their body is covered by thick hair.
$(c)$ They use dry seeds as food and do not require drinking water.
$(d)$ They excrete very concentrated urine and do not use water to regulate body temperature.
Which two of the above statements are true for such animals?

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 $B$.

Just as a person moving from Delhi to Shimla to escape the heat for the duration of hot summer,thousands of migratory birds from Siberia and other extremely cold northern regions move to:

The organisms spending most of the time in the transitional area between two communities are called: