Organisms restricted to a narrow range of salinity are $- P$.
Organisms that tolerate a wide range of salinity are $- Q$.
Choose the correct option for $P$ and $Q$.
$P$ $Q$

Assertion : Biotic community has higher position than population in ecological hierarchy.
Reason : Population of similar individuals remains isolated in the community.

Explain the life history variations in organisms.

An elephant has very few hairs,while a bear has thick fur because the bear:

Plants growing on sand and gravel are called

$A$ 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 $D$.