Many freshwater fishes cannot live in seawater and vice versa because of:

Which of the following is a characteristic of a biological community?

How many of the following statements are correct about niche?
$i$. It denotes the functional role played by an organism.
$ii$. It deals with the flow of energy from one organism to another.
$iii$. As soon as a niche is left vacant,other organisms fill that position.
$iv$. The same niche is shared by two or more species.
$v$. Organisms living in the same habitat differ in their niches.

Give scientific reasons: Freshwater animals cannot survive for long in seawater.

Rhododendron is the characteristic vegetation of

In summer,when the outside temperature is higher than our body temperature,we sweat profusely. The resulting evaporative cooling,similar to what happens with a desert cooler in operation,brings down the body temperature. In winter,when the temperature is much lower than $37^{\circ}C$,we start to shiver,a kind of exercise which produces heat and raises the body temperature. These organisms are called: