Define/Explain: Ecotype.

The organism which tolerates a wide range of salinity is called ...$A$...
$II.$ The organism which tolerates a narrow range of salinity is called ...$B$...
Choose the correct option for $A$ and $B$.

Which one of the following correctly represents an organism and its ecological niche?

Alpine tundra is found in

Consider the following four statements $(1-4)$ about certain desert animals such as kangaroo rat.
$(1)$ They have dark colour and high rate of reproduction and excrete solid urine.
$(2)$ They do not drink water,breathe at a slow rate to conserve water and have their body covered with thick hairs.
$(3)$ They feed on dry seeds and do not require drinking water.
$(4)$ They excrete very concentrated urine and do not use water to regulate body temperature.
Which two of the above statements for such animals are true?

Despite variations in external environment,organisms try to maintain constancy of its internal environment which is called . . . . . . .