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 ?

Which element is responsible for causing soil salinity ? At what concentration does the soil become saline ?

$A$ : The soil of tropical rain forest has low base content.
$R$ : Such soil shows less percolation and leaching

Why do all the fresh water organisms have contractile vacuoles whereas majority of marine organisms lack them ?

What is diapause and its significance ?