The upper part of sea water mainly contains

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

An animal which comes out at night and hides during the day is called:

The flora and fauna in lakes or ponds are known as:

Phenotypic variants formed in a population due to change in environment are called

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?