Why do organisms adapt?

Mammals from colder climates generally have shorter ears and limbs to minimize heat loss. This is known as:

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?

The wide variety of natural habitats is based on which of the following?

How is a biological community formed?

$A$ population characteristic of a species susceptible to extinction is