The hypothalamus controls excretions from the pituitary gland. it causes the release of some hormones from the pituitary by direct nervous control, and others by secreting releasing and inhibiting factors that stimulate the pituitary to secrete hormones.
which best describes the hypothalamus?

it is a connection point between the nervous and endocrine systems.
it is both an exocrine and endocrine gland.
it is referred to as the “master gland.”
it secretes its contents into ducts.

It is a connection point between the nervous and endocrine systems.

Explanation:

Hypothalamus is the part of the diencephalon. As a part of the endocrine system, it releases releasing and inhibiting hormones to regulate the release of hormones from the anterior pituitary gland. Example:  thyrotropin-releasing hormone from hypothalamus makes the anterior pituitary to release thyrotropin hormone.

However, to maintain homeostasis, the hypothalamus also regulates the hormone secretion from the pituitary gland through nervous control. Therefore, hypothalamus serves as a link between the nervous and endocrine system.

the correct answer is:

a population changes in response to a change in the environment.