The diagram shows the internal structure of a typical fish.
What is a function of the structure labeled X?
O exchange gases
pumps blood
maintain balance
sense water temperature
X

Which organelle releases chemicals that break down large food particles into smaller ones?

What are the doorways into and out of cells, attached to the membrane, and built in the rough er.

The nervous system interacts with the endocrine system by a. using hormones as connections b. sending nerve impulses directly to glands c. using neuroendocrine cells as connections d. sending neurotransmitters directly to neurons