Viruses cause a variety of diseases in animals, including humans, ranging from the common cold…

A virus must “take over” a cell to replicate. The viral replication cycle can produce…

Figure 12.1 (a) This smallpox (variola) vaccine is derived from calves exposed to cowpox virus.…

The central nervous system (CNS) is made up of the brain and spinal cord and…

As you read this, your nervous system is performing several functions simultaneously. The visual system…

Muscles allow for movement such as walking, and they also facilitate bodily processes such as…

The muscular and skeletal systems provide support to the body and allow for movement. The…

The endocrine system produces hormones that function to control and regulate many different body processes.…

The circulatory system is a network of vessels—the arteries, veins, and capillaries—and a pump, the…

Animals are complex multicellular organisms that require a mechanism for transporting nutrients throughout their bodies…