The first line of defense against body cells infected by viruses is produced by __________.

The __________ is a structure shared by the digestive and respiratory systems.

What anatomical feature is missing in animals with radial symmetry that is found in animals with bilateral symmetry?

Vaccinations provide immunity by presenting the immune system with __________.

Reptiles are better adapted to land dwelling than are amphibians because of their __________.

Which immune system organ filters the blood, allowing white blood cells to remove foreign particles and aged red blood cells?

What physical characteristics define insects?

Deoxygenated blood is delivered to the heart through __________.

When a person takes a drug, the drug will eventually be eliminated from the body. One of the primary mechanisms for this removal is tubular secretion. Which of the following would produce the greatest reduction in the ability of our kidneys to remove drugs?

What is the plant alternation of generations?