Which scientist studied biology by traveling by ship to different islands observing animal life, and developed a hypothesis about how species change?
A: Charles Darwin

Cancer is best described as
A: abnormal cell division

Which illness is associated with a weakened immune system in the body?
A: cancer

Scientists dig in a dry area at the bottom of a mountain range. Fossilized shells of freshwater mussels are found in the area. Which is a likely conclusion that scientists will draw based on this evidence?
A:
Rivers once flowed through the area.