Biologist (noun)

1. A person who studies biology, the science of living organisms and their interactions with each other and the environment.
2. An expert in biology.

Origin:

From the greek words "bios" meaning "life" and "logos" meaning "study".

Examples:

1. He is a marine biologist who studies whales.
2. She is a molecular biologist who specializes in genetics.
3. The biologist discovered a new species of frog.
4. The class was taught by a well-known ecologist and biologist.
5. The biologist's research on the effects of pollution on fish populations.