SAT Biology Subject Test Practice Questions

Answer: B, Niche. The niche is the specific role a group of one species in an area. If two groups share a niche, competition ensues.

Key Takeaway: In ecology, smaller units combine to form larger ones. A group of a single species is a population, and groups of populations exist in a community. The niche defines the role each population plays in a community. The niche defines every aspect of an organism, including lifespan, size, morphology, and place in the food chain.