Which term best describes all the different species present in a lake?

• A. Community
• B. Population
• C. Species
• D. Ecosystem

Answer: (A)

All the different species present in a lake form a community. In ecology, a community is the assemblage of populations of multiple species that live in the same area and interact with each other, such as fish, zooplankton, aquatic plants, and bacteria in a lake. This is different from a population, which would mean all individuals of a single species in that area (for example, the population of bluegill in the lake). The term ecosystem goes a step further by including the abiotic environment and the processes that connect the living and nonliving parts, like energy flow and nutrient cycling. So, the best fit for all the species together is the community.