Which of the following is a population in a lake ecosystem?

• A. Water
• B. Perch
• C. Soil
• D. Temperature

Answer: (B)

A population means all individuals of the same species living in a particular area. In a lake, the perch are a group of fish all belonging to the same species, living in that lake, so they form the perch population. Water, soil, and temperature are nonliving parts of the environment (abiotic factors) and do not represent a group of organisms. So the perch population is the correct fit.