Which of the following factors can reduce the population of a community?

Step 1: Analyze the question The question asks which factor can reduce (decrease) the population of a community. We need to find the option that causes a loss of individuals.

Step 2: Explain the concepts Population size changes through four main processes:

• Increase: natality (birth) and immigration (individuals moving in)
• Decrease: mortality (death) and emigration (individuals moving out)

Other factors act on these processes:

• Predation is a relationship where one organism (the predator) kills and feeds on another (the prey). It directly causes deaths, so it lowers the prey population.
• Mutualism is a relationship where both organisms benefit, so it tends to support population growth.
• Edaphic factors are soil-related factors (soil pH, texture, nutrients, water content). They affect where plants and soil organisms can grow, but they are not a direct way of reducing a population in the way predation is.

Step 3: Evaluate each option

• A. Immigration: individuals move into the area, so the population increases. Incorrect.
• B. Edaphic: a soil factor that influences the habitat. It is not a typical population-reducing interaction, so it is not the best answer here.
• C. Predation: predators kill and consume prey, so the prey population decreases. Correct.
• D. Mutualism: both partners benefit, so it does not reduce the population. Incorrect.

Step 4: Answer The correct option is **C.

Tip: Remember "BIDE" for population change: Birth and Immigration add individuals, while Death and Emigration remove them. Predation is a cause of death, so it reduces numbers. Also remember that mutualism and commensalism are "friendly" relationships, while predation and parasitism are "harmful" to one partner.