Question

Which of the following factors do you think can affect the size and structure of a population?

the number of individuals who enter a population

the number of individuals who exit a population

limitation of resources

natural events

human activity

Answer 1

All of them. Each factor you listed can change population size and/or structure:

- Number entering (immigration or births): raises population size and can change age, sex, and genetic composition.
- Number exiting (emigration or deaths): lowers size and can skew age/sex ratios and gene frequencies.
- Limitation of resources (food, water, space): sets carrying capacity, alters birth and death rates, and drives competition that changes age/size structure.
- Natural events (storms, droughts, disease outbreaks): can cause sudden mortality or bottlenecks and change population composition.
- Human activity (habitat loss, pollution, hunting, species introductions, conservation): can increase or decrease populations and profoundly alter their demographic and genetic structure.

These factors often act together (e.g., a drought plus habitat loss) to determine population dynamics.