Question

Differentiate between density-dependent and density-independent limiting factors and give at least two examples from the lesson of each.

Answer 1

Density-dependent limiting factors are those whose impact on a population changes with population density (they get stronger as density increases). They tend to regulate population size around the carrying capacity (K). Examples and why they fit:
- Competition for food, space, or mates — as population density rises, individuals compete more, reducing birth rates and/or increasing death rates.
- Predation — predators can remove proportionally more prey when prey are abundant; predator-prey interactions often intensify at higher prey densities.
- Disease and parasitism — pathogens spread more easily when hosts are close together, causing higher mortality or lower reproduction at high density.

Density-independent limiting factors affect population size regardless of how dense the population is; their effects are usually caused by abiotic events. Examples and why they fit:
- Weather extremes (drought, severe freeze) — a drought can kill individuals or reduce reproduction whether the population is small or large.
- Natural disasters (wildfire, flood, hurricane) — these can rapidly reduce populations without regard to density.
- Human-caused habitat destruction or pollution events — a toxic spill or clear-cut can reduce numbers independently of how many organisms were present.

If you want, I can match examples specifically to the items in your lesson if you tell me which examples were covered.