Question

Give an example of how density-dependent and density-independent factors might interact.

Short answer

In a forest population of rabbits, density-dependent food availability could limit population growth. Meanwhile, a density-independent factor like an extreme cold winter could also affect the population by killing some rabbits irregardless of the population density.

Step-by-step solution

Define Density Dependent Factors

Density dependent factors are factors whose effects on the size or growth of the population vary with the density of the population itself. Common examples include competition and predation which can be more intense in densely populated areas.

Define Density Independent Factors

Density independent factors are factors that affect the population size or growth rate regardless of the population density. These are typically abiotic environmental factors such as natural disasters or weather conditions.

Interaction Scenario

Now, consider a scenario in which a population of rabbits in a forest are impacted by both types of factors. On one hand, the availability of food (a density-dependent factor) limits the population growth—more rabbits mean less food per rabbit, thus slowing down population increase. On the other hand, an exceptionally cold winter (a density-independent factor) could also reduce the rabbit population by causing some to die from exposure.