Chapter 5.2 Limits to Growth

Limiting Factors Limiting Factor – a factor that causes population growth to decrease. Limiting factors can be food, a nutrient, or anything that would cause the population to decrease.

Density-dependent Factors This is a limiting factor that depends on population size. Population density is the number of organisms per unit area. These factors mostly affect a population when a population is large and dense. These factors include: competition, predation, parasitism, and disease.

Competition When there are many organisms in one area they have to compete for food, water, space, sunlight, and other essentials. Competition among a population is dependent on the size of the population. If the population is large there is more competition than if it is not large. There can also be competition between different species.

Predation Predator-prey relationship – this maintains population control. For example sea otters eat sea urchin and are eaten by killer whales. How many sea otters there are affects both of the other species based on predator- prey relationships. The rise and fall of both the predator and the prey coincides with one another.

Parasitism and disease Parasites can limit the growth of a population.

Density-independent Factors Density-independent limiting factors affect a population regardless of the size of the population. These are things like: weather, natural disasters, seasonal cycles, and human activities. Usually these cause a crash in population size. Most populations can recover but some are permanently damaged.