5 2 Limits to Growth Learning Objectives Identify

5. 2 Limits to Growth

Learning Objectives § Identify factors affecting carrying capacity. § Identify limiting factors that depend on population density. § Identify limiting factors that do not depend on population density. § Explain the relationship between limiting factors and population extinction. Vocabulary § limiting factor-any factor that controls growth of a population, determine the carrying capacity. § density-dependent limiting factors-limiting factors that act strongly when population density get too high such as competition, stress, parasitism, predation & herbivory.

Vocabulary § density-independent limiting factor-factors that affect population regardless of density. Extreme weather events.

Limiting Factors • Limiting factors determine the carrying capacity of an environment for a species. • There are two types of limiting factors: density-dependent and density-independent.

Density-Dependent Factors • Density-dependent limiting factors operate strongly when population density reaches a certain level. • Densitydependent limiting factors include: competition, parasitism and disease, stress from overcrowding, predation, and herbivory.

Competition • More individuals use up resources sooner. • Individuals may compete for food, water, space, sunlight, shelter, mates, territories.

Parasitism and Disease • Parasites and diseases can spread quickly through dense host populations. • Stress from overcrowding can lead to lower birth rates, higher death rates, and higher emigration rates.

Predator–Prey Relationships

Herbivore Effects Populations of herbivores and plants cycle up and down like populations of predators and prey.

Density-Independent Factors • Density-independent limiting factors affect all populations regardless of population size and density. • Density-independent limiting factors include natural disasters and usual weather.

Density-Independent Factors • Examples: hurricanes, droughts, floods, wildfires • Density-independent factors may actually vary with population density.

Limiting Factors and Extinction If carrying capacity falls low enough, populations can be wiped out, leading to species extinction.