Download - pre-AP Bio 5.2
Limits to Growth
Learning Objectives Identify factors that determine carrying capacity. Identify the limiting factors that depend on population
density. Identify the limiting factors that do not depend on
population density.
Limiting Factors
Limiting factors determine the carrying capacity of an environment for a species.
Density dependent Density independent
Density-Dependent Factors
Density-dependent limiting factors operate strongly when population density reaches a certain level.
Competition
• More individuals use up resources sooner.
• Individuals may compete for food, water, space, sunlight, shelter, mates, territories.
Predator–Prey Relationships
Herbivore Effects
Populations of herbivores and plants cycle up and down like populations of predators and prey.
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.
Density-Independent Factors
Density-independent limiting factors affect all populations regardless of population size and density.
Density-Independent Factors
• Examples: hurricanes, droughts, floods, wildfires
• Density-independent factors may actually vary with population density.
Canyon Lake, TX
Controlling Invasive Species
Density-independent measures?• Herbicides, mechanical removal
Density-dependent measures? • Predation
Expensive, temporary
Another invasive species?
Salvinia
Overview: Limits to Growth
Density dependent
Density independent
Flood waters cover a field of wildflowers.
Non-native snakes released into a wetland prey on native rodents.
Flu virus spreads quickly in schools.
Wildfires spread through a grassland.