L5: Population Growth

E. Goodman

Exponential growth

Growth pattern where the birth rate is higher than the death rate.

Logistic growth

A growth pattern where populations of organisms reach a plateau.

Carrying Capacity

The y-axis limitation in logistic growth.

Population

A group of organisms living in the same habitat that belong to the same species.

Population Growth

Number of organisms in a population can go up, down, or stay constant over time

Factors that cause a population to increase/decrease.

Food availability, Predators, Parasites, Catastrophic events, Competition from other species, Migration/Movement, Habitat depletion, Human interference.

Limiting Factors

Anything that puts a limit on population growth. All living things have necessities, availability matters when it comes to population growth.
2 Factors: Density Independent and Density Dependent

Density independent factors

Limitations to population growth that are not reliant on the population. Overall impacts how successful a population can be, thus influencing the growth.

Examples of Density Independent Factors

Natural disasters, Temperature, Sunlight, Physical Characteristics, Human activities, Behaviors

Density dependent factors

Factors that only affect a population when it reaches a certain density.

Examples of Density Dependent Factors

Competition, Predation, Disease, Parasitism, Space availability

Abiotic Factors

Non-living factors that influence an ecosystem.

Biotic Factors

Living things that influence an ecosystem.

Direct competition

Individuals fight for a specific resource.

Indirect competition

Deer eat all the grass, leaving none for rabbits.

Pathogen

Factors that cause disease

Natural disasters

• can be devastating to life

Temperature

• influences the activity and growth of organisms, determines which type of organisms can live in an ecosystem

Sunlight

• can only penetrate to a depth of 30 meters in water, in forest ecosystems the amount of sunlight decreases from the canopy to the forest floor

Physical characteristics

• can affect their population, adaptation and evolution increase their chance of survival

Human activities

Can lead to density dependency

Behaviors

• some organisms might migrate to find new food sources or mate, some organisms create societies or feeding territories

Competition

• can occur between many organism that live in the same habitat, resources are limited in a habitat so organism must compete

Predation

• occurs when the population density of predators is high, prey will decrease while predators will increase
  Lack of predation will cause problems for the prey’s population

Disease

• increases with the density of that population, higher densities make it easier for parasites to find hosts and spread diseases

Space Availability

the amount of space available for an organism to live, organisms require a certain amount of space in order to survive, overcrowding can cause a depletion of resources, disease and stress