Population Ecology Concepts

Study Notes

Population Ecology

Populations are groups of individuals of the same species in a given area.
Population size is affected by birth rates, death rates, immigration, and emigration.
Factors influencing population growth include biotic potential (the maximum rate at which a population could increase under ideal conditions) and environmental resistance (all factors that limit population growth).
Exponential growth occurs when a population increases by a fixed percentage each year, resulting in a J-shaped curve.
Logistic growth occurs when a population's growth rate slows as it approaches its carrying capacity, resulting in an S-shaped curve.
Carrying capacity is the maximum population size that a particular environment can sustainably support.
Density-dependent factors affect a population's size in proportion to the population's density, including competition for resources, predation, and disease.
Density-independent factors affect a population's size regardless of the population's density, including natural disasters (e.g., floods, hurricanes).
Age structure diagrams (population pyramids) show the relative numbers of individuals at different ages in a population, helping predict future population trends.

Community Ecology

A community is all the interacting populations in a given area.
Interspecies competition occurs when resources are limited and two or more species compete for the same resources.
Predation is an interaction where one species (predator) hunts and kills another species (prey).
Symbiosis is a close ecological relationship where two or more species live together.
Mutualism (+/+) is where both species benefit.
Commensalism (+/0) is where one species benefits and the other is unaffected.
Parasitism (+/-) is where one species benefits and the other is harmed.
Ecological succession is the gradual process of change and replacement of species in a community over time.
Primary succession begins in lifeless areas and proceeds slowly as soil forms.
Secondary succession occurs in areas previously inhabited by living organisms.
Keystone species are species that have a disproportionately large effect on their environment relative to their abundance. Their removal can have significant community-wide effects.
Disturbances are events that impact communities (e.g., fires, floods, clear-cutting).

Ecosystems

An ecosystem includes all the organisms in a given area along with the non-living (abiotic) factors such as water, sunlight, temperature, and minerals.
Energy flow describes the movement of energy through an ecosystem.
Producers (autotrophs) are at the base of the food web, capturing energy (usually from sunlight) and converting it into chemical energy (food).
Consumers (heterotrophs) obtain energy by consuming other organisms; herbivores eat producers, carnivores eat other consumers, and omnivores eat both.
Decomposers and detritivores break down dead organisms and return nutrients to the ecosystem.
Trophic levels represent different feeding positions in an ecosystem.
Food webs illustrate the complex feeding relationships between organisms in an ecosystem.
Biogeochemical cycles involve the movement of nutrients through the biotic and abiotic parts of an ecosystem (e.g., water cycle, carbon cycle, nitrogen cycle).
Biomes are large geographic areas with similar climates and dominant plant life. Tropical rainforests, deserts, and grasslands are examples.
Conservation efforts aim to protect biodiversity and maintain ecosystem services that benefit humans.

Biosphere

The biosphere encompasses all life on Earth and the environments where they live.
Global ecology examines the interactions between organisms across large geographic scales.
Global climate patterns and human activities impact biodiversity.
Biodiversity is the variety of life at all levels, from genes to ecosystems.

Description

Test your knowledge on the principles of population ecology, including factors that influence population growth and the differences between exponential and logistic growth. Explore concepts such as carrying capacity and density-dependent and independent factors affecting populations.