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Populations, communities and ecosystems: core concepts

Key ideas • Key ideas

Key concepts

What you'll likely be quizzed about

  • A population includes all individuals of one species in a designated area, which may vary in size.
  • A community consists of two or more populations of different species that coexist and interact in the same space.
  • An ecosystem encompasses both the biological community and the abiotic environment, where biotic and abiotic factors shape the ecosystem's structure.
  • Factors such as food availability, space, predation, disease, temperature, and water influence population size and distribution.
  • Fluctuations in these variables prompt shifts within populations and can affect the broader community and ecosystem.

Flashcards

Test your knowledge with interactive flashcards

Name three limiting factors that affect population size.

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Food availability, predation or disease, and abiotic conditions like temperature or water.

Key notes

Important points to keep in mind

Population: same species in a defined area; community: multiple populations together.

Ecosystems include biotic and abiotic components that interact to determine stability.

Producers form the base of most food webs; energy transfer between trophic levels is inefficient.

Adaptations improve survival or reproduction and can be structural, behavioral, or physiological.

Competition (intra- and interspecific) limits population growth and influences selection.

Quadrats and transects estimate abundance; replication reduces sampling error.

Carbon cycles through essential processes; decomposers play a key role.

Human actions impact carbon levels, disrupting ecosystem balance.

High biodiversity enhances ecosystem stability and reduces reliance on individual species.

Extremophiles show specialized adaptations to survive in extreme environments.

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