2.1 Individuals, populations, communities and ecosystemsIB Environmental Systems and Societies SL: Flashcards
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Define population.
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- Define population.
- A group of organisms of the same species living in the same area at the same time and capable of interbreeding.
- What is the difference between habitat and niche?
- Habitat is the location where an organism lives; niche is the set of abiotic and biotic conditions and resources it depends on.
- Name six abiotic factors that affect species distribution.
- Temperature, sunlight, pH, salinity, dissolved oxygen and soil texture.
- List six ways populations interact.
- Herbivory, predation, parasitism, mutualism, disease and competition.
- Define carrying capacity.
- The maximum population size that can be supported, determined by competition for limited resources.
- What kind of factor regulates population size, and what kind of feedback?
- Density-dependent factors, acting through negative feedback.
- What are the two patterns of population growth?
- Exponential growth, or growth limited by carrying capacity (levelling off).
- Why is human carrying capacity hard to assess?
- Technology, consumption and trade change the resources available, and limiting factors have increasingly been removed.
- Which sampling method suits non-mobile organisms?
- Random quadrat sampling.
- Write the Lincoln index.
- N = (n₁ × n₂) ÷ m₂, where n₁ is the number marked, n₂ the second sample and m₂ the marked recaptures.
- Why are ecosystems called open systems?
- Both energy and matter can enter and exit.
- What is a keystone species? Give an example.
- A species with a much larger effect on its ecosystem than its abundance suggests, e.g. sea otters controlling urchins in kelp forests.
- What does the planetary boundaries model say about the biosphere?
- Biosphere integrity has passed a critical threshold, so its loss must be reversed to avoid tipping points.
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).