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Human Impact on the Environment

Endangered species and extinction

  • 3 things to know
  • Component 1

Overview

Endangered species, five human activities that put species at risk of extinction and species endangered by overexploitation.

What you need to know

Answer each one before you reveal it.

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Key term

Give three reasons for wanting to prevent species from becoming extinct.

Evaluation

State the case for accepting that some extinction is inevitable, and the argument against it.

Key term

What is meant by extinction?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is an endangered species?

    Model answer

    One whose numbers or range have fallen so far that it is likely to become extinct in the near future unless the causes of its decline are removed.

  2. 2

    What is meant by extinction?

    Model answer

    The permanent loss of a species, which happens when its last surviving individual dies.

  3. 3

    Name five human activities that put species at risk of extinction.

    Model answer

    Destruction of habitat, overexploitation by hunting or collecting, pollution, the introduction of species from elsewhere, and the changing of the climate.

  4. 4

    Why is the destruction of habitat the commonest cause of species becoming endangered?

    Model answer

    Every species depends on its habitat for food, shelter and breeding sites, so clearing it removes all of these at once and leaves the population nowhere to go.

  5. 5

    How does the fragmentation of a habitat endanger a species even where some habitat survives?

    Model answer

    The population is broken into small isolated groups between which individuals cannot move, so each is separately vulnerable to chance events and no group can be replenished from another.

  6. 6

    Why is a very small population at particular genetic risk?

    Model answer

    Alleles are lost by chance, close relatives are forced to breed together, and the reduced variation leaves the population less able to adapt to any further change.

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