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Ecosystems

Threats to biodiversity from local to global scale

  • 3 things to know
  • Component 3 Section B

Overview

Five direct threats to biodiversity, habitat fragmentation and edge effect.

What you need to know

Answer each one before you reveal it.

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Key term

Distinguish direct and indirect threats to biodiversity.

Key term

Name five direct threats to biodiversity.

Key term

Why is habitat loss the greatest single threat?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Distinguish direct and indirect threats to biodiversity.

    Model answer

    A direct threat physically removes or damages organisms and habitat, such as logging or hunting. An indirect threat alters the conditions on which species depend, such as climate change.

  2. 2

    Name five direct threats to biodiversity.

    Model answer

    Habitat clearance, overexploitation, pollution, invasive species and direct persecution are five direct threats. Habitat loss is the largest of them.

  3. 3

    Why is habitat loss the greatest single threat?

    Model answer

    Clearance for farming, settlement and infrastructure removes the space species need to live. Around three-quarters of the ice-free land surface has been significantly altered by people.

  4. 4

    What is habitat fragmentation, and why does it matter?

    Model answer

    Fragmentation breaks a continuous habitat into small, isolated patches. Small populations lose genetic diversity, and species cannot migrate between the fragments.

  5. 5

    What is the edge effect?

    Model answer

    The edge effect is the change in conditions at the boundary of a habitat fragment. Higher light, wind and temperature at the edge favour different species from the interior.

  6. 6

    Give an example of overexploitation.

    Model answer

    Atlantic cod stocks off Newfoundland collapsed in 1992 after decades of industrial trawling. A moratorium was imposed and the stock has still not fully recovered.

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