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Ecosystems and Material Cycles

Human impact on ecosystems and biodiversity

  • 3 things to know
  • Paper 2

Overview

Biodiversity, the harm and benefits of fish farming, non-indigenous species and their effects on native wildlife, eutrophication from fertiliser and sewage, why biodiversity keeps ecosystems stable, conserving endangered species through captive breeding and protected habitats, reforestation, and the economic value of biodiversity.

What you need to know

Answer each one before you reveal it.

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Process

Describe the sequence of events in eutrophication after fertiliser runs off a field into a lake.

Key term

What is biodiversity?

Key term

Describe two ways in which fish farming can damage the surrounding ecosystem.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is biodiversity?

    Model answer

    Biodiversity is the variety of different species living in an area or on Earth as a whole.

  2. 2

    Describe two ways in which fish farming can damage the surrounding ecosystem.

    Model answer

    Uneaten food and fish waste enrich the water and cause algal growth, and parasites and diseases spread from the cages to wild fish.

  3. 3

    Give one way in which fish farming can benefit biodiversity.

    Model answer

    It reduces the need to catch wild fish, allowing overfished wild populations to recover.

  4. 4

    What is a non-indigenous species?

    Model answer

    A non-indigenous species is one that has been brought into an area where it does not naturally live.

  5. 5

    Explain how an introduced species can reduce the numbers of a native species.

    Model answer

    It competes with the native species for the same food and space, or preys on it, so native numbers fall.

  6. 6

    Give one way, other than competition or predation, in which an introduced species can harm native wildlife.

    Model answer

    It can bring in a new disease that the native species have no resistance to.

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Key Concepts in Biology
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Natural Selection and Genetic Modification

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ANitrates cause an algal bloom that blocks the light.
BWater plants die and decay.
CThe decomposers use up the dissolved oxygen.

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A millimetre is 10⁻³ of a metre.
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