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Cambridge IGCSE Biology practice

Paper 4 structured question: Pollution

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Pollution

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Paper 4Theory (Extended)2 marks

A pond receives runoff containing high levels of nitrates from nearby farmland.

Description

Effects of Nitrate Runoff

The nitrate increase causes a chain of events in the pond ecosystem, including increased producer growth, decomposition, oxygen reduction, and death of aquatic animals.

  1. a

    Identify two consequences of increased nitrate availability in the pond.

    Aim for approximately 2 distinct marking points.

    [2]

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Paper 4 structured question: Pollution

Paper 4Theory (Extended)4 marks

Description

Eutrophication Process

Nitrate levels increase in a lake due to fertilizer runoff. This causes algae to grow rapidly. When the algae die, decomposers break down the dead algae using oxygen, reducing oxygen levels in the water. Fish in the lake begin to die due to lack of oxygen.

  1. a

    Explain how increased nitrate availability leads to the death of oxygen-dependent organisms in the lake.

    Aim for approximately 4 distinct marking points.

    [4]