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Exam questions · Biology · Cycles in Ecosystems

The Water Cycle

  • 7 exam questions
  • 20 marks
  • 8 quick checks
  1. 1 Name [3 marks]

    Figure 1 shows the water cycle. Name the processes shown at A, B and C.

    The water cycle with three processes marked A, B and C.
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    Model answer

    A is evaporation. B is condensation. C is precipitation.

    Mark scheme

    • A: evaporation — 1 mark
    • B: condensation — 1 mark
    • C: precipitation — 1 mark
  2. 2 State [2 marks]

    State two ways in which water vapour gets into the air.

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    Model answer

    Evaporation (from the sea, lakes and soil) and transpiration (from plants).

    Mark scheme

    • Evaporation — 1 mark
    • Transpiration — 1 mark
  3. 3 Describe [3 marks]

    Describe how clouds form.

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    Model answer

    The Sun heats water, which evaporates and rises as water vapour. The air higher up is colder, so the vapour cools. It condenses into tiny droplets of liquid water, which form clouds.

    Mark scheme

    • Water evaporates and rises as vapour — 1 mark
    • The vapour cools — 1 mark
    • It condenses into droplets that form clouds — 1 mark
  4. 4 Explain [3 marks]

    Explain why the rain that falls on land is fresh water even though most of the water that evaporates comes from the sea.

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    Model answer

    When sea water evaporates, only the water turns into vapour. The salt and other dissolved substances are left behind in the sea. The vapour condenses to make clouds of pure water, so the rain is fresh water.

    Mark scheme

    • Only the water evaporates — 1 mark
    • The salt is left behind — 1 mark
    • The vapour condenses into fresh water — 1 mark
  5. 5 Explain [3 marks]

    Explain why the water cycle is important in maintaining habitats.

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    Model answer

    Rain refills rivers, lakes and ponds, which are the habitats of aquatic organisms. It also keeps the soil moist, which land plants and animals need. Without it, the habitats would dry up.

    Mark scheme

    • Rain refills rivers, lakes and ponds — 1 mark
    • It keeps the soil moist — 1 mark
    • Habitats would dry up without it — 1 mark
  6. 6 Explain [3 marks]

    Explain how the water cycle helps the flow of nutrients in an ecosystem.

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    Model answer

    Water dissolves mineral ions in the soil. The water in the soil carries the mineral ions to the roots of plants, so the plants can take them up. Rain and run-off also carry nutrients from the land into rivers and lakes.

    Mark scheme

    • Water dissolves mineral ions — 1 mark
    • Plants take up the dissolved ions through their roots — 1 mark
    • Run-off carries nutrients into rivers and lakes — 1 mark
  7. 7 Suggest [3 marks]

    A forest is cut down. Suggest how this could change the water cycle in the area.

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    Model answer

    The trees no longer take up water or lose water vapour by transpiration, so less water vapour enters the air and there may be less rain. More rain runs off the surface instead of soaking into the soil, which can cause floods and wash away nutrients.

    Mark scheme

    • Less transpiration, so less water vapour in the air — 1 mark
    • More run-off, less infiltration — 1 mark
    • Nutrients may be washed away / floods — 1 mark

Quick check

  1. 1

    What is the source of energy for the water cycle?

    1. AThe Moon
    2. BThe wind
    3. CThe Sun
    4. DThe soil
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    C: The Sun

    Heat from the Sun makes water evaporate and drives the cycle.

  2. 2

    What is transpiration?

    1. AWater vapour lost from plant leaves
    2. BWater falling as rain
    3. CWater flowing over land
    4. DWater turning to ice
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    A: Water vapour lost from plant leaves

    Transpiration is the loss of water vapour from the leaves of plants.

  3. 3

    What happens in condensation?

    1. AWater turns into vapour
    2. BRain falls
    3. CWater soaks into the soil
    4. DWater vapour turns into droplets
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    D: Water vapour turns into droplets

    Water vapour cools and turns into liquid water droplets.

  4. 4

    Which of these is precipitation?

    1. AWater vapour
    2. BSnow
    3. CGroundwater
    4. DFog on the sea
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    B: Snow

    Rain, snow, sleet and hail are all precipitation.

  5. 5

    What is run-off?

    1. AWater soaking into soil
    2. BWater rising from the sea
    3. CWater flowing over the land surface
    4. DWater in clouds
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    C: Water flowing over the land surface

    Run-off is water flowing over the surface of the land into rivers and the sea.

  6. 6

    Why is the rain fresh water?

    1. AThe salt is left behind when water evaporates
    2. BThe Sun removes the salt from the clouds
    3. CRain washes the salt out of the air
    4. DPlants take the salt out
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    A: The salt is left behind when water evaporates

    The salt is left behind in the sea when the water evaporates.

  7. 7

    How does the water cycle help plants?

    1. AIt gives them energy
    2. BIt makes sugar
    3. CIt makes carbon dioxide
    4. DIt supplies water to the soil
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    D: It supplies water to the soil

    It supplies water to the soil, which plants take up through their roots.

  8. 8

    Which two processes put water vapour into the air?

    1. ARun-off and infiltration
    2. BEvaporation and transpiration
    3. CCondensation and precipitation
    4. DRun-off and condensation
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    B: Evaporation and transpiration

    Evaporation and transpiration both put water vapour into the air.