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Exam questions · Biology · Plant Hormones

Gibberellins and Ethene (Higher tier)

  • 6 exam questions
  • 18 marks
  • 9 quick checks
  1. 1 State [1 mark]

    State the plant hormone that is important in initiating seed germination.

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    Model answer

    Gibberellin.

    Mark scheme

    • Gibberellin — 1 mark
  2. 2 State [2 marks]

    State two effects of ethene on a plant.

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    Model answer

    It controls cell division, and it controls the ripening of fruits.

    Mark scheme

    • Controls cell division — 1 mark
    • Controls ripening of fruit — 1 mark
  3. 3 Explain [3 marks]

    A farmer puts a bag of ripe bananas next to some green mangoes. The mangoes ripen faster than mangoes in another room. Explain why.

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    Model answer

    The ripe bananas produce ethene, which is a gas. The ethene spreads through the air to the mangoes. Ethene controls the ripening of fruits, so it makes the mangoes ripen faster.

    Mark scheme

    • Bananas make ethene — 1 mark
    • It is a gas that spreads to the mangoes — 1 mark
    • Ethene makes fruit ripen — 1 mark
  4. 4 Calculate [3 marks]

    In an experiment, 60 of 200 seeds in water, and 150 of 200 seeds in gibberellin solution, germinated. Calculate the percentage of each group that germinated.

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    Model answer

    Water: 60 ÷ 200 × 100 = 30%. Gibberellin: 150 ÷ 200 × 100 = 75%.

    Mark scheme

    • 30% — 1 mark
    • 75% — 1 mark
    • Correct method — 1 mark
  5. 5 Explain [3 marks]

    Explain why a control is needed in an experiment on the effect of gibberellin on seeds.

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    Model answer

    The control, in which seeds are given water only, shows how many seeds would germinate without gibberellin. If more seeds germinate with the gibberellin than in the control, the difference is likely to be caused by the gibberellin.

    Mark scheme

    • Control has no gibberellin — 1 mark
    • Shows germination without the hormone — 1 mark
    • Any difference is due to the gibberellin — 1 mark
  6. 6 Evaluate [6 marks]

    A store manager wants to keep a large amount of apples fresh for six months. Use your knowledge of ethene to suggest how this could be done, and explain how it works.

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    Model answer

    Ripe fruit makes ethene, which controls the ripening of fruits and makes other fruits ripen. If the ethene builds up in the store, all the apples will ripen quickly and then go bad. The manager should remove the ethene from the air, for example by using good ventilation or a chemical that absorbs it. Ripening is also slower in cold conditions, so the apples should be kept cool. Any apples that are overripe or damaged should be removed, because they make more ethene and will make the rest of the apples ripen faster. The apples should be picked before they are fully ripe, so they last longer.

    Mark scheme

    • Ripe fruit makes ethene — 1 mark
    • Ethene makes other fruit ripen — 1 mark
    • Remove the ethene from the store — 1 mark
    • Keep the apples cool — 1 mark
    • Remove damaged or overripe apples — 1 mark
    • Pick before fully ripe — 1 mark

Quick check

  1. 1

    Which hormone is important in initiating seed germination?

    1. AEthene
    2. BGibberellin
    3. CAuxin
    4. DInsulin
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    B: Gibberellin

    Gibberellin.

  2. 2

    Which hormone controls the ripening of fruits?

    1. AEthene
    2. BGibberellin
    3. CAuxin
    4. DAdrenalin
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    A: Ethene

    Ethene.

  3. 3

    What state is ethene at room temperature?

    1. ASolid
    2. BLiquid
    3. CGas
    4. DPlasma
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    C: Gas

    It is a gas.

  4. 4

    What does ethene also control, apart from ripening?

    1. APhotosynthesis
    2. BRespiration
    3. CTranspiration
    4. DCell division
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    D: Cell division

    Cell division.

  5. 5

    What is seed dormancy?

    1. ADeath of the seed
    2. BA resting state
    3. CFast growth
    4. DSeed dispersal
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    B: A resting state

    A resting state in which the seed does not germinate.

  6. 6

    40 of 50 seeds germinated with a hormone. What percentage is this?

    1. A80%
    2. B40%
    3. C50%
    4. D20%
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    A: 80%

    \(40 \div 50 \times 100 = 80\%\).

  7. 7

    Why can a ripe fruit make other fruits ripen?

    1. AIt gives them water
    2. BIt gives them light
    3. CIt gives off ethene gas
    4. DIt touches them
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    C: It gives off ethene gas

    It makes ethene gas, which spreads to the other fruits.

  8. 8

    Do students need to know the mechanism of how gibberellins work?

    1. AYes, in detail
    2. BYes, for ethene only
    3. CYes, for both
    4. DNo
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    D: No

    No, the specification says that the mechanisms are not required.

  9. 9

    Fruit in a sealed bag with ethene ripened in 3 days, and fruit in a sealed bag without it took 9 days. What does this show?

    1. AEthene slows ripening
    2. BEthene speeds up ripening
    3. CBags make fruit ripen
    4. DEthene has no effect
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    B: Ethene speeds up ripening

    Ethene speeds up ripening, because the bag without ethene is the control.