OpenRevise

Exam questions · Biology · Selective Breeding and Genetic Engineering

Feeding a Growing Population

  • 6 exam questions
  • 20 marks
  • 9 quick checks
  1. 1 State [2 marks]

    State two minerals that plants need and one function of each.

    Show answerHide answer

    Model answer

    Nitrate is needed to make proteins, and phosphate is needed to make DNA or for root growth. Potassium is needed for enzymes.

    Mark scheme

    • A mineral — 1 mark
    • A correct function — 1 mark
  2. 2 Define [2 marks]

    Define the term biological control, and give one example.

    Show answerHide answer

    Model answer

    Biological control is using a living organism to control a pest. An example is the use of ladybirds to eat aphids.

    Mark scheme

    • Using a living organism to control a pest — 1 mark
    • An example — 1 mark
  3. 3 Calculate [3 marks]

    A farmer adds 100 kg of fertiliser to a field. The yield of potatoes increases from 20 tonnes to 32 tonnes. Calculate the percentage increase in yield.

    Show answerHide answer

    Model answer

    The increase is 12 tonnes. The percentage increase is 12 ÷ 20 × 100 = 60%.

    Mark scheme

    • Increase of 12 — 1 mark
    • Divides by 20, times 100 — 1 mark
    • 60% — 1 mark
  4. 4 Explain [4 marks]

    Explain how fertiliser running off a field can lead to the death of fish in a nearby river.

    Show answerHide answer

    Model answer

    The nitrates and phosphates in the fertiliser cause algae in the water to grow rapidly. The algae block out the light, so the plants under them die. Bacteria then break down the dead material and use up the oxygen in the water, so fish die from a lack of oxygen.

    Mark scheme

    • Nitrates / phosphates cause algal growth — 1 mark
    • Light blocked, plants die — 1 mark
    • Bacteria decompose them and use up oxygen — 1 mark
    • Fish die from lack of oxygen — 1 mark
  5. 5 Describe [3 marks]

    The graph shows that the yield of wheat levels off at high levels of fertiliser. Describe the pattern and suggest why a farmer might not apply more than 200 kg per hectare.

    Show answerHide answer

    Model answer

    The yield increases quickly at first, and then levels off, with very little extra above about 200 kg per hectare. Adding more fertiliser would be a waste of money, and could cause pollution, because the yield does not increase.

    Mark scheme

    • Rises then levels off — 1 mark
    • Little extra yield above 200 kg — 1 mark
    • Waste of money / pollution — 1 mark
  6. 6 Evaluate [6 marks]

    A farmer wants to protect a crop from aphids. Evaluate the use of ladybirds (biological control) compared with the use of a chemical pesticide.

    Show answerHide answer

    Model answer

    Ladybirds feed on aphids but do not harm the crop, they do not leave chemicals in the food or water, and they will breed and may keep the pest down over a long time. A pesticide acts quickly and kills most of the aphids, but it may kill useful insects such as bees, can pollute the environment, and the aphids can evolve resistance. However, ladybirds work slowly and will not remove all of the aphids, and they may fly away. Overall, biological control is better for the environment and over the long term, but the farmer may need to use both, with the pesticide only when it is really necessary.

    Mark scheme

    • Ladybirds: no chemicals, specific — 1 mark
    • Ladybirds: may breed and last — 1 mark
    • Pesticide: fast and effective — 1 mark
    • Pesticide: harms other insects, pollutes, resistance — 1 mark
    • Ladybirds slow, not complete — 1 mark
    • A reasoned conclusion — 1 mark

Quick check

  1. 1

    What do plants use nitrates for?

    1. ATo make sugars
    2. BTo make proteins
    3. CTo make oxygen
    4. DTo make cell walls
    Show answerHide answer

    B: To make proteins

    Nitrates are used to make proteins and chlorophyll.

  2. 2

    What is eutrophication?

    1. APlant growth in the soil
    2. BThe growth of ladybirds
    3. CAlgal growth caused by excess nutrients
    4. DA kind of pollution from smoke
    Show answerHide answer

    C: Algal growth caused by excess nutrients

    Too many nutrients cause algae to grow rapidly, which leads to a lack of oxygen and the death of aquatic life.

  3. 3

    Which is a disadvantage of fertilisers?

    1. AThey can run off and cause eutrophication
    2. BThey reduce yield
    3. CThey are free
    4. DThey have no nutrients
    Show answerHide answer

    A: They can run off and cause eutrophication

    Run-off causes eutrophication in rivers and lakes.

  4. 4

    Which is an example of biological control?

    1. ASpraying with insecticide
    2. BAdding fertiliser
    3. CPloughing a field
    4. DReleasing ladybirds to eat aphids
    Show answerHide answer

    D: Releasing ladybirds to eat aphids

    Ladybirds are predators of aphids.

  5. 5

    Which is an advantage of biological control?

    1. AIt works very quickly
    2. BIt does not leave chemical residues
    3. CIt removes all of the pest
    4. DIt needs no planning
    Show answerHide answer

    B: It does not leave chemical residues

    It does not leave chemicals in the food or the environment.

  6. 6

    What happened with cane toads in Australia?

    1. AThey controlled the beetles well
    2. BThey died out
    3. CThey became an invasive species
    4. DThey were eaten by the beetles
    Show answerHide answer

    C: They became an invasive species

    They did not control the cane beetles, and became an invasive pest.

  7. 7

    What does NPK stand for?

    1. ANitrogen, phosphorus, potassium
    2. BNitrate, protein, kelp
    3. CNutrients, pests, killers
    4. DNitrogen, potassium, protein
    Show answerHide answer

    A: Nitrogen, phosphorus, potassium

    NPK is nitrogen, phosphorus and potassium.

  8. 8

    A yield rises from 4 to 6 tonnes after adding fertiliser. What is the percentage increase?

    1. A2%
    2. B20%
    3. C33%
    4. D50%
    Show answerHide answer

    D: 50%

    The increase is 2, and \(2 \div 4 \times 100 = 50\%\).

  9. 9

    Why does the yield stop rising at high fertiliser levels?

    1. AFertiliser becomes harmful immediately
    2. BAnother factor becomes limiting
    3. CPlants do not need minerals
    4. DThe soil is full of water
    Show answerHide answer

    B: Another factor becomes limiting

    Other factors, such as water or light, become limiting, so extra fertiliser has no further effect.