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Plants for food and fibre

Ten questions of mixed difficulty, covering Plants for food and fibre. Print it, or work through it on screen — the answer key starts on its own page.

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Plants for food and fibre

Science 7 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. A strawberry plant sends out runners, stems that creep along the ground and take root to form new plants. Compared with the parent, the new plants have

    1. a) different genes, because each one roots in different soil
    2. b) the same genes, because the runner carries pollen to them
    3. c) a mix of genes from two parents, since strawberries flower
    4. d) the same genes, because this is asexual reproduction

  2. A wheat breeder has one variety that ripens early and another that resists a disease. She wants a wheat that does both. Using selective breeding, what should she do?

    1. a) Plant the early variety beside the resistant one so it picks up the resistance
    2. b) Expose the early variety to the disease each year until it becomes resistant
    3. c) Grow only the resistant variety, since resisting disease matters most
    4. d) Cross the two varieties, then keep breeding the offspring that show both traits

  3. A greenhouse grows lettuce with its roots hanging in water instead of soil. For this hydroponic system to work, the growers must add

    1. a) carbon dioxide to the water, for the roots to make food
    2. b) nutrients such as nitrogen and potassium, dissolved in the water
    3. c) sugar to the water, since the roots cannot reach any soil
    4. d) sand to the water, so the roots have something to grip

  4. Many First Nations and Métis families dried saskatoon berries to store and eat through the winter. Why does drying keep food from spoiling?

    1. a) Dried berries are too hard for insects to bite into
    2. b) Heat from the sun kills every germ, so none can return
    3. c) The moulds and bacteria that spoil food need water to grow
    4. d) Drying adds vitamins that stop the berries from rotting

  5. Lodgepole pine is named for its use as poles for lodges, or tipis. Which property of its trunk best suits it to that job?

    1. a) It is very heavy and hard to move
    2. b) It rots quickly once it is cut
    3. c) It bends easily into round hoops
    4. d) It grows tall, straight and slim

  6. A student ties clear plastic bags around the leafy stems of two identical plants, one in the sun and one in the shade. After two hours, the bag in the sun holds more water droplets. Which best explains this?

    1. a) Warm air outside the bag condenses and seeps in through it
    2. b) Sunlight breaks down the plant's sugar into water droplets
    3. c) Leaves give off water vapour faster in warm, sunny conditions
    4. d) Only the plant in the sun is taking up any water at all

  7. Students pour 100 mL of water through equal amounts of three soils and measure what drains out in 5 minutes: soil X, 85 mL; soil Y, 50 mL; soil Z, 20 mL. Which soil held the most water, and how much?

    1. a) Soil Y, 50 mL
    2. b) Soil X, 85 mL
    3. c) Soil Z, 20 mL
    4. d) Soil Z, 80 mL

  8. A soil test shows a field has plenty of nitrogen but very little phosphorus. Last year the farmer added extra nitrogen, and the crop still grew poorly. Which change is most likely to help this year?

    1. a) Watering the field twice as often
    2. b) Adding twice as much nitrogen as last year
    3. c) Adding a fertilizer high in potassium
    4. d) Adding a fertilizer high in phosphorus

  9. A bag of fertilizer is labelled 5-10-15. Which nutrient does it contain the most of?

    1. a) Phosphorus
    2. b) Potassium
    3. c) Nitrogen
    4. d) Calcium

  10. A student sorts the fibres in her clothes by where they come from. Which of these fibres comes from a plant?

    1. a) Wool
    2. b) Polyester
    3. c) Silk
    4. d) Cotton

Answer key · Plants for food and fibre

Science 7 · maddyhelps.com

  1. d) the same genes, because this is asexual reproduction — A runner is part of the parent plant, so each new plant is a clone with exactly the parent's genes: vegetative, or asexual, reproduction. Strawberries also make seeds from their flowers, and it is those seeds, after pollination, that mix genes from two parents.
  2. d) Cross the two varieties, then keep breeding the offspring that show both traits — Selective breeding works with the genes plants already have: cross the parents that carry each trait, then keep choosing the offspring that inherited both, over many generations. Exposing plants to a disease does not build resistance into their seeds, because changes during a plant's life are not inherited. Canadian scientists bred canola from rapeseed by this kind of careful selection.
  3. b) nutrients such as nitrogen and potassium, dissolved in the water — Soil is where roots normally find minerals, so without soil those nutrients must be dissolved in the water. The leaves still make their own sugar by photosynthesis, using carbon dioxide from the air, so sugar and carbon dioxide in the water are not what the plant is missing.
  4. c) The moulds and bacteria that spoil food need water to grow — Moulds and bacteria need water, so taking it out slows them almost to a stop, and dried food keeps for months. Drying does not sterilize food or add anything to it: germs still land on it, but without water they cannot grow.
  5. d) It grows tall, straight and slim — Tipi poles must be long, straight and light enough to carry and raise, which describes a young lodgepole pine. A wood that bends easily is good for hoops and baskets, but a pole that bent would not hold up the covering.
  6. c) Leaves give off water vapour faster in warm, sunny conditions — Transpiration is the loss of water vapour through tiny openings in the leaves, and warmth and light speed it up. The bag traps the vapour, which condenses into droplets; the shaded plant is losing water too, just more slowly.
  7. d) Soil Z, 80 mL — The water that did not drain out stayed in the soil, so soil Z held 100 − 20 = 80 mL, the most of the three. Choosing soil X mixes up the water that passed through with the water that was held; soil X is behaving like sand, and soil Z like clay or humus.
  8. d) Adding a fertilizer high in phosphorus — The nutrient in shortest supply holds back a plant's growth, so no amount of extra nitrogen can make up for missing phosphorus. Potassium is the other trap: its symbol is K, and phosphorus is the P in N-P-K.
  9. b) Potassium — The three numbers always stand for nitrogen, phosphorus and potassium (N-P-K), in that order, so the largest number, 15, is potassium. Choosing nitrogen because it comes first on every label is the usual slip.
  10. d) Cotton — Cotton grows as fluffy fibres around the seeds of the cotton plant. Wool and silk are natural too, but they come from animals, sheep and silkworms, so natural does not always mean plant; polyester is made from oil.