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Mixed review · Ecosystems and plants

Ten questions of mixed difficulty, covering Interactions and ecosystems, 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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Mixed review · Ecosystems and plants

Science 7 · maddyhelps.com

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

  1. Before a large project such as a new mine is approved, the company usually has to prepare an environmental impact assessment. Its main purpose is to

    1. a) prove that the project will cause no harm to the environment at all
    2. b) work out how much money the project will earn over its lifetime
    3. c) predict the project's effects on land, water and wildlife, and how to reduce them
    4. d) choose the workers and machines that will be needed to build it

  2. In a pond, water fleas eat algae, small fish eat water fleas, and herons eat small fish. Which of these is the producer?

    1. a) The water fleas
    2. b) The small fish
    3. c) The herons
    4. d) The algae

  3. Mushrooms and other fungi growing on a fallen log slowly break it down and return its nutrients to the soil. They are acting as

    1. a) producers
    2. b) scavengers
    3. c) herbivores
    4. d) decomposers

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

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

  5. In a boreal forest, snowshoe hares eat willow shrubs, and lynx eat snowshoe hares. If a disease kills most of the lynx, what will most likely happen next?

    1. a) More hares survive, and more willow gets eaten
    2. b) Fewer hares survive, since their predator is gone
    3. c) The willows are not affected, since lynx never eat them
    4. d) More willow grows, since the hares have less to eat

  6. A raccoon eats frogs, bird eggs, berries and corn. A raccoon is

    1. a) an omnivore
    2. b) a carnivore
    3. c) a herbivore
    4. d) a decomposer

  7. Purple loosestrife, a garden flower from Europe and Asia, can take over Canadian wetlands and crowd out native plants. Why do invasive species like this often spread so fast in a new place?

    1. a) Native animals prefer to eat them over the plants they know
    2. b) They make more food by photosynthesis than any native plant can
    3. c) The insects and diseases that kept them in check were left behind
    4. d) They grow only in places where no native plant can survive

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

  9. A sealed jar holds pond water, a water plant and a snail, and sits near a window. Both stay alive for weeks. Which best explains why the snail does not run out of oxygen?

    1. a) The plant's photosynthesis gives off oxygen and uses the snail's carbon dioxide
    2. b) The plant gives off oxygen through respiration, both day and night
    3. c) The snail gives off oxygen when it breathes, and the plant takes it in
    4. d) The water held enough oxygen at the start to last for many weeks

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

Answer key · Mixed review · Ecosystems and plants

Science 7 · maddyhelps.com

  1. c) predict the project's effects on land, water and wildlife, and how to reduce them — An assessment looks ahead at what a project could do to the environment and how the damage could be avoided or reduced, so the people deciding can weigh it before saying yes. Almost every project has some effect, so its job is not to prove there will be none.
  2. d) The algae — A producer makes its own food using energy from sunlight, and in this chain only the algae can do that. The water fleas are the first animals in the chain, but they are consumers: they get their energy by eating the algae.
  3. d) decomposers — Decomposers break dead matter down into nutrients that plants can take up again, which is how matter gets recycled. A scavenger, such as a raven, eats dead animals but leaves the final breakdown to decomposers, and fungi are not producers, because they cannot make food from sunlight.
  4. c) 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.
  5. a) More hares survive, and more willow gets eaten — With fewer lynx hunting them, more hares survive, and more hares eat more willow. A change at one level of a food web passes along the chain, so it reaches the willows even though a lynx never eats a plant.
  6. a) an omnivore — An omnivore eats both plants and animals: berries and corn are plants, while frogs and eggs come from animals. Carnivore is the answer you get if you notice only the frogs and eggs, so look at the whole diet before deciding.
  7. c) The insects and diseases that kept them in check were left behind — At home, a plant is kept in check by the animals that eat it and the diseases that infect it; in a new place none of these came along, so nothing slows it down. If native animals preferred to eat it, it would be eaten back rather than spreading.
  8. a) 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.
  9. a) The plant's photosynthesis gives off oxygen and uses the snail's carbon dioxide — In light, photosynthesis takes in carbon dioxide and gives off oxygen, while the snail's respiration does the reverse, so the two keep recycling the same gases. Plants respire too, and respiration always uses oxygen, so the plant only gives off oxygen while it has light.
  10. 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.