Matter Cycling in Ecosystems · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Matter Cycling in Ecosystems

Science · Ecosystems & Habitats · ages 10-11
Name ______________________   Date ____________

  1. The same nutrients that helped an old tree grow can later help a new plant grow.

    Circle one:   True   False

  2. Which of these is a decomposer?

    • Butterfly
    • Worm
    • Rose bush

  3. A dead log in the forest is slowly crumbling away. Which living things are doing most of that work?

    • Only the sun and the rain
    • Birds nesting in the log
    • Decomposers like fungi, bacteria, and worms

  4. Look at the diagram. What comes right after 'Decomposers' in the matter cycle?

    SoilPlantAnimalDecomposers
    • Soil
    • Animal
    • Plant

  5. After decomposers finish breaking down a dead plant, what happens to the nutrients inside it?

    • They disappear into the air forever
    • They stay locked inside the decomposer forever
    • They return to the soil

  6. A deer eats leaves. Where was the matter in those leaves before the plant grew?

    • It did not exist anywhere before
    • In the air, as wind
    • In the soil, as nutrients

  7. Priya keeps a compost bin. Worms have chewed the old banana peels into tiny bits. What happens to those tiny bits next?

    • Bacteria and fungi finish the job, turning the bits into nutrients for the soil
    • The bits stay unchanged in the bin forever
    • The bits turn back into whole banana peels

  8. A leaf falls onto the forest floor. What breaks it down first?

    • Fungi and bacteria in the soil
    • Only sunlight and rain
    • Other trees nearby

  9. In one forest, fallen leaves stop rotting away. They pile deeper on the ground every year, and the new plants grow smaller and weaker. What has this forest most likely lost?

    • The fungi, bacteria, and worms that break dead matter down
    • The birds that nest in its trees
    • The clouds that bring it rain

  10. A fox dies in the forest. How does the matter in its body get back into a new plant?

    • The body sinks into the ground and becomes a plant overnight
    • The body turns into sunlight, which shines onto a new plant
    • Decomposers break the body down, the nutrients return to the soil, and a plant's roots soak them up
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Matter Cycling in Ecosystems W1-mt_0ajzcoKAKw-s1

  1. True · Matter never disappears. When the tree dies, decomposers return its nutrients to the soil, ready for new plants.
  2. Worm · A worm chews dead leaves into tiny pieces, which is decomposer work. A butterfly and a rose bush do not break down dead matter.
  3. Decomposers like fungi, bacteria, and worms · Fungi, bacteria, and worms break down dead wood and return its nutrients to the soil.
  4. Soil · Decomposers return nutrients to the soil, so the cycle loops back to Soil.
  5. They return to the soil · Decomposers release the nutrients into the soil, where new plants can use them.
  6. In the soil, as nutrients · The plant grew by taking nutrients from the soil, so the leaf's matter was in the soil before the plant grew.
  7. Bacteria and fungi finish the job, turning the bits into nutrients for the soil · After the chewing comes the finishing breakdown: bacteria and fungi turn the tiny bits into nutrients that mix into the soil.
  8. Fungi and bacteria in the soil · Fungi and bacteria in the soil start breaking down the leaf's tissue.
  9. The fungi, bacteria, and worms that break dead matter down · Piling leaves and weak plants are the signs that decomposers are gone: dead matter is not breaking down, so nutrients never reach the soil.
  10. Decomposers break the body down, the nutrients return to the soil, and a plant's roots soak them up · Decomposers break the fox's body down, its nutrients mix into the soil, and a new plant's roots soak those nutrients up.
Worksheet · LightMySky