Food webs: where energy and matter go in an ecosystem

Grade 7 Science Worksheet

Circle the best answer.

1. 1.

   Ari reads a grassland web: arrows run from prairie grass to grasshoppers and from grasshoppers to meadowlarks. What role do the meadowlarks have?

   • Producer: arrows lead to it, so it is the food source
   • First-level consumer: it gets energy from the prairie grass
   • Second-level consumer: it gets energy from grasshoppers
   • Decomposer: it comes last in the chain
2. 2.

   Bo reads that kelp grows fixed to rocks on a sea floor. In a coast web, an arrow runs from the sun to the kelp. What role does kelp have?

   • Consumer: the arrow from the sun leads into it
   • Consumer: it takes its food from the sea floor
   • Producer: it makes its own food using light
   • Decomposer: it stays fixed in one place
3. 3.

   Esme reads a compost bin web: an arrow runs from fruit peels and fallen leaves to fungi, which release nutrients into the soil. What role do fungi have?

   • Producer: it makes its own food using light
   • Not part of the web: peels and leaves are not living
   • Decomposer: it breaks down remains and returns nutrients
   • Consumer: it takes energy and returns nothing to the soil
4. 4.

   Less light reaches Jun's stream one summer, so less stream algae grows. An arrow runs from the algae to mayfly larvae. What happens to the energy reaching the larvae?

   • The larvae keep more energy, because the algae get energy from them
   • Less energy passes to the larvae
   • The same amount of energy passes to the larvae
   • Energy cycles back from the trout to the larvae
5. 5.

   Kira reads that sunlight energy reaches kelp on a coast, and later bacteria break down kelp remains. What happens to the nutrients and the energy over time?

   • Both leave the coast and are gone for good
   • Energy is used again, but nutrients leave for good
   • Nutrients are used again; energy ends up as heat
   • Both are used again by the kelp
6. 6.

   Ren reads model data on the energy in a stream web. Which sentence fits the table?

   • Energy units rise at each higher level
   • The first-level consumers hold the most energy
   • Energy units fall at each higher level
   • Energy units stay the same at each level
7. 7.

   Tala reads model data: grasshoppers hold 2,000 energy units but meadowlarks hold 200. Where does most of the missing energy go?

   • Most of it waits in the soil for later use
   • Most of it passes on to the hawks as extra energy
   • Most is used by the grasshoppers or lost as heat
   • Most of it flows back to the prairie grass again

8. Read this first

   Use this

   Two compost bins, not to scale (model data). Boxes: fallen leaves; fungi and bacteria (decomposer tag). Arrows: from fallen leaves to fungi and bacteria, arrowhead at fungi and bacteria. Graph (model data): x axis Week, ticks every 2 weeks from 0 to 6; y axis Height of the leaf pile (cm), ticks every 10 cm from 0 to 50. Line Bin 1 (fungi and bacteria present): (0, 40), (2, 32), (4, 24), (6, 15). Line Bin 2 (fungi and bacteria removed): (0, 40), (2, 40), (4, 39), (6, 39).

9. 8.

   Zee compares two compost bins with the same fallen leaves. Bin 2 had its fungi and bacteria removed. What does the graph show?

   • Fungi and bacteria make the leaf pile in Bin 1 taller
   • Fungi and bacteria are not needed, since both piles change the same way
   • Fungi and bacteria break down leaves, so Bin 1 shrinks
   • Plant roots shrink Bin 1 by taking in the leaves as food
10. 9.

    Milo reads model data: stream algae hold 10,000 energy units, and about 10% passes to the first-level consumers. About how many units pass?

    • About 9,000 units
    • About 100 units
    • About 1,000 units
    • About 10,000 units
11. 10.

    Pia reads model data: sea urchins on a kelp coast hold 4,000 energy units, and sea stars get about 10% of that. About how many units do sea stars get?

    • About 400 units
    • About 4,000 units
    • About 40 units
    • About 3,600 units