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?

   • Second-level consumer: it gets energy from grasshoppers
   • First-level consumer: it gets energy from the prairie grass
   • Producer: arrows lead to it, so it is the food source
   • 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?

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

   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 same amount of energy passes to the larvae
   • Less energy passes to the larvae
   • Energy cycles back from the trout to the larvae
   • The larvae keep more energy, because the algae get energy from them
4. 4.

   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 are used again by the kelp
   • Nutrients are used again; energy ends up as heat
   • Both leave the coast and are gone for good
   • Energy is used again, but nutrients leave for good
5. 5.

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

   • Energy units rise at each higher level
   • Energy units stay the same at each level
   • Energy units fall at each higher level
   • The first-level consumers hold the most energy
6. 6.

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

7. 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).

8. 7.

   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 break down leaves, so Bin 1 shrinks
   • Fungi and bacteria make the leaf pile in Bin 1 taller
   • Plant roots shrink Bin 1 by taking in the leaves as food
   • Fungi and bacteria are not needed, since both piles change the same way
9. 8.

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

    Noah reads model data: grasshoppers hold 5,000 energy units, and about 10% passes to the meadowlarks. About how many units reach the meadowlarks?

    • About 500 units
    • About 50,000 units
    • About 50 units
    • About 4,500 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 4,000 units
    • About 400 units
    • About 40 units
    • About 3,600 units