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
   • Decomposer: it comes last in the chain
   • Second-level consumer: it gets energy from grasshoppers
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?

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

   • Energy cycles back from the trout to 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
4. 4.

   No arrows are drawn. Luz sets up a compost bin where fungi and bacteria cannot live. Fallen leaves are added each week. What happens to the leaves?

   • Plants take the leaves into their roots as food
   • They pile up, and their nutrients stay locked inside
   • They vanish, and extra nutrients reach the soil
   • They break down anyway, so decomposers are not needed
5. 5.

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

   • Energy units fall at each higher level
   • Energy units rise at each higher level
   • The first-level consumers hold the most energy
   • Energy units stay the same at each level
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 waits in the soil for later use
   • Most is used by the grasshoppers or lost as heat
   • Most of it flows back to the prairie grass again
   • Most of it passes on to the hawks as extra energy

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 are not needed, since both piles change the same way
   • 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
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 9,000 units
   • About 100 units
   • About 1,000 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 4,500 units
    • About 50 units
    • About 50,000 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 40 units
    • About 4,000 units
    • About 400 units
    • About 3,600 units