Energy Loss Between Levels · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Energy Loss Between Levels

Science · Ecosystems & Habitats · ages 11-12
Name ______________________   Date ____________

  1. A lake's algae hold 5,000 kg of biomass. About 10% of that energy passes to the tiny fish that eat the algae. How many kg of tiny fish can it support?

    Answer: ______________

  2. About how much energy is lost at each step of a food chain?

    • 10%
    • 50%
    • 90%

  3. Put this chain in order from the most energy to the least: hawk, grass, grasshopper.

    • Hawk, grasshopper, grass
    • Grasshopper, grass, hawk
    • Grass, grasshopper, hawk

  4. The level with the least biomass sits at the bottom of a pyramid of biomass.

    Circle one:   True   False

  5. Look at the pyramid of biomass. Which level holds the least biomass?

    Producers1000Herbivores100Carnivores10
    • Producers
    • Herbivores
    • Carnivores

  6. A rabbit eats grass. Where does most of that energy go?

    • Used for movement and lost as heat
    • Stored forever in the rabbit's body
    • Passed straight on to the fox that eats the rabbit

  7. A pond survey measured: algae 6,000 kg, tadpoles 600 kg, fish 60 kg. Which pyramid of biomass matches this data?

    • All three levels the same width
    • Algae at the bottom, tadpoles in the middle, fish on top
    • Fish at the bottom, tadpoles in the middle, algae on top

  8. Energy lost as heat at one level can be gathered up and used again by the next level.

    Circle one:   True   False

  9. Amara says: 'If people eat the crops from a field directly, more food energy reaches them than if the crops are fed to cows first.' Is she right?

    • No, energy grows as it moves up the chain
    • No difference, the energy is the same either way
    • Yes, skipping the cow level keeps about ten times more energy

  10. A forest starts with 500,000 kg of producers. If about 10% of the energy passes up at each step, how many kg of biomass reach the top predators, three steps up?

    Answer: ______________

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Answer key

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

Energy Loss Between Levels W1-mt_BOG5zRYtQz-s1

  1. 500 · 10% of 5,000 kg is 500 kg, since one step up keeps about a tenth.
  2. 90% · If about 10% passes on, then about 90% is lost along the way as heat, movement, and waste.
  3. Grass, grasshopper, hawk · Energy starts with the producers and shrinks at each step up, so grass holds the most and the hawk the least.
  4. False · The bottom level is the producers, and they hold the most biomass. The least biomass is at the top.
  5. Carnivores · Carnivores sit at the top, so they have the least biomass after two steps of energy loss.
  6. Used for movement and lost as heat · The rabbit uses most of that energy to move and stay warm, and it escapes as heat.
  7. Algae at the bottom, tadpoles in the middle, fish on top · The level with the most biomass goes at the bottom. Algae at 6,000 kg is the widest, then tadpoles, then the 60 kg of fish on top.
  8. False · Once energy escapes as heat, it is gone from the food chain for good. The next level can only use what is stored in the bodies it eats.
  9. Yes, skipping the cow level keeps about ten times more energy · Feeding crops to cows adds a step that loses about 90% of the energy. Eating the crops directly skips that loss, so about ten times more reaches people.
  10. 500 · 500,000 kg becomes 50,000 kg, then 5,000 kg, then 500 kg. Three steps up means dividing by ten three times.
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