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Energy transfer through a food chain

BiologySuggested ages: 10–15

Why is less energy usually available to the next trophic level higher in a food chain?

Adjust producer energy and transfer efficiencies between trophic levels to track how energy decreases step by step.

Learning goals

  • Distinguish producers, primary consumers, and higher trophic levels.
  • Calculate available energy sequentially using each level’s transfer efficiency.
  • Distinguish energy flow from matter cycling in ecosystems.

Before you begin

  • Calculate a percentage of a quantity.
  • Know that plants use light energy to build organic matter.

Interactive science experiment

  1. 1Trace the input
  2. 2Change first transfer
  3. 3Multiply stepwise
  4. 4Compare inputs
Available energy: 1000 kJ → 100 kJ → 10 kJ → 1 kJ
Experiment presets

Bar length uses a linear scale with the producer at 100%; very small values remain visible as a thin line. Values are teaching assumptions, not an ecological forecast.

Observe, then explain

Work through four steps. Each button moves the interactive model to the matching observation state.

  1. The model starts with a teaching amount of 1000 kJ stored by producers. Arrows point toward feeders to show energy transfer, not which organism is stronger.

    Your task: Read all four trophic levels and explain what each arrow means.

  2. If producer-to-primary efficiency changes from 10% to 20%, the teaching energy at primary consumers changes from 100 kJ to 200 kJ, changing every later starting point.

    Your task: Change only the first efficiency and compare every later energy value.

  3. Each level uses the adjacent previous level: 1000×20%=200, 200×15%=30, and 30×10%=3 kJ. The three percentages do not each act directly on 1000.

    Your task: Choose the sequential-efficiency preset and recalculate 200, 30, and 3 kJ in order.

  4. Doubling producer energy with fixed efficiencies doubles every level. Changing one efficiency directly changes that level and all levels after it.

    Your task: Switch to higher producer input and identify the three ratios that stay fixed.

Build an explanation

Energy is dissipated through life processes

Not all consumed energy becomes biomass available to the next level. Respiration, movement, temperature regulation, and uneaten or undigested matter all reduce transfer.

Food webs are more complex than one chain

Real organisms often have several foods and predators. This four-level chain isolates the sequential calculation; it does not imply an ecosystem has only one route.

Energy flows; matter cycles

Energy enters from sources such as light, transfers, and dissipates as heat. Matter such as carbon, nitrogen, and water can cycle among producers, consumers, decomposers, and the environment.

Check your understanding

1Starting with 1000 kJ and transferring 20%, 15%, then 10%, how much reaches the tertiary consumer?
2Why does the next trophic level usually receive less energy?
3Which statement correctly distinguishes energy and matter?
4Why can this model not predict the number of foxes in a real place?

Printable worksheet

Complete the worksheet first. Answers and explanations are on a separate page.

Biology

Energy transfer through a food chain

Name: __________________Date: __________________

Why is less energy usually available to the next trophic level higher in a food chain?

  1. Starting with 1000 kJ and transferring 20%, 15%, then 10%, how much reaches the tertiary consumer?

    A. 3 kJ B. 30 kJ C. 200 kJ

  2. Why does the next trophic level usually receive less energy?

    A. Energy supports life processes, and not all biomass is eaten and digested B. Higher levels need no energy C. Energy becomes more matter and vanishes

  3. Which statement correctly distinguishes energy and matter?

    A. Energy flows and dissipates, while matter can cycle B. Both cycle forever without loss C. Matter flows away while energy cycles completely

  4. Why can this model not predict the number of foxes in a real place?

    A. Efficiencies are teaching assumptions and the model omits food webs, populations, and environmental change B. Foxes are not consumers C. Energy is never related to populations

Answer page

Energy transfer through a food chain

  1. 3 kJ

    Calculate level by level: 1000×0.20=200, 200×0.15=30, and 30×0.10=3 kJ.

  2. Energy supports life processes, and not all biomass is eaten and digested

    Respiration and activity dissipate energy, while uneaten or undigested material is not directly transferred to the next level.

  3. Energy flows and dissipates, while matter can cycle

    Ecosystems need continued energy input, while atoms and molecules can be reused through processes linking organisms and environment.

  4. Efficiencies are teaching assumptions and the model omits food webs, populations, and environmental change

    Real populations also depend on web structure, reproduction, movement, disease, seasons, and habitat, so a four-level energy chain is insufficient.