Energy Loss Between Levels

Activities to try

1. 1

   Watch the energy leak up the pyramid

   Why it works: Because only about a tenth of the energy survives each transfer, far less energy — and therefore usually far less living mass — is available at each higher level, which gives the energy pyramid its wide-base/narrow-top shape, makes most biomass pyramids the same shape, and limits chain length. 'Lost' means transferred out as heat/movement/waste, obeying conservation of energy.

   1. Start with a fixed pot of energy (e.g. 10,000 kJ) at the producer level at the wide base.
   2. Move up one level and track what reaches it: roughly 10% passes on while about 90% peels off along labelled streams — heat from respiration, energy burned in movement, energy locked in waste and uneaten parts.
   3. Follow the running total up the levels: 10,000 → 1,000 → 100 → 10 kJ, saying the proportion lost each step aloud.
   4. Try to add a fifth or sixth level and notice there is essentially no energy left to support it; state in your own words why food chains are short.
   5. Change the transfer efficiency between 5%, 10% and 20% and describe how the pyramid steepens or flattens and how many levels become possible.
2. 2

   Lift-the-flap pyramid for pre-teaching and reference

   Why it works: The ~10% rule and the named loss pathways crisply introduce or revise the concept and connect the pyramid shape to the rule.

   1. Tap or lift each level of a labelled energy pyramid to reveal its loss breakdown: '~90% lost as heat (respiration), movement, waste; ~10% passed on'.
   2. Read off the fixed worked example 10,000 → 1,000 → 100 → 10 kJ and restate where each lost portion goes.
   3. Name the shape (wide base, narrow top) and explain in one sentence how it follows from the 10% rule.
3. 3

   Reason it out loud: why can't the chain be longer?

   Why it works: Verbalising where the energy goes and tying predator scarcity to the energy budget distinguishes genuine energy-tracking reasoning from rote recall.

   1. Answer the prompt: 'Only about 10% of the energy at one level reaches the next. When a rabbit eats grass, what happens to the other ~90% of the grass's energy — is it destroyed?'
   2. Name at least two places the missing energy actually goes (heat from respiration, movement, undigested waste).
   3. Explain why a field can feed many rabbits but only a few foxes, using the energy available rather than animal size or strength.
   4. Explain why food chains almost never have more than about five links.