Year 7 Science · Unit 1 · Lesson 14
Challenge Worksheet
Learning Goals
Explain it to a Year 5 student
Imagine your younger cousin has never heard of the 10% rule. Use the sentence starters below to explain it clearly. Use real examples from everyday life — no scientific jargon allowed.
"The 10% rule means…"
"Imagine energy like pocket money: each time it's passed on…"
"This matters for the real world because…"
"A common mistake is thinking that…"
1. A scientist claims to have discovered a food chain with 8 trophic levels, starting with 10 000 kJ in grass. Is this possible? Show a calculation for each trophic level up to level 8, then use your results to justify whether such a chain could support a real top predator.
2. Energy is not destroyed as it moves through a food chain — yet energy pyramids always narrow upwards. Explain this apparent contradiction. In your answer, state where the "lost" energy actually goes and why it cannot be used by the next trophic level.
Wrap Up
In one sentence, what was the main idea of this lesson?