Ocean ecosystems and food webs
KS4 · 30 minutes · Explain productivity and trophic cascades.
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Our learning goal
Explain productivity and trophic cascades.
Your turn: Choose one thing you would like to understand by the end.
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My lesson notes & project
Full teaching script
- Today: Ocean ecosystems and food webs. Our goal: Explain productivity and trophic cascades.
- Take one idea at a time. Pause after each sentence; ask for repetition whenever you need it.
- Nearly all ocean life depends on phytoplankton catching sunlight in the top sunlit layer. Cold upwellings carry nutrients up and make the richest fisheries. Energy falls by roughly 90% each trophic level, which is why big predators are rare and slow to recover. Remove a top predator and the level below explodes — otters gone, urchins multiply, kelp forests are grazed to bare rock. That knock-on is a trophic cascade.
- Together: choose one example from the explanation and show how it works. What do you notice?
- Your turn: Draw a kelp-forest food web and predict the effect of removing one species.
- Reflect: what made sense, and what would you like explained differently?
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