Teacher sheet · Ages 10–11 · about 45–50 minutes
Food chains, webs and energy
Lesson page: echoesof.science/school/food-chains/ages-10-11/ · Pupil worksheet: echoesof.science/school/food-chains/ages-10-11/print/
Learning aims
- Name the levels of a food chain: producer, primary, secondary and tertiary consumers, apex predator.
- Explain how food chains link into a food web and how a change in one population affects others.
- Use the 10% rule to estimate energy passed up a food chain.
- Describe the role of detritivores and decomposers.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: draw the longest food chain you can think of. |
| 10 min | Read the text; label a food chain with the level names. |
| 20 min | The food web string game and the energy maths. |
| 5 min | Discuss the sea otter example. |
| 5 min | Quiz or the Which level? game. |
Materials for the experiment
- Cards with the names or pictures of: grass, tree leaves, caterpillar, grasshopper, rabbit, sparrow, rat, snake, fox, hawk
- A ball of wool or string
- Calculator
Safety: Pull the wool gently and keep it below shoulder height. Clear bags and chairs from the circle so nobody trips.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Energy is recycled round a food chain. | Nutrients are recycled by decomposers, but most energy is lost as heat at each step. |
| Top predators are the most common animals. | There is less energy at each level, so there are usually fewer animals at the top. |
| Removing one species only affects its predator. | Food webs are linked: the change can spread to many other species. |
Worksheet answers
- Any web with at least five organisms and arrows pointing to the eaters; producer and apex predator labelled correctly.
- A food chain is one path of who eats whom; a food web is all the linked, overlapping food chains in an ecosystem.
- 20,000 → 2,000 (rabbit) → 200 kJ (fox).
- Only about 10% of the energy passes on at each step, so after about five steps there is too little energy left to support another level.
Quiz answers
- What is a primary consumer? An animal that eats producers. Primary consumers are herbivores.[1]
- In grass → grasshopper → rat → snake → hawk, which is the apex predator? The hawk. Nothing hunts the hawk in this chain.[1]
- What is a food web? All the linked food chains in an ecosystem. Food chains overlap to form a food web.[2]
- Grass holds 10,000 units of energy. About how much reaches the rabbit that eats it? About 1,000 units. On average about 10% passes to the next level.[3]
- Where does most of the energy at each level go? It is used for living and lost as heat and waste. Only about a tenth is passed on.[3]
- If the sea otters disappear from a kelp forest, what can happen? Sea urchins can destroy the kelp. Otters eat the urchins that graze on kelp.[2]
Going further
Build a food web for a local pond or park from observations and pictures. Which animal is linked to the most others?
Sources used in this lesson
- [1] Food Chain (National Geographic Education): reliability Medium-high
- [2] Food Web (National Geographic Education): reliability Medium-high
- [3] Energy Flow and the 10 Percent Rule (National Geographic Education): reliability Medium-high
Full list with links and a note on each source's reliability: echoesof.science/school/food-chains/sources/
Privacy: the lesson pages have no ads, no tracking and no cookies. Quiz answers and game scores stay in the pupil's browser. A short video for each age is coming.