Food webs and interdependence

Ecosystems and food chains

CCSS NGSS.MS-LS2-1CCSS NGSS.MS-LS2-2CCSS NGSS.MS-LS2-4England: KS3 Biology: Interactions and interdependenciesEngland: KS4 Combined Science: Ecosystems

Objective and success criteria

Students will: Food webs and interdependence.

I can answer questions on today's skill on my own, without help.
I can explain each step and say why it works.
I can check my answer and spot a mistake.

Before and after

Needs first: Producers, consumers, predators and prey

Leads to: Energy transfer and pyramids; Sampling with quadrats; Biodiversity under pressure and how we protect it

Materials: Food web cards, Arrows to build chains, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 5 min

Quick retrieval from earlier learning (Producers, consumers, predators and prey). Students answer on mini whiteboards.
Show answers together and note who needs support in the main task.

lettuce → slug → hedgehog → badger What is the badger in this food chain? (tertiary consumer / primary consumer / producer / secondary consumer) → tertiary consumerPrompt: Start at the plant and count the arrows.
grass → zebra → lion Which animal is the predator of the zebra? (grass / lion / zebra) → lionPrompt: A predator hunts and eats other animals; its prey is the animal it eats.
Food chains: which statement is true? (An animal can be both a predator and prey. / Herbivores are predators. / Producers eat consumers. / A food chain can start with a lion.) → An animal can be both a predator and prey.Prompt: Producers make food; consumers eat.

Hook · 5 min

Show a food web and ask what would happen if one animal disappeared.
Share the objective: Food webs and interdependence. Read the success criteria together.

I do: model it · 10 min

Work through the example out loud, saying why you do each step, not just what you do.
Example: Pond food web: algae are eaten by tadpoles and water fleas. Tadpoles and water fleas are eaten by small fish. Small fish are eaten by herons. If the small fish died, what would happen to the herons?
Step 1: Herons lose their food source, so their numbers fall.
Step 2: So the answer is: They would decrease or move away
Answer: They would decrease or move away
Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 min

Do these together. Students try each step on whiteboards before you reveal it.
Use the hints as prompts rather than giving the answer.

Pond food web: algae are eaten by tadpoles and water fleas. Tadpoles and water fleas are eaten by small fish. Small fish are eaten by herons. If all the small fish died, what would probably happen to the tadpoles at first? (They would stay exactly the same / They would decrease / They would increase / They would turn into fish) → They would increasePrompt: What eats tadpoles?
What does "interdependence" mean in an ecosystem? (Living things depend on each other, so a change to one affects others / Every animal lives alone / Plants do not need animals at all / Only predators matter) → Living things depend on each other, so a change to one affects othersPrompt: Think of bees and flowers.

You do: independent practice · 10 min

Students work on the student sheet. Circulate and check the first two answers of every student early.
Students who finish: write a question of their own for a partner, with the answer.

The 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

Food webs: which statement is NOT true? (Removing a predator always helps every other species. / Predator and prey populations often rise and fall in cycles. / Removing one species can affect many others in a food web. / Plants compete for light, water and minerals.) → Removing a predator always helps every other species.Prompt: Think about what happens when one population changes.
Bees are declining. Why could this affect fruit farmers? (Fruit trees need honey to grow / Fewer flowers would be pollinated, so less fruit forms / Bees eat fruit / Bees make the rain) → Fewer flowers would be pollinated, so less fruit formsPrompt: What do bees carry between flowers?

Watch out for

Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

Review first: Producers, consumers, predators and prey.
Use concrete materials: food web cards.
Give the first step of each question, or a partly worked example to finish.
Pair with a confident partner for the guided practice.

Stretch

Move on to: Energy transfer and pyramids; Sampling with quadrats; Biodiversity under pressure and how we protect it.
Explain a common mistake in writing and how to fix it.
Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-6.

Free lesson plan from eurekami.com/lesson-plan-builder

eurekami

Food webs and interdependence

Name

Date

Score/ 8

1
Question 1
Food webs: which statement is NOT true?
- A. Predator and prey populations often rise and fall in cycles.
- B. Removing a predator always helps every other species.
- C. Animals often compete for food, water and space.
- D. Removing one species can affect many others in a food web.
2
Question 2
Pond food web: algae are eaten by tadpoles and water fleas. Tadpoles and water fleas are eaten by small fish. Small fish are eaten by herons. If all the small fish died, what would probably happen to the tadpoles at first?
- A. They would increase
- B. They would decrease
- C. They would stay exactly the same
- D. They would turn into fish
3
Question 3
Why is a food web more realistic than a single food chain?
- A. Most animals eat, and are eaten by, more than one kind of living thing
- B. Food webs have no producers
- C. Animals only ever eat one food
- D. Food webs only show plants
4
Question 4
Pond food web: algae are eaten by tadpoles and water fleas. Tadpoles and water fleas are eaten by small fish. Small fish are eaten by herons. If the small fish died, what would happen to the herons?
- A. They would increase
- B. They would decrease or move away
- C. They would eat algae
- D. Nothing
5
Question 5
Rabbits and sheep both eat grass in the same field. This is an example of…
- A. decomposition
- B. photosynthesis
- C. competition
- D. predation
6
Question 6
Woodland food web: grass is eaten by rabbits and mice. Seeds are eaten by mice. Rabbits are eaten by foxes. Mice are eaten by foxes and owls. Which animal is eaten by two different predators?
- A. mice
- B. rabbits
- C. foxes
- D. owls
7
Question 7
What does "interdependence" mean in an ecosystem?
- A. Every animal lives alone
- B. Plants do not need animals at all
- C. Only predators matter
- D. Living things depend on each other, so a change to one affects others
8
Question 8
Woodland food web: grass is eaten by rabbits and mice. Seeds are eaten by mice. Rabbits are eaten by foxes. Mice are eaten by foxes and owls. If disease killed most rabbits, what might happen to the mice?
- A. Their numbers fall, because foxes eat more mice
- B. They become rabbits
- C. They stop eating seeds
- D. They increase, because foxes stop eating

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Answer key: Food webs and interdependence

1. B. Removing a predator always helps every other species.
2. A. They would increase
3. A. Most animals eat, and are eaten by, more than one kind of living thing
4. B. They would decrease or move away
5. C. competition
6. A. mice
7. D. Living things depend on each other, so a change to one affects others
8. A. Their numbers fall, because foxes eat more mice