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 · 6 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 lettuce in this food chain? (producer / primary consumer / secondary consumer / tertiary consumer) → producerPrompt: Start at the plant and count the arrows.
acacia leaves → giraffe → lion Which animal is the prey of the lion? (acacia leaves / giraffe / lion) → giraffePrompt: A predator hunts and eats other animals; its prey is the animal it eats.
Food chains: which statement is true? (Plants are producers because they make their own food. / A food chain can start with a lion. / Herbivores are predators. / Producers eat consumers.) → Plants are producers because they make their own food.Prompt: Producers make food; consumers eat.

Hook · 6 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 · 12 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 · 12 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 the small fish died, what would happen to the herons? (They would decrease or move away / They would increase / They would eat algae / Nothing) → They would decrease or move awayPrompt: What do herons eat in this web?
Rabbits and sheep both eat grass in the same field. This is an example of… (competition / photosynthesis / predation / decomposition) → competitionPrompt: They both want the same limited resource.

You do: independent practice · 17 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 · 7 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? (Animals often compete for food, water and space. / Plants compete for light, water and minerals. / Removing one species can affect many others in a food web. / A food web contains only one food chain.) → A food web contains only one food chain.Prompt: Think about what happens when one population changes.
Why is a food web more realistic than a single food chain? (Food webs only show plants / Food webs have no producers / Most animals eat, and are eaten by, more than one kind of living thing / Animals only ever eat one food) → Most animals eat, and are eaten by, more than one kind of living thingPrompt: Does a fox eat only rabbits?

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
Why is a food web more realistic than a single food chain?
- A. Food webs only show plants
- B. Animals only ever eat one food
- C. Food webs have no producers
- D. Most animals eat, and are eaten by, more than one kind of living thing
2
Question 2
Food webs: which statement is NOT true?
- A. Plants compete for light, water and minerals.
- B. Animals often compete for food, water and space.
- C. Predator and prey populations often rise and fall in cycles.
- D. Removing a predator always helps every other species.
3
Question 3
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 turn into fish
- C. They would stay exactly the same
- D. They would decrease
4
Question 4
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. They stop eating seeds
- B. They become rabbits
- C. Their numbers fall, because foxes eat more mice
- D. They increase, because foxes stop eating
5
Question 5
Rabbits and sheep both eat grass in the same field. This is an example of…
- A. photosynthesis
- B. decomposition
- C. competition
- D. predation
6
Question 6
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 eat algae
- B. Nothing
- C. They would decrease or move away
- D. They would increase
7
Question 7
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. foxes
- B. mice
- C. rabbits
- D. owls
8
Question 8
Bees are declining. Why could this affect fruit farmers?
- A. Bees eat fruit
- B. Fruit trees need honey to grow
- C. Bees make the rain
- D. Fewer flowers would be pollinated, so less fruit forms

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Answer key: Food webs and interdependence

1. D. Most animals eat, and are eaten by, more than one kind of living thing
2. D. Removing a predator always helps every other species.
3. A. They would increase
4. C. Their numbers fall, because foxes eat more mice
5. C. competition
6. C. They would decrease or move away
7. B. mice
8. D. Fewer flowers would be pollinated, so less fruit forms