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Primary Science · Year 4Chapter 4 · Habitats, change and food chains
Year 4 · Chapter 4

Habitats, change and food chains

By the end of this chapter you will be able to

  • Give examples of natural and human changes to a habitat
  • Explain how a change in the environment can be a danger to living things, using a pond survey
  • Read a food chain, and say which living thing is the producer, the prey and the predator
  • Draw a food chain with arrows that point from the food to the eater
  • Explain that a food chain starts with a plant, because plants make their own food
  • Predict what would happen in a food chain if one living thing were removed

You should already know

  • Habitats, and how living things depend on each other (Year 2 Science, Chapter 3)
  • Animals need food to live, and they cannot make their own food (Year 3 Science, Chapter 5)

Where this leads

  • Classification keys, to name the living things in a habitat (Year 4 Science, Chapter 3)
  • Food chains in more detail, and the food webs of a habitat (Year 5 and Year 6 Science)

National Curriculum for England, Key Stage 2 science, Year 4. Content: LH3: recognise that environments can change and that this can sometimes pose dangers to living things, A3: construct and interpret a variety of food chains, identifying producers, predators and prey.

Exercise P  Do you remember?

1
FWhich living thing makes its own food, using light? Write the word: plant or animal.
2
FWhat is the name for an animal that is hunted and eaten by another animal? Write the word: predator or prey.
3
FName one habitat, such as a pond or a woodland. Write one habitat.
4
FWhich season comes after summer? Write the word.
5
FDo frogs lay their eggs in water? Write yes or no.
4.1

Environments can change

Year 4
LH3: recognise that environments can change
Video lesson: Environments can changeComing soon
Story. Yusuf and his sister Mei visit a pond in the park every spring. One year, the builders come and a fence goes up around the field. “The pond looks different now,” says Mei. Mr Patel says, “A habitat can change. Some changes are natural, and some are made by people.”

A habitat is the place where a living thing lives. The environment is everything around a living thing, such as the weather, the water, the soil and the other living things. The environment can change.

Some changes are natural, such as the seasons, a flood or a long dry summer. Other changes are caused by people, such as cutting down a hedge, building on a field, or dropping litter.

Wet summerLong dry summerno water left
A pond in a wet summer, and the same pond in a long dry summer. The change in the environment has changed the habitat.

Key ideas

  • A habitat is the place where a living thing lives.
  • The environment includes the weather, the water, the soil and the other living things.
  • Some changes are natural, such as the seasons or a flood.
  • Some changes are made by people, such as building on a field or dropping litter.
Worked example 4.1.1
Is a flood a natural change or a change made by people? Write natural or people.

Method. Think about where a flood comes from.

  1. Think about the cause. A flood is caused by heavy rain, and no person has made it.
    heavy rain
  2. Decide. A change that nature causes on its own is natural.
    natural
  3. Write the answer.
    natural

Check. Floods happen when rain fills the ground and rivers. ✓

Worked example 4.1.2
A hedge is cut down to build a road. Is this change natural or made by people? Write natural or people.

Method. Think about who makes the change.

  1. Read the sentence. A person cuts the hedge down, to build a road.
    a person
  2. Decide. A change made by a person is a change made by people.
    people
  3. Write the answer.
    people

Check. The hedge is not cut down by nature. ✓

Worked example 4.1.3
Look at the picture of the pond in section 4.1. In which summer is the pond dry? Write the words: wet summer or long dry summer.

Method. Look at the two pictures.

  1. Look at the right-hand picture. The right-hand picture shows the pond with no water left.
    no water left
  2. Read the label. The label above that picture says long dry summer.
    long dry summer
  3. Write the answer.
    long dry summer

Check. The left-hand pond still has water in it. ✓

Watch out

Watch out: a change is not always bad. Some living things are helped by a change, such as a plant that grows well after a fire. The key question is whether the change is dangerous.

Try it at home or school (with a grown-up). Walk around a park or garden with a grown-up. Find one change in the environment, such as a fallen tree or a puddle, and say whether it is natural or made by people.

Exam tip

Grown-up tip. Ask: “What changed? Did nature change it, or did people?” Let your child name one natural change and one change made by people.

Exercise 4A  Environments can change

1
FName one change in the environment that happens every year. Write one change.
2
FTrue or false: a habitat can change over time. Write true or false.
3
FIs cutting down a hedge a change made by people? Write yes or no.
4
FIs a flood a change made by people? Write yes or no.
5
FWhich is a change made by people: a flood or building on a field? Write the words: building on a field.
6
FFill in the gap: a change that happens quickly is a sudden change, and a change that happens over many years is a ___ change. Write the word.
7
FWhich season do the leaves fall from deciduous trees in the UK? Write the word.
8
FWrite one way that a pond can change in a dry summer.
9
PSRuby says every change in a habitat is bad for living things. Is Ruby right? Write yes or no.
10
PSA road is built across a field. Is this a change made by people? Write yes or no.
11
PSWorking scientifically. Predict what will happen to the frogs if the pond dries up. Write one prediction, with a reason.
12
RExplain why a habitat can change. Write one sentence.
4.2

Dangers to living things

Year 4
LH3: environments can change, and this can sometimes pose dangers to living things
Video lesson: Dangers to living thingsComing soon
Story. After a long dry summer, Mr Patel counts the animals in the school pond. “We counted lots of them last year,” says Aisha. “Some have gone,” says Leo. Mr Patel says, “Let us look at the numbers, and find out what changed.”

Some changes in the environment are dangerous to living things. A change can take away their water, their food, or their place to hide and nest. The table gives five changes, and the danger each one can pose.

Change in the environmentDanger to living things
A pond dries up in a long hot summerfrogs, newts and water beetles have no water to live in
Litter, such as plastic bags, is left in a parkanimals can eat it, or get tangled in it
A hedge is cut downbirds and small animals lose a place to nest and hide
Chemicals spill into a riverfish and water plants can die
A field floods after heavy rainsoil animals and plants can be drowned, and die

The pond survey counted the same living things before and after the dry summer. The fall in number is the number before, minus the number after.

Living thingBefore the dry summerAfter the dry summerFall in number
Frogs1239
Newts808
Snails25205
Water beetles15411
Total602733
04812fall in number9Frogs8Newts5Snails11Water beetles
The fall in number for each group of living things in the pond. Water beetles had the biggest fall.

Key ideas

  • A change in the environment can pose a danger to living things.
  • A dry summer can take away the water that frogs and newts need.
  • The fall in number is the number before the change, minus the number after.
  • Add the numbers in a column to find the total.
Worked example 4.2.1
In the pond survey, how many frogs were counted before the dry summer? Write the number.

Method. Read the table.

  1. Find the frogs row. The frogs row shows 12 before the dry summer.
    12
  2. Read the number. So 12 frogs were counted before the dry summer.
    12
  3. Write the answer.
    12

Check. After the dry summer there were 3 frogs. ✓

Worked example 4.2.2
In the pond survey, how many newts were counted after the dry summer? Write the number.

Method. Read the newts row.

  1. Find the newts row. The newts row shows 8 before, and 0 after.
    8 and 0
  2. Read the after number. So no newts were counted after the dry summer.
    0
  3. Write the answer.
    0

Check. Newts disappeared from the pond. ✓

Worked example 4.2.3
How many snails fell in number during the dry summer? Write the number.

Method. Subtract the after number from the before number.

  1. Read the snails row. Snails were 25 before, and 20 after.
    25 and 20
  2. Subtract. 25 minus 20 is 5, so 5 snails fell in number.
    25 - 20 = 5
  3. Write the answer.
    5

Check. Check: 20 plus 5 makes 25. ✓

Watch out. Subtract the number after the change from the number before.

Watch out

Watch out: a fall in number is the number before, minus the number after. If the number after is bigger, the number went up, not down.

Try it at home or school (with a grown-up). Count the number of different leaves, or small stones, in a pot with a grown-up. Then take away a few, and count again. Record the numbers in a table, and find how many fell. Do not touch any animals in a pond.

Exam tip

Grown-up tip. Ask: “How many were there before? How many are there now? What is the difference?” Let your child subtract the smaller number from the bigger number.

Exercise 4B  Dangers to living things

1
FLook at the table in section 4.2. Which change can trap animals in litter? Write the change.
2
FLook at the table in section 4.2. Which living things are in danger when chemicals spill into a river? Write one name.
3
FLook at the pond survey in section 4.2. How many frogs were counted before the dry summer? Write the number.
4
FLook at the pond survey in section 4.2. How many frogs were counted after the dry summer? Write the number.
5
FLook at the pond survey in section 4.2. How many fewer frogs were there after the dry summer? Write the number.
6
FLook at the pond survey in section 4.2. How many newts were counted after the dry summer? Write the number.
7
FLook at the pond survey in section 4.2. Which group had the biggest fall in number? Write the name.
8
FLook at the pond survey in section 4.2. Add the numbers before the dry summer. What is the total? Write the number.
9
FLook at the pond survey in section 4.2. Which group fell by 5? Write the name.
10
PSLook at the pond survey in section 4.2. How many living things fell in number altogether? Write the number.
11
PSWorking scientifically. Write one question you could ask to find out why the snail numbers fell.
12
RAli says the pond survey shows the snails were not harmed by the dry summer. Is Ali right? Write no, and give one reason.
4.3

Food chains

Year 4
A3: construct and interpret a variety of food chains, identifying producers, predators and prey
Video lesson: Food chainsComing soon
Story. Leo watches a leaf in the garden. A caterpillar is eating a hole in it. Then a small blue tit lands on a branch and eats the caterpillar. “The leaf feeds the caterpillar, and the caterpillar feeds the bird,” says Leo. Mr Patel says, “You have just made a food chain.”

A food chain shows what eats what. It starts with a plant, and each arrow points from the food to the eater.

A food chain starts with a producer. A producer is a plant, because plants make their own food, using light, water and air. Animals cannot make their own food, so they eat plants or other animals.

GrassProducerRabbitPreyFoxPredatorarrows point from the food to the eater
A food chain: grass, then rabbit, then fox. The arrows point from the food to the eater.

The table shows four food chains. Each has a producer, a prey and a predator.

Food chainProducerPreyPredator
Grass → Rabbit → FoxGrassRabbitFox
Leaf → Caterpillar → Blue titLeafCaterpillarBlue tit
Grass → Grasshopper → FrogGrassGrasshopperFrog
Grass → Mouse → OwlGrassMouseOwl

Key ideas

  • A food chain starts with a producer, which is a plant.
  • Arrows in a food chain point from the food to the eater.
  • A food chain with three living things has two arrows.
  • Animals eat plants or other animals, but they cannot make their own food.
Worked example 4.3.1
In the food chain grass → rabbit → fox, which living thing is the producer? Write the name.

Method. Look at the first living thing in the chain.

  1. Look at the start of the chain. The chain starts with grass, which is a plant.
    grass
  2. Name the producer. A plant at the start of a chain is the producer.
    Grass
  3. Write the answer.
    Grass

Check. Grass makes its own food, using light. ✓

Worked example 4.3.2
In the food chain leaf → caterpillar → blue tit, how many arrows are there? Write the number.

Method. Count the arrows between the living things.

  1. Look at the chain. There are three living things in the chain.
    three
  2. Count the arrows. Three living things need two arrows between them.
    2
  3. Write the answer.
    2

Check. Each arrow joins one living thing to the next. ✓

Worked example 4.3.3
In the food chain grass → grasshopper → frog, which way do the arrows point? Write the words: from the food to the eater.

Method. Think about what an arrow shows.

  1. Read the rule. An arrow shows the direction in which food passes.
    food passes
  2. Apply the rule. The grasshopper eats the grass, so the arrow points from the grass to the grasshopper.
    from the grass
  3. Write the answer.
    from the food to the eater

Check. The arrow points to the eater. ✓

Watch out

Watch out: the arrow points to the eater, not to the food. A fox eats a rabbit, so the arrow goes from the rabbit to the fox.

Try it at home or school (with a grown-up). Look at a plant and any small creature on it in a garden, with a grown-up. Draw a food chain with arrows that show who eats what. Do not touch unknown creatures.

Exam tip

Grown-up tip. Ask: “What does the animal eat? Which way does the arrow go?” Let your child draw the arrows from the food to the eater.

Exercise 4C  Food chains

1
FIn the food chain grass → rabbit → fox, which living thing is the producer? Write the name.
2
FIn the food chain grass → rabbit → fox, which living thing is the predator? Write the name.
3
FIn the food chain grass → rabbit → fox, which living thing is the prey? Write the name.
4
FHow many arrows are in the food chain leaf → caterpillar → blue tit? Write the number.
5
FFill in the gap: the arrows in a food chain point from the food to the ___. Write the word.
6
FWhich living thing is at the start of every food chain? Write the word: producer or predator.
7
FIn the food chain grass → grasshopper → frog, what does the frog eat? Write the name.
8
FHow many living things are in the food chain grass → mouse → owl? Write the number.
9
FWrite the food chain for this: a leaf is eaten by a caterpillar, which is eaten by a blue tit. Write it with arrows.
10
PSWhich food chain is correct? Write a or b. a) Fox → Rabbit → Grass b) Grass → Rabbit → Fox
11
PSWorking scientifically. Predict what would happen to the rabbits if there were no grass. Write one prediction with a reason.
12
RExplain why a food chain always starts with a plant. Write one sentence.
4.4

Producers, predators and prey

Year 4
A3: identify producers, predators and prey in a food chain
Video lesson: Producers, predators and preyComing soon
Story. In the pond, Ruby sees a grasshopper jump into the grass. Later a frog catches the grasshopper, and a grass snake hunts the frog. “So the frog is eaten, and it eats too,” says Ruby. Mr Patel says, “Yes. Some animals are both a predator and prey.”

A predator is an animal that hunts and eats other animals. A prey animal is an animal that is hunted and eaten by a predator.

An animal can be a predator in one link of a chain, and prey in the next. In the chain below, the frog is prey for the grass snake, and it is a predator of the grasshopper.

GrassProducerGrasshopperPreyFrogPreyGrass snakePredatorarrows point from the food to the eater
A food chain: grass, then grasshopper, then frog, then grass snake. The first is the producer, the middle ones are prey, and the last is the predator.

Key ideas

  • A producer is a plant at the start of a food chain.
  • A predator hunts and eats other animals.
  • Prey is an animal that is hunted and eaten.
  • An animal can be both a predator and prey in a longer chain.
Worked example 4.4.1
In the food chain grass → grasshopper → frog → grass snake, which living thing is the predator of the frog? Write the name.

Method. Find the animal that eats the frog.

  1. Read the chain. The arrow points from the frog to the grass snake, so the grass snake eats the frog.
    grass snake
  2. Name the predator. So the grass snake is the predator of the frog.
    Grass snake
  3. Write the answer.
    Grass snake

Check. A grass snake hunts and eats frogs. ✓

Worked example 4.4.2
In the food chain grass → mouse → owl, which living thing is the prey? Write the name.

Method. Find the animal that is eaten by a predator.

  1. Read the chain. The owl eats the mouse, so the mouse is eaten by a predator.
    mouse is eaten
  2. Name the prey. So the mouse is the prey.
    Mouse
  3. Write the answer.
    Mouse

Check. The owl is the predator in this chain. ✓

Worked example 4.4.3
In the food chain grass → grasshopper → frog → grass snake, is the frog a predator, prey or both? Write the word: predator, prey or both.

Method. Think about what the frog does in the chain.

  1. Read the first link. The frog eats the grasshopper, so the frog is the predator in that link.
    predator
  2. Read the second link. The grass snake eats the frog, so the frog is also prey in that link.
    prey
  3. Write the answer.
    both

Check. The frog is both a predator and prey in this chain. ✓

Watch out

Watch out: the producer is always a plant. A grasshopper is not a producer, because it eats plants and cannot make its own food.

Try it at home or school (with a grown-up). Look at a garden pond or a bird feeder with a grown-up, from a safe distance. Name one living thing that could be a predator, and one that could be prey. Do not touch any animal.

Exam tip

Grown-up tip. Ask: “Who eats whom? Is this one a predator or prey?” Let your child say which living thing is hunted, and which one hunts.

Exercise 4D  Producers, predators and prey

1
FIn the food chain grass → grasshopper → frog → grass snake, which living thing is the predator of the frog? Write the name.
2
FIn the food chain grass → grasshopper → frog → grass snake, which living thing is the prey of the grass snake? Write the name.
3
FIn the food chain grass → grasshopper → frog → grass snake, which living thing is the prey of the frog? Write the name.
4
FHow many arrows are in the food chain grass → grasshopper → frog → grass snake? Write the number.
5
FWrite the type of living thing that is always a producer in a food chain. Write the word.
6
FFill in the gap: a predator ___ other animals. Write the word.
7
FFill in the gap: a prey animal is one that is ___ by a predator. Write the word.
8
FIn the food chain grass → mouse → owl, which animal is the prey? Write the name.
9
FIn the food chain grass → mouse → owl, which animal is the predator? Write the name.
10
PSIs a frog a predator in the chain grass → grasshopper → frog? Write yes or no.
11
PSIs a grasshopper a producer in the chain grass → grasshopper → frog? Write yes or no.
12
PSWorking scientifically. Predict what would happen to the number of grasshoppers if all the frogs were removed from the pond. Write one prediction.
13
RExplain why the frog is both a predator and prey in the long food chain. Write one sentence.
4.5

Longer food chains and the effects of change

Year 4
A3: construct and interpret a variety of food chains; LH3: a change can pose a danger to living things
Video lesson: Longer food chains and the effects of changeComing soon
Story. Mr Patel draws a long food chain on the board. “If the grass died, what would happen to the whole chain?” he asks. Priya says, “The grasshoppers would have no food, and then the frogs and the snake would lose their food too.”

A food chain shows how each living thing depends on the one before it. If one link is removed, the living things after it lose their food. If the producer disappears, the whole chain is affected.

To count the arrows, take one away from the number of living things: a chain with five living things has four arrows.

Key ideas

  • A chain with five living things has four arrows.
  • If a producer dies, every living thing above it in the chain is affected.
  • Removing one link changes the living things that depend on it.
  • Every food chain starts with a plant.
Worked example 4.5.1
How many living things are in the long food chain grass → grasshopper → frog → grass snake? Write the number.

Method. Count the names in the chain.

  1. Read the chain. The chain has grass, grasshopper, frog and grass snake.
    four names
  2. Count them. So there are four living things in the chain.
    4
  3. Write the answer.
    4

Check. Four living things have three arrows. ✓

Worked example 4.5.2
In the food chain grass → grasshopper → frog → grass snake, a chain of four living things has how many arrows? Write the number.

Method. Count the arrows.

  1. Count the gaps. Four living things have three gaps between them.
    three gaps
  2. Write the number. So the chain has three arrows.
    3
  3. Write the answer.
    3

Check. One fewer arrow than living things. ✓

Worked example 4.5.3
If the grass died in the long chain, which living thing would lose its food first? Write the name.

Method. Think about what eats the grass.

  1. Look at the chain. The grasshopper eats the grass, so it is the first living thing to lose its food.
    grasshopper
  2. Name the living thing. So the grasshopper loses its food first.
    Grasshopper
  3. Write the answer.
    Grasshopper

Check. The grasshopper is the first eater after the grass. ✓

Watch out

Watch out: a chain with four living things has three arrows, not four. Count the gaps between the living things, not the names.

Try it at home or school (with a grown-up). Draw a short food chain of three living things from a garden, with a grown-up. Then cover one living thing with a piece of paper, and say what would happen to the others.

Exam tip

Grown-up tip. Ask: “If this one was gone, who would lose their food?” Let your child count the arrows, and then the living things.

Exercise 4E  Longer food chains and the effects of change

1
FHow many living things are in the chain grass → mouse → owl? Write the number.
2
FHow many arrows are in the chain grass → mouse → owl? Write the number.
3
FIn the long chain grass → grasshopper → frog → grass snake, which living thing is at the end? Write the name.
4
FIn the long chain grass → grasshopper → frog → grass snake, which living thing is the producer? Write the name.
5
FIn the long chain, if the grass died, which living thing would lose its food first? Write the name.
6
FHow many arrows are in a food chain with five living things? Write the number.
7
PSIn the chain grass → mouse → owl, how many predators are there? Write the number.
8
PSRuby removes the grass snake from the long chain. Does the number of arrows change? Write yes or no.
9
PSIs the grass snake prey in the long chain? Write yes or no.
10
PSWorking scientifically. Predict what would happen to the frogs if the pond dried up and the grasshoppers could not survive. Write one prediction with a reason.
11
RExplain why a change to the grass can affect the grass snake. Write one sentence.

Chapter summary

SkillMethod
Changes in a habitatEnvironments change naturally, or because of people. Some changes are dangerous to living things.
Dangers to living thingsA change can take away water, food, or a place to hide and nest. A fall in number is the before number minus the after number.
Food chainsA food chain starts with a producer, a plant. Arrows point from the food to the eater.
Predators and preyA predator hunts and eats other animals. Prey is the animal that is eaten.
Effects along a chainA chain with five living things has four arrows. Removing a link affects the living things that depend on it.

Can you…?

  • I can give natural and human changes to a habitat
  • I can explain how a change can pose a danger to living things, using numbers from a table
  • I can read a food chain, and count its arrows
  • I can name the producer, the predator and the prey in a food chain
  • I can predict what would happen in a chain if one living thing were removed

Key terms

habitat
the place where a living thing lives
environment
everything around a living thing, such as the weather, the water, the soil and other living things
food chain
a diagram that shows what eats what, with arrows from the food to the eater
producer
a plant, which makes its own food at the start of a food chain
predator
an animal that hunts and eats other animals
prey
an animal that is hunted and eaten by a predator
natural change
a change to the environment caused by nature, such as a flood
human change
a change to the environment caused by people, such as building on a field
fall in number
the number before a change, minus the number after it

Exercise 4Z  Check-up

1
Name one change to a habitat made by people. Write one change.
2
Look at the pond survey in section 4.2. Which group had the biggest fall in number? Write the name.
3
Look at the pond survey in section 4.2. Add the numbers after the dry summer. What is the total? Write the number.
4
In the food chain grass → rabbit → fox, which living thing is the prey? Write the name.
5
How many arrows are in the food chain grass → grasshopper → frog? Write the number.
6
Which living thing is the producer in a food chain? Write the word: plant or animal.
7
Write the food chain with arrows: a leaf is eaten by a caterpillar, which is eaten by a blue tit.
8
In the chain grass → mouse → owl, which living thing is the predator? Write the name.
9
Ali says a grasshopper is a producer. Is Ali right? Write no, and give one reason in one sentence.

Total 17 marks. Allow about 17 minutes.

Exercise 4X  Practice test questions

1
FName one change to a habitat that is caused by nature. Write one change.[1 mark]
2
FIn a food chain, which living thing is always a producer? Write the word: plant or animal.[1 mark]
3
FIn the food chain leaf → caterpillar → blue tit, how many arrows are there? Write the number.[1 mark]
4
FIn the food chain grass → grasshopper → frog, which living thing is the prey of the frog? Write the name.[1 mark]
5
PSA pond has these numbers of frogs: 12 before a dry summer, and 3 after. How many fewer frogs were there after? Write the number.[2 marks]
6
PSIn a pond survey, 25 snails were counted before a dry summer, and 20 after. How many snails fell in number? Write the number.[2 marks]
7
RWrite one way that a change in the environment could be dangerous to living things.[2 marks]
8
FWrite the food chain for this: grass is eaten by a grasshopper, which is eaten by a frog. Write it with arrows.[2 marks]
9
FIn the food chain grass → mouse → owl, name the predator, and name the prey it hunts. Write the two names.[2 marks]
10
RExplain why every food chain starts with a plant. Write one sentence.[3 marks]
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