S2.2.5 Chapter 5
Fit for the habitat
How can a camel live in a hot desert?
Your guess
Pick one before you read on. It is fine to be wrong.
By the end you can
- Explain how a camel, a fish and a cactus suit their habitats
- Match body features to habitats, such as webbed feet to water
A camel lives in a hot desert. A fish lives in a river. A cactus grows where rain is rare.
Each one has a body that suits its home. A feature is a body part that helps a living thing. It helps the living thing live in its home.
Look at a camel. Its feet are wide and flat. They do not sink in sand.
Its eyelashes are long. They keep sand out of its eyes. It can close its nostrils against blowing sand.
A desert has very little water. A camel can go many days without a drink. Then it drinks a lot at once.
Its hump stores fat. Fat is stored food. It is not water.
A fish lives in water. It breathes with gills. Gills let a fish breathe in water.
Fins help a fish swim and steer. Its shape is smooth and pointed. It slides through water. Scales cover its skin.
A cactus lives where rain is rare. Its stem is thick. The stem stores water.
It has spines, not wide leaves. Spines lose less water than wide leaves. They also keep animals off.
Its skin is waxy. Its roots spread wide near the top of the soil. They catch rain fast.
Draw it first
Draw a cactus
1 Draw the ground and a thick stem. Write thick stem.
2 Draw short spines all round the stem. Write spines.
3 Draw roots that spread wide near the top of the soil. Write roots.
Ducks and frogs have webbed feet. Skin joins their toes. Each foot is like a paddle.
A webbed foot pushes more water. Animals in cold places have thick fur. It keeps them warm.
See it three ways
As a picture
In words
A webbed foot has skin between the toes. It works like a paddle. It pushes more water than bare toes.
How did living things get such features? Not in one life. A duck cannot grow webbed feet by wanting them.
It took very many generations of parents and young. Those that suited the habitat best lived and had young. The young had the same features.
Try it
Does a web make a paddle?
You need: a bowl or bucket of clean water, your hand.
Be safe: Never drink the water in this activity. Wash your hands after.
- Half fill the bowl with clean water. Do not drink it.
- Spread your fingers wide. Push your hand through the water.
- Feel the water slip between your fingers.
- Now press your fingers together, flat like a paddle. Push again.
- Which way pushes more water?
What you will see: With your fingers apart, water slips past. With your fingers together, your hand pushes more water. The skin on a duck's foot works like your flat hand.
A wrong idea many people have
A camel's hump is full of water.
Why it feels right: A camel can go many days without a drink. So the water must be stored somewhere.
The test that breaks it: Look at what changes. A camel with no food for days has a small hump. The hump flops to one side. When it eats well, the hump is firm again. Look at pictures of thin and well fed camels.
What is true: The hump stores fat, not water. The camel lives on the fat when food is short.
Key words
- feature
- a body part that helps a living thing live in its home.
- gills
- parts that let a fish breathe in water.
- spines
- sharp points on a cactus, used instead of wide leaves.
- webbed feet
- feet with skin between the toes, for pushing water.
Back to your guess
The answer is A: Its body has features that suit the desert.
A camel has features that suit the desert. Its hump stores fat, not water. No animal changes its body just by wanting to.
Check yourself
Try each one before you look. A wrong answer tells you where to go next.
What does a camel store in its hump?
See the answer
Fat
The hump stores fat. The camel lives on it when food is short.
- If you chose A: A hungry camel's hump shrinks and flops. Fat is stored food, so the hump holds fat.
- If you chose C: Sand stays out. Long eyelashes and closing nostrils keep it away.
Which feature helps a fish breathe in water?
See the answer
Gills
Gills let a fish breathe in water.
- If you chose A: Fins help a fish swim and steer. They do not help it breathe.
- If you chose B: Scales cover the skin of a fish. Gills help it breathe.
- If you chose C: A fish has no nose for breathing. Its gills let it breathe in water.
A cactus has spines, not wide leaves. How does that help it?
See the answer
It loses less water.
Wide leaves lose water fast. Spines lose less, and they keep animals off.
- If you chose A: Wide roots near the top of the soil catch the rain. Spines do not.
- If you chose B: The thick stem stores the water. Spines help it lose less.
Ana sees a frog with webbed feet. Which habitat suits it best?
See the answer
In or near water
Webbed feet are paddles. They suit a frog that swims.
- If you chose B: Webbed feet push water. A desert has very little.
- If you chose C: Thick fur suits cold places. Webbed feet suit water.
Can a duck grow bigger webbed feet just by wanting them?
See the answer
No. Features come over very many generations.
Those that suited the habitat best had young. The young had the same features.
- If you chose A: One animal cannot change its body by wanting to. Features take very many generations.
- If you chose B: Swimming does not change the feet a duck has. Features come over very many generations.
From an earlier chapter
A rabbit sleeps in a burrow. What does the burrow give it?
Which feature suits an animal in a very cold place?
See the answer
Thick fur
Thick fur keeps an animal warm in a cold place.
- If you chose A: Webbed feet push water. They suit a pond or a river.
- If you chose B: Spines help a cactus lose less water in a desert.
- If you chose C: Gills let a fish breathe in water.
Keep it
Copy this into your exercise book.
Living things have features that suit their habitat. A camel has wide feet and a fat store in its hump. A fish has gills. A cactus has a thick stem and spines. These came over many generations.
Draw: A cactus with a thick stem, spines and wide roots. Label each one.