E. Earth and Space Systems · Air and Water in the Environment

Living Things Need Air and Water

E2.5 A1.2 A1.5About 40 minutes

Learning goals

I can explain how people depend on air and water.
I can describe how plants use air and water.
I can describe how animals on land and in water get the air and water they need.
I can name ways people use air and water for travel, energy, food and fun.

Words to know

depend on
To need something in order to live or to do a job.

oxygen
A gas in air (and mixed into water) that people and animals need to breathe.

lungs
Body parts in your chest that take in air when you breathe.

gills
Body parts that let fish take oxygen out of the water.

roots
The parts of a plant that take in water from the soil.

habitat
The place where a plant or animal lives and finds what it needs.

carbon dioxide
A gas in air that plants take in to help make their food. We breathe it out.

Hold your breath!

Take a big breath and hold it. Count: 1, 2, 3, 4, 5... Okay, breathe!

It didn't take long before you needed air, did it? Your body needs air all the time, even when you sleep. And every day, you need water too.

Today you'll find out how all living things depend on air and water.

Remember from Grade 1

In Grade 1 you learned that all living things have basic needs: air, water, food, heat, shelter and space. Air and water are two of the most important!

People need air and water

Air: Every time you breathe in, your lungs take oxygen from the air. Your body uses oxygen to stay alive and to have energy. A person can live only a few minutes without air.
Water: More than half of your body is water! You lose water when you sweat, breathe out and go to the bathroom, so you need to drink every day. A person can live only a few days without water.

That's why clean air and clean water matter so much.

Plants need air and water

Plants take in water through their roots. The water travels up the stem to the leaves.
Plants take in a gas from the air called carbon dioxide through tiny holes in their leaves.
Using sunlight, the plant turns water and carbon dioxide into food (sugar) for itself.
While they do this, plants give off oxygen into the air. Most of the oxygen we breathe was made by plants and by tiny plant-like living things in lakes and oceans!

Plants also give off water vapour from their leaves, which goes into the water cycle.

A plant takes in water through its roots and carbon dioxide from the air through its leaves. With sunlight it makes its food, and it gives off oxygen and water vapour.

Animals need air and water

Land animals, like deer, raccoons and robins, breathe air with lungs and drink water from lakes, streams and puddles.
Fish live in water and breathe with gills. There is oxygen mixed into the water, and gills take it out.
Some animals live in water but breathe air. Beavers, loons, whales and turtles come up to the surface to breathe.
Frogs lay their eggs in water. Tadpoles live in water and breathe with gills. Grown-up frogs breathe air.
Many animals have their habitat in or near water: ducks, muskrats, herons, dragonflies and many more.

A white-tailed deer standing in a forest stream and drinking the water. — Land animals like this deer breathe air with lungs and drink water from streams, lakes and puddles. AI-generated image

🐟🦫🐸🦆🦌🌳

Fish, beaver, frog, duck, deer and a tree: every one of them depends on air and water.

Living thing	How it gets air	How it gets water
person	breathes with lungs	drinks; also from food
maple tree	takes in carbon dioxide through its leaves	roots soak it up from soil
fish	gills take oxygen from the water	lives in water
beaver	comes up to breathe with lungs	lives in and near water
deer	breathes with lungs	drinks from streams and ponds

How some living things get air and water

People use air and water in many other ways

Food: Farmers water crops and animals. We catch fish. We cook with water.
Cleaning: washing hands, clothes, dishes.
Travel: ships, canoes and ferries travel on water. Sailboats are pushed by wind. Airplanes fly through the air.
Energy: Moving water spins machines that make electricity. Ontario makes lots of electricity from moving water, for example at Niagara Falls. Wind turbines make electricity from moving air.
Fun: swimming, paddling, skating on frozen ponds, flying kites.
First Nations, Métis and Inuit communities have depended on lakes, rivers and the sea for travel, food and much more for a very, very long time.

Worked example

Let's do a fair test: Do plants need water?

Ben has two bean plants that are the same size. How can he test whether plants need water?

Question: Do bean plants need water to stay healthy?
Predict: Ben thinks the plant without water will droop.
Fair test: Keep everything the same: same kind of plant, same size pot, same soil, same sunny window. Change only one thing: Plant A gets water. Plant B gets no water.
Observe for 5 days and record: Plant A stays green and stands up. By day 4, Plant B's leaves droop and look wilted.
Conclude: Plants need water. (Ben waters Plant B right away so it can recover!)

The plant with water stayed healthy. The plant without water wilted. Plants depend on water.

Worked example

Let's explain: How does a fish breathe?

A goldfish lives in a bowl of water. It never comes up to take a breath. How does it get oxygen?

Oxygen from the air mixes into the water. (That's why fish tanks often have a bubbler.)
The fish takes water into its mouth.
The water passes over its gills. The gills take the oxygen out of the water.
The water goes out through openings on the sides of its head.

The fish uses its gills to take oxygen from the water.

Just for fun

At the start of this lesson you held your breath for about 5 seconds. A beaver can stay underwater for about 15 minutes! What a show-off.

Hands-on activity

Watch water travel up a plant

You need: a stalk of celery with leaves (or a white carnation), a clear glass, water, food colouring and a knife (a grown-up cuts).

Fill the glass half full of water and add lots of food colouring (blue or red works best).
A grown-up cuts a little off the bottom of the celery.
Stand the celery in the coloured water.
Predict: What will happen?
Check after 2 hours and again the next day. Look at the leaves. Then a grown-up cuts across the stalk so you can see the little coloured dots inside.

What did you observe? The coloured water travelled up the stalk to the leaves. That's how plants move water from their roots to their leaves!

Your turn

What gas in air do people and animals need to breathe?

What body parts do people use to breathe?

How does a plant take in water?

How does a fish get oxygen?

Name an animal that lives in water but breathes air.

Name one way people use moving water or moving air to make electricity.

What do plants give off that we need to breathe?

More practice: warm-up

Do you need air when you are sleeping?

Name one way you use water every day.

Is more than half of your body water? Yes or no.

What do we call the place where an animal lives and finds what it needs?

Name one thing the wind can push to help people travel or have fun.

More practice: on your own

Why do you need to drink water every day?

Plants need air too. What gas do they take in, and what do they make with it?

Why does a fish tank often have a bubbler?

In Ben's plant test, why did he keep the soil, pot and window the same?

Name two ways a beaver depends on water.

Challenge

A loon dives under the lake to catch fish. Why must it come back up?

Ben's watered plant grew 2 cm each day for 5 days. How much did it grow in all?

People and plants help each other with air. Explain how.

Check your understanding

Quiz

What do fish use to get oxygen from water?

How does a plant get water?

Plants give off a gas we need to breathe. It is...

Which animal lives in water but breathes air?

In a fair test about plants and water, what should be different between the two plants?

Which is a way people use moving air?

For parents and teachers

Big idea (E2.5): All living things depend on air and water. People and animals need oxygen and water; plants need water and carbon dioxide and release oxygen. Humans also use air and water for food, cleaning, travel, energy and recreation.

How to help: Do the celery activity and look at the cut stalk together. On walks near a pond or creek, look for animals and talk about how each gets air and water. Discuss your family's own uses of water to prepare for the next lesson.

Fair tests (A1.2): Ben's plant test models changing only one variable. You don't need to repeat it at home (a wilted plant is a sad result), but you can talk through how you would set it up.

Common difficulties:

"Fish breathe water." They take oxygen from water with their gills.
"Plants don't need air." They need carbon dioxide from air (and their roots need air in the soil too).
"All animals in water have gills." Beavers, loons, whales and turtles breathe air.