Sunshine Reading Club
Title
26/02/16 4:31 pm
What is Air?
What is Air?
All living things breathe air. Every moment of every day people breathe air. Air is all around us.
It
is an invisible mixture of gases, mainly oxygen and nitrogen. Without air, animals and plants
would die.
The Earth’s Atmosphere
The air we breathe is a mixture of gases, mainly oxygen and nitrogen, and some carbon
dioxide.
21% oxygen
78% nitrogen
very small amounts of other gases and water vapor.
Animals and plants get the air they need by breathing, but they breathe in different ways.
How Plants Breathe
Air enters plants through tiny holes, which are found mainly in the leaves.
Rants take carbon dioxide from the air, and they return oxygen to the air. Plants need carbon
dioxide to live.
The breathing holes on a leaf are called pores. You can't see them without a microscope.
Close-up of a waterlily stem, showing the large air passages
Waterlilies have tubes in their stems to take air to their roots.
How Animals Breathe
We breathe air in through our nose and mouth and into our lungs.
Our lungs absorb (or take) from the air the oxygen that we need to live and we breathe out
carbon dioxide.
Giraffes, horses, cows, cats and dogs all have lungs like ours. But many animals breathe
differently.
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This diagram shows what your lungs look like. The lungs take in oxygen when we breathe.
Slugs and snails have breathing holes in their sides. The holes open and shut as they breathe
air.
From the air, slugs and snails absorb the oxygen they need to live and breathe out the rest.
A snail breathes through its breathing hole.
Worms breathe through their soft, moist skin. They absorb water which has oxygen in it.
A worm breathes through its skin. Gases move in and out all over the worm's body.
Spiders breathe air through special openings underneath their bodies, called book lungs. The
book lungs absorb the oxygen.
A spider breathes through its book lungs.
Water spiders breathe air, too. Some water spiders build a silken trap in the water and fill it with
air to breathe.
A water spider traps the air bubbles in its underwater web. It uses this air to breathe
underwater.
How Fish and Frogs Breathe
Fish have noses and nostrils - but not for breathing. Fish gulp water in through their mouths.
The water goes over feathery gills that absorb the oxygen from the water.
A fish breathes through its gills.
Frogs breathe by gulping air down into their lungs. But they also breathe through their skins.
A frog’s skin needs to be kept moist so that air can be absorbed through it.
That is why frogs live in damp, wet places, like swamps.
A frog breathes through its nostrils, mouth and skin.
When they hatch, tadpoles have gills like fish. As they grow into frogs, tadpoles grow lungs and
the
gills disappear.
Life Cycle of a Frog
1. The frog lays thousands of eggs called frog spawn.
2. The newly hatched tadpole breathes through gills on the outside of its body.
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3. Four weeks after hatching, the outside gills have withered away. Now the tadpole breathes
through gills covered by a flap of skin inside its body.
4. Twelve weeks after hatching, the tadpole has changed into a froglet. Its inside gills have
disappeared. It now has lungs and comes up to the surface to breathe air.
5. Sixteen weeks after hatching, the tadpole has changed into a young frog.
How Insects Breathe
Insects, such as grasshoppers, flies and moths, breathe air through spiracles. These are tiny
holes found along each side of their bodies.
A moth breathes through its spiracles. Air tubes take the oxygen around its body.
Caterpillars and some other insect larvae also breathe like this.
A caterpillar breathes through spiracles, too.
Some insects breathe air, even though they live in water. The water beetle collects air under its
wing cases and uses it when it dives for food.
The water beetle holds air under its wings so it can breathe underwater.
Some insect larvae live in water. The larvae of the mosquito breathe air through breathing
tubes.
A mosquito larva must come to the surface of the water to breathe.
An adult mosquito breathes through spiracles, like other insects.
How Birds Breathe
Birds breathe air into their lungs. Their lungs are not very big but they have lots of air sacs
connected to them.
Birds also have air spaces inside their bones. This makes them very light so they can fly.
There are many air sacs on a bird’s lungs.
How Reptiles Breathe
Reptiles, such as snakes, have lungs. Snakes have one or sometimes two lungs, one behind
the other, in their thin bodies.
A snake breathes using lungs.
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A snake's body is too thin for its lungs to lie side by side so its lungs lie in a straight line.
Did You Know?
• We breathe 23,000 times a day.
• Two-thirds of the human body is made of oxygen. Oxygen is the most common chemical
element on Earth. Water is 90 per cent oxygen.
• A person at rest uses half a litre of oxygen per minute for breathing. That's more than quarter
of a million liters per year!
• A tree absorbs up to 4 kilograms of carbon dioxide from the air in a year.
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