About the AIR

Air is the mixture of gases on the earth.

A thick blanket of air surrounding the earth’s surface is called as atmosphere.

The moving air is called as wind.

These are the figures that moves with the help of wind.

COMPOSITION OF AIR

These substances which made up air can be now individually identified.

The composition of the air is shown below.

Air contains mainly oxygen, nitrogen and remaining includes carbon dioxide, noble gases, water vapour, dust particles, and traces of other gases.

Nitrogen and oxygen

Air contains about 78% nitrogen and 28% oxygen.

Oxygen in air supports burning whereas nitrogen does not.

Carbon dioxide

Air contains about 0.003% of carbon dioxide.

Plants and animals take in oxygen and give out carbon dioxide during respiration.

During burning, carbon dioxide is also produced.

Water Vapour

Air contains varying amounts of water vapour depending on the weather of a place.

The sun heats the water in oceans and seas. This water evaporates and forms.

Here is an image of wet clothes dry.

Dust and Smoke

Air contains dust. Air also contains smoke.

Now that we know the constitutions of air.

Now we learn the importance of survival of living beings on this planet.

AIR SUPPORTS LIFE

We all need air to survive. Air contains oxygen and carbon dioxide useful to plants and animals.

Plants use carbon dioxide of the air to make their own food by a process called photosynthesis.

Let us see how air supports life in plants and animals.

In Plants

All animals need to respire, be it a cockroach, a fish, or an elephant. It is just that they use different organs and mechanisms for respiration.

Given below is a cockroach click any button to see its functions.

Insects, e.g., cockroach, housefly, etc.respire through

tiny holes in their bodies called SPIRACLES.

In Aquatic animals

Most aquatic animals such as fish, tadpoles, crabs and shrimps have special organs for respiration called gills.

They take in the air dissolved in water.

Click any button to see about dolphins.

Some animals such as dolphins and whales come

out to the surface of the water to take in air, since they have

lungs to breathe.

In Amphibians

Amphibians such as frogs, newts and salamanders need breathing systems for both air and water.

Crocodiles and alligators swim through water with part of their snout above the water surface to breathe easily through nostrils

Frogs have well-developed lungs to breathe air when on land. In water, frogs breathe with the help of their moist

skin.

In Birds Birds have a very efficient respiratory system as they

need high levels of oxygen during flight.

Birds have a pair of lungs with air sacs that remain open all the time, so that air can easily pass through them.

In Mammals Most mammals breathe with the help of lungs.

They take in oxygen and give out carbon dioxide.

This picture shows the human respiratory system.

BALANCE OF OXYGEN AND CARBONDIOXIDE IN THE AIR

The balance of oxygen and carbon dioxide in the atmosphere is maintained through respiration in plants and animals and by photosynthesis by plants.

Plants produce oxygen during photosynthesis and utilize oxygen during respiration.

They produce much more oxygen during photosynthesis than they consume.

This is how the oxygen consumed by plants and to large extent by animals is replenished in the air through photosynthesis.

Fill in the blanks1) Air is a …………. (solution/mixture) of gases

2) …………. (Oxygen/Nitrogen) constitutes about 78% of air.

3) ………... (Oxygen/Nitrogen) is needed for burning.

4) During respiration, we utilize ……….. (oxygen/carbon dioxide) and give out ……….. (oxygen/carbon dioxide).

5) Plants take in ………….. (oxygen/carbon dioxide) during photosynthesis.

End of lesson

THE END