The document discusses the composition and importance of air. Air is a mixture of gases that surrounds the Earth's surface, called the atmosphere. It is composed mainly of nitrogen (78%), oxygen (21%), and trace amounts of other gases like carbon dioxide and water vapor. Oxygen supports burning and respiration, while plants and animals exchange oxygen and carbon dioxide to carry out photosynthesis and respiration. This balance in gases is essential for life on Earth.

2. 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.

3. 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.

4. Nitrogen and oxygen
 Air contains about 78% nitrogen and 28% oxygen.
 Oxygen in air supports burning whereas nitrogen does
not.

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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.

15. Fill in the blanks
1) 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.

16. End of lesson
THE END