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.


Points to Remember:

•           Breathing is a physical act of taking in oxygen and giving out carbon dioxide.

•           Respiration is a chemical process by which glucose in the body breaks down to give energy.


In Plants:

•           Plants have tiny pores called stomata, found on the underside of a leaf.

•           Air containing carbon dioxide and oxygen enters the plant through these openings where it gets used in photosynthesis and respiration.


In Animals:

•           All animals need to respire, be it a cockroach, a fish, or an elephant.

•           They all have different organs to respire. For example, in insects like cockroach, housefly, etc. respire through tiny holes in their bodies called spiracles.

•           In other organisms like earthworms take in air through their skin surface. The skin is kept moist with the help of a substance called mucous.

•           Oxygen of the air gets directly absorbed through the moist skin and carbon dioxide is given out.

•           Earthworms come to the surface during rains, because they can travel more quickly in moist conditions.

•           Exposure to direct sunlight can kill the earthworms. Therefore, they come out only in moist conditions so that they can travel without dehydrating.

•           It is also believed that when there is excessive rain, the soil becomes waterlogged and the earthworms cannot breathe.


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.

•           When water enters the body of the fish through the mouth, it flows over the gills.

•           Gills help to take in oxygen and give out carbon dioxide.

•           Some aquatic animals such as dolphins and whales come to the surface of the water regularly to take in air, since they breathe with the help of lungs.


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.

Human respiratory system

•           They take in oxygen and give out carbon dioxide.