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.
• 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.
• 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.
• 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.
• 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.
• Most mammals breathe with the help of lungs.
Human respiratory system
• They take in oxygen and give out carbon dioxide.