Air Around Us
IMPORTANT TERMS
Atmosphere: - Layer of Earth surrounding the surface of the Earth.
Pollution: - Presence of substances in the environment in quantities that are harmful to living beings.
Gills: - Special organs for respiration in aquatic animals such as fish.
Stomata: - Tiny pores for exchange of gases in plants.
Spiracles: - Insects have tiny holes on the sides of their body used for respiration.
Amphibian: - An amphibian is an animal that can live both on land and in water. E.g. Frog.
THE ATMOSPHERE
The earth is surrounded by a layer of air that is known as Atmosphere. The blanket of atmosphere surrounds the Earth for 1000 km in space.
COMPOSITION OF AIR
The movement of air is known as wind. Air is a mixture of gases. Nitrogen and oxygen make up about 99% of the air. The remaining 1% is a mixture of other gases which includes carbon dioxide, argon and other noble gases.
Nitrogen
Nitrogen is a major component of air and is the most abundant gas in the atmosphere. Nitrogen occupies nearly four-fifths of the space that is filled by air. Air contains about 78% nitrogen. Nitrogen does not support the process of combustion.
Plants cannot use nitrogen directly from the atmosphere. There are certain bacteria found in the soil and in the roots of certain plants such as peas which convert nitrogen into the form that can be used by plants. It is necessary for the growth of plants.
Oxygen
Oxygen makes up 21% of air around us. Oxygen is essential for respiration and combustion. Oxygen is released as a by-product during the process of photosynthesis.
Carbon Dioxide
Carbon dioxide is present in very small amounts in air. Air contains about 0.03% of carbon dioxide. Carbon dioxide is released as a waste product during respiration. Carbon dioxide is produced by complete combustion of fossil fuels. It is required by plants to produce food.
Water Vapour
The amount of water vapour present in the air varies from place to place and depends on the weather of a place. The amount of water vapour present in the air is known as humidity. The presence of water vapour in air is important for the water cycle. Water evaporates from water bodies in the form of water vapour in air and is restored back in the form of rain.
Dust and Smoke
Air contains dust. The dust particles can be seen in the beam of sunlight. Air also contains smoke released from factories and vehicles.
PROPERTIES OF AIR
Air occupies space.
Air has weight and anything which has weight exerts pressure.
Air is colourless and cannot be seen.
Air cannot be seen but it can be felt when it moves.
AIR SUPPORTS LIFE
Air contains oxygen which is essential for respiration. Air also contains carbon dioxide which is needed for the process of photosynthesis. Plants take carbon dioxide present in the air and convert it into carbohydrates by using sunlight and water. Plants are consumed by herbivorous animals which in turn, are consumed by carnivorous animals.
Plants
Plants have tiny pores called stomata, which are found on the underside of leaves. The exchange of gases takes place through these stomata.
Insects
Insects have small openings on the sides of their body which are called spiracles. They have a network of air tubes called tracheae for the exchange of gases. Oxygen passes through spiracles and reaches the tracheal tubes. It further, diffuses into the body tissue and reaches every cell of the body.
Earthworms
Earthworms breathe through their skin. They have moist skin which is supplied with a network of tiny blood vessels which absorb oxygen and supply it to the rest of the body.
Aquatic Animals
The animals that live in water are known as aquatic animals. Fishes and other aquatic animals absorb dissolved oxygen with the help of gills, which are projections of the skin. They are well supplied with blood vessels for exchange of gases.
Amphibians
An amphibian is an animal that can live both on land and in water. E.g. frog, toad, salamander. Frogs have a pair of lungs to breathe in air when on land. They can also breathe in water through their skin which is moist and slippery and is supplied with blood capillaries.
Birds
Birds have a pair of lungs with air sacs that remain open all the time.
AIR POLLUTION
Air pollution occurs when the air contains harmful gases such as carbon monoxide, dust, fumes or chemicals in quantities harmful to human health and environment.
Burning of fossil fuels such as coal releases harmful substances in the atmosphere, which cause air pollution.
Deforestation or cutting down of trees also leads to an increase in air pollution.
Vehicles that are driven by petrol and diesel produce high levels of pollutants such as carbon monoxide, carbon dioxide, nitrogen oxides and smoke.
Industrialization is one of the major causes of air pollution. Various industries release poisonous gases into the air that are harmful for human beings, plants and animals.
IMPORTANCE OF AIR
INTERESTING FACTS