Category : 9th Class
Our earth is a unique planet. It supports all forms of life. To support all these forms of life, the nature has endowed this planet with vast resources such as land, air, water, atmosphere, minerals, etc. All these resources are divided into two components, biotic and abiotic. Biotic components constitute all the living things whereas abiotic components constitute all the non-living things.
Abiotic components consist of air, water, soil, land, weather, climate, etc. These all components are very vital to support all forms of life on this planet.
Air is a mixture of many gases such as nitrogen, oxygen, carbon, water vapour, etc. Air is one of the most important factors that supports life on this planet. Our atmosphere constitutes the air. The sunlight is filtered by this atmosphere so that no harmful rays can reach to the earth. The atmosphere has five layers. They are the following:
The Movement of Air: Wind
Cool breezes that blow on the earth are called winds. They bring a great relief after a hot day. All the phenomena such as the causes of the movement of air, speed of wind, rainfall, etc. are the result of changes that take place in our atmosphere due to the heating of air and the formation of water vapour. Water vapour is formed due to evaporation of water. The atmosphere gets heated from the radiation that is reflected back or reradiated by the land or water bodies. Convection currents are set up in the air when it gets heated.
Air pollution is like a giant monster which has been destroying the life from the earth slowly and gradually. The process of deforestation has deteriorated the quality of air that directly affects our health.
The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur. Inhalation of these gases is very dangerous for our health. They also cause acid rain as the air in the atmosphere is mixed with these gases. The combustion of fossil fuels also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. Presence of high levels of all these pollutants reduced the visibility. Especially in cold weather when water also condenses out of air. This is known as smog and is a visible indication of air pollution. Air pollution can cause respiratory problems, skin disease, cancer, high blood pressure, irritation, etc. It also affects the life cycle of plants and several other animals. The increase amount of carbon dioxide in the atmosphere is causing green-house effect and damaging the ozone layer, which protect the earth from harmful ultraviolet rays.
Dramatic loss of ozone (a hole in the ozone layer) in the lower stratosphere over Antarctica was first noticed in 1970s by a research group. This was mainly due to the release of man-made chemicals containing CFCS, Br, other related halogen compounds when these chemicals diffuse into the atmosphere, they react with the UV radiations from sun and release chlorine atoms that destroy ozone. This results in the reduction of the ozone layer.
Water is an important natural resource that carries out various life activities. It occupies a very large area of the earth and it is also found underground. The other form water is found in the atmosphere as water vapour. The main source of drinking wateris found in the form of snow and frozen ice caps. Inspite the presence of large amount of water, very little percent of all the available water is potable. The potable water if found in rivers, lakes and ponds. Water is found in all the forms such as solid, liquid and gas. Water is an agent of soil formation and a medium for several ecosystems. Even 70% of human body consists of water. Thus, water is one of the most important things that support life on the earth. It is also the dwelling place for many aquatic animals and plants. All cellular processes take place in water medium, thus the importance of water increases automatically.
Water is a precious resource. We must conserve it not only for ourselves but also for future generation. Man's disinclination towards its conservation causes water pollution on large scale that pollutes almost all the sources of pure water like river, lake, glacier, etc. There are many factors that are responsible for water pollution. Water dissolves the fertilisers and pesticides that we use in our farms. So some percentages of these substances are washed into the water bodies. Sewage from our towns and cities and the waste from factories are also dumped into rivers or lakes. Some industries also use water as coolant in various operations and later return this hot water to water-bodies. The water inside the deep reservoir would be colder than the water at the surface which gets heated by the sun. All this can affect the life-forms that are found in these water bodies in various ways. It can encourage the growth of some life-forms and harm some other life-forms. This affects the balance between various organisms.
The following are the harmful effects of water pollution:
(i) It causes fatal diseases such as typhoid, cholera, jaundice and hepatitis.
(ii) It disturbs the ecological balance on the earth and thus harms the various life forms available on the earth.
(iii) It is an ideal breeding ground for disease causing bacteria and germs.
(iv) It affects the aquatic forms of life and thus endangers many animals and plants living in water.
As we all know that water is a renewable source of energy. It gets renewed naturally through water cycle. Water from water bodies gets evaporated due to sunlight and reaches the atmosphere as water vapour. In the atmosphere, water vapour forms cloud and condenses. The condensation of water changes it into tiny drops of water and it comes down as rain. The same cycle is repeated continuously.
Soil is an upper portion of the earth that supports the growth of plants and animals. Soil contains many valuable nutrients that support life forms. Soil is a mixture. It contains small particles of rock of different sizes, humus and various forms of microscopic life. The average size of soil particles decides its types and the amount of humus and microscopic organisms decides its quality. Soil supports all kinds of vegetation. Without soil nothing can grow on this earth. Formation of soil takes millions of years.
The following are the types of soil:
Clayey soil is very fine and smooth in texture. This kind of soil is prone to water logging in spring season. If there is adequate drainage, clayey soil contains high nutrient levels for the growth of plants.
Sandy soil has rough texture. It is composed of silica particles, quartz particles and very small amount of clay soil mixed with it. This soil is prone to over-draining and summer dehydration.
Silty soil has smooth texture. This soil is the most fertile soil. It is composed of minerals and fine organic particles. This soil contains good amount of nutrients and allows good drainage of water.
Loamy soil is composed of nearly 40% sand, 40% silt and 20% clay. This soil is perfect for cultivation of crops. This soil is very fertile and full of organic matter. This soil allows good drainage, retains moisture and is rich in nutrients.
Peaty soil has fewer nutrients than other soils. This soil is prone to over-retention of water. This soil can be used for cultivation with the use of fertilizer and artificial drainage.
Chalky soil is light brown in colour. This soil contains large quantities of stones of different sizes. This soil is not suitable for cultivation. This soil .blocks the availability of trace elements such as iron and manganese and makes these elements unavailable to plants. Unavailability of nutrients causes poor growth and yellowing of leaves.
Soil erosion is a matter of great concern. It causes enough harm to the environment and affects the growth of vegetation of a place. The topsoil is carried away by various eroding agents and makes the soil of a place infertile. The following are the effects of soil erosion:
(i) The soil loses its fertility.
(ii) It causes land slide in hilly areas.
(iii) It causes floods.
(iv) It causes drought.
The following are the methods of soil conservation:
(i) Planting more trees or afforestation
(ii) Intensive cropping
(iii) Terrace farming
(iv) Constructing dams or embankments
(v) Developing proper canal system around the field
Soil pollution is mainly caused by disposing the chemical wastes from factories to the fields, dumping the non-biodegradable wastes into the soil, cutting the trees on large scale, excessive use of fertilisers and chemicals, etc. Soil pollution reduces the fertility of the soil and turns a fertile land into barren land and thus causes ecological imbalance.
The air contains 78% of nitrogen, which is essential for the growth of many life forms. It is present in all the living organisms in the form of protein, amino acid and nucleic acids. It is converted into nitrates by nitrogen fixing bacteria that is used by plants.
During lightning nitrogen of atmosphere reacts with oxygen and form dilute nitric acid. The following figure shows a nitrogen cycle in nature:
Carbon is an important gas that is found on the earth. It is found in various forms on the earth. It is found as diamond and graphite in the elemental form, as carbon dioxide gas in the atmosphere, as carbonate and hydrogen carbonate salts in minerals, etc. The nutrients such as proteins, carbohydrates, fats, nucleic acids and vitamins contain carbon. Various animals contain carbon in the form of endoskeletons and exoskeletons. Carbon is also used in the process of photosynthesis by green plants to make their own food and thus supports all forms of life on the earth. In the process of photosynthesis, carbon is converted into glucose molecules that are either converted into other substances or used to provide energy for the synthesis of other biologically i m p o r t a n t molecules. This carbon dioxide goes back into the atmosphere during the process of respiration. Combustion of fuels also adds the carbon dioxide into the atmosphere. The process of industrialization has added a large amount of carbon dioxide into the atmosphere. The increase amount of carbon dioxide in the atmosphere leads to global warming. The following figure shows carbon cycle in the atmosphere.
You need to login to perform this action.
You will be redirected in 3 sec