Resources provided by nature on Earth which can be utilized by living organisms to sustain their life are called natural resources. These include air, water, soil, sunlight, minerals, etc. All these resources are found accumulated in different layers of Earth which are as follows: –
(i) Lithosphere– The outer crust of our planet Earth, which we call as land.
(ii) Hydrosphere – The Earth’s surface is covered with 75% water. This water is found to be present in seas, oceans, rivers, lakes, streams, ponds, underground water, etc. Earth is known as Blue Planet because of the presence of plenty of water.
(iii) Atmosphere -The multi-layered gaseous envelope of air that covers the whole Earth like a blanket.
The biosphere is the life-supporting zone of the Earth. Here, the atmosphere, the hydrosphere and the lithosphere interact and make life possible.
Living things like plants and animals form the biotic components of the biosphere. Non-living things like air, water and land form the abiotic components of the biosphere.
1. RESOURCES ON EARTH AND THEIR IMPORTANCE
Natural resources are the non-living (abiotic) components of nature. They are used by human beings in order to meet their basic requirements. The natural resources present on the Earth are air, water and land.
Air is a mixture of many gases like nitrogen (N2), oxygen (O2), carbon dioxide (CO2) and water vapours. The precise composition of these gases makes life possible on the Earth. The layer of gaseous envelope surrounding the Earth is called atmosphere. It has many significant roles to play, such as protection from ultraviolet rays, helping in the mode of communication, etc.
All kinds of cells, whether eukaryotic or prokaryotic need oxygen to break-down glucose molecules to get energy for their various activities (by the process of respiration). This phenomenon releases carbon dioxide into the atmosphere. The other sources of CO2 in the air include:-
(i) Combustion of fuels by humans and
(ii) Forest fires
These sources liberate a high amount of CO2 in the atmosphere, but still, the percentage of carbon dioxide in the air is a fraction of a pe recent. This is because CO2 is fixed in two ways which are as follows:
(i) Green plants convert carbon dioxide into glucose in the presence of sunlight by the process of photosynthesis.
(ii) Many marine animals use carbonates (dissolved in seawater) to make their shells.
On planets such as Venus and Mars, no life is known to exist. The major component of the atmosphere on these planets is carbon dioxide (constitutes 95-97% of the atmosphere). The core significances of the atmosphere are discussed below
1. Role of Atmosphere in Climate Control
The atmosphere covers the Earth like a protective blanket. The air is a bad conductor of heat. So, the atmosphere prevents the sudden increase in temperature during the daylight hours. Similarly, during the night, it slows down the escape of heat into the outer space.
Thus, it keeps the average temperature of Earth fairly steady during the day and even during the course of the whole year. The atmosphere, therefore, ensures that the right amount of heat is received by Earth. It controls and allows the living organisms to survive.
Note: Moon has no atmosphere and its temperature ranges from -190°C to 110°C.
2. Winds: The Movement of Air
Winds result due to changes taking place in our atmosphere like heating of air and formation of water vapours.
Winds occur by the following events in the atmosphere
(i) When solar radiations fall on the Earth, the majority of these radiations are reflected back (re-radiated) by land and water bodies. Some of them are absorbed. These reflected solar radiations heat the atmosphere from below. Due to this, convection currents are set up in the air. Since land gets heated faster than water, the air over land would also be heated faster than the air over water bodies.
(ii) In coastal regions during the day, the air above the land gets heated faster and starts rising. As this air rises, a region of low pressure is created. Air over the sea moves to this area of low pressure. The movement of air from one region to the other creates winds. The direction of the wind would be from the sea to the land during the day.
(iii) At night, both land and sea cool down. Since water cools down slowly than land, the air above the water would be warmer than the air above the land. Now, the air above the sea will start rising. Land air moves to the low-pressure area, i.e. the direction of wind would be from land to sea during the night.
(iv) Other factors that influence the winds are a rotation of Earth and the presence of mountain ranges in the path of winds. Various phenomena occurring in the atmosphere, such as cyclones, thunderstorm, are also due to movements of air caused by uneven heating of atmosphere in different regions.
Rainfall occurs by the following events in the atmosphere: –
(i) Waterbodies are heated by solar radiations during the day. Due to this a large amount of water evaporates. This goes into the air as water vapours. Various biological activities also add some amount of water vapours in the atmosphere.
(ii) Air also becomes hot due to sunlight. It starts rising up along with water vapours. As the air rises, it expands and cools. This cooling causes the water vapours in the air to condense in the form of tiny droplets.
(iii) Condensation of water is facilitated by dust and other suspended panicles. They act as a nucleus for these drops to adhere around. An excessive collection of tiny droplets of water appears in the form of clouds.
(iv) Once the water droplets are formed, they grow bigger by their further condensation. When the drops have grown big and heavy, they fall down in the form of rain.
(v) Sometimes when the temperature of the air is low enough, precipitation may occur in the form of snow, sleet or hail.
Rainfall patterns are decided by the prevailing wind patterns. In large parts of our country, rains are mostly brought by the South-West or North-East monsoons. In some areas, these are caused by the depressions in the Bay of Bengal. ·
An increase in the composition of harmful or undesirable substances in the air is called air pollution. These undesirable substances are called air pollutants. Air pollution can also be defined as an undesirable alteration in physical, chemical or biological characteristics of air.
Causes of Air Pollution
Following activities could lead to air pollution
(i) Excessive burning of fossil fuels (like coal and petroleum) produces a high amount of oxides of nitrogen and sulphur (e.g. NO2 and SO2). These oxides get mixed with air moisture and cause acid rain. It leads to many harmful effects like corrosion of monuments. For e.g., Taj Mahal is facing a great threat due to Mathura refinery. It produces a huge amount of NO2 and SO2 that contributes to acid rain. Combustion of fossil fuel also increases the number of suspended particles in the air. These suspended particles could be unburnt carbon particles or substances, known as hydrocarbons.
(ii) Many industries release a high amount of poisonous gases like CO into the atmosphere causing air pollution.
(iii) Dust also causes pollution. Its inhalation causes allergic ailments like asthma, cold etc.
Effects of Air Pollution
The harmful effects of air pollution are as follows:-
(i) It affects the respiratory system and causes diseases like asthma, lung cancer, pneumonia, etc.
(ii) Pollutant gases cause allergies, irritation in the eyes, lungs, etc.
(iii) Gases like NO2, SO2, etc., get dissolved in rain to give rise to acid rain.
(iv) The presence of high levels of pollutants in the air reduces visibility. In cold weather, when water also condenses out of the air, forms smog. It is a visible indication of air pollution.
(v) It causes the greenhouse effect and leads to global warming.
Note Organisms called lichens are sensitive to pollutants like SO2 and do not grow near industries and in areas with high air pollution.
Water: A Wonder Liquid
Water is an inexhaustible natural resource. It occupies a very large area of the Earth’s surface (both above and under the ground). Some amount of water exists m the form of water vapours in the atmosphere. Most of the water on Earth’s surface (found in seas and oceans), is saline. Freshwater is found as frozen ice caps at poles and on snow-covered mountains. The underground water and the water in rivers, lakes and ponds are also fresh.
Importance of water for Living Beings
Water is essential for Living beings because: –
(i) It provides a medium for all the cellular processes to take place.
(ii) It is necessary for the transportation of substances from one part of the body to the other in dissolved form.
(iii) It helps to maintain body temperature.
(iv) It is required to maintain the balance of salts thin the body.
(v) Terrestrial life forms require freshwater. Their bodies cannot tolerate or get rid of the high amount of dissolved salts in saline water.
(vi) All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
(vii) All the organisms need to maintain the level of water within their bodies in order to survive.
Therefore, water is essential for the sustenance of life. The availability of water decides the number of individuals of each species that are able to survive in a particular area and also the diversity of life there.
Note: The other Factors that decide the sustainability of life in a region are temperature, nature of the soil, etc.
It is defined as an undesirable change in the physical, chemical and biological quality of water. It occurs due to the addition of unwanted and harmful substances called water pollutants into water. Water pollution adversely affects living organisms by making the water unsuitable for use.
Causes of Water Pollution
Water pollution is caused due to the following reasons: –
(i) Water dissolves fertilisers and pesticides from agricultural fields with surface runoff rainwater. It drains them to the nearby water bodies, where they cause harmful effects on aquatic life.
(ii) Dumping of sewage and other wastes into water-bodies adversely affects the water quality.
(iii) Industries use water for cooling in various operations. Later this hot water is released into water bodies. This causes sudden changes in the temperature of a waterbody that affects the breeding of aquatic organisms.
Effects of Water Pollution
Polluted water can affect the life forms in various ways as mentioned below: –
(i) Addition of undesirable substances to water-bodies – Fertilisers, pesticides, dirt, sewage, industrial wastes like heavy metals (mercury and lead) and disease-causing microorganisms get mixed with water, making it unfit for consumption.
(ii) Death of flora and fauna of water-bodies – As the amount of organic wastes increases in water, bacteria and other organisms multiply very fast by using the dissolved oxygen present in the water. Thus, making the waterbody deficient m oxygen. This lack of oxygen, in turn, kills the fishes and affects aquatic animals.
(iii) Thermal pollution or change in temperature – Sudden marked change in the temperature range of waterbody in which the aquatic organisms are living, can be dangerous for them or may affect their breeding. Eggs and larvae are particularly susceptible to temperature changes.
(iv) Human diseases – Water provides a home to pathogens, which causes infections in human. These pathogens include viruses, bacteria, fungi, nematodes, protozoans, etc. They cause diseases such as typhoid, cholera, jaundice, etc., in humans.
It is the portion of the outermost layer of the Earth (crust), which provides’ support for the growth of the plants. The minerals present in the soil, supply a variety of nutrients to life forms. It is an important resource that decides the diversity of life in an area.
Formation of Soil
Soil takes a long period of time to form. For millions of years, the rocks at or near the surface of the earth are broken down by various physical, chemical and biological processes. The end product of this breaking down is the fine particles of soil.
Factors Responsible for the Soil Formation
Following are the factors responsible for soil formation: –
The Sun heats up the rocks during the day so that they expand. During the night, these rocks cool down and contract. Since all parts of rock do not expand and contract at the same rate, this results in the formation of cracks. Ultimately, the huge rocks break up into smaller pieces.
It helps in the formation of soil in two ways. First, water could get into the cracks in the rocks formed due to uneven heating by the Sun. Freezing of this water would lead to widening up of cracks later.
Second, flowing water wears away even hard rock over long periods of time. Fast flowing water often carries big and small particles of rock downstream. These rocks rub against other rocks. It results in abrasion that causes the rocks to break down into smaller particles. The water then takes these particles along with it and deposits them further down its path. That is why soil is found in distant places from its parent rock.
It acts similarly as water. Strong winds erode rocks down. It carries sand from one place to another.
4. Living Organisms
These also influence the formation of soil. The lichens grow on the surface of rocks. They release certain substances that cause the rock surface to powder down and form a thin layer of soil. Other small plants like mosses grow on the surface of rocks. They cause further breakdown of rocks. Roots of big trees also break rocks by penetrating deeper into the rock bed (biological weathering).
Constituents of Soil
The soil is a mixture of small particles of rocks, bits of decayed living organisms (humus) and partially decomposed plant and animal matter (detritus). It also contains various forms of microorganisms. The main constituents of soil are minerals, air, water, organic matter and living organisms.
The type of soil is decided by the average size of particles found in it. Quality of soil is decided by the amount of humus, organic matter, microscopic organisms, etc. For e.g. black soil is rich in Ca, Fe, Mg, Al whereas red soil is rich in iron oxides.
(i) Humus – It is a dark coloured organic substance that plays a major role in deciding the soil structure. It causes the soil to become more porous and allows water and air to penetrate deep underground.
(ii) The mineral nutrients that are found in a particular soil depend on the rock from which it was formed.
(iii) The nutrient content of a soil, the amount of humus present in it and depth of the soil are some of the basic factors that decide which plants will grow on a particular soil.
(iv) Topsoil is the topmost layer of the soil. It contains humus and living organisms in addition to soil panicles. The quality of the topsoil is an important factor that decides the biodiversity of a particular area.
Removal of useful components from the soil and the addition of hazardous substances (both solid and liquid) into it, is called soil pollution. It destroys the soil structure by killing the microorganisms that recycle nutrients in the soil. It also kills the earthworms, which are helpful in making rich humus. Fertile soil can quickly become unfertile if sustainable practices are not followed. One of the major causes of soil pollution is modern farming practices. They involve the use of a large amount of pesticides and fertilisers. These substances adversely affect the soil fertility.
It is the removal of the top fertile layer of the soil due to strong winds and flowing water. Vegetation cover helps in the percolation of water into deeper layers. It also helps to prevent the removal of top soil. In the absence of this cover, topsoil is likely to be removed very quickly. Soil erosion is more likely to occur in hilly or mountain regions if all the soil gets washed away, the underneath rocks are exposed. These rocks have very low fertility.