Natural Resources

"Environment is everything which surrounds an organism and influences its life. It includes biotic and abiotic components."

1.0Introduction

The materials present in natural environment and useful to living organisms are called natural resources. A resource satisfies human needs. Water, air, sunshine, land, soil, forests, wildlife, fishes, minerals and power resources all are useful to human. All basic needs of food, shelter and clothing are supplied by natural resources on earth. Natural resource includes total natural environment, that is the entire surface of earth, because all parts of earth's surface are of some use to man as they contribute to the production of necessities and comfort to mankind.

2.0Natural resources

Substances used by man in bulk for survival are called resources and since they are found in nature, they are called natural resources. Probably, the earth is the only planet on which life exists. Life exists on earth because it has all the physical conditions necessary for sustaining it. An ambient temperature, water and food are the basic needs of all life forms. These basic needs of the life forms are to be met by the resources available on the earth and the energy from the sun. The resources available on earth include land [Lithosphere], water [Hydrosphere] and Air [Atmosphere]. The outer crust of the earth is called lithosphere. The water present on the earth's surface and underground constitute hydrosphere. About 75% of the earth's surface is covered with water. The air that covers the whole of the earth like a blanket is called atmosphere.

The life sustaining zone of the earth where the lithosphere, the hydrosphere and the atmosphere interact and make life possible is called the biosphere. Living things constitute the biotic component of biosphere. The air, the water and the soil form the abiotic or non-living component of the biosphere.

• Fossil fuels are considered as non-renewable resources because it takes millions of years to recycle.
  

3.0The breath of life: Air

Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide, water vapour and some others present in the atmosphere. Air is an important inexhaustible natural resource.

Note: Composition of air is the result of life on Earth. In planets such as Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide. In fact, carbon dioxide constitutes up to $95-97\%$ of the of the atmosphere on Venus and Mars.

• Q. If there is no atmosphere around the Earth, what will happen to its temperature? Explanation: The atmosphere around the Earth prevents the heat radiation to escape into the outer space. Thus, in the absence of the atmosphere, the temperature of Earth will decrease upto freezing point during night and increase during day because atmosphere is no longer there to absorb radiations.

• Eukaryotic cells and many prokaryotic cells need oxygen to break down glucose molecules and get energy for their activities. This results in the production of carbon dioxide.
• Another process which results in the consumption of oxygen and the concomitant production of carbon dioxide is combustion. This includes not just human activities, which burn fuels to get energy, but also forest fires.
• Despite this, the percentage of carbon dioxide in our atmosphere is a mere fraction of a percent because carbon dioxide is 'fixed' in two ways - (a) Green plants convert carbon dioxide into glucose in the presence of sunlight. (b) Many marine animals use carbonates dissolved in sea-water to make their shells.

Earth's atmosphere has a series of layers. Moving upward from ground level, these layers are named the troposphere, stratosphere, mesosphere, thermosphere and exosphere.

(1) Troposphere:

(2) Stratosphere:

(3) Mesosphere:

(4) Thermosphere:

(5) Exosphere:

Importance of atmosphere

(i) Role of atmosphere in climate control: The atmosphere acts as a protective blanket for the Earth. Since atmosphere is a bad conductor of heat, it keeps the average temperature of the Earth fairly constant during the day and even during the course of the whole year. The atmosphere prevents the sudden increase in temperature during daylight hours. And during the night, it slows down the escape of heat into outer space. Thus, the Earth receives just the right amount of heat, which helps in climate control and allows living organisms to exist. Note: Moon is about the same distance from the sun that the Earth is. Despite that, on the surface of the moon, with no atmosphere, the temperature ranges from $-190^{\circ }\mathrm{C}$ to $110^{\circ }\mathrm{C}$. (ii) The movement of air-winds: The atmosphere gets heated from the radiation that is reflected back or reradiated by the land or water bodies. As a result of heating, convection currents are set up in the air. Since land gets heated faster than water, the air over land gets heated faster than the air above water bodies.

In coastal regions, during the day, the air above the land gets heated faster and starts rising. So a region of low pressure is created and air over sea moves into this area of low pressure. The movement of air from one region to the other region causes winds. During the day, the direction of wind would be from the sea to the land. At night, both land and sea starts to cool. Since water cools down slower than the land, the air above water would be warmer than the air above land, thus the direction of wind would be from the land to the sea.

Movement of wind due to uneven heating of the air:

Note: Various other factors also influence these winds - the rotation of the Earth and the presence of mountain ranges in the paths of the wind are a couple of these factors.

• Q. How does the presence of the Himalayas change the flow of wind blowing from Allahabad towards the north? Explanation: Himalayas work like a wall. It blocks the winds coming from central Asia and forcing them to rise. So its pressure will be low. Wind moves from high to low pressure. So flow of wind blowing from Allahabad (high pressure) to north (low pressure).
• Q. How does the temperature of Earth's atmosphere remain fairly uniform during the day? Explanation: Air being a bad conductor of heat, forms a protective blanket around the Earth. During daytime it prevents sudden rise in temperature. At night, it slows down escape of heat into outer space. Thus, it maintains fairly uniform temperature during the day and night cycle.

(iii) Rain:

Once the water droplets are formed, they grow bigger by the 'condensation' on these water droplets. When the drops have grown big and heavy, they fall down in the form of rain. Sometimes, when the temperature of 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 India, rains are mostly brought by the south west or north east monsoons.

Air pollution:

It is an undesirable change in the physical, chemical or biological characteristics of the air. It is caused due to an increase in the content of harmful substances (air pollutants) in air such as oxides of nitrogen and sulphur, etc. The major sources of air pollution are burning of fossil fuels like coal and petroleum, automobiles, thermal power plants and industries.

Harmful effects of air pollution

(i) Air pollution affects the respiratory system causing breathing difficulties and diseases such as bronchitis, asthma, lung cancer, tuberculosis and pneumonia. (ii) Burning of fossil fuels like coal and petroleum release oxides of nitrogen and sulphur inhalation of these gases is dangerous. These gases also dissolve in rain to give rise to acid rain. (iii) The combustion of fossil fuel also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. The presence of high levels of all these pollutants, reduce visibility in cold weather where water also condenses out of air forming smog. Smog is an indication of air pollution. (iv) Regular breathing in the polluted air increases the incidence of allergies, cancer and heart diseases.

• Acid Rain is the rain which contains small amount of acid in it that is formed from the gases like sulphur dioxide and nitrogen oxides present in polluted air. It causes damage to the living and non-living things.

• Q. Why is the air near the busy roads more polluted than air at a distance from the busy roads? Explanation: Burning of gasoline in power cars and trucks gives out particulate carbon, carbon dioxide, carbon monoxide, hydrocarbons, oxides of nitrogen and sulphur. Emissions released directly into the atmosphere from the vehicles remain confined in the congested areas near busy roads.

4.0Water-a wonder liquid

(i) The oceans, rivers, streams, lakes, ponds, pools, polar ice caps, water vapour, etc. collectively form the hydrosphere, the main component of which is water. Major part of water is found in seas and oceans and is saline. (ii) Water is the most essential component of life. (iii) Fresh water is found in icecaps at the two poles and on snow

Necessity of Water:

(i) All cellular processes take place in water medium. (ii) All reactions that take place within our body and within the cells occur between substances that are dissolved in water. (iii) Substances are also transported from one part of the body to the other in a dissolved form. (iv) Organisms need to maintain the level of water within their bodies in order to survive. (v) Terrestrial life forms require fresh water because their bodies cannot tolerate or cannot get rid of the high amount of dissolved salts in saline water. (vi) Water regulates the Earth's temperature. It also regulates the temperature of the human body, carries nutrients and oxygen to cells, cushions joints, protects organs and tissues and removes waste. (vii) The availability of water is the major resource which determines the diversity of life on land. (viii) Thus, water is essential for sustenance of life.

Note: Availability of water is not the only factor that decides the sustainability of life in a region. other factors like the temperature and nature of soil also matter. But water is one of the major resources which determine life on lands.

Water pollution:

Thus, water pollution refers to: (i) Addition of undesirable substances to water bodies: The substances like fertilisers and pesticides used in farming, mercury salts used by paper industries could be poisonous. There could also be disease-causing organisms like the bacteria which causes-cholera. (ii) Removal of desirable substances from water bodies: Industrial or household waste reduces the dissolved oxygen in water bodies, thereby affecting the aquatic life. (iii) A change in temperature: Aquatic organisms can stay alive in a certain range of temperature. Sudden change in temperature of water bodies is dangerous for aquatic organisms and affects their breeding. The eggs and larvae of many animals are particularly susceptible to temperature changes.

• Eutrophication: When nitrates and phosphates from farmland and sewage escape into water they cause excessive growth of microscopic green plants. This may result in a serious oxygen shortage in the water.
• High concentration of DDT disturbs calcium metabolism in birds, it causes thinning of egg shell and their premature breaking, it causes decline in bird populations.

5.0Soil

It forms the upper surface of the land and supports plant growth. Soil is the layer of unconsolidated particles derived from weathered rock, organic matter (humus), water and air. Soil is an important resource that decides the diversity of life in an area. The outermost layer of our Earth is called the crust and the minerals found in this layer supply a variety of nutrients to life forms. Formation of soil: The formation of soil depends on the parent rock material, the climate and topography of the area, the organisms present in the soil and the time over which the soil has been developing. Over long periods of time, thousands and millions of years, the rocks near the surface of the Earth are broken down by various physical, chemical and some biological processes. The end product of this breaking down is the fine particles of soil.

Factors or processes for soil formation

Secondly, fast flowing water carries big and small particles of rock downstream, causing breakdown of rock particles into smaller, finer particles through their abrasive effects. (iii) Wind: Strong winds also erode rocks down. They also carry sand from one place to the other like the water does. (iv) Living organisms also influence the formation of soil. While lichens grow on surface of rocks, they release certain substances that cause the rock surface to powder down and form a thin layer of soil. Small plants like moss and roots of big trees also break the rocks. Components of soil: soil is a mixture. (i) It contains small particles of rocks that vary in size (sand > silt > clay). (ii) It contains bits of decayed living organisms which is called humus. (iii) Soil also contains various forms of microscopic life. (iv) It contains nutrients and availability of which depends on the rocks from which it was formed. (v) It contains air & water.

Top soil

Soil pollution

It is the removal of useful components from the soil and addition of other substances, which adversely affect the fertility of the soil and kill the diversity of organisms that live in it. Use of large amounts of fertilizers and pesticides destroy the soil structure by killing soil microorganisms that recycle nutrients in the soil. It also kills the earthworms which are instrumental in making the

Soil pollution rich humus thus affect the fertility of soil.

• Q. What happens when rain falls on soil without vegetation cover? Explanation: Vegetation helps in binding the soil and maintains its fertility. If rain falls on soil without vegetational cover, the rain water will cause the loss of surface fertile soil or the top soil.

Soil erosion

It is the removal and thinning of the fertile top soil from a region due to climatic and physical processes, such as high rainfall and wind etc. Soil erosion occurs easily where the soil is not covered by vegetation.

Causes of soil erosion

Prevention of soil erosion

6.0Biogeochemical cycles

The cyclic flow of nutrients between non-living environment and living organisms is known as biogeochemical cycles. It is the process of transfer and circulation of the essential chemical nutrients such as Carbon, Hydrogen, Oxygen and Nitrogen in a biosphere.

• Q. The flow of energy is unidirectional whereas the biogeochemical transfer is cyclic. Why is it so? Explanation: A large amount of energy is always lost during its transfer from one level to another. This lost energy cannot be replenished from the atmosphere. Thus, the energy flow is unidirectional. On the other hand, the biogeochemical substances are never lost in the biogeochemical cycle. They are only recycled.

The water cycle:

The whole process in which water evaporates and falls on the land as rain into the sea via river is known as water cycle. It is the whole process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers. But all the water that falls on the land does not immediately flow back into the sea. Some water moves inside the soil and reaches the underground water. Some of the underground water comes up to surface through springs or wells. Plants also release water to the atmosphere through transpiration. Water is also released into the atmosphere from soil, rivers and oceans by evaporation. Three important processes in water cycle are evaporation, condensation and precipitation. Evaporation add water as vapour to the atmosphere. The air gets heated and rises up carrying the water vapour with it. As this air rises, it expands and cools causing the water vapour in the air to condense in the form of tiny droplets. The presence of dust and other suspended particles in air also facilitates the process of condensation.

Once the water droplets are formed, they grow bigger by the 'condensation' on these water droplets. When the drops grow big and heavy, they fall down in the form of rain. Water leaves the atmosphere through precipitation. The amount of water, the atmosphere can hold depends on abiotic factors, such as temperature and air pressure. Once the atmosphere becomes saturated with water vapour, precipitation occurs in the form of rain, snow, hail or fog.

Water cycle in nature The Nitrogen cycle: The source of nitrogen is atmosphere which contains 78 percent of nitrogen in the form of gas. Nitrogen is thus an essential nutrient for all life forms. Nitrogen-cycle in the biosphere involves the following important steps. (i) Nitrogen fixation: The process is converting atmospheric nitrogen into usable form (nitrates, ammonium ions) which are soluble in water. This is done by various ${\mathrm{N}}_2$ fixing bacteria e.g. Rhizobium, blue green algae and bacterium Azotobacter. Other than these bacteria, the only other manner in which the nitrogen molecule is converted to nitrates and nitrites is by a physical process. During lightning, the high temperature and pressure created in the air convert nitrogen into oxides of nitrogen which dissolve in water to give nitric and nitrous acids and fall on land along with rain which is then utilised. (ii) Ammonification: It is the process of decomposing complex, dead organic matter into ammonia. This is done by microorganisms living in the soil e.g. bacteria and fungi. (iii) Nitrification: It is the process of conversion of ammonia into nitrites and then into nitrates. This is done by nitrifying bacteria e.g. Nitrosomonas and Nitrobacter. (iv) Denitrification: It is the process of reducing nitrates present in the soil to release nitrogen gas back into the atmosphere e.g. Pseudomonas.

Thus, there is a nitrogen cycle in nature in which nitrogen passes from its elemental form in the atmosphere into simple molecules in the soil and water, which gets converted into more complex molecules in living beings and back again to the simple nitrogen molecule in the atmosphere.

• Nitrogen is in a liquid state when at a very low temperature. Liquid nitrogen boils at 77 Kelvin $\left(-196{}^{\circ }\mathrm{C}\right)$. It is easily transported and has many useful applications including storing items at cold temperatures, in the field of cryogenics (how materials behave at very low temperatures), and as a computer coolant.
• Nitrogen compounds are found in foods, fertilizers, poisons, and explosives. Your body is $3\%$ nitrogen by weight. It is a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins.

• Q. When we breathe in air nitrogen also goes inside along with oxygen. What is the fate of this nitrogen? Explanation: The nitrogen inhaled during respiration is not used in the body and it comes out with ${\mathrm{CO}}_2$ during exhalation.

The carbon cycle:

Plants utilise the atmospheric carbon dioxide in photosynthesis to produce carbohydrates which are taken by herbivores and then pass through small and large carnivores. Many marine animals use carbonates dissolved in sea water to make their shells.

• Carbon compounds have limitless uses. In its elemental form, diamond is a gemstone and used for drilling/cutting; graphite is used in pencils, as a lubricant and to protect against rust, while charcoal is used to remove toxins etc. The isotope Carbon-14 is used in radiocarbon dating. Carbon dioxide returns to the biosphere in the following ways - (i) Both plants and animals release carbon dioxide to the atmosphere as a product of respiration. (ii) By decomposition of organic wastes and dead bodies by decomposers. (iii) By burning of fossil fuels like coal and petroleum. (iv) By forest fires. Carbon is thus cycled repeatedly through different forms by the various physical and biological activities.

The Green house effect:

• Q. A motor car, with its glass totally closed, is parked directly under the Sun. The inside temperature of the car rises very high. Explain why? Explanation: Infrared radiations in sunlight pass through the glass and heat the interior of the car. The radiation emitted by the inner parts of the car cannot pass out of the glass, so the heat trapped inside raises the temperature of the interior. This is because glass is transparent to infrared radiation from the sun having smaller wavelengths than that emitted by the interior of the car which are of longer wavelengths to which the glass is opaque.

The oxygen cycle:

Oxygen cycle maintains the level of oxygen in the atmosphere. Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen.

Almost all living organisms, plants, animals and decomposers take oxygen from their surroundings and utilise it for respiration.

Oxygen is returned to the atmosphere in only one major process, i.e., photosynthesis. Green plants are the major source of oxygen in the atmosphere.

Ozone layer:

Satellite picture showing the hole (magenta colour) in the ozone layer over Antarctica

Harmful effect of ozone layer depletion:

Note:

• Consequences of global warming are drought, food, threats to biodiversity, rise in sea level etc.
• Green house gases are ${\mathrm{CO}}_2,{\mathrm{CH}}_4,{\mathrm{N}}_2\mathrm{O},{\mathrm{SF}}_6,{\mathrm{NF}}_3$.
• Besides ${\mathrm{CO}}_2$, methane $\left({\mathrm{CH}}_4\right)$ and oxides of nitrogen $\left({\mathrm{NO}}_2\right)$ also cause destruction of ozone.
• Biomagnification: The phenomenon of increase in the concentration of harmful nonbiodegradable chemical substance in the body of living organisms at each trophic level of the food chain is called biological magnification. e.g. DDT, Lead and Mercury.

7.0Biology Diagrams made Easy

8.0Chapter At a Glance