Chapter : Natural Resources
Earth is the only planet on which, life exists till date. There are many factors responsible for life on earth. Most of the life depends on ambient temperature, food and water. The resources available on the earth and the energy from the sun are very much essential to meet the basic requirements of all forms of life on the earth.
Resources on Earth:
The main resources on earth are land, water and air. The outer crust of the earth is called lithosphere. 75% of the earth is covered by water and this is called hydrosphere. The air covers whole of the earth like a blanket that is called atmosphere. Biosphere, which is the life-supporting zone of earth, is formed by the interaction of atmosphere, lithosphere and hydrosphere. Biosphere constitutes both biotic and abiotic factors. Living things in the biosphere form the biotic component. The air, water and soil make non-living or abiotic component of biosphere.
Air: The Breath of Life
Air is a heterogeneous mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour. Oxygen, which is a major component of air, plays a very important role in the life of a living organism. 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. Combustion is another process that utilizes oxygen and produces carbon dioxide. Though carbon dioxide is produced in huge amounts through this process, its percentage in the atmosphere is very less and this is because carbon dioxide gets fixed. Carbon dioxide fixation occurs 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.
The movement of air:
The movement of air is the result of the changes that occur in our atmosphere due to the heating of the air and the formation of water vapor.
Rain is formed when several water bodies are heated during a day and a huge amount of water evaporates and this vapor goes into the air. Some amount of this vapor also gets into the atmosphere due to various biological activities and gets heated. The hot air that is carrying water, vapor rises up and expands and hence gets cooled. These cooling results in condensation of vapor and tiny droplets are formed. Such tiny droplets grow bigger and heavier due to continuous condensation and they fall down on the earth in the form of rain. Snow, sleet, hail are some of the forms of precipitation.
Rainfall patterns are decided by the prevailing wind patterns. In many parts of India, rains are mostly brought by the southwest or north-east monsoons and weather reports says that ‘depressions’ in the Bay of Bengal have caused rains in some areas.
Water: A Wonder Liquid
A very large amount of the earth is covered by water. Some part of this water exists as vapor and the rest is found as saline water and fresh water. Seas and oceans form the saline water and fresh water is found in frozen state in the ice caps and on the snow enclosed mountains. Underground water, lakes and rivers also come under fresh water.
Water is necessary for the existence of life. All the reactions that take place in our body and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form. Hence, to stay alive, organisms need to retain the level of water within their bodies. Water is required in our daily life for cleaning, drinking, laundry, cooking, etc. Terrestrial life needs fresh water because bodies cannot withstand salts present in the saline water.
Mineral: Riches in the Soil
Soil is an important resource that decides the diversity of life in an area. Minerals are found in the outer most layer of the earth. They supply a variety of nutrients to all life forms. Soil is formed by four major factors namely:-
The rocks expand due to the heat produced by sun during the day and in the night, they contract on cooling. But as all the parts of rock do not expand and contract at the same rate, cracks form. Rocks start breaking due to the formation of cracks.
Water helps in soil formation in two ways:-
- Water gets into the cracks formed due to the uneven heating by the sun and it will result in widening of cracks.
- The water coming from rivers and lakes flow through the rocks. Due to this continuous movement of water on rocks, the rocks wear away and get converted into small sized rocks. These rocks again rub against each other and dissolve into much more reduced size and hence soil forms.
Strong winds erode rocks down in the same way as water does and wind also carries sand from one place to the other and hence soil forms.
4. Living organisms
Livings organisms also influence soil formation. Lichens that grow on the surface of rocks release certain substances that make the rock surface into powder and these forms as a thin layer of soil.
Types of Pollution
1. Air Pollution
The quality of air is getting affected a lot these days due to the carbon dioxide released by vehicles and factories. This is producing an adverse effect on us and other life organisms too. Air contamination must be minimized for a healthy environment. Regularly breathing of such contaminated air leads to dreadful diseases such as cancer and heart diseases. Such an increase in the content of these harmful substances in air is called as air pollution
Causes of air pollution:
- Fossil fuels like coal and petroleum contain nitrogen and sulphur. Burning of these fuels will also result in the burning of nitrogen and sulphur. When nitrogen and sulphur are burnt, they produce different oxides. Inhalation of these gases is very dangerous. When these gases dissolve in rain, they form acid rains.
- Combustion of fossil fuels increases the amount of suspended particles in air. Hydrocarbons are the result of burning of these suspended particles.
Due to the above mentioned hydrocarbons getting formed in atmosphere, Ozone layer is getting depleted. Ozone is represented as O3 and it is termed as a molecule containing three atoms of Oxygen. Ozone is poisonous for life but it absorbs harmful radiations from sun such as ultra violet radiations and saving us from it.
2. Water Pollution
Water pollution is the contamination of water bodies such as lakes, rivers, oceans etc. This contamination also affects the life of organisms and causes several health problems.
Causes of water pollution:
- Fertilizers and pesticides used in the farms are dissolved in the water bodies thereby contaminating water.
- Sewage from towns and cities and wastes from factories are dumped into rivers or lakes.
- Industrial wastes are also getting dissolved in water bodies.