What are the Physical Resources and Explain the Role of Air
The materials present in natural environment & useful to living organism are called natural resources.
Natural Resources can be classified into two groups.
- Physical resources : E.g, Air, water, soil, minerals, coal etc.
- Biological resources : E.g. Microorganisms, plants & animals.
The Breath of life : Air
Air is a mixture of gases which is odourless, tasteless & invisible. Air also holds water vapour & dust particles.
Atmosphere :
The envelop of air that surrounds the earth is called Atmosphere.
Role of atmosphere in climate control :
Air is a bad conductor of heat. It act as a protective blanket for the living organisms to exist in the following way –
- Atmosphere prevent the sudden increase in temperature during the day hours. During night it slow down the escape of heat into the outer space. Thereby preventing excessive cooling during night.
- The ozone shield of atmosphere absorb most of the harmful UV radiations coming from the sun. The excessive heat & sun rays are reffected back into the outer space by dust particles.
Movement of Air :
Heating of air occur due to reradiation of solar radiations by the land & water bodies. In fact, when the solar radiation fall on the earth, some are absorbed & majority of these are reflected back or reradiated by the land & water bodies. These solar radiations heat up the atmosphere from below. As a result, convection currents are set up in the air. But since the land gets heated faster than the water, the air over land also gets heated faster than the air over water bodies. Hot air on land rises upwards thereby producing an area of the low air pressure. Air from region of high pressure will move towards this region of low pressure producing breez or wind.
Rain :
The air carrying water vapour also get heated. This hot air rises up in the atmosphere carrying water vapour with it. As the air rises. it expands & cool. This cooling cause the water vapour to condense in the form of tiny droplets. Suspended particles of dust & other materials act as nuclei to facilitate the process of condensation of water around them. A collection of tiny droplets of water appear in the form of ‘clouds’. These droplets of water slowly grown bigger by the condensation of more water droplets.
When the droplets have grown big & heavy they fall down in the form of ‘rain’.
Water
Water is one of the basic necessities of life. It is an inexhaustible natural resource which is liquid between 0ºC and 100ºC. We need water for various activites such as drinking, cooking of food, bathing and washing. It is also needed for irrigation of crop in agriculature, as an essential requirement in industries, and for navigation.
Water plays a vital role in the metabolic reactions taking place within the organism’s body. It acts as a universal solvent, providing a medium for the chemical reactions to occur. In fact, all the chemical reactions that occur within body cells involve substances that are dissolved in water. Substances are also transported from one part of the body to the other in dissolved form.
97.5% of the water on the planet earth is found in seas and oceans as saline water and is not available to us for use directly. Only 2.5% of the total water resources of the world consist of fresh water. Majority of it (about 2%) is found frozen in the ice-caps at the two poles and on snow-covered mountains. Remaining (0.6% of the total) is available to support terrestrial life. Majority (90%) of this fresh water is found underground as ground water and only 10% occurs as surface water in lakes, ponds, streams, rivers etc. Limited amount of fresh water is available to us as a renewable souce through water cycle but its distribution is uneven.
Soil
The top surface layer of this exposed, solid part of crust containing weathered minerals and humus and capable of supporting plant growth is called soil.
Soil Formation
The process of soil formation is so slow that the soil is regarded as a non-renewable resource.
Pedogenesis
It is the process of formation of soil from rocky earth’s crust. It involves following two processes:
Weathering
Decomposition of organic matter and subsequent humification and mineralization.
Main factors that influence the formation of soil from the rocks are –
- Temperature variations due to radiactions of the sun.
- Rain water
- Winds
- Living organisms