CBSE Class 9 Science Natural Resources Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.
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.
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.
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