Class 9 Science

Natural Resources

Biosphere: The whole combination of animals, plants and non-living beings which by their interaction make the planet earth a live and vibrant place is called biosphere.

Biotic Components: Living things constitute the biotic component of the biosphere.

Abiotic Components: The air, the water and the soil form the non-living or a biotic component of the biosphere. The air is called the hygrosphere, the water is hydrosphere and the soil is called lithosphere.


Air is a mixture of many gases like nitrogen, oxygen, carbon dioxide and water vapour.

The Role of the Atmosphere in Climate Control:

Atmosphere covers the Earth, like a blanket. We know that air is a bad conductor of heat. Thus, air prevents the earth from becoming too hot. Air also prevents solar radiation from escaping the earth. Thus, it prevents the earth from becoming too cold during night.


Earth’s surface gets different amount of heat from the sun at different places. This causes uneven heating of the earth’s surface. Heating of the earth’s surface creates convection currents in air. Convection currents cause movement of air.

Air Pollution: Addition of harmful substances in air so that the air becomes unfit for living beings is called air pollution.

Primary Pollutant: If a pollutant is directly emitted from a process, it is called a primary pollutant. Examples; carbon dioxide from vehicle exhaust, ash from volcano, etc.

Secondary Pollutant: If a pollutant if formed after interaction or reaction of primary pollutants, it is called secondary pollutant. Example: ground level ozone, smog, etc.

Rain: Heating of water bodies during the day causes evaporation of water. Water vapor rises in the air. Once the water vapor goes up to a height, it cools down to form clouds. Formation of clouds is facilitated by some particles which act as the ‘nucleus’ around which water droplets coalesce to make cloud. Further condensation of vapor results in precipitation.


Importance of Water

All cellular processes take place in a water medium. All the reactions that take place within 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, organisms need to maintain the level of water within their bodies in order to stay alive.

Water Pollution

Contamination of water bodies to make it harmful for organisms is called water pollution.

We use the term water-pollution to cover the following effects:


The top layer of the earth’s crust which is loosely bound is called soil.

Formation of soil: