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.

Table of Contents


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:

Biogeochemical Cycles

Water Cycle

The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the earth. Water changes into different states of matter during water cycle.

Nitrogen Cycle

The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature.

Living beings cannot utilize the gaseous form of nitrogen. Hence, gaseous nitrogen needs to be changed into a form so that plants can take up and utilize nitrogen. The process of converting gaseous nitrogen into a suitable form for green plants is called nitrogen fixation.

Carbon Cycle

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Greenhouse Effect

Some gases trap infrared radiation in atmosphere. This results in a general rise of atmospheric temperature. This is called greenhouse effect. Examples of greenhouse gases are; carbon dioxide, methane and water vapor.

Oxygen Cycle

The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs: the atmosphere (air), the biosphere (living things), and the lithosphere (earth’s crust). The main driving factor of the oxygen cycle is photosynthesis, which is responsible for the modern Earth's atmosphere and life.

Energy Cycle

All the above mentioned cycle can be grouped or explained as energy cycle on this earth. The sun is the main source of energy for every activity on earth. This energy facilitates the everlasting cycle of all resources in the biosphere. This system ensures that whatever we take from earth and its atmosphere we return it in some way or other.

Ozone Layer

The ozone layer is a layer in earth’s atmosphere which contains relatively high concentrations of ozone. This layer absorbs 93-99% of the sun’s high frequency ultraviolet light, which is potentially damaging to life on earth. Over 91% of the ozone in Earth's atmosphere is present here. It is mainly located in the lower portion of the stratosphere from approximately 10 km to 50 km above Earth's surface, though the thickness varies seasonally and geographically.

Because of heavy use of CFCs (Chlorofuorocarbons) in refrigerators and pressurized cans by human the ozone layer has broken at some places. This has caused an alarming rise in ultraviolet radiation leading to increased cases of skin cancers.