Class 9 science Solutions English Medium

14. Natural Resources

Q - How does the atmosphere act as a blanket?

A – The air is bad conductor of temperature. It keeps constant the average temperature of the earth during the day and the whole year. It regulates the raising day temperature. Thus the atmosphere act as a blanket.

Q – Write three activities of human being which is helpful in air pollution.

A –

1. Combustion of fossil fuels.
2. Colloidal particles of incomplete combustion of carbon  smog and fog.
3. Toxic smoke of industries.

Q – How is lichen helpful in soil formation?

A – Lichen grows on the surface of stones. In this order they release a substance which make the surface of stone like powder and form a thin layer of soil.

Q – Describe that processes or factors which help in soil formation.

Ans: 

(i) The sun: Rocks expand on sun's heat during day and contract at night, this results in the formation of cracks on the surcafes of rocks causing breaking up into smaller pieces. 

(ii) Water: Fast flowing water often carries big and small particles of rock downstream. This causes loss in surface particles, thus soil is formed. 

(iii) Wind: Wind also caused rubing and breaking down rocks and also flows out sands one places to other.

(iv) Lichen : Lichen grows on the surface of rocks and they release certain substances that cause the rock surface to powder down and form a thin layer of soil.

Q – Write two ways by which carbone dioxide is fixed?

A – carbon dioxide is ‘fixed’ in two ways:

1. Green plants convert carbon dioxide into glucose in the presence of Sunlight
2. many marine animals use carbonates dissolved in sea-water to make their shells.

Q – Name the abiotic components of biosphere.

A – Air, water and soil.

Q – Name the biotic components of biosphere.

A – All living things.

Q – What is biosphere?

A – life-supporting zone of the Earth where the atmosphere, the hydrosphere and the lithosphere interact and make life possible, is known as the biosphere.

Q – How do convection currents produce?

A – The atmosphere can be heated from below by the radiation that is reflected back or re-radiated by the land or water bodies. On being heated, convection currents are set up in the air.

Q – How much carbon dioxide present in the atmosphere of Venus and Mars?

A – 95 to 97%

Q – Write the factors which influence the winds?

A –

1.    Temperature.
2. Rotation of the earth.
3. Presence of mountain ranges in the paths of the wind.

Q – How does rain occur ?

A – The hot air rises up carrying the water vapour with it. As the air rises, it

expands and cools. This cooling causes the water vapour in the air to condense in the form of tiny droplets. By the ‘condensation’ of these water droplets. When the drops have grown big and heavy, they fall down in the form of rain.

Q – What are regions for rains in large parts of India?

A – In large parts of India, rains are mostly brought by the southwest or north-east monsoons.

Q – What is acid rain?

A – Nitrogen oxide and sulpher oxide are produced due to combustion of fossil fuels. They dissolve in air to give rise to acid rain.

Q – Name two pollutants which is responsible for acid rain.

A – Nitrogen oxide and sulpher oxide.

Q – What is the main source of pollutants Nitrogen oxide and sulpher oxide?

A – Fossil fuels like coal and petroleum.

Q – What is air pollution?

A – An increase in the content of harmful substances in air is called air pollution.

Q – What is smog? What does it indicate?

A – Presence of high levels of all pollutants cause visibility to be lowered, especially in cold weather when water also condenses out of air. This is known as smog. These indicate of air pollution.

Q – Why do we need water?

A – we need water as;

1. All cellular processes take place in a water medium.
2. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.
3. Substances are also transported from one part of the body to the other in a dissolved form.
4. organisms need to maintain the level of water within their bodies in order to stay alive.