NCERT solution for class 9 science natural resources ( Chapter 14)

Solution for Exercise Questions

1. Why is the atmosphere essential for life?
Answer :

The atmosphere is essential for life because of the following reasons:

1. The atmosphere constitutes of various main gases like O2, N2, and CO2

2. Photosynthesis is due to earth’s atmosphere

3. The constant temperature of the earth is the cause of the earth’s atmosphere

4. Processes like respiration, burning, and combustion are due to the atmosphere

5. The atmosphere is the main reason to restrict UV rays into the earth.

2. Why is water essential for life?
Answer :

Water is essential for life because of the following reasons:

1. All the biological activities are respiration, digestion and other biological reactions are supported by water

2. Living beings are composed of more than 70% of water

3. Transportation of substances from one form to another takes place due to the presence of water.

3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Answer :

All living organisms on the earth directly or indirectly dependent on soil for a living. Plants obtain water and minerals through the soil and prepare their food. Other living organisms that live in water are entirely not totally independent of soil because the microbes growing on the soil in water are the primary producers. Primary producers are the main and chief element of the food chain. Various microbes found in soil help in the decomposition of dead plants and animals in water which helps in returning the nutrients and elements back to the water.

4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Answer :

Weather is studied as the collection of various elements like high and low temperatures, humidity, rainfall, wind speed and more using various figures and facts with relevant instruments. Hence on the data collected by the meteorologists, we are able to forecast the weather.

5. We know that many human activities lead to increasing levels of pollution of the air, water-bodies, and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
Answer :

Human activities are the main reason for the pollution in the air. Air is the medium to spread the pollutants into various sources like water and soil. Hence we can say that limiting activities certain place will definitely help the air pollution to be controlled to some extent.

6. Write a note on how forests influence the quality of our air, soil and water resources.
Answer :

Forests influence the quality of our air, soil and water resources by:

1. Forests help in purifying and increasing the content of oxygen in the air by absorbing carbon dioxide and releasing oxygen.

2. Forest helps in restoring water resources.

3. Forest helps in the prevention of soil erosion.

Solution for Intext Question

Q. How is our atmosphere different from the atmospheres on Venus and Mars?
Answer :

Earth's atmosphere is different from Venus and Mars in the composition of air. Earth’s atmosphere is composed of various gases like oxygen, carbon dioxide, nitrogen, water vapour along with various gases in small quantities. Planets like Venus and Mars have more than 95% of carbon dioxide in the air making the existence of life impossible.

Q. How does the atmosphere act as a blanket?
Answer :

The atmosphere act as a blanket as:

(i) It regulates the temperature throughout the day making it a comfortable place to stay.

(ii) The ozone in the atmosphere is responsible for not allowing harmful ultra-violet ray to pass and reach us.

Q. What causes winds?
Answer :

All the movements of air resulting in diverse atmospheric phenomena are caused by the uneven heating of the atmosphere in different regions of the Earth. On being heated more the air raises up and hence low pressure is created. Hence the air in high pressure occupy the low-pressure region causing the wind. But various other factors also influence these winds, such as the rotation of the Earth and the presence of mountain ranges in the paths of the wind are a couple of these factors.

Q. How are clouds formed?
Answer :

During the day time in the presence of sunlight water from sources like well, lake, pond, sea, river and various other sources get evaporated and this water vapour rises up with the hot air. At a particular height, the air cools and the water vapour condenses to form minute droplets to form clouds.

Q. List any three human activities that you think would lead to air pollution.
Answer :

Three human activities that would lead to air pollution are:

1. Burning of fuels like petroleum, kerosene, and coal in the atmosphere

2. The smoke released from manufacturing industries

3. Smoke from vehicles

Q. Why do organisms need water?
Answer :

Organisms need water for various purposes like:

1. To carry out cellular process needs water

2. Photosynthesis in plants

3. Transportation of substances in the body takes place through water.

Q. What is the major source of fresh water in the city/town/village where you live?
Answer :

The major source of fresh water in the city/town/village are:

1. Rainfall

2. Underground water from wells

3. Water sources like pond, river, and lake

Q. Do you know of any activity which may be polluting this water source?
Answer :

Activities which pollutes water sources are:

1. Dumping waste products in the river, sea or any other water bodies.

2. Factory waste

3. Sewage waste.

Q. How is soil formed?
Answer :

The outermost layer of our Earth is called the crust and the minerals found in this layer supply a variety of nutrients to life-forms. But these minerals will not be available to the organisms if the minerals are bound up in huge rocks. Over long periods of time, thousands and millions of years, the rocks at or near the surface of the Earth are broken down by various physical, chemical and some biological processes. The end product of this breaking down is the fine particles of soil.

The factors or processes that make soil are:

1. The Sun

2. Water

3. Wind

4. Living organism

Q. What is soil erosion?
Answer :

Removal of the most fertile top layer of soil through water, wind is called soil erosion.

Q. What are the methods of preventing or reducing soil erosion?
Answer :

The methods of preventing or reducing soil erosion are:

1. By planting trees or afforestation.

2. By preventing overgrazing.

3. By preventing removal of top soil.

Q. What are the different states in which water is found during the water cycle?
Answer :

Water is found in three states during the water cycle, which are:

1. A solid-state in the form of Snow, ice

2. Liquid state in the form river water, underground water

3. Gaseous state in the form water vapour

Q. Name two biologically important compounds that contain both oxygen and nitrogen
Answer :

Two biologically important compounds that contain both oxygen and nitrogen are:

1. DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid)

2. Amino acids

Q. List any three human activities which would lead to an increase in the carbon dioxide content of the air.
Answer :

Three human activities which would lead to an increase in the carbon dioxide content of the air are:

1. Breathing process

2. Burning of petrol, coal, and fuel

3. Using fridge, air conditioners, and oven

Q. What is the greenhouse effect?
Answer :

Gases like Carbon dioxide and methane trap sun’s radiation and does not allow it to go back and hence causing warming of the atmosphere, resulting in the greenhouse effect.

Q. What are the two forms of oxygen found in the atmosphere?
Answer :

Two forms of oxygen found in the atmosphere are:

1. Oxygen- \( O_2 \)

2. Ozone- \( O_3 \)