Natural Resources (NCERT Solutions, Class 9)

Page 193

(1) How is our atmosphere different from the atmospheres on Venus and Mars?

Ans- Difference between our atmosphere and atmosphere of Venus and Mars

SN Atmosphere of the Earth Atmosphere of planet Venus and Mars
1. Life is possible. Life is not possible.
2. Carbon – dioxide is only .04%. Carbon – dioxide is almost 97%.

(2) How does the atmosphere act as a blanket?

Ans- Atmosphere works lake a cover to The Earth. It also keeps the temperature of the Earth steady during day and not allows heat to go in outer space. Therefore, we say that atmosphere act as a blanket.

(3) What causes winds?

Ans- The movement of air from high pressure to low pressure area is called winds.

(4) How are clouds formed?

Ans- When water bodies are heated during the day, water evaporates. The air above water bodies also gets warm, which rises up with water vapours. Air rises up, it expands and cools there. This cooling causes the water vapours to condense in the form of tiny droplets. These droplets grow bigger because of condensation and forms cloud.

(5) List any three human activities that you think would lead to air pollution.

Ans– three human activities that lead to air pollution are listed below –

(a) Automobiles or vehicles produce high level of pollutants like carbon mono oxide and smoke. Carbon mono oxide is a very dangerous gas which is produced from the incomplete burning of the fuels like petrol and diesel. Carbon mono oxide reduces the oxygen carrying capacity of the blood.

(b) The smog is a thick fog like layer that is made up from a combination of oxides of nitrogen with air pollutants and fog.

(c) Many industries like petroleum refineries are responsible for producing air pollutant like sulphur dioxide and nitrogen dioxide. Sulphur dioxide is produced by combustion of fuels like coal in power plant.

Page 194

(1) Why do organisms need water?

Ans– Necessity of water

(i) All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.

(ii) Substances are transported in body in a dissolved form.

(iii) Organisms need water to stay alive.

(2) What is the major source of fresh water in the city/town/village where you live?

Ans- Fresh water sources –

(i) Frozen the ice – caps at the two poles

(ii) Snow covered mountain

(iii) Underground water

(iv) Water of lakes, rivers and ponds

(3) Do you know of any activity which may be polluting this water source?

Ans- Activities which are polluting water sources-

(i) Throwing garbage

(ii) Throwing dead bodies

(iii) Untreated sewage directly flow in the Ganga.

(iv) Industries discharge also goes into the river. Examples are oil refineries, paper factories, textiles and sugar mills, etc. These industries contaminate water by releasing arsenic, lead and fluorides which are very harmful for living organisms

(v) Pesticides and the weedicides are used for the protection of the crops. These chemicals dissolve in water and washed into water bodies from the fields. They also seep into the ground to pollute ground water.

(vi) A lot of algae grow in ponds it is caused by the excessive quantities of chemicals which get washed from the fields.

The chemicals used in the fields and washed into ponds or water bodies from the fields are nutrients for the algae grow in water bodies. A lot of oxygen in the water body gets used by algae. It results in a decrease in the oxygen level which may kill aquatic organisms.

(vii) Hot water from the industries raises the temperature of the water and adversely affects the animals and plants living in water bodies.

Page 196

(1) How is soil formed?

Ans- Factors those are responsible to make soil –

(i) The sun heats up the rock and expands. Its cools down at night and contract. But, all parts of the rock do not expand and contracts at the same rate, therefore, cracks forms. Ultimately the huge rocks break up into smaller pieces.

(ii) Water

(a) Water could get into the cracks of the rocks and freezes there. It would cause the cracks to widen.

(b) The fast flow of water brings big pieces of rocks down which rub against other rocks and causes the rocks to wear down in to small pieces.

(iii)The strong winds also erode rocks down. The wind also carries sand from one place to another.

(iv) Living organisms like lichen, moss etc. grow on the surface of rock and releases certain substances which powder down the rock surface.

(2) What is soil erosion?

Ans- The process in which fertile soil is removed by wind, water or ice is known as soil erosion. In absence of plants, soil becomes loose. So, soil erosion can easily happen. Soil erosion is more severe in areas of no vegetation or less vegetation such as desert or bare land.

(3) What are the methods of preventing or reducing soil erosion?

Ans- Prevention of soil Erosion:

(i) Prevent cutting of trees.

(ii) Plant more trees.

(iii) Manage rain water in dams or reservoirs

(iv) Prevent grazing

Page 201

(1) What are the different states in which water is found during the water cycle?

Ans- Water – liquid

Water vapour – Gaseous state

Snow – Soild

(2) Name two biologically important compounds that contain both oxygen and nitrogen.

Ans – Two biologically important compounds that contain both oxygen and nitrogen are

(i) Proteins

(ii) Nucleic acid

(3) List any three human activities which would lead to an increase in the carbon – dioxide content of air?

Ans – Any three human activities which would lead to an increase in the carbon – dioxide content of air are listed below –

(i) Many industries like petroleum refineries are responsible for producing air pollutant like sulphur dioxide and nitrogen dioxide. Sulphur dioxide is produced by combustion of fuels like coal in power plant.

(ii) Refrigerators, air conditioners and aerosol sprays are producing air pollutants chlorofluorocarbons (CFCs) which damage the ozone layer. The ozone layer protects us from the harmful ultraviolet rays of the sun.

(iii) When diesel and petrol burns in automobiles, it produces tiny pollutant particles that remain suspended in the air for long time period. Such particles are produced in steel making and mining . Power plants give out tiny ash particles which also pollute the atmosphere.

(4) What is the green house effect?

Ans- Greenhouse effect is a natural process in which radiation from the sun rays fall on the atmosphere of the Earth and a part of it is radiated back to space as heat by atmosphere. But, other part is absorbed by the earth’s surface. Now, earth heats up and released back radiation into atmosphere and space. The greenhouse gases which are present in the atmosphere absorbed reflected back radiation (heat). Less part of it emitted back to space and large part is absorbed by the greenhouse gases. These gases do not allow the absorbed heat to go back in space. The trapped radiation or absorbed radiation is good for human life because it keeps earth warm and makes life possible on the earth. Hence, the trapping of radiations by the Earth’s atmosphere is known as greenhouse effect. It is very necessary for life on the Earth.

(5) What are the two forms of oxygen found in the atmosphere?

Ans- Diatomic oxygen O2 and ozone O3 are the two forms of oxygen found in the atmosphere.

Exercises

(1) Why is the atmosphere essential for life?

Ans- Atmosphere is very essential for our life because it works as a blanket.

(i) It keeps us safe from ultraviolet rays of the Sun.

(ii) It keeps temperature of the Earth steady in day.

(iii) It also does not allow heat to go in outer space fast.

(2) Why is water essential for life?

Ans- Necessity of water

(i) All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.

(ii) Substances are transported in body in a dissolved form.

(iii) Organisms need water to stay alive.

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

Ans- Importance of soil:-

(i) It holds the root of the plant firmly.

(ii) It supplies water and nutrients to the plant through roots.

(iii) Many organisms live in the soil.

(iv) It is necessary for agriculture.

(v) The earthy fragrance of the soil after the first rain is always refreshing

No, the organisms that live in water are not totally independent of soil as a resource. The dependence of organisms that live in water are given below –   (i) Many organisms eat aquatic plants which grow on sea soil.

(ii) Minerals come with rain in water bodies which taken by aquatic organisms.

(iii) Many aquatic animals like crocodile; tortoise came out from the water and stay some time on the land.

(iv) Some animals also lay egg on land.

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

Ans-  Our meteorological department observes temperature change, pressure of wind, precipitation etc and predict 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?

Ans- Yes, isolating activities which lead to increasing levels of pollution of the air, water – bodies and soil, will help in reducing pollution.

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

Ans- Forests influences the quality of our soil, air and water positively.

Air –

(i)Forests have many trees which increases the quantity of oxygen and reducing carbon – dioxide in the atmosphere.

(ii) Air pollution will decreases.

Water –

(i) Trees cause rain which will increase the level of water in our water bodies.

(ii) Rain will also increase underground water level.

Soil –

(i) Soil erosion will not be possible.

(ii) Soil will be nourished with nutrients which will be provided by the trees of forests.

Helping Topics

Natural Resources

Practice sheet, class 9

Picture1

Leave a comment