14. Natural Resources-page 2 Science Class 9 In English-CBSE Notes

Important Questions-Answers:

Q1. Why is the process of nitrogen fixing not taken place in the presence of oxygen by bacteria?

Ans: Some organisms like bacteria becomes poisonous by elemental oxygen, therefore the process of nitrogen fixing is not taken place in the presence of oxygen.

Q2. What is ozone? 

Ans: In the upper reaches of the atmosphere, a molecule containing three atoms of oxygen is found. This would mean a formula of O3 and this is called ozone.

Q3. How is ozone molecule differ from oxygen molecule? 

Ans: Triatomic ozone is a poisonous while diatomic oxygen is life giving agent. 

Q4. What is the major function of ozone layer? 

Ans: Major functions of ozone are 

(i) It absorbs harmful radiations from the Sun.

(ii) This prevents those harmful radiations from reaching the surface of the Earth where they may damage many forms of life.

Q5. Name a man made chemical substances that harms ozone layer? 

Ans: Chloro fluro carbons (CFCs).

Q6. What is chloro fluro carbons (CFCs) ?

Ans: It is a carbon compounds having both fluorine and chlorine which is very stable and not degraded by any biological process. Once this CFCs compound reached the ozone layer, they would react with ozone molecule and causes ozone reduction. 

Q7. Which part of ozone is there found a hole?

Ans:  There discovered a hole in the ozone layer above the Antartica.

Q8. In what forms oxygen is found in nature ?

Ans: Oxygen is found in nature in various form these are as follows;

(i) It is found in the elemental form in the atmosphere to the extent of 21%.

(ii) It also occurs extensively in the combined form in the Earth’s crust as well as also in the air in the form of carbon dioxide.

(iii) In the crust, it is found as the oxides of most metals and silicon, and also as carbonate, sulphate, nitrate and other minerals.

(iv) It is also an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats (or lipids).

Q9. Name a atmospheric phenomenon, in which some gases prevent the escape of heat from the Earth. 

Ans: Green house effect.

Q10. Name a major green house gas.

Ans: Carbon dixoide. 

Q11. List the four major green house gas.

Ans: CO₂, Methene, Carbon mono oxide and nitrous oxide. 

Q12. What are biotic components? 

Ans: There are many living components present in biosphere. These living components are called biotic components. Example: trees, plants, animals, micro organisms etc. 

Q13. What are abiotic components ?

Ans: There are so many non-living components in a biosphere along with living components, these non-living components are known as abiotic components. Example: soil, water, air, temperature etc. 

Q14. What is biogeochemical cycles? 

Ans: A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic process, but stable system. These interactions consist of a transfer of matter and energy between the different components of the biosphere and forms a cycles, such cycles are known as biogeochemical cycles. 

Q15: what is soil-polution? 

Ans: Removal of useful components from the soil and addition of other substances, which adversely affect the fertility of the soil and kill the diversity of
organisms that live in it, is called soil pollution.

Q16: Write down the two main harmful effects of soil-pollution.

Ans: 

(I) Soil-pollution reduces the fertility of the soil. 

(ii) It also kills the diversity of organisms that live in it.

Q17: Write two ways by which carbone dioxide is fixed?

Ans:Carbon dioxide is ‘fixed’ in two ways;

(i) Green plants convert carbon dioxide into glucose in the presence of Sunlight

(ii) many marine animals use carbonates dissolved in sea-water to make their shells.

Q18. What is biosphere?

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

Q19: How do convection currents produce?

Ans: 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.

Q20: Write the factors which influence the winds?

Ans: There are following factors that influence the winds;

       (i)  Temperature.

       (ii) Rotation of the earth.

       (iii) Presence of mountain ranges in the paths of the wind.

Q21: How does rain occur?

Ans: 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.

Q22: What are regions for rains in large parts of India?

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

Q23: What is acid rain?

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

Q24: Name two pollutants which is responsible for acid rain.

Ans: Nitrogen oxide and sulpher oxide.

Q25: What is the main source of pollutants like Nitrogen oxide and sulpher oxide?

Ans: Fossil fuels like coal and petroleum. 

Q26: What is smog? What does it indicate?

Ans: 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.

Q27: What is global warming? what can be far-reaching consequences of global warming? 

Ans: Green house gases are rising up regularily in Earth's atmosphere, which obsorb the heat radiations coming from the sun. Hence our atmosphere works as blanket, so it prevents the escape of heat from the Earth. consequently, the world temperature rising up. This is known as global warming. 

Far-reaching consequences of global warming;

  (i) It causes fload and dry.

  (ii) Increasing in sea-water levels from melting grassley.

  (iii) Increasing in avarage temperature of world. 

Q4. How does the atmosphere act as a blanket?

Ans: 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. 

Q5. How is our atmosphere different from the atmosphere on Venus and Mars? 

Ans: Earth's atmosphere is quite different from the atmosphere present on Venus and Mars. The atmosphere of earth consisits of Nitrogen 79%, Oxygen 21% and Carbon dioxide in very less percentage. Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide. In fact, carbon dioxide constitutes up to 95-97% of the atmosphere on Venus and Mars.

Q6. What causes winds?

Ans: The uneven heating of the atmosphere in different regions of the Earth like earth's surface and water surface cause winds. On heating up the air creating a low pressure region. The movement of air from high pressure region to low pressure region creates winds.

There are other factors that enfluence these winds: 

(i) The rotation of the Earth.

(ii) The presence of mountain ranges in the paths of the wind.

During the day, the direction of the wind would be from the sea to the land.
At night, both land and sea start to cool. Since water cools down slower than the land, the air above water would be warmer than the air above land.

Q7. How are clouds formed? 

Ans: When water bodies are heated during the day, a large amount of water evaporates and goes into the air. Some amount of water vapour also get into the atmosphere because of various biological activities. This air also gets heated. The hot air rises up carrying the water vapour with it. As the air rises, it expands and cools. Thus vapours condense onto a tiny droplets salt particles called condensation nuclei which form clouds. 

Q8.  List any three human activities that you think would lead to air pollution.

Ans: Three human activities leading to air pollution are as follows;

        (i) Combustion of fossil fuels like coal and petroleum. 

       (ii) Deforestaion that causes reduction of carbon dioxide utilisation. 

      (iii) Toxic smoke of industries and colloidal particles of incomplete

            combustion of carbon smog and fog.

Q9.

Q10. 

Q11. 

Q12. 

Q13. 

Q14. 

Q15. 

1. Why do organisms need water?

Ans: Organisms need water because;

(i) All cellular processes take place in a water medium.

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

(iii)  Substances are also transported from one part of the body to the other in a dissolved form.

(iv) Hence, organisms need to maintain the level of water within their bodies in order to stay alive.

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

Ans: River and ground water. 

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

Ans: There are following activities that polluting this water source.

(i) Adding poisonous and harmful chemical substances used by industries. 

(ii) Leaving dead and decay body into rivers.

(iii) Human activities like washing clothes, adding home wastes and sewage water etc. 

Q1. How is soil formed?

Ans: The rocks at or near the surface of the Earth are broken down by various
physical, chemical and some biological processes. This broken down rocks fine particles forms soil. 

Q. What are the factors or processes that make soil? 

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.

Q2. What is soil erosion?

Ans: The upper most layer of soil contains humus and it is quite fertile. It is also lighter. Sometimes soil of this layer carried out by water or wind. The process of removing of soil surfaces is known as soil erosion.  

Q3. What are the methods of preventing or reducing soil erosion?

Ans: Deforestation is the main couse of soil erosion, so preventing or reducing this we should encourage the plantaion in very large scale. Because the roots of plants ties soil and it stops the removal of soil surface.   

Q1. What are the different states in which water is found during the water cycle?

Ans: The different states in which water is found during the water cycle,

Soild, Liquid and Gas

Q2. Name two biologically important compounds that contain both oxygen and nitrogen.

Ans: 

(i) Amino acids

(ii) Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)

Q3. List any three human activities which would lead to an increase in the carbon dioxide content of air.

Ans: 

(i) Excessive using/burning fossil fuels in various process like coal, petrolium and industrial uses.  

(ii) Release of harmful gases from vehicles.

(iii) Human Induces forest in fire and deforestaion causes decreased uptake of carbon dioxide and releasing of oxygen. 

Q4. What is the greenhouse effect?

Ans: Some gases like carbon dioxide, methane, carbon monooxide and nitrous oxide absorb heat present in atmosphere and prevent the escape of heat from the Earth. ​This heat is trapped by our atmosphere. This is an atmospheric phenomenon.  An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the greenhouse effect.

Q5. What are the two forms of oxygen found in the atmosphere?

Ans: The two forms of oxygen found in atmosphere are as follows;

(i) Diatomic molecular atom with chemical formula O₂.

(ii) Triatomic molecular atom with chemical formula O₃.

Q: How does lichen help in soil formation?

                         Or 

     Living organisms also influence the formation of soil. How? 

A:  Lichen grows on the surface of rocks. While growing, they release certain substances that cause the rock surface to powder down and form a thin layer of soil. Other small plants like moss, are able to grow on this surface now and they cause the rock to break up further.

Q: which gets heated faster land or water?

Ans: Land.

Q: which gets cooled faster land or water? 

Ans: Land 

Q: How soil is so important resorces ?

A - Soil is an important resource that decides the diversity of life in an area.

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.

Exercise:

Q1. Why is the atmosphere essential for life?

Ans: Atmospher is very essential for life because of following reasons;

(i) It keeps the avearge temperature of earth rather steady. 

(ii) Oxygen is available from atmosphere in the form of life air. 

(iii) Ozone layer of our atmosphere protect us from harmful radiation coming from the sun. 

Q2. Why is water essential for life?

Ans: Water is essential for life because;

        (i) All cellular processes take place in a water medium.

       (ii) All the reactions that take place within our body and within the cells

            occur between substances that are dissolved in water.

       (iii) Substances are also transported from one part of the body to the

             other in a dissolved form.

       (iv) organisms need to maintain the level of water within their bodies in

             order to stay alive.

Q3. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?

Ans: 

Q4. You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?

Ans: 

Q5. 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: 

Q6. Write a note on how forests influence the quality of our air, soil and water resources.

Ans:  

Q. Describe nitrogen-cycle with the help of diagram.

Ans: There are many forms of nitrogen atoms present in nature. Some special bacteria living in plants roots converts atmospheric nitrogen into nitrates and nitrites, these nitrates and nitrites are further converted into amino acid by the plant to synthesise them protiens and other complex compound which is consumed by animals as food. Once the animal or the plant dies, other bacteria in the soil convert the various compounds of nitrogen back into nitrates and nitrites. A different type of bacteria converts the nitrates and nitrites into elemental nitrogen. Thus forms a cycle in nature which is called Nitrogen-Cycle. 

Q. Describe Carbon-cycle with the help of diagram. 

All life-forms are based on carbon-containing molecules like proteins, carbohydrates, fats, nucleic acids and vitamins. Green plants uses CO₂ in photosynthesis to form glucose molecules in presence of sunlight. These glucose molecules are provided to another living organisms as food energy or synthesis of other biologically important molecules like coal and pertroleum. After combustion of these fuels in various human activities it produces carbon dioxide that mixes in atmosphere. Living organisms uses food energy to convert glucose back into carbon dioxide in cellular respiration and produces carbon dioxide to atmosphere. Thus create a cycle in the nature by the various physical and biological activities is known as carbon-cycle.   

Q. Describe oxygen-cycle with the help of diagram.

Ans: Oxygen from the atmosphere is used up in three processes, namely
combustion, respiration and in the formation of oxides of nitrogen. Oxygen is returned to the atmosphere in only one major process, that is, photosynthesis. And this forms the broad outline of the oxygen-cycle in nature.