Natural Resources CLass 9 BIOLOGY MCQ & SAQ

Natural Resources CLass 9 BIOLOGY NCERT SOLUTION:

 

Q1. How is our atmosphere different from the atmosphere on Venus and Mars?

Ans: Our atmosphere consists of a mixture of many glasses like oxygen, nitrogen, carbon dioxide and water vapor which are life-supporting whereas the atmosphere of Venus and Mars contains 95-97% of carbon dioxide and life-supporting gasses are not present.

 

Q2. How does the atmosphere act as a blanket?

Ans: The atmosphere prevents the sudden increase in temperature during the daylight hours and it slows down the escape of heat into outer space during the night. This is because air is a bad conductor of heat and our atmosphere mainly contains air. Thus, the atmosphere mainly keeps the average temperature of the Earth fairly steady.

Q3. What causes winds?

Ans: Winds are caused due to unequal heating of atmospheric air in different regions of the Earth. This phenomenon can be easily seen near the coastal regions during the daytime. The air above the land gets heated faster and starts rising. As this air rises, a region of low pressure is created and air over the sea moves into this area of low pressure. These air movements from one region to another result in winds.

 

Q4. How are clouds formed?

Ans: When water bodies are heated during the day then a large amount of water evaporates and goes into the air. Some amount of water vapor also gets into the atmosphere because of various biological activities. The air gets heated and rises up carrying the water vapor with it. The air expands on rising and cools which causes the water vapor in the air to condense in the form of tiny droplets. These water droplets get bigger and form clouds.

 

Q5. List any three human activities that you think would lead to air pollution.

Ans: Human activities that would lead to air pollution are:

• Excessive use and burning of fossil fuels like coal and petroleum.

• Deforestation, which would decrease the amount of CO2.

• Smoke from industries and automobiles.

Page No. 194

Q1. Why do organisms need water?

Ans: Organisms need water to carry out the following activities:

• All cellular processes in an organism take place in a water medium.

• Water acts as a universal solvent and helps in transporting substances from one part of the body to another in a dissolved form.

• Water is also required by organisms for many of their activities such as drinking, cooking, agriculture, transportation, production of hydel power, etc.

Q2. What is the major source of freshwater in the city/town/village where you live?

Ans: The major source of freshwater in the city I live in is the underground water which is drawn out by tube wells and at household level by hand pumps. Also, huge tanks have been built by the municipal department from where it is supplied to households through a network of pipelines. Apart from that, the rivers flowing in the nearby areas and ponds also serve as a source of freshwater.

 

Q3. Do you know about any activity which may be polluting this water source?

Ans: Dumping of sewage and wastes from factories and households into these water bodies pollute this water source. Moreover, washing clothes and bathing at river shore also pollutes water

 

Page No. 196

Q1. How is soil formed?

Ans: The following factors help in the formation of soil.

Sun: Rays of the sun gradually heat the rocks and they expand during the daytime. During the night, the rocks cool and contract, uneven expansion and contraction of rocks develop cracks.

Water: Water helps in the formation of soil in two ways:

• The cracks formed due to the heat of the Sun are filled with water. This water on freezing widens the gap and loosens the rock into small pieces.

• The running water in rivers wears away hard rocks over long periods of time. Fast flowing water carries small stone pieces and due to rubbing with other rocks they further break down into smaller pieces.

Wind: Strong wind erodes down rocks and also carries sand from one place to another.

Living organisms: Living organisms also help in the process of soil formation. Lichens grow on rock surfaces. While growing, they release certain substances that convert the rocks into powdery form and make a thin soil layer. Other small plants like moss grow on this surface and Lily because Lite rock breaks further.

 

Q2. What is soil erosion?

Ans: It is the removal and thinning of the fertile topsoil from a region due to climate and physical processes, such as high rainfall, wind, etc.

 

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

Ans: The various methods for preventing and reducing soil erosion are:

• Preventing excessive grazing.

• Planting more and more trees, as the roots of the trees hold the soil in place.

• Contour plowing.

• Keeping the vegetation cover on the ground to reduce the effect of wind and water.

Page No. 201

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

Ans: During the water cycle, water is found in all three states, i.e., solid (ice, snow, hail or sleet), liquid and gaseous (water vapors).

 

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

Ans: Proteins and Nucleic acid are biologically important compounds containing both oxygen and nitrogen.

 

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

Ans: The three human activities leading to an increase in the carbon dioxide content of air are:

• Burning of fossil fuel such as petrol, diesel and coal in various activities like transportation and industrial processes.

• Burning of wood and charcoal for heating, cooking, etc.

• Deforestation reduces the green plant and tree population and utilization of atmospheric CO2 during photosynthesis.

Q4. What is the greenhouse effect?

Ans: The increase in the percentage of the gasses in the atmosphere which prevents the escape of heat from the surface of the Earth, which thus causes the average temperature to increase worldwide is called the greenhouse effect.

 

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

Ans: In the atmosphere, oxygen is found in two forms:

• Diatomic molecules having two oxygen atoms (O2), and

• Triatomic molecules having three oxygen atoms (O3) that are found in the upper reaches of the atmosphere.

 

Q1. Why is atmosphere essential for life?

Ans: Atmosphere is essential for life because of the following reasons:

• It acts as a blanket and keeps the average temperature of the Earth fairly steady by preventing a sudden increase in temperature during the day and slowing down the escape of heat into outer space during the night.

• It contains all the gasses which are essential for sustaining life on the Earth.

• Ozone layer present in the atmosphere prevents harmful UV rays from reaching the Earth.

• Winds are generated due to the movement of air present in the atmosphere, and rain and rainfall patterns are decided by these winds.

• Water cycle is not possible without the atmosphere.

 

Q2. Why is water essential for life?

Ans: The Human body contains 60%-70% of water. All the substances are transported from one part of the body to the other in a dissolved form. Almost all the cellular processes take place in a water medium. In fact, all the reactions that take place within our body occur between substances that are dissolved in water. Hence, water is essential for life.

 

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

Ans: Living organisms are dependent on the soil in the following ways:

• All the plants (even aquatic), on which almost all the organisms depend directly or indirectly for food, grow in the soil, which provides them with nutrients and water for development.

• Soil also supports the very existence of forests, which provide us with wood, building material, fiber, medicinal plants. Forests are also a natural habitat for a number of animal species.

• A number of insects and animals make their homes in the soil.

The organisms that live in water are not totally independent of soil as a resource. The mineral nutrients are present in -water in the dissolved form. But their recycling takes place with the help of decomposers that are present in the soil. Water bodies like rivers get the supply of minerals from the soil.

 

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

Ans: Weather can be predicted by studying wind patterns that decide rainfall patterns. It also shows areas of low pressure and high pressure. In India, rains are mostly bought by southwest or northeast monsoons. The weather forecast predicted by the meteorological department on TV provides vital information to farmers, fishermen and also saves lives from national disasters.

 

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: Yes, isolating these activities to specific and limited areas would help in reducing pollution, example: industries set up in isolated areas will not pollute the air, soil and contaminate water used for agricultural and domestic purposes and thus not harm living beings.

 

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

Ans: Forests influence the quality of our air, soil and water resources in the following ways:

• Carbon dioxide: Oxygen balance in the atmosphere: Forests have a large number of trees, shrubs and herbs. They take in CO2 and give out O2 during photosynthesis in daylight. Thus, oxygen is consumed during combustion and also by respiration of organisms is replenished by forests.

• Prevention of soil erosion: Forest trees and other plant roots bind the soil particles They form a vegetation cover over the fertile topsoil. Thus, they prevent the removal of topsoil and consequently soil erosion.

• Replenishment of water resources: Forest trees are large in number and give out an enormous amount of water during transpiration in the form of water vapor. The water vapor helps in the formation of clouds which on precipitation cause rain. If forests are cut and not replenished, there will be a reduction in rainfall and change in the climate.

Natural Resources CLass 9 BIOLOGY MCQ: 

Question: The life supporting zone of the earth is

• a) Biosphere

• b) Lithosphere

• c) Hydrosphere

• d) Atmosphere

Answer: Biosphere

Question: Depletion of ozone molecules in the stratosphere is due to

• a) Halogen compound

• b) Fluorine compound

• c) Chlorine compound

• d) None of the options

Answer: Halogen compound

Question: On the moon the temperature ranges from -190 degree C to 110 degree C. This is due to

• a) No atmosphere

• b) No bio geo chemical cycle

• c) Water bodies present

• d) No water bodies present

Answer: No atmosphere

Question: Life cannot sustain on Mars and Venus because major component in atmosphere is

• a) Carbon dioxide

• b) Oxygen

• c) Nitrogen

• d) Ozone

Answer: Carbon dioxide

Question: Molecules of proteins contain

• a) All of the options

• b) Carbon

• c) Nitrogen

• d) Oxygen

Answer: All of the options

Question: Atmosphere maintain the temperature of earth because

• a) It hold air, which is bad conductor of heat

• b) It contains water vapor

• c) It reflects the heat rays

• d) It absorbs the heat rays

Answer: It hold air, which is bad conductor of heat

Question: Nitrogen fixation can be done by

• a) All of the options

• b) Industries

• c) Rhizobium

• d) Lightening

Answer: All of the options

Question: Greenhouse gasses are

• a) All of the options

• b) Lightening

• c) Rhizobium

• d) Industries

Answer: All of the options

Question: Burning of fossil fuels add

• a) CO2, SO2, NO2, gasses in air

• b) C, SO2, N2, gasses in air

• c) CH4, CO2, NO2, gasses in air

• d) CO, SO3, NO3, gasses in air

Answer: CO2, SO2, NO2, gasses in air

Question: The microorganisms which helps in formation of soil is

• a) Lichen

• b) Bacteria

• c) Moss

• d) B and c

Answer: Lichen

Question. If there were no atmosphere around the Earth, the temperature of the Earth will

(a) increase

(b) go on decreasing

(c) increase during day and decrease during night

(d) be unaffected

Answer :   C

Question. Outer crust of earth is called ……………..

(a) Outer sphere

(b) Lithosphere

(c) Hydrosphere

(d) None of them

Answer :   B

Question. When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of nitrogen?

(a) It moves along with oxygen into the cells

(b) It comes out with the carbon dioxide during exhalation

(c) It is absorbed only by the nasal cells

(d) Nitrogen concentration is already more in the cells, so it is not at all absorbed

Answer :   B

Question. Microorganism living in pond called ………….. which is autotrophic

(a) Crab

(b) Fish

(c) Blue green algae

(d) Fungus

Answer :   C

Question. What would happen, if all the oxygen present in the environment is converted to ozone?

(a) We will be protected more

(b) It will become poisonous and kill all living forms

(c) Ozone is not stable, hence it will be toxic

(d) It will allow harmful sun radiations to reach earth and damage many life forms

Answer :   B

Question. Rainfall patterns depend on

(a) the underground water table

(b) the number of water bodies in an area

(c) the density pattern of human population in an area

(d) the prevailing season in an area

Answer :   B

Question. The protein deposited in the dead superficial cells that make the skin epithelium impervious to water is

(a) keratin

(b) elastin

(c) collagen

(d) mucus

Answer :    A

Question. In nutrient cycle, minerals tend to be dispersed through

(a) evaporation

(b) assimilation

(c) surface and subsurface runoff

(d) convection

Answer :   C

Question. Air, water, and soil is…………………….. component

(a) Biotic component

(b) Abiotic component

(c) A and b both

(d) None of them

Answer:    B

Question. Increase harmful substances in air called as……………..

(a) Air pollution

(b) Droplets

(c) Water vapor

(d) None of them

Answer :   A

Question. If the carbon dioxide content in the atmosphere is increased then which one of the following would not get affected?

(a) Amount of the heat retained by the environment

(b) Process of photosynthesis in plants

(c) Global warming

(d) Existence of desert plants

Answer:    D

Question. Ozone layer is getting depleted because of

(a) excessive use of automobiles

(b) excessive formation of industrial units

(c) excessive use of man-made compounds containing both fluorine and chlorine

(d) excessive deforestation

Answer :   C

Question. Total Earth’s surface covered by water is

(a) 75%

(b) 60%

(c) 85%

(d) 50%

Answer :   A

Question. Which step is not involved in the carbon-cycle?

(o) Photosynthesis

(b) Transpiration

(c) Respiration

(d) Burning of fossil fuels

Answer :   B

Question. Marked temperature changes in an aquatic environment can affect

(a) breeding of animals

(b) more growth of aquatic plants

(c) process of digestion in animals

(d) availability of nutrients.

Answer :   A

Question. mog is the mixture of

(a) smoke + CO2

(b) smoke + nitrogen

(c) smoke + fog

(d) smoke + ozone

Answer :   C

Question. Through which process is oxygen returned to the atmosphere?

(a) Combustion

(b) Photosynthesis

(c) Respiration

(d) Formation of nitrogen oxides

Answer :   B

Question. Which of the following is not a "Greenhouse gas" ?

(a) SO2

(b) CO2

(c) N2O

(d) CH4

Answer :   A

Question. The ‘water pollution’ can be defined in several ways. Which of the following statements does not give the correct definition?

(a) The addition of the undesirable substances to water bodies

(b) The removal of the desirable substances from water bodies

(c) A change in pressure of the water bodies

(d) A change in temperature of the water bodies

Answer:   C

Question. A pollutant is any substance, chemical or other factor that changes natural :

(a) Geo-chemical cycle

(b) Flora of a place

(c) Balance of our environment

(d) Wild life of a region

Answer:   C

Question. Water is ……………….. conductor of heat

(a) Good

(b) Bad

(c) More

(d) Less

Answer :   A

Question. Major component of the atmosphere on Mars and Venus is

(a) Carbon dioxide

(b) Oxygen

(c) Nitrogen

(d) Water vapor

Answer:   C

1. When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of nitrogen?

(a) It moves along with oxygen into the cells

(b) It comes out with the carbon dioxide during exhalation

(c) It is absorbed only by the nasal cells

(d) Nitrogen concentration is already more in the cells, so it is not at all absorbed

► (b) It comes out with the carbon dioxide during exhalation

2. Out of the total land area, how many million hectares of land suffer from degradation?

(a) 150

(b) 175

(c) 200

(d) 225

► (b) 175

3. If there were no atmosphere around the earth, the temperature of the earth will

(a) increase

(b) go on decreasing

(c) increase during day and decrease during night

(d) be unaffected

► (c) increase during day and decrease during night

4. Approximately 70 percent of the earth is covered by water. Of this amount, approximately _____ percent of it is suitable for human use.

(a) 10

(b) 25

(c) 50

(d) less than one

► (d) less than one

5. Light bands of muscle fiber are made of the protein:

(a) Tubulin

(b) Myosin

(c) Actin

(d) Myoglobin

► (c) Actin

6. Carbon is incorporated into life-forms through:

(a) Combustion

(b) Photosynthesis

(c) Digestion

(d) Respiration

► (b) Photosynthesis

7. Ozone layer is getting depleted because of

(a) excessive use of automobiles

(b) excessive formation of industrial units

(c) excessive use of man-made compounds containing both fluorine and chlorine

(d) excessive deforestation

► (c) excessive use of man-made compounds containing both fluorine and chlorine

8. Lichens do not like to grow in cities because of :-

(a) SO2 pollution

(b) Missing natural habitat

(c) Absence of right type of algae and fungi

(d) Lack of moisture

► (a) SO2 pollution

9. In the nitrogen cycle, which bacteria are responsible for nitrification?

(a) Rhizobium

(b) Nitrosomonas

(c) Nitrosomonas and Nitrobacter

(d) Clostridium

► (c) Nitrosomonas and Nitrobacter

10. Haversian system is typically found in bones of

(a) fishes

(b) aves

(c) reptiles

(d) mammals

► (d) mammals

11. mog is the mixture of

(a) smoke + CO2

(b) smoke + nitrogen

(c) smoke + fog

(d) smoke + ozone

► (c) smoke + fog

12. Which of the following tissues has a matrix, that is the source of its structural and functional performances?

(a) connective tissue

(b) muscular tissue

(c) nervous tissue

(d) epithelial tissue

► (a) connective tissue

13. Which is not a function of humus?

(a) It allows water and air to penetrate deep underground.

(b) Humus greatly influences the soil structure of a region.

(c) Humus kills the harmful bacteria present in soil.

(d) Humus causes the soil to become more porous.

► (c) Humus kills the harmful bacteria present in soil.

14. Major protein of connective tissue is:

(a) Myosin

(b) Melanin

(c) Collagen

(d) Keratin

► (c) Collagen

15. Nitrogen-fixation by bacteria does not occur in the presence of:

(a) Oxygen

(b) Hydrogen

(c) Carbon dioxide

(d) Sulfur

► (a) Oxygen

16. Through which process is oxygen returned to the atmosphere?

(a) Combustion

(b) Photosynthesis

(c) Respiration

(d) Formation of nitrogen oxides

► (b) Photosynthesis

17. Breakdown of bigger rocks into fine smaller mineral particles is called:

(a) Paedogenesis

(b) Mineralization

(c) Cracking

(d) Weathering

► (d) Weathering

18. The greenhouse effect is due to :

(a) Impermeability of long wavelength radiations through CO2 of the atmosphere

(b) Penetrability of low wavelength radiations through O3 layer

(c) Penetrability of low wavelength radiations through CO2

(d) Impermeability of long wavelength radiations through O3 layer

► (a) Impermeability of long wavelength radiations through CO2 of the atmosphere

19. Which of the following mainly decides biodiversity in a particular area?

(a) Depth of bottom soil

(b) Different layers of soil

(c) Chemical composition of middle soil

(d) Quality of topsoil

► (d) Quality of topsoil

20. Carbon dioxide in atmospheric air amounts to be about :

(a) 0.003%

(b) 33%

(c) 0.03%

(d) 0.3%

► (c) 0.03%

21. In nutrient cycle, minerals tend to be dispersed through

(a) evaporation

(b) assimilation

(c) surface and subsurface runoff

(d) convection

► (c) surface and subsurface runoff

22. Which of the following does not cause water pollution?

(a) Addition of mercury salts to the water body.

(b) Addition of disease-causing bacteria to the water body.

(c) Addition of dissolved oxygen to the water body.

(d) Addition of fertilizers to the water body.

► (c) Addition of dissolved oxygen to the water body.

23. Which of the following is a free living nitrogen fixing bacteria present in soil ?

(a) Azotobacter

(b) Nitrosomonas

(c) Rhizobium

(d) Pseudomonas

► (a) Azotobacter

23. Volkmann's canals occur in :-

(a) Cartilage

(b) Bone

(c) Internal ear

(d) Liver

► (b) Bone

24. The bone marrow is composed of :

(a) Muscle fibers and adipose tissue

(b) Areolar tissue and adipose tissue

(c) Adipose tissue and calcified cartilage

(d) Adipose tissue, areolar tissue and blood vessels

► (d) Adipose tissue, areolar tissue and blood vessels

25. Wrinkling in old age is due to

(a) collagen

(b) myosin

(c) keratin

(d) actin

► (a) collagen

26. Which of the following is not a "Greenhouse gas" ?

(a) SO2

(b) CO2

(c) N2O

(d) CH4

► (a) SO2

27. Fat is abundant in

(a) liver cells

(b) alveolar tissue

(c) lymph glands

(d) adipose tissue

► (d) adipose tissue

28. Which of the following gasses contributes maximum to the 'Greenhouse effect' on earth ?

(a) Carbon dioxide

(b) Methane

(c) Chlorofluorocarbon

(d) Freon

► (a) Carbon dioxide

29. A logical sequence of carbon cycle is:

(a) Producer - Consumer - Decomposer

(b) Decomposer - Producer - Decomposer

(c) Consumer - Producer - Consumer

(d) Producer - Decomposer - Consumer

► (a) Producer - Consumer - Decomposer

30. Agroforestry and social forestry both includes

(a) Production forestry

(b) Commercial forestry

(c) Afforestation

(d) Plantation of trees

► (d) Plantation of trees

31. Bone marrow is important for

(a) breakdown of WBC

(b) production of RBC

(c) breakdown of RBC

(d) production of WBC

► (b) production of RBC

32. The process of nitrogen-fixation by bacteria does not take place in the presence of

(a) molecular form of hydrogen

(b) elemental form of oxygen

(c) water

(d) elemental form of nitrogen

► (b) elemental form of oxygen

33. The protein deposited in the dead superficial cells that make the skin epithelium impervious to water is

(a) keratin

(b) elastin

(c) collagen

(d) mucus

► (a) keratin

34. Foot and Mouth Disease is a highly contagious disease almost exclusive to cattle, sheep, swine, goats, and other cloven-hoofed animals. It is caused by

(a) fungi

(b) bacteria

(c) protozoa

(d) virus

► (d) virus

35. What happens when rain falls on soil without vegetation cover?

(a) Rain water percolates in soil efficiently

(b) Rain water causes loss of surface soil

(c) Rain water leads to fertility of the soil

(d) Rain water does not cause any change in soil

► (b) Rain water causes loss of surface soil

36. The longitudinal canals of the bone are called :

(a) Volkmann's canals

(b) Haversian canals

(c) Periosteum

(d) Endosteum

► (b) Haversian canals

37. A pollutant is any substance, chemical or other factor that changes natural :

(a) Geo-chemical cycle

(b) Flora of a place

(c) Balance of our environment

(d) Wild life of a region

► (c) Balance of our environment

38. Mammalian erythrocytes are

(a) circular

(b) biconcave

(c) non-nucleated

(d) all the above

► (d) all the above

Natural Resources CLass 9 BIOLOGY SAQ:

Q1. Name two greenhouse gasses.

Ans. Methane and CO2.

 

Q2. Name two chemicals that are depleting the ozone layer?

Ans. Chlorofluorocarbons and compounds of chlorine and fluorine or halogen gasses.

 

Q3. Name two gasses released by fossil fuels and cause acid rain.

Ans. SO2 and NO2 which form sulfurous acid and nitric acid.

 

Q4. Name types of soil?

Ans. Soil based on size of particles—sandy, clay.

Soil based on nutrient and nature—laterite soil, black soil, red soil, alluvial soil. 

 

Q5. What is nitrification?

Ans. Conversion of free nitrogen present in the atmosphere into a compound of nitrogen i.e. nitrite and then nitrite to nitrates is called nitrification.

 

Q6. Name a nitrogen fixing bacteria.

Ans. Rhizobium bacteria.

 

Q7. State three methods by which free nitrogen can be converted into nitrates.

Ans. Biological fixation, lightning and industrial fixation.

 

Q8. Name four factors which lead to soil formation.

Ans. Sun, water, wind and living organisms.

 

Q9. What is humus?

Ans. The top most part of the soil which contains dead remains of plants and animal wastes like excreta, that adds nutrients to the soil.

 

Q10. What is soil erosion?

Ans. The topmost layer of soil that is loose, fertile and helps in the growth of vegetation gets carried away by wind and rain water is called soil erosion.

 

Q11. What is denitrification?

Ans. Conversion of nitrates into free nitrogen is called denitrification.

 

Q12. How does carbon exist in all life forms?

Ans. Carbon is present in all life forms in the form of proteins, carbohydrates, fats, nucleic acids and vitamins.

 

Q13. Name two biological important compounds of nitrogen.

Ans. Alkaloids, urea, DNA, RNA and proteins.

 

Q14. Name two elemental forms of carbon.

Ans. Graphite and Diamond.

 

 

 

 

 

Q15. Name two combined forms of carbon.

Ans. CO2, carbonate and hydrogen carbonate.

 

Q16. Give two biotic components of the biosphere.

Ans. Plants and animals.

 

Q17. Name the free living nitrogen fixing bacteria.

Ans. Rhizopus bacteria

 

Q18. What is the role of photosynthesis in the carbon cycle?

Ans. Photosynthesis helps in the intake of carbon dioxide and thereby reduces the percentage of carbon dioxide in the environment.

 

Q19. Name a chemical responsible for the depletion of the ozone layer in the atmosphere.

Ans. CFC is also known as chloro-fluoro carbon.

 

Q20. What would happen if the ozone layer in the atmosphere disappears?

Ans. The harmful radiation of UV light from the sun will enter the earth’s biosphere and kill many living organisms.

Q1. What is bad ozone and good ozone?

Ans. Ozone when present on the earth’s surface is a very poisonous gas hence called bad ozone. Ozone, when present in the stratosphere, is very protective in nature as it does not allow the harmful ultraviolet radiation to enter the earth’s atmosphere.

 

Q2. State two harmful effects of ozone hole or ozone layer depletion.

Ans. (1) Ozone layer depletion allows harmful ultraviolet radiations to reach the earth surface that may cause skin cancer, cataract etc.

(2) U.V. rays also ionize the cells, changing the gene structure in animals and plants.

 

Q3. What makes the quality and type of soils?

Ans. Type of soil is decided by the average size of particles found in it and the quality of soil is decided by the amount of humus and the microscopic organisms found in it.

 

 

 

 

 

Q4. What is topsoil?

Ans. The top most layer of the soil that contains humus and living organisms in addition to the soil particles is called the topsoil.

 

Q5. What is global warming?

Ans. An increase in the carbon dioxide content in the atmosphere would cause more heat to be trapped and retained by the atmosphere which leads to increase in the temperature of earth’s surface and is called global warming.

 

Q6. What is a biogeochemical cycle?

Ans. A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic but stable system. This flow of components is in cycle form and is called biogeochemical cycle.

 

Q7. How do fossil fuels cause air pollution?

Ans. The fossil fuels, like coal and petroleum, contain small amounts of nitrogen and sulfur. When these fuels are burnt, nitrogen and sulfur are also burnt and produce the oxides of nitrogen and sulfur, which pollutes air. The combustion of fossil fuels also increases the amount of suspended particles in air which leads to air pollution.

 

Q8. What is smog?

Ans. Presence of high levels of all the pollutants like unburnt carbon particles, smoke, oxides of nitrogen, sulfur, carbon etc. lowers the visibility in cold weather when water also condenses in air. This is known as smog.

 

Q9. What are the diseases caused by air pollution?

Ans. The pollutants present in air cause many breathing problems like asthma, it increases the allergy, cancer, heart diseases and respiratory problems.

 

Q10. How can lichen help in indicating the pollutants in air?

Ans. Lichens are very sensitive to the levels of contaminants like sulfur dioxide in the air. Lichens generally grow on the barks of the trees. The trees on the road-side do not show this lichen growth, if in any area the growth of lichens decreases or vanishes the air will be polluted.

 

 

 

 

 

 

Q11. In Spite of breathing out carbon-dioxide in a large amount and released by combustion, the atmosphere has a mere fraction of CO2 only. Why?

Ans. The percentage of carbon-dioxide in our atmosphere is just a mere fraction  because 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.

 

Q12. Why is Earth a unique planet on which life exists?

Ans. Life exists only on Earth because many factors responsible for the life to sustain on it are

(1) Comfortable temperature

(2) Atmosphere

(3) Water

 

Q13. What is the biosphere?

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

 

Q14. How does the atmosphere help in climate control?

Ans. (a) The atmosphere keeps the average temperature of the Earth fairly steady during the day and night.

(b) It prevents the sudden increase in temperature during the daylight hours.

(c) During night, it does not allow the heat to escape out into space.

 

Q15. How are winds caused and what decides the breeze to be gentle, strong wind or a terrible storm?

Ans. Heated air rises creating a low pressure area. This low pressure area is filled by air from cooler areas. The cycle creates flow of air causing wind.

The other factors that influence the wind flow is the rotation of the Earth and the presence of mountain ranges in the paths of the wind.

 

Q16. What is air pollution? How is it caused? Give its two harmful effects?

Ans. The contamination of air with unwanted gasses, particles like dust etc which makes it unfit for inhalation is called air pollution.

Causes: (a) Burning of fossil fuels releases SO2, CO2 and NO2 gasses.

(b) Burning of fuels releases unburnt carbon particles and smoke.

(c) Smoke from industries.

Harmful effects:

(a) It causes respiratory problems.

(b) It causes allergies, asthma, cancer and heart diseases.

 

Q17. What is water pollution? Give its causes and harmful effects?

Ans. Water when contaminated with unwanted substances, chemicals which makes it unfit for use and causes diseases is called water pollution.

Causes: (1) Sewage from towns and cities is dumped in the water.

(2) Fertilizers, pesticides, and insecticides get washed away by water from farm lands.

(3) Effluent from industries.

 

Harmful effects:

(1) Polluted water when consumed causes many diseases which are water-borne like cholera, typhoid, etc.

(2) Mercury in salts dumped by industries causes brain disorders—Minamata disease.

(3) Many life-forms which are susceptible to temperature changes die.

 

Q18. Explain the physical, chemical and biological factors which lead to the formation of soil.

Ans. Physical factors Wind: When the wind blows it erodes big rocks which rub and hit with the other rocks breaking into smaller pieces which are further carried by wind to form soil.

Sun: The heat of the sun causes expansion of the rocks due to heating during day time and it contracts at night. This expansion and contraction causes cracks in the rocks, which breaks slowly to form soil.

Water: When it rains the force of rain water erodes the rocks which break to form soil. At times this water enters the cracks present in the rocks and freezes when temperature falls which breaks the rocks to form soil.

Chemical factor Water: Water when reacts with carbonates and phosphates present in the rocks, it forms soluble compounds which make the rock hollow from inside.

Biological factor: Living organisms also help in the formation of soil. The lichen that grows on the moist surface of rocks releases 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.

The roots of big trees sometimes go into cracks in the rocks and when the tree grows bigger the crack in the rocks is forced bigger.

 

Q19. Explain the water cycle with a diagram.

Ans. 1. Water from different water bodies evaporates due to the sun's heat.

Plants also lose water during transpiration.

2. The hot air rises up with this water vapor.

3. Water vapor condenses to form big water droplets and clouds.

4. Rain water falls from clouds.

5. The rain water re-enters the water-bodies. This process in which water evaporates, falls on the land as rain and later flows back into the sea, rivers is known as water cycle.

Q20. What is acid rain? Give its harmful effects.

Ans. The gasses released due to combustion of fossil fuels are SO2, NO2, CO2, these gasses remain suspended in the air. When it rains the rain water mixes with these gasses to form sulphuric acid, nitrous acid, carbonic acid and comes down on the surface of the earth in the form of acid rain.

Harmful effects of acid-rain:

1. It corrodes statues, monuments of marble, buildings etc.

2. It makes the soil acidic.

3. It damages crops and plantations.

 

Q21. State in brief the role of photosynthesis and respiration in the carbon cycle in nature.

Ans. Photosynthesis: Plants take in carbon-dioxide to prepare food and give out oxygen.

Respiration: Plants/animals take in oxygen and give out carbon-dioxide.

Both these processes are involved in balancing the carbon dioxide gas in nature.

 

Q22. What is the difference between fog and smog? Give two harmful effects of smog.

Ans. The water-vapor present in air when condenses due to very low temperature is called fog. The smoke released in the air due to burning of fuels mixes with the fog and forms smog. (smoke + fog = smog) Harmful effects of smog:

1. It decreases visibility and causes adverse effects on airplane landing, railways and road transport.

 

Q23. Explain the importance of ozone to mankind.

Ans. Ozone is a molecule of oxygen with three atoms of oxygen O3.

It covers the Earth’s atmosphere and is present in the stratosphere. It does not allow the harmful ultraviolet radiation coming from the sun to enter our Earth.

These ultra-violet radiations cause ionizing effects, and can cause cancer and genetic disorders in any life-forms.

The ozone is getting depleted at the south pole near Antarctica. The ozone depletion is due to the halogens like CFC (chlorofluorocarbon) released in the air. Chlorine, fluorine reacts with the ozone and splits it, thereby leading to formation of a big hole called ozone hole.

 

 

Q24. What is the greenhouse effect? Why is it named so?

Ans. In cold countries where the temperature is low and vegetation does not grow, heat is trapped by a glass enclosure which allows the heat radiation to enter into the glass but cannot escape out from the glass. These enclosures where plants grow are called greenhouses. Greenhouse effect: In nature, there are certain gasses in the atmosphere like CO2 and methane, which allows the sun’s heat to enter the Earth’s atmosphere but prevents these radiations from escaping out of the atmosphere. These gasses are known as greenhouse gasses. They help in increasing the temperature and hence this effect is called the greenhouse effect.

 

 

Q25. How does oxygen occur in nature? Explain the oxygen-cycle in nature.

Ans. Oxygen exists in two different forms in nature.

Free form: 21% as oxygen gas.

Combined form: In the form of oxides of metals and non-metals in the earth’s crust, atmosphere and water. It is also present in carbohydrates, fats and proteins.

Oxygen cycle: 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 by a process called photosynthesis.

 

Q26. (a) Give the existence of carbon.

(b) Explain the carbon-cycle in nature.

Ans. (a) Carbon exists in two different forms in nature-free and combined form.

Free form: It occurs in the elemental form as diamond and graphite.

Combined form: It occurs as carbon-dioxide, carbonates and hydrogen carbonate, salts in various minerals. It is also present in proteins, carbohydrates, fats, nucleic acids and vitamins.

(b) Carbon cycle:

(i) Carbon-dioxide present in nature is used by plants during photosynthesis to form glucose and carbohydrate.

 

(ii) CO2 dissolves in water to form carbonates which form limestone.

(iii) Plants contain carbon in the form of glucose, carbohydrates which are eaten by other animals.

(iv) Plants and animals can form petroleum if submerged under the Earth and plants form coal. But if they decompose after dying they release   carbon back to the atmosphere by decomposition (dead) and respiration (living).

 

Q27. Discuss the uses of nitrogen.

Ans. Nitrogen is a crucially important component for all life. It is an important part of many cells and processes such as amino acids, proteins and even our DNA. It is also needed to make chlorophyll in plants, which is used in photosynthesis to make their food.

 

Q28. What is meant by the water cycle? How are nutrients from the land made available to marine organisms by this cycle?

Ans. Water cycle is a continuous process by which water is circulated throughout the earth by the atmosphere through evaporation, condensation, precipitation, and the transpiration of plants and animals. The rain water washes the top soil with minerals and nutrients in it and the nutrients are carried away and discharged to the water bodies and this is how these are made available to aquatic bodies.

 

Q29. State the role of respiration in oxygen cycle.

Ans. Respiration uses oxygen and releases carbon dioxide. From the oxygen cycle the oxygen is utilized and all animals undergoing aerobic respiration use the oxygen for breaking down food to release energy.

 

Q30. How is carbon dioxide fixed in the atmosphere?

Ans. The carbon dioxide gas is released in the atmosphere by activities like respiration and combustion. This gas is used by all the autotrophs containing chlorophyll for the photosynthesis and some amount of this gas also gets dissolved in the water and very little amount of gas gets dissolved in the rain water to form carbonic acid and is brought down from the atmosphere to land.

 

Q31. Name two biologically important compounds that contain both oxygen and nitrogen. What is the role of nitrogen fixing bacteria?

Ans. Nitrites and nitrate contain both oxygen and nitrogen. The plants need nitrogen for their growth and they cannot absorb the free nitrogen available in the air. Hence the nitrogen fixing bacteria available in the soil converts this nitrogen into compounds like nitrates which dissolves in water and is taken by plants through roots. Nitrogen fixing bacteria like rhizobium is commonly found in the root nodules of leguminous plants like peas and ground nuts.

Natural Resources CLass 9 BIOLOGY LONG QUESTION:

Q1. Explain the nitrogen-cycle in nature and define all the terms involved in it.

Ans. Terms involved in nitrogen-cycle are

(a) Nitrogen fixation: Plants cannot use free nitrogen present in the air. This nitrogen molecule is converted into nitrates and nitrites which can be taken up and used to make the required molecule.

This is called nitrogen fixation which can be done by the bacteria that live in the root nodules of leguminous plants. By physical process i.e., during lightning, the high temperature and pressure created in the air convert nitrogen into oxides of nitrogen which dissolve in water and come down along with rain. This is also called nitrification.

(b) Ammonification: The nitrogen compounds formed are taken by plants to form proteins which are further converted into ammonia.

(c) Denitrification: The nitrates and nitrites of nitrogen are acted upon by other groups of microbes e.g. Pseudomonas bacteria, which convert these compounds into free nitrogen gas.

 

Nitrogen cycle: 1. Free nitrogen from the atmosphere is converted into nitrates by bacteria or by lightning.

2. Nitrates mix with soil, and are absorbed by the plants to make proteins.

3. The proteins in plants and animals are converted into amino acids and ammonia.

4. Ammonia is converted into nitrates and then these nitrates and nitrites present in soil are acted upon by another group of bacteria called denitrifying bacteria.

This process is called denitrification, nitrates are converted into free nitrogen and are released back to the atmosphere.

Q2. Explain the biosphere.

Ans. Biosphere: It consists of the sphere where life exists. Life can exist if all the spheres given below are present.

(a) Lithosphere: The crust of the earth also called land which forms the upper layer of the earth i.e. soil. The soil provides all the nutrients for all organisms.

(b) Hydrosphere: Water available in various forms on the earth is called hydrosphere. Water exists in solid—(ice), liquid—(water and gaseous)—(water vapor). It is used by all life forms for their survival.

Water helps in the transportation of nutrients, dissolves nutrients and minerals in it, and makes it available for the plants.

(c) Atmosphere: Atmosphere consists of air with different gasses present in it like O2, N2, CO2 and other gasses. Ozone present in the stratosphere helps the life-forms from harmful ultraviolet radiations of the sunlight.

Various gasses present in the atmosphere are useful for combustion (O2), respiration (O2), photosynthesis (CO2) etc.

 

Q3. What are biogeochemical cycles? Explain the pathway of carbon cycle with the help of a labeled diagram.

Ans. A biogeochemical cycle is defined as the movement of elements through organisms and the environment. The geological activities add the elements present in them into the easily accessible environment from which all living (bio) organisms can use them. This happens due to the chemical processes, such as the formation of molecules.

The Carbon cycle is usually thought of as four major reservoirs of carbon; the atmosphere, the terrestrial biosphere (freshwater systems and non-living organic material, e.g. soil, carbon), the oceans (that has dissolved inorganic carbon, living and non-living marine biotic factors) and the sediments (which includes fossil fuels) interconnected by pathways of exchange.

The movement of carbon occurs because of various chemical, physical, geological, and biological processes. The ocean contains the largest active pool of carbon near the surface of the Earth, but the deep ocean does not rapidly exchange with the atmosphere.

Q4. What is nitrogen fixation? Mention two differences between nitrification and denitrification processes. Name the organisms involved in these processes.

Ans. As part of these life processes, nitrogen is transformed from one chemical form to another. The transformations that nitrogen undergoes as it moves between the atmosphere, the land and living things make up the nitrogen cycle.

Nitrogen in its gaseous form can’t be used by most of the living organisms. It needs to be converted( or ‘fixed’ )to a more usable form through a process called fixation. There are three ways by which nitrogen can be fixed to be useful for living things:

 

(i) Biologically: Nitrogen gas diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as rhizobium ) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.

(ii) Through lightning: Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.

(iii) Industries: In industries nitrogen gas is converted into ammonia (NH3–) and nitrogen-rich fertilizers to supplement the amount of nitrogen fixed naturally.

Nitrification: Nitrifying bacteria in the soil convert ammonia into nitrite (NO2–) and then into nitrate (NO3–). This process is called nitrification. Compounds such as nitrate, nitrite, ammonia and ammonium can be taken up from soils by plants and then used in the formation of plant and animal proteins. For examples:

• The bacteria that convert ammonia to nitrite—Nitrosomonas, Nitrosococcus, Nitrosospira.

• Bacteria that convert nitrite to nitrate—Nitrobacter, Nitrospina, Nitrococcus, Nitrospira.

Denitrification: Denitrification completes the nitrogen cycle by converting nitrate (NO3–) back to gaseous nitrogen (N2). Denitrifying bacteria are the agents of this process. These bacteria use nitrate instead of oxygen when obtaining energy, releasing nitrogen gas to the atmosphere. For examples: Thiobacillus denitrificans, Micrococcus denitrificans, Paracoccus denitrificans, Pseudomonas.

 

Q5. Explain how nitrogen compounds add to the environment and what are the impacts of it?

Ans. Increased nitrogen inputs (into the soil) has helped in the production of food which can feed more people. The agricultural practices are responsible for the nitrogen fixation on Earth through fertilizers and the cultivation of nitrogen-fixing crops. The nitrogen in excess can reach from soils into waterways. The nitrogen that collects in water contributes to eutrophication. The other problem that can occur during nitrification and denitrification is when the chemical process is not completed and nitrous oxide (N2O) is formed. This is of concern, as N2O is a greenhouse gas and it contributes to global warming. A balance of nitrogen compounds in the environment supports plant life and is not a threat to animals. It is only when the cycle is not balanced and the problems occur.

 

Q6. What is the greenhouse effect? List the two greenhouse gasses. State the ultimate effect of increase in greenhouse gasses in the environment.

Ans. The rise in the temperature of the environment due to the increased layers of gasses enveloping the globe which allows the heat radiations i.e. Infra-red radiation entering the earth but does not allow them to escape is called the greenhouse effect.

Greenhouse gasses are carbon dioxide, methane, water vapor and nitrous oxide.

The increase in the emission of these greenhouse gasses has caused the rise in the temperature of the earth which has further led to the melting of the glaciers resulting in rise of the sea level. It is predicted that in the coming years the coral reefs will be destroyed and most of the coastal areas will be submerged under water.