CBSE Class 9 Science Natural Resources Sure Shot Questions Set 02

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ASSIGNMENT QUESTIONS SET - 2
CHAPTER - 14
NATURAL RESOURCES

1. The atmosphere of the earth is heated by radiations which are mainly [1 Mark]
(a) Radiated by the sun
(b) Re-radiated by land
(c) Re-radiated by water
(d) Re-radiated by land and water

Answer: (d) Re-radiated by land and water

1. The incoming solar radiation passes through the atmosphere and heats the earth's surface.
2. The heated land and water surfaces re-radiate heat in the form of infrared radiation.
3. This re-radiated energy heats the greenhouse gases present in the lower atmosphere.
4. Hence, the correct option is (d).

Teacher's Note:
a) The atmosphere is primarily heated from below by terrestrial radiation rather than directly by incoming solar radiation.
b) Students often mistakenly choose direct solar radiation as the main source of atmospheric heating.

2. If there were no atmosphere around the earth, the temperature of the earth will [1 Mark]
(a) Increase
(b) Go on decreasing
(c) increase during day and decrease during night
(d) Be unaffected

Answer: (c) increase during day and decrease during night

1. The atmosphere acts as a blanket that traps heat and maintains a moderate average temperature on earth.
2. Without an atmosphere, extreme heat from the sun would reach the surface unhindered during the day, causing a rapid temperature rise.
3. At night, all the heat would escape quickly into outer space, causing a drastic drop in temperature.
4. Hence, the correct option is (c).

Teacher's Note:
a) This phenomenon is clearly observed on the moon, which has no atmosphere and experiences extreme temperature fluctuations.
b) Remember that the atmosphere moderates diurnal temperature ranges.

3. What would happen, if all the oxygen present in the environment is converted to ozone? [1 Mark]
(a) We will be protected more
(b) It will become poisonous and kill living forms
(c) Ozone is not stable, hence it will be toxic
(d) It will help harmful sun radiations to reach earth and damage many life forms.

Answer: (b) It will become poisonous and kill living forms

1. Oxygen is essential for aerobic respiration in most living organisms.
2. Ozone (O₃) is a powerful oxidizing agent that is extremely toxic and poisonous to living tissues at high concentrations.
3. Converting all atmospheric oxygen to ozone would destroy breathable air and kill all aerobic life forms.
4. Hence, the correct option is (b).

Teacher's Note:
a) While ozone in the stratosphere protects us from UV rays, ground-level ozone in high amounts is a dangerous pollutant.
b) Do not confuse the protective role of the ozone layer with the biological necessity of diatomic oxygen.

4. One of the following factors does not lead to soil formation in nature [1 Mark]
(a) The sun
(b) Water
(c) Wind
(d) Polythene bags

Answer: (d) Polythene bags

1. Soil is formed by the weathering of rocks over millions of years due to physical, chemical, and biological factors.
2. The sun causes rocks to expand and crack, water enters cracks to break them down, and wind causes abrasive wear.
3. Polythene bags are non-biodegradable synthetic pollutants that hinder soil processes rather than contribute to soil formation.
4. Hence, the correct option is (d).

Teacher's Note:
a) Natural weathering agents include sun, water, wind, and lichens.
b) Polythene bags cause soil degradation and prevent percolation of water.

5. The two forms of oxygen found in the atmosphere are [1 Mark]
(a) Water and ozone
(b) Water and oxygen
(c) Ozone and oxygen
(d) Water and carbon-dioxide

Answer: (c) Ozone and oxygen

1. Elemental oxygen exists in the atmosphere primarily as diatomic oxygen (O₂) in the lower troposphere.
2. It also exists as triatomic ozone (O₃) in the stratosphere.
3. These are the two elemental allotropic forms of oxygen found in the atmosphere.
4. Hence, the correct option is (c).

Teacher's Note:
a) Diatomic oxygen supports life and combustion, while ozone shields the earth from ultraviolet radiation.
b) Water is a compound containing hydrogen and oxygen, not a form of atmospheric oxygen.

6. Name the process in which water vapour changes to a liquid. [1 Mark]

Answer:
1. The process in which water vapour changes into liquid water is called condensation.
2. It occurs when warm air rises, cools down, and water molecules lose thermal energy to form tiny droplets.

Teacher's Note:
a) Condensation is a key phase change in the global water cycle responsible for cloud formation.
b) Ensure students distinguish between evaporation and condensation clearly.

7. Which gas is the chief component of Earth’s atmosphere? [1 Mark]

Answer:
1. Nitrogen gas (N₂) is the chief component of Earth's atmosphere.
2. It constitutes approximately 78% of the total volume of the atmosphere.

Teacher's Note:
a) Nitrogen is largely inert and dilutes ambient oxygen to prevent rapid combustion.
b) Oxygen is the second most abundant gas at about 21%.

8. Name the substance that reduces the amount of dissolved oxygen in water. [1 Mark]

Answer:
1. Organic wastes, sewage, and excess fertilizers (nutrients causing eutrophication) reduce the amount of dissolved oxygen in water.
2. Microbial decomposition of these organic pollutants consumes large amounts of dissolved oxygen.

Teacher's Note:
a) Oxygen depletion leads to biological oxygen demand (BOD) spikes in aquatic ecosystems.
b) Thermal pollution by warm industrial effluents also decreases oxygen solubility in water.

9. Which gas is formed in the layers of Earth due to bacterial decomposition in the absence of oxygen? [1 Mark]

Answer:
1. Methane gas (CH₄), also known as marsh gas, is formed due to anaerobic bacterial decomposition.
2. This process occurs deep in sediment layers, marshes, or biogas plants where oxygen is absent.

Teacher's Note:
a) Methanogenic bacteria thrive in anaerobic conditions.
b) Methane is a potent greenhouse gas contributing to global warming.

10. Name the rays essential for formation of ozone in atmosphere. [1 Mark]

Answer:
1. Ultraviolet (UV) rays from the sun are essential for the formation of ozone.
2. High-energy UV rays split molecular oxygen (O₂) into free oxygen atoms, which then react with O₂ to form ozone (O₃).

Teacher's Note:
a) UV radiation drives both the creation and destruction of stratospheric ozone in a dynamic equilibrium.
b) Mentioning ultraviolet radiation specifically satisfies the requirement.

11. Name the elements present in fossil fuels, which cause air pollution. [1 Mark]

Answer:
1. The main elements present in fossil fuels that cause air pollution upon combustion are carbon, hydrogen, nitrogen, and sulphur.
2. Their oxides and unburnt carbon particles lead to smog, acid rain, and respiratory hazards.

Teacher's Note:
a) Combustion of carbon and hydrogen produces carbon dioxide and water vapour, alongside carbon monoxide from incomplete combustion.
b) Impurities like sulphur and nitrogen produce sulphur dioxide and nitrogen oxides.

12. In a coastal region, what would be the direction of wind during the day? [1 Mark]

Answer:
1. During the day, the direction of wind is from the sea towards the land (sea breeze).
2. This happens because land gets heated faster than the sea, causing air above land to rise and create a low pressure area.

Teacher's Note:
a) Convection currents drive coastal winds due to differential heating of land and water.
b) Remember that wind always blows from high pressure (cooler sea) to low pressure (warmer land).

13. When clouds cool down, water droplets fall to the land as rain, hail or snow. Name the phenomenon. [1 Mark]

Answer:
1. The phenomenon is called precipitation.

Teacher's Note:
a) Precipitation is a key phase of the water cycle responsible for returning fresh water to the earth surface.
b) Condensation leads to cloud formation, followed by precipitation when droplets become too heavy.

14. Name the organisms found to be very sensitive to the levels of contaminants like sulphur dioxide in the air. [1 Mark]

Answer:
1. Lichens are the organisms highly sensitive to sulphur dioxide pollution.

Teacher's Note:
a) Lichens act as natural bioindicators for air pollution, particularly sulfur dioxide.
b) They fail to grow in polluted areas, making them useful for environmental monitoring.

15. What do you mean by humus? [1 Mark]

Answer:
1. Humus is the major organic component of soil formed by the decomposition of dead plants and animals by microbes.

Teacher's Note:
a) Humus gives soil its dark color and helps in retaining water and nutrients.
b) It plays a vital role in maintaining soil fertility and structure.

16. Give two examples of exhaustible natural resources. [1 Mark]

Answer:
1. Coal and Petroleum.

Teacher's Note:
a) Exhaustible resources are present in limited quantities and can get depleted by human activities.
b) Alternative acceptable examples include natural gas and minerals.

17. Name two atmospheric gases responsible for causing acid rain. [1 Mark]

Answer:
1. Sulphur dioxide and Nitrogen dioxide.

Teacher's Note:
a) These gases dissolve in rainwater to form sulphuric acid and nitric acid.
b) Industrial emissions and vehicle exhausts are their primary anthropogenic sources.

18. How would you define the term atmosphere? [1 Mark]

Answer:
1. The protective envelope of air that surrounds the Earth is called the atmosphere.

Teacher's Note:
a) It is held in place by the gravitational pull of the planet.
b) It shields life from harmful solar radiation and maintains stable temperatures.

19. What do you understand by the term 'Natural resources'? [1 Mark]

Answer:
1. Resources provided by nature, such as air, water, soil, minerals, forests, and wildlife, that are useful to mankind are called natural resources.

Teacher's Note:
a) They are essential for the survival and sustenance of life on Earth.
b) They are broadly classified into renewable and non-renewable resources.

20. What is strip-cropping? [1 Mark]

Answer:
1. Strip-cropping is an agricultural technique where different crops are grown in alternate strips to prevent soil erosion by wind and water.

Teacher's Note:
a) It breaks the force of wind and slows down water runoff across slopes.
b) It is an effective soil conservation method in sustainable farming.

21. What portion of our country's geographical area is covered by forest? [1 Mark]

Answer:
1. Approximately 33 percent of the geographical area should ideally be covered by forests according to the National Forest Policy, though actual coverage is lower.

Teacher's Note:
a) This target is vital for maintaining ecological balance and environmental stability.
b) Forests regulate climate, water cycle, and preserve biodiversity.

22. Name any two examples of inexhaustible natural resources. [1 Mark]

Answer:
1. Solar energy and Wind energy.

Teacher's Note:
a) Inexhaustible resources are unlimited and cannot be depleted by human consumption.
b) They are also known as renewable or sustainable energy sources.

23. How much air is required by a normal human being in one day? [1 Mark]

Answer:
1. A normal human being requires about 10 to 15 kg of air every day, which is several times more than the food they eat.

Teacher's Note:
a) This highlights the critical importance of clean air for human health.
b) Air intake happens continuously through respiration.

24. What is conversion of ammonia into nitrates called? [1 Mark]

Answer:
1. The conversion of ammonia into nitrates is called nitrification.

Teacher's Note:
a) This is an essential step in the nitrogen cycle carried out by soil bacteria.
b) Nitrates can then be readily absorbed by plants for protein synthesis.

25. State the role of the atmosphere in climate control? [2 Marks]

Answer:
1. The atmosphere acts as a blanket that prevents sudden, sharp increases in temperature during daylight hours.
2. During the night, it slows down the escape of heat into outer space, keeping the average temperature of the Earth fairly steady.

Teacher's Note:
a) Air is a poor conductor of heat, which helps maintain thermal insulation.
b) Wind movements and atmospheric circulation also distribute heat globally.

26. How following factors contribute in formation of soil ? (a) wind (b) water (c) Sun [3 Marks]

Answer:
1. (a) Wind: High-speed winds cause friction and erosion of rocks, carrying abrasive particles that break down large rocks into smaller particles.
2. (b) Water: Flowing water wears down hard rocks over long periods, and water entering rock crevices freezes and expands, cracking the rocks apart.
3. (c) Sun: The sun heats rocks during the day causing them to expand and cools them at night causing them to contract, creating cracks due to uneven expansion.

Teacher's Note:
a) These are physical and mechanical weathering processes in pedogenesis.
b) Temperature fluctuations weaken the structural integrity of large rock masses.
c) Water acts as both a physical weathering agent and a chemical solvent.

27. Acid rain and smog are said to be the consequences of air pollution. How are they caused? What are the ill effects of breathing polluted air on human health? [3 Marks]

Answer:
1. Acid rain is caused by emissions of sulphur dioxide and nitrogen oxides reacting with water vapor, while smog is caused by smoke and fog mixing with air pollutants.
2. Breathing polluted air leads to respiratory diseases like asthma, bronchitis, and lung cancer.
3. It can also cause cardiovascular problems, eye irritation, and allergies.

Teacher's Note:
a) Pollutants like particulate matter, carbon monoxide, and nitrogen oxides severely damage lung tissues.
b) Smog significantly reduces visibility and traps ground-level ozone.
c) Acid rain lowers soil and water pH, harming aquatic and plant life.

28. What is Smog? [1 Mark]

Answer:
1. Smog is a visible fog-like layer in the atmosphere formed by a mixture of smoke and fog, heavily laden with air pollutants.

Teacher's Note:
a) The word is a blend of smoke and fog.
b) It is a common indicator of severe urban and industrial air pollution.

29. What is green house effect? List two green house gases. State the ultimate effect of increase in green house gases in the environment. [3 Marks]

Answer:
1. The greenhouse effect is the trapping of heat by certain atmospheric gases, preventing it from escaping back into space and keeping the Earth warm.
2. Two greenhouse gases are carbon dioxide and methane.
3. The ultimate effect of an increase in greenhouse gases is global warming, leading to climate change and melting of polar ice caps.

Teacher's Note:
a) Greenhouse gases absorb and re-emit infrared radiation.
b) Water vapour and nitrous oxide are other major greenhouse gases.
c) Unchecked emissions disrupt weather patterns and sea levels globally.

30. What makes the biosphere dynamic but stable system ? [2 Marks]

Answer:
1. The continuous flow of energy from the Sun and the cycling of materials (nutrients) between biotic and abiotic components maintain stability.
2. Interdependence and interactions among living organisms and their physical environment keep the biosphere dynamic.

Teacher's Note:
a) Biogeochemical cycles ensure matter is continuously reused.
b) Ecosystem homeostasis provides resilience against environmental disruptions.

31. The atmosphere acts as a blanket. How ? [2 Marks]

Answer:
1. Air is a bad conductor of heat, which allows the atmosphere to trap thermal energy near the Earth surface.
2. It prevents rapid loss of heat into outer space during night and shields the planet from extreme temperature fluctuations.

Teacher's Note:
a) This thermal blanket effect maintains habitable temperatures across the globe.
b) Ozone layer in the stratosphere also acts as a protective shield against UV rays.

32. What is soil? How is it formed? State the major factor that decides the structure of a soil. What role does it play ? [3 Marks]

Answer:
1. Soil is the outermost layer of the Earth containing mineral particles, organic matter, air, water, and living organisms, formed by the weathering of rocks over millions of years.
2. The major factor that decides soil structure is the amount of humus and the size of mineral particles present.
3. Soil provides anchorage and nutrients to plants, houses numerous organisms, and acts as a reservoir for water.

Teacher's Note:
a) Weathering can be physical, chemical, or biological.
b) Soil texture determines water retention and aeration capacity.
c) It is a crucial renewable resource that supports terrestrial life.

33. Write the importance of ozone in the atmosphere. [2 Marks]

Answer:
1. Ozone absorbs harmful ultraviolet (UV) radiations coming from the Sun.
2. This prevents dangerous UV rays from reaching the Earth surface, protecting living organisms from skin cancer, eye damage, and genetic mutations.

Teacher's Note:
a) Ozone is found primarily in the stratosphere layer.
b) Depletion of ozone by CFCs poses a serious threat to global ecosystems.

34. (a) List two activities of man which lead to environmental pollution. (b) List any two uses of carbon in living organisms. [2 Marks]

Answer:
1. (a) Burning of fossil fuels in vehicles and factories, and indiscriminate disposal of industrial and plastic waste.
2. (b) Carbon is the backbone of all organic molecules like carbohydrates, proteins, fats, and nucleic acids, and it is utilized during photosynthesis to produce glucose.

Teacher's Note:
a) Human activities disrupt natural biogeochemical cycles.
b) Carbon compounds form the structural and functional basis of cellular life.

35. List two forms of oxygen found in the atmosphere. Name the process(s) by which (i) oxygen from the atmosphere is used up. (ii) oxygen is returned to the atmosphere [3 Marks]

Answer:
1. Two forms of oxygen found in the atmosphere are diatomic oxygen (\(O_2\)) and ozone (\(O_3\)).
2. (i) Oxygen is used up by respiration, combustion, and nitrogen fixation processes.
3. (ii) Oxygen is returned to the atmosphere primarily through photosynthesis.

Teacher's Note:
a) Diatomic oxygen is essential for aerobic respiration in living organisms.
b) Photosynthesis by green plants and algae maintains the atmospheric oxygen balance.
c) Ozone protects the biosphere from harmful solar radiation.

36. State various steps and processes involved in the nitrogen cycle in nature. Also show cycling of various nutrients in this cycle. [4 Marks]

Answer:
1. Nitrogen fixation converts atmospheric nitrogen into nitrates by lightning or nitrogen-fixing bacteria like Rhizobium.
2. Assimilation involves plants absorbing nitrates to synthesize plant proteins, which are then consumed by animals.
3. Ammonification and nitrification convert dead organic matter and animal waste into ammonia and then into nitrites and nitrates.
4. Denitrification converts nitrates back into free atmospheric nitrogen gas by denitrifying bacteria, completing the cycle.

Teacher's Note:
a) Nitrogen is vital for amino acids, proteins, and nucleic acids.
b) Microorganisms play an indispensable role driving every stage of this cycle.
c) Lightning provides high-energy fixation of atmospheric nitrogen.
d) The cycle maintains a steady reserve of nitrogen in the atmosphere.

37. Write a note on how forests influence the quality of air, soil and water resources. [4 Marks]

Answer:
1. Air quality: Forests absorb carbon dioxide and release oxygen through photosynthesis, helping regulate greenhouse gases and reducing air pollution.
2. Soil quality: Tree roots bind soil particles firmly, preventing soil erosion, while fallen leaves decompose to form humus and enrich soil fertility.
3. Water resources: Forests enhance groundwater table recharge by slowing down surface runoff and facilitating rainwater infiltration into the soil.
4. Climate regulation: Transpiration from trees increases atmospheric humidity, which promotes cloud formation and regular rainfall.

Teacher's Note:
a) Forests function as natural carbon sinks and biodiversity hotspots.
b) Deforestation directly leads to soil erosion, desertification, and water scarcity.
c) Canopy cover reduces the direct impact of heavy raindrops on bare soil.
d) Maintaining forest ecosystems is essential for sustainable natural resource management.

38. How is atmosphere on our Earth different from the atmosphere on Venus and Mars ? State two ways by which percentage of carbon dioxide is fixed on the earth. [3 Marks]

Answer:
1. The atmospheres of Venus and Mars are mainly composed of 95% to 97% carbon dioxide, whereas Earth's atmosphere is a mixture of nitrogen, oxygen, carbon dioxide, and water vapour.
2. Carbon dioxide is fixed on Earth by plants converting carbon dioxide into glucose during photosynthesis.
3. Marine animals use carbonate dissolved in sea water to make their shells.

Teacher's Note:
a) Life exists on Earth due to a balanced composition of gases in the atmosphere.
b) Venus and Mars lack life-supporting oxygen and have extreme surface temperatures.
c) Carbon fixation helps regulate the global greenhouse effect and planetary temperature.

39. "Urbanization and industrialisation is mainly responsible for the increase in environment pollution" Justify this statement and suggest ways and means to check it. [3 Marks]

Answer:
1. Urbanization and industrialization lead to massive burning of fossil fuels, releasing toxic gases and particulate matter into the air.
2. Industrial effluents and untreated sewage are discharged directly into water bodies, causing severe water pollution.
3. Pollution can be checked by using cleaner fuels like CNG, treating industrial waste before disposal, and increasing green cover.

Teacher's Note:
a) Rapid development often compromises ecological balance if sustainable practices are ignored.
b) Students should mention both causes and preventive measures clearly.
c) Afforestation and recycling are key strategies to mitigate industrial impact.

40. Why is the atmosphere essential for life? [2 Marks]

Answer:
1. The atmosphere blankets the Earth and maintains a steady average temperature by preventing sudden temperature surges during the day and heat escape at night.
2. It provides essential gases like oxygen for respiration, carbon dioxide for photosynthesis, and nitrogen for plant growth.

Teacher's Note:
a) The atmosphere acts as a protective shield against harmful cosmic radiation.
b) Without the atmosphere, Earth would experience extreme temperature conditions similar to the moon.

41. Why is water essential for life? [2 Marks]

Answer:
1. All cellular processes take place in a water medium inside living organisms.
2. Substances are transported dissolved in water from one part of the body to another, and terrestrial organisms require freshwater to maintain survival.

Teacher's Note:
a) Water makes up a major portion of living body weight.
b) Availability of water determines the diversity of life in any region.

42. How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource? [3 Marks]

Answer:
1. Plants grow in soil and obtain essential minerals and water from it, forming the base of all food chains on land.
2. Terrestrial animals depend directly or indirectly on plants for food, and many organisms live inside the soil.
3. Organisms living in water are not totally independent of soil because mineral nutrients are washed down from land into water bodies, sustaining aquatic flora and food webs.

Teacher's Note:
a) Soil links the biotic and abiotic components of ecosystems.
b) Runoff from land enriches water bodies with essential minerals.
c) Decomposers in water and soil recycle nutrients continuously.

43. You have seen weather reports on television and in news paper. How do you think we are able to predict the weather? [3 Marks]

Answer:
1. Meteorologists measure temperature, wind speed, wind direction, and humidity using instruments like thermometers and barometers.
2. Weather data is gathered across regions using satellite imaging and radar networks.
3. Supercomputers process this vast data using meteorological models to forecast future weather patterns.

Teacher's Note:
a) Weather forecasting relies heavily on remote sensing and atmospheric physics.
b) Predictions help in disaster management and agricultural planning.

44. We know that many human activities lead to increasing levels of pollution of air, water bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution? [3 Marks]

Answer:
1. Isolating polluting activities into specific zones, such as industrial estates, can help monitor and manage waste more effectively.
2. However, it does not completely eliminate pollution because pollutants like gases and airborne particulate matter spread globally through winds.
3. Similarly, water pollutants travel downstream across geographical boundaries, making complete containment difficult without actual reduction at source.

Teacher's Note:
a) Zonal segregation helps in centralized waste treatment.
b) Natural cycles disperse pollutants beyond local boundaries.
c) Sustainable reduction of pollution requires cleaner production rather than mere isolation.

45. Write a note on how forests influence the air, soil and water resources. [3 Marks]

Answer:
1. Forests purify air by absorbing carbon dioxide and releasing oxygen through photosynthesis.
2. Tree roots bind soil particles firmly, preventing soil erosion and maintaining soil fertility.
3. Forests promote rainfall and increase groundwater levels by facilitating percolation of rainwater into the ground.

Teacher's Note:
a) Forests act as major carbon sinks on Earth.
b) Canopy cover reduces the direct impact of heavy rain on soil.
c) Vegetation plays a vital role in the hydrological cycle.

46. What is ‘Water Cycle’ ? Explain the process of water cycle. [3 Marks]

Answer:
1. The continuous movement of water from the Earth's surface as water vapour to the atmosphere and back down as precipitation is called the water cycle.
2. Water evaporates from water bodies and transpires from plants, rising into the air as vapour.
3. The vapour cools, condenses to form clouds, and falls back to the Earth as rain, snow, or sleet.

Teacher's Note:
a) Solar energy drives the evaporation phase of the water cycle.
b) Precipitation replenishes freshwater resources on land.
c) This biogeochemical cycle maintains water balance on the planet.

47. Write a short note on ‘Nitrogen Fixation’ [2 Marks]

Answer:
1. Nitrogen fixation is the process of converting atmospheric nitrogen gas into nitrates and nitrites that plants can absorb and use.
2. This is carried out naturally by nitrogen-fixing bacteria like Rhizobium in legume root nodules, during lightning discharges, and by industrial processes for fertilizers.

Teacher's Note:
a) Atmospheric nitrogen cannot be utilized directly by most living organisms.
b) Rhizobium bacteria share a symbiotic relationship with leguminous plants.

48. Explain the ‘Nitrogen Cycle [3 Marks]

Answer:
1. Atmospheric nitrogen is fixed into nitrates by bacteria, lightning, and industrial methods.
2. Plants absorb nitrates and convert them into organic compounds like proteins, which pass along the food chain to animals.
3. Decomposers break down dead organic matter, and other bacteria convert nitrogen compounds back into atmospheric nitrogen gas through denitrification.

Teacher's Note:
a) The nitrogen cycle maintains a constant percentage of nitrogen in the atmosphere.
b) Microorganisms play a central role in converting nitrogen across different chemical forms.
c) Protein synthesis in living organisms depends entirely on this cycle.

49. Discuss the consequences of the increase in the concentration of Carbon Dioxide and other Green House gases in the atmosphere [3 Marks]

Answer:
1. An increase in greenhouse gases traps more heat in the atmosphere, leading to global warming.
2. Global warming causes polar ice caps to melt, resulting in a rise in sea levels and flooding of coastal areas.
3. It alters global weather patterns, causing erratic rainfall, droughts, and extreme climate events.

Teacher's Note:
a) Carbon dioxide, methane, and water vapour are primary greenhouse gases.
b) Enhanced greenhouse effect accelerates climate change globally.
c) Mitigation requires reduced fossil fuel consumption and expanded afforestation.

50. What are the causes of Soil Erosion? [2 Marks]

Answer:
1. Deforestation and overgrazing remove vegetation cover, leaving the topsoil loose and vulnerable to wind and water.
2. Heavy rains, floods, and strong winds wash or blow away exposed topsoil layers rapidly.

Teacher's Note:
a) Roots of plants bind soil particles together effectively.
b) Human activities like faulty farming techniques and mining also accelerate soil erosion.