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CBSE Questions for Class 9 Biology Natural Resources Quiz 6 - MCQExams.com
CBSE
Class 9 Biology
Natural Resources
Quiz 6
Choose the incorrect statement from the following.
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Air is a good conductor of heat.
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Air helps in transmitting sound.
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Burning of fire takes place in presence of oxygen.
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Ozone layer of the atmosphere protects the living organisms from harmful radiations of the sun.
Identify the option which correctly explains the processes mentioned as A,B and C in the nitrogen cycle.
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A = Nitrogen compounds are broken
B = Nitrogen is broken
C = Nitrogen compounds formed
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A = Nitrogen converted into Nitrogenin containing compounds
B = Animals eats plants
C = Nitrogen compounds converted into Nitrogen gas
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A = Nitrogen compounds formed
B = Animals excretes nitrogen compound
C = Nitrogen $$\rightarrow N_{2} $$ gas
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None of the above
Explanation
A = Nitrogen is converted into nitrogen compounds.
B = Animals eat plants.
C = Nitrogen compounds converted into nitrogen gas.
The atmospheric nitrogen is converted into nitrogen compounds using several methods i.e. nitrogen fixation. These nitrogen compounds all up took by plants. Animals eat plants and both the animal and plant biomass is decomposed and converted into ammonia by the process called ammonification. Nitrification is a process of the biological oxidation of ammonia or ammonium to nitrite followed by the oxidation of the nitrite to nitrate. Denitrification is the process by which the nitrogen compounds are converted into nitrogen gas.
Oxygen is a gas produced by _____ and used by _____.
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Plants, animals
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Animals, plants
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Photosynthesis, carbon dioxide
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Carbon dioxide, photosynthesis
Explanation
Photosynthesis produces oxygen as a byproduct. Plants and algae breathe out this oxygen into the atmosphere. Humans and animals then breathe in this oxygen ($$\displaystyle { O }_{ 2 }$$) for cellular respiration to release the energy from glucose. Oxygen is needed for cellular respiration, but it does not come from this process.
Thus, the correct answer is option A.
Oxygen from the atmosphere is used up in processes, namely:
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Combustion
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Respiration
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Forming oxides of nitrogen
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All of the above
Explanation
Oxygen is one of the most important elements of the Earth's atmosphere. It is consumed by every living creature in every natural process.
In respiration, living organisms take in oxygen to generate energy from the food that they eat.
Any combustion reaction requires oxygen.
Forming oxides of any element requires oxygen.
Therefore, the correct answer is option D.
If there is a fire in the forest, there will be less _________ in the environment.
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Carbon dioxide
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Nitrogen
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Sunlight
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Oxygen
Explanation
Oxygen supports burning and hence, oxygen is needed for the fire, for the woods to burn. The organic plants, trees, etc. use up the oxygen present in the atmosphere, thus reducing its amount.
So, the correct answer is option D.
In the upper atmosphere, _____ becomes ozone, a substance that protects the earth from UV radiation and makes life on land possible.
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Carbondioxide
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Oxygen
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Nitrogen
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Water vapour
Explanation
Ozone is a gas found in the atmosphere consisting of three oxygen atoms: $$\displaystyle { O }_{ 3 }$$. Ozone is formed in the atmosphere when energetic ultraviolet (UV) radiation dissociates molecules of oxygen,
$$\displaystyle { O }_{ 2 }$$
,
into separate oxygen atoms. Free oxygen atoms can recombine to form oxygen molecules but if a free oxygen atom collides with an oxygen molecule, it joins up, forming ozone.
So, the correct answer is 'Oxygen.'
Water can get polluted naturally due to
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Volcanoes
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Storms
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Earthquakes
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All of the above
Explanation
The process of addition of adulterant in the water which adversely affects the quality of water is known as water pollution. The polluted water doesn't support human use, such as drinking water and undergoes a marked shift in its ability to support its constituent biotic communities, such as fish. Natural phenomena such as volcanoes, algae blooms, storms, and earthquakes also cause major changes in water quality and the ecological status of water.
Thus, the correct answer is option D.
Which phase of water cycle gives us fresh water?
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Condensation
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Evaporation
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Precipitation
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Runoff
Explanation
The hydrological cycle is a prominent method to rejuvenate the fresh water resources. It involves the evaporation of water into water vapor by the heat of the sun which further condenses into tiny water droplets which fall on the earth as rain. The process of condensation that forms rain is also known as precipitation.
So, the correct answer is option C.
Which element from the atmosphere is a part of all the processes: respiration, combustion, and formation of oxides of nitrogen?
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Oxygen
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Nitrogen
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Carbon dioxide
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Carbon
Explanation
Oxygen is one of the most important elements of the Earth's atmosphere. It is consumed by every living creature in every natural process.
In respiration, living organisms take in oxygen to generate energy from the food that they eat.
Any combustion reaction requires oxygen.
Forming oxides of any element requires oxygen.
Therefore, the correct answer is option A.
................... is one of the ways by which water moves on the Earth.
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Condensation
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Precipitation
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Runoff
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None of the above
Explanation
Runoff is one of the ways by which water moves across earth's surface, it can be both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, stored in lakes or reservoirs, which are then to be extracted for agricultural or other human uses.
Water pollution causes damage to the
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Humans only
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Entire ecosystem
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Plants only
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None of the above
Explanation
Water pollution affects the entire biosphere, plants and organisms as all the life forms depend on water for their survival. In almost all cases, the effect is damaging not only to individual species and population but also to the natural biological communities.
The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from
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An increase in cellular respiration
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Increased decomposition by bacteria
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An increase in the burning of fossil fuels
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An increase in photosynthesis
Explanation
Cellular Respiration (a) and Decomposition (b) both add to carbon dioxide, but there is no evidence that these have increased over the last 50 years. Photosynthesis (d) decrease carbon dioxide. However, an increase in the burning of fossil fuels (C) has increased. For example, there are many more vehicles burning gasoline than in the past, coal is used in household and industries, diesel is used for in working of certain construction equipments etc
moreover, urbanisation and industrialization has lead to deforestation, leading to decrease in number of trees that fix carbon dioxide.
So, the correct answer is '
An increase in the burning of fossil fuels'
Water cycle leads to change in _______.
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Pressure
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Humidity
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Temperature
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Both B and C
Explanation
During evaporation, water takes up energy from its surroundings and cools the environment. It releases energy when it condenses and warms the environment. This causes a change in the temperature as well as the humidity of the surrounding.
Thus, the correct answer is option D.
During water cycle, the water undergoes .......... phase.
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Ice
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Liquid
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Gas
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All of the above
Explanation
The hydrological cycle is a prominent method to rejuvenate freshwater resources.
It involves the evaporation of water into water vapor by the heat of the sun which further condenses into tiny water droplets that fall on the earth as rain. This continuous recycling of water leads to the recharging of water resources.
It includes the interconversion of different states of water. The ice present in the glaciers melts due to the overheating of the earth and enters the hydrological cycle.
So, the correct answer is option D.
In oxygen cycle, the movement of oxygen takes place within
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Atmosphere
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Biosphere
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Lithosphere
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All of the above
Explanation
The oxygen cycle is the biogeochemical cycle that allows the exchange of oxygen between biotic and abiotic components in the environment by two major processes like respiration and photosynthesis.
So, the correct answer is option D.
The greenhouse effect is useful because:
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it reduces water pollution
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it increases normal temperature of earth
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it keeps the temperatures on our planet mild and suitable for living things
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it reduces greenhouse gases
Explanation
The greenhouse effect is useful because trapping some energy keeps the temperatures on our planet mild and suitable for living things. Without its atmosphere and the greenhouse effect, the average temperature at the surface of the Earth would have been very low.
Identify the constituents of soil from the following:
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Gravel
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Salt
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Mineral
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All of the above
Which of the following is the main source of free oxygen?
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Respiration
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Conduction
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Photosynthesis
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All of the above
Explanation
In plants, during the process of photosynthesis, starch and free oxygen are produced from carbon dioxide and water in the presence of sunlight.
$$6C{O}_{2} + 6{H}_{2}O + $$energy $$\longrightarrow {C}_{6}{H}_{12}{O}_{6} + 6{O}_{2}$$
During respiration, the plants use free oxygen molecules to produce water, carbon dioxide, and energy, required for plants to grow.
Conduction is the transfer of heat through matter.
So, the correct answer is option C.
Loss of free oxygen can be seen in case of
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Photosynthesis
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Respiration
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Evaporation
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Condensation
Explanation
Oxygen from the atmosphere is taken in by animals for carrying out the process of respiration. Photosynthesis is the process in which autotrophs such as green plants use carbon dioxide and water in presence of sunlight to synthesize nutrients such carbohydrates in the form of glucose and release oxygen. Hence there is loss of oxygen that is returned to the atmosphere by photosynthesis. Thus the correct answer is option A.
How can soil erosion by river floods be controlled?
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By making canals
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By pumping water from river
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By constructing dams across the rivers
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By letting water flow freely at high speed
Explanation
The soil erosion by river floods can be avoided by constructing dams across the rivers. This checks the speed of water and saves soil from erosion. Therefore, the correct answer is option C.
Animals obtain all their carbon through:
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Plants
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Soil
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Air
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Water
Explanation
Carbon is bound to oxygen in carbon dioxide gas, and it transfers from the air to plants through photosynthesis.
Animals get carbon from plants in the form of food as plants produce food by carbon dioxide and water in the presence of sunlight.
The carbon cycle plays an important role in the circulation of carbon.
So, the correct answer is option A.
What is soil erosion?
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It is the process by which soil is formed
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A harmful process that involves the removal and transport of soil by wind and water
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A natural method of filtering harmful pollutants
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A process often referred to as the 'greenhouse' effect
Explanation
Correct Answer- B
Explanation-
Soil erosion
can be defined as the process in which the upper layer of the soil is carried away or displaced.
The carrier which causes soil erosion can be water and air.
Making shelter belts and constructing dams are two ways to prevent soil erosion.
Greenhouse gases cause:
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ocean acidification
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ozone depletion
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smog pollution
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all of above
Explanation
Increases in the different greenhouse gases have other effects apart from global warming, including ocean acidification (by acid rain), smog pollution (contaminated particles in air) and ozone depletion as well as changes to plant growth and nutrition levels.
Why is organic matter (humus) an important part of soil?
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It helps to improve water infiltration
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It can break down organic pollutants
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It converts nitrogen in the air into nitrates used by plants
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It is rich in nutrients, which is important for fertility
Explanation
Humus controls and regulates many soil functions, as well as plant growth. The better the humus count in the soil, the healthier and more productive soil will be. Regardless of the program one uses in farming operations, the higher the humus count, the better the crop is grown yield. Good humus count in the soil will hold soil moisture longer, thus less water is required for crop production. Also, good humus count reduces both water and wind erosion of soil.
What causes movement in air?
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Difference in temperature
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Difference in pressure
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Difference in volume
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Both A and B
Explanation
When air is heated by radiation from the heated land or water, it rises. But since land gets heated faster than water, the air over land would also be heated faster than the air over water bodies.
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 in to this area of low pressure.
The movement of air from one region to the other creates winds. 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. Thus, differences in temperature and pressure cause movement in the air.
So, the correct answer is option D.
Conversion of nitrogen-containing organic molecules into nitrates is done by:
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Decomposers.
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Producers.
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Primary consumers.
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Secondary consumers.
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Tertiary consumers.
Explanation
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 nitrates and nitrites into elemental nitrogen.
These bacteria are known as decomposers.
Thus, the correct answer is option A.
The nutrient cycle that has largest reservoir in the atmosphere is
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Carbon cycle
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Nitrogen cycle
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Potassium cycle
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Phosphorus cycle
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Water cycle
Explanation
Nitrogen is the gas which is maximally present in the atmosphere. Up to 78% of the atmosphere contains Nitrogen gas. The second most abundant is oxygen which consists of 21% of the atmosphere. All other gases are present less than 1%.
So the correct answer is 'Nitrogen cycle'.
Observe the above diagram and answer the following questions.
Can both animals and plants obtain their nitrogen from the atmosphere?
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Yes, both animals and plants take in nitrogen during respiration.
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Yes, most of the nitrogen in the cycle is in the atmosphere.
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No, only plants can take in nitrogen from the atmosphere.
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No, they must consume it through eating or uptake from the soil.
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No, they must obtain it through symbiotic relationships.
Explanation
Plants take up nitrogen from the soil or obtain it through nitrogen-fixing bacteria in their roots, and animals obtain nitrogen by eating plants.
The nitrogen fixation is the biochemical process by which atmospheric nitrogen is converted into a usable form and absorbed by the plants. Plants are consumed by animal and animal gets nitrogen in the form of protein from plants only.
Thus, the correct answer is option D.
Where do nitrogen-fixing bacteria exist in an environment?
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Stomach of a reptile
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Lower epidermis of leaves
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Gills of freshwater fish
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Large intestine of humans
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Root systems of plants
Explanation
Nitrogen-fixing bacteria exists in the root system of plants so that they can take up the available nitrogen in the soil and carry out its conversion into usable form i.e., ammonia.
Therefore, the correct answer is option E.
What is the harm from the depletion of Earth's ozone layer?
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The average temperature of Earth's surface will increase gradually.
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The oxygen content of the atmosphere will decrease.
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Increased amount of ultraviolet radiation will reach the Earth's surface.
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Sea levels will rise as the polar ice caps will gradually melt.
Explanation
The ozone layer is responsible for most of the absorption of harmful UV rays. Depletion of the ozone layer allows the harmful UV rays to enter the Earth's surface causing various damages to the living organisms. Exposure to UV rays can lead to
skin cancer, defective eyesight, reduction in immunity, increased number of mutations, and reduction in crop yield.
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