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Class 10 Science Chapter 15 Important Questions with Answers Our Environment
Class 10 Chemistry Chapter 15 Important Questions with Answers Our Environment
Our Environment Class 10 Important Questions Very Short Answer Type
Question 1.
What will happen if we kill all the organisms in one trophic level? (2011 D)
Answer:
It will disturb the food chains and food web, which in turn will decrease the chances of food availability to the succeeding trophic levels and will result in instability of the ecosystem.
Question 2.
Which compounds are responsible for the depletion of ozone layer? (2011 D)
Answer:
Chlorofluorocarbons (CFCs) are the chemicals which are responsible for the depletion of ozone.
Question 3.
Define, ‘trophic level’. (2011 D)
The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels. In a food chain, each step representing an organism forms a trophic level.
Question 4.
What are the various steps in a food chain called? (2011 D)
Answer:
The various steps of a food chain are called trophic levels. These steps are:
- First trophic level consists of producers.
- Second trophic level consists of primary consumers or herbivores.
- Third trophic level consists of secondary consumers or carnivores.
- Fourth trophic level consists of tertiary consumers or top carnivores.
Question 5.
What is the important function of presence of ozone in earth’s atmosphere? (2011 D)
Answer:
Ozone layer absorbs the harmful UV radiations of the sunlight, so this layer is very important for the survival and existence of life on earth.
Question 6.
What is meant by biological magnification? (2011 OD)
Answer:
Some harmful chemicals like pesticides, when absorbed by the plants through soil and water, get transferred from first trophic to the last trophic level of the food chain. As these chemicals are non- degradable, their concentration in the bodies of living organisms at each trophic level progressively increases. This increase in the concentration of harmful chemicals in the body of living organisms at the each trophic level of a food chain is called biological magnification.
Question 7.
Why is it necessary to conserve our environment? (2011 OD)
Answer:
Human beings are an important part of the environment. But human activities change the environment and the changes in the environment affect life on earth.
For example: An environmental problem caused by human activities is depletion of ozone layer. If the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the Sun would reach the earth and would cause skin cancer and other ailments. Therefore it is necessary to conserve our environment.
Question 8.
Distinguish between biodegradable and non-biodegradable wastes. (2011 OD)
Answer:
Difference between biodegradable and non-biodegradable wastes.
Biodegradable waste:
- Wastes which can be broken down into non-poisonous substances in nature in due course of time by the action of micro-organisms are called bio-degradable wastes.
- Plastic, glass, etc.
Non-biodegradable waste:
- Wastes which cannot be broken down into non-poisonous substances in nature are called non-biodegradable wastes.
- Sewage, peals of fruits and vegetables, etc.
Question 9.
Name two decomposers operating in our environment. (2011 OD)
Answer:
Bacteria and fungi are the two decomposers operating in our environment.
Question 10.
What is meant by a biodegradable waste? (2011 OD)
Answer:
Those waste materials which can be broken down to non-poisonous substances in nature in due course of time by the action of micro-organisms like certain bacteria and fungi are called biodegradable waste.
For example, peels of fruits and vegetables, cattle dung etc.
Question 11.
Which class of chemicals is linked to the decrease in the amount of ozone in the upper atmosphere of the earth? (2011 D)
Answer:
The depletion of ozone layer is due to the use of chemicals called chlorofluorocarbons.
Question 12.
Depletion of ozone in the ozone layer is a cause for our worry. Why? (2012 D, 2016 OD)
Answer:
Depletion of ozone in the ozone layer is a cause for our worry because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiation coming from the Sun would reach the earth. These ultraviolet radiations would cause skin cancer and other ailments in men and animals, and also damage the plants.
Question 13.
What happens when higher energy ultraviolet radiations act on the oxygen at the higher level of the atmosphere? (2012 OD)
Answer:
The high energy ultraviolet radiation (UV radiation) coming from the Sun splits oxygen gas into free oxygen atoms
The free oxygen atoms thus produced react with an oxygen molecule to form ozone molecule
Question 14.
State one harmful effect of depletion of ozone layer on the living organisms of the ecosystem. (2012 OD)
Answer:
If the ozone layer in the atmosphere depletes then the extremely harmful ultraviolet radiations coming from the Sun would reach the earth. These uv-radiations would cause skin cancer and other ailments in men, animals and plants.
Question 15.
Why should biodegradable and non-biodegradable wastes be discarded in two separate dustbins? (2013, 2015 D)
Answer:
Biodegradable and non-biodegradable wastes should be discarded in two separate dust- bins because biodegradable waste is decomposed by the micro-organisms to form simple harmless substances which can be used as manures for the plants (e.g., in the potted plants in our garden/terrace garden). Non- biodegradable waste cannot be broken down naturally.
Question 16.
Mention one negative effect of our affluent life style on the environment. (2013 D)
Answer:
Chlorofluorocarbons (CFCs) are the chemicals which are used in refrigerators and air conditioners as coolant when released into the air react with ozone gas present in the ozone layer and destroy it gradually. If the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations coming from the Sun would reach the earth and cause skin cancer and other ailments in humans, animals and plants.
Question 17.
What is the function of ozone in the upper atmosphere? (2015 D)
Answer:
Ozone layer is very important for the existence of life on earth. The function of the ozone layer in the upper atmosphere is to absorb most of the harmful ultraviolet radiations coming from the sun and prevent them from reaching the earth’s surface.
Question 18.
What will be the amount of energy available to the organisms of the 2nd trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules? (2015 OD)
Answer:
According to 10% law, only 10% of energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.
Energy available to 1st Trophic level = 10,000 J
1% of this energy = 100 J
So, First Trophic level has energy = 100 J
Energy to 2nd Trophic level = 10% of 100 J = 10 Joules
Question 19.
The first trophic level in a food chain is always a green plant. Why? (2015 OD)
Answer:
The first trophic level in a food chain is always a green plant because green plants have a mechanism for trapping solar energy with the help of their green pigment called chlorophyll and convert it into chemical energy which is stored as carbohydrates in the plant for the use of the next tropic level.
Question 20.
Which of the following are always at the second trophic level of food chains? (2016 OD)
Carnivores, Autotrophs, Herbivores
Answer:
Herbivores are always at the second trophic level of food chains.
Question 21.
List two natural ecosystems. (2016 D)
Answer:
Two natural ecosystems are Lake and River.
Question 22.
Why are green plants called producers? (2016 D)
Answer:
Green plants are called producers because green plants synthesize their own food during photosynthesis by taking raw materials from the earth and energy from the Sun.
Question 23.
Write one negative effect, on the environment, of affluent lifestyle of few persons of society. (2014, 2016 OD)
Answer:
- Excessive use of air conditioners which is a part of affluent lifestyle emits a lot of heat in the atmosphere.
- Excessive use of packaging materials which are mostly made up of non-biodegradable material are not environment friendly.
- Excessive use of petrol in vehicles also causes pollution.
Thus, affluent lifestyle results in the generation of excessive waste materials.
Question 24.
In a food chain of frog, grass, insect and snake, assign trophic level of frog. (2016 OD)
Answer:
Food chain. Grass → insect → frog → snake
∴ Frog belongs to 3rd trophic level.
Question 25.
What is an ecosystem? (2017 D)
Answer:
Ecosystem is a unit of biosphere where interaction between biotic community and abiotic factors of an area or place takes place with each other.
Question 26.
In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?
Plants → Deer → Lion (2017 OD)
Answer:
10,00,000 Joules.
Our Environment Class 10 Important Questions Short Answer Type I
Question 1.
What makes the earth’s atmosphere a heterogeneous mixture? (2012 D)
Answer:
Density of various components of the atmosphere is different. Therefore the earth’s atmosphere is a heterogeneous mixture, for example, the heavier gases like CO2, O2 and N2 of the atmosphere occupy the lower level (i.e., near the earth’s surface) of the atmosphere whereas lighter gases like O3 occupy the higher level of the atmosphere.
So the components of atmosphere are not equally distributed.
Question 2.
List any four disadvantages of using fossil fuels for the production of energy. (2012 OD)
Answer:
Disadvantages of fossil fuels:
- Fossil fuels are non-renewable source of energy.
- The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxides. These acidic gases cause acid rain.
- The burning of fossil fuels produces smoke which pollutes the air.
- The burning of fossil fuels, especially coal, leaves behind a lot of ash.
Question 3.
In a food chain, if 10,000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer? (2012 OD)
Answer:
Producer. Energy available = 10,000 J
[∴ Plants are able to synthesize only 1 % of total energy available to them]
∴ Energy produced by producer = 1% of 10,000 = \(\frac{1}{100}\) × 10,000 = 100 J
Primary consumer. Energy available = 100 J
∴ Energy transfer from producer to primary consumer = 10% of 100 J = \(\frac{1}{100}\) × 100 = 10 J
Secondary consumer. Energy available = 10 J
∴ Energy transfer from primary consumer to secondary consumer = 10% of 10 J = \(\frac{1}{100}\) × 10 = 1 J
Tertiary consumer. Energy available = 1 J
∴Energy transfer from secondary consumer to tertiary consumer = 10% of 1 J = \(\frac{1}{100}\) × 1 = 0.1 J
Question 4.
Write the harmful effects of using plastic bags on the environment. Suggest alternatives to plastic bags. (2013 OD)
Answer:
Harmful effects of using plastic bags:
- Plastic is non-biodegradable so it will remain as such and pollute the environment.
- Burning of plastic bags produces toxic gases.
- Plastic bags can block the drainage system.
- Discarded plastic bags when eaten by cows and other stray animals can block their alimentary canal and cause harm to them.
- Plastic bags when thrown in the water bodies, can cause water pollution as these do not decompose. Cloth bags and bags made from recycled paper should be used in place of plastic bags.
Question 5.
Why is the Government of India imposing a ban on the use of polythene bags? Suggest two alternatives to these bags and explain how this ban is likely to improve the environment. (2014 D)
Answer:
Plastic bags are non-biodegradable which can not be broken down into non-poisonous substances in nature. Plastic bags are the main cause of sewer blockages as plastic bags are not decomposed by micro-organisms. Plastic bags if eaten by stray animals (like cows) can block their alimentary canal.
Two alternatives:
- We should take our own jute or cloth bags while going for purchasing articles from the market.
- Disposable paper cups should be used for serving tea in trains instead of plastic cups.
- Shopkeepers can use paper bags instead of plastic bags.
Question 6.
List two environment friendly practices or habits which need to be followed by every member of a family/community. Explain how these practices will support the “Save the Environment” mission. (2014 D)
Answer:
Two environment friendly practices to help save the environment are:
- Disposal of wastes after separating them into biodegradable and non-biodegradable waste material.
- Use of unleaded petrol and alternate sources of energy, keeping the car engines properly tuned and serviced and tyres inflated to the right pressure, so that the vehicle runs smoothly.
Question 7.
What are decomposers? List two important roles they play in the environment. (2014 OD)
Answer:
Decomposers are microorganisms that break down complex organic substances (dead remains and waste products of organisms) into simpler inorganic substances that go into the soil and are used up once more by the plants.
Roles:
- Decomposers play an important role in the cycling of materials in the biosphere.
- By decomposing dead bodies of plants and animals they help in cleansing the environment. Example, Bacteria and fungi are examples of decomposers.
Question 8.
List two reasons to show that the existence of decomposers is essential in an ecosystem. (2014 OD)
Answer:
Role of decomposers:
- Decomposers naturally replenish the nutrients in the soil, air and water.
- Decomposers help in keeping the environment clean. They play an important role in the cycling of materials in the biosphere.
Question 9.
State with reason any two possible consequences of elimination of decomposers from the Earth. (2014 OD)
Answer:
If there were no decomposers, then the dead bodies of plants and animals would keep lying as such and the elements of which plant and animals bodies are made, would never be returned to their original pools like soil, air and water. In that case, the cycling process of life and death would be disrupted. All the nutrients present in soil, air and water would soon be exhausted and evolution of life would come to an end.
Question 10.
We often observe domestic waste decomposing in the bylanes of our homes. List four ways to make the residents aware that the improper disposal of wastes is harmful to the environment and also for their own health. (2013 D, 2015 OD)
Answer:
The various ways to make residents aware of the harmful effects of improper disposal of wastes are as follows:
- By putting posters and hoardings.
- By distributing pamphlets to the residents.
- By conducting meetings of residents, welfare society, etc.
- By advertisements through TV/radio/cable operators, etc.
- There should be a strict fine imposed by the sanitary officer from the families which throw their domestic wastes on the roads.
Through all these mediums we can make the residents aware of how such waste serves as a breeding ground for mosquitoes, releases harmful gases, reduces soil fertility, etc.
Our Environment Class 10 Important Questions Short Answer Type II
Question 1.
(a) List any two characteristics of a good fuel.
(b) What are non-renewable resources of energy? Give two examples of such resources. (2011 D)
Answer:
(a) Characteristics of a good fuel:
- It should have a high calorific value.
- It should bum without giving out any smoke or harmful gases.
- Its ignition temperature should neither be too low nor too high.
- After burning it should not leave much ash behind.
(b) Those sources of energy which have accumulated in nature over a very very long time and cannot be quickly replaced when exhausted, are called non-renewable sources of energy.
Example: Fossil fuels (coal, petroleum, natural gas) and nuclear fuels (uranium) are non-renewable sources of energy.
Question 2.
List any two disadvantages of using fossil fuels for the production of energy. (2011 OD)
Give two examples each of the following:
(i) Renewable sources of energy; (ii) Non-renewable sources of energy.
Answer:
(a) Disadvantages of using fossil fuels are:
- Fossil fuels are non-renewable source of energy.
- Elements like carbon, nitrogen and sulfur are present in fossil fuels. When fossil fuels are burnt, these elements react with oxygen of air to produce oxides which are acidic in nature. This leads to acid rain which adversely affects the quality of water and soil.
- CO2 is a gas which produces greenhouse effect. This leads to global warming.
- CO produced is a toxic gas that causes respiratory problems.
(b) (i) Examples of renewable sources of energy:
- Solar energy
- Tidal energy
- Hydel power
(ii) Examples of non-renewable sources of energy:
- Diesel
- Petrol
- CNG
Question 3.
Subhash has started the project of constructing his building. His architect suggested that he should add a system of rain water harvesting in his building. He thought by adopting water harvesting in his project he can solve his water crisis problem in the years to come. Is Subhash correct in his approach? Support your answer. (2012 D)
Answer:
Rainwater collected on the roof is not allowed to go into the drain. It is allowed to percolate under the ground by a specially made passage so as to recharge the ground-water. This process is called rainwater harvesting.
Advantages of rainwater harvesting:
- Rainwater stored as underground water does not evaporate.
- The water stored in ground does not promote breeding of mosquitoes.
- It is protected from contamination by human and animal waste.
- This water recharges wells.
Question 4.
List three problems which arise due to construction of big dams. Suggest a solution for these problems. (2011 OD, 2012 OD)
Answer:
Three problems that arise due to constmction of big dams:
1. Social problems. Due to the construction of high rise dams, a large number of human settlements are submerged in the water of large reservoir formed by the dam and many people are rendered homeless.
2. Environmental problems. The construction of high-rise dams leads to deforestation and loss of biodiversity as vast variety of flora and fauna get submerged in the water of large reservoir formed by the dam and disturbs the ecological balance.
3. Economic problems. Some people believe that the construction of high-rise dams involves the spending of huge amounts of public money without the generation of proportionate benefits.
Suggestions for these problems. All the people who are displaced from the dam site should be given adequate compensation by the Government for rehabilitation so as to start their life afresh.
Question 5.
List the products of combustion of fossil fuels. What are their adverse effects on the environment? (2012 OD)
Answer:
When fossil fuels are burnt, the products of combustion are – carbon dioxide, water, sulphur dioxide and nitrogen oxides. If combustion takes place in an insufficient supply of air then carbon monoxide is produced. All these products are harmful and create some adverse effects on the environment.
- Sulphur dioxide dissolves in rainwater making it acidic. The acid rain thus produced damages trees, plants, buildings and metal structures.
- Nitrogen oxide also causes acid rain.
- Carbon monoxide is a greenhouse gas which traps Sun’s heat energy falling on the earth. The increased carbon dioxide in the atmosphere causes increased greenhouse effects leading to global warming.
Question 6.
(a) What is an ecosystem? List its two main components. (2013 D, 2015 OD)
(b) We do not clean ponds or lakes, but an aquarium needs to be cleaned regularly. Explain.
Answer:
(a) An ecosystem is a self-contained unit of living things (plants, animals and decomposers) and their non-living environment (soil, air and water). An ecosystem needs only the input of sunlight energy for its functioning.
The two main components of an ecosystem are:
- Abiotic component. It includes all non-living components like soil, water, air temperature, light, pressure, etc.
- Biotic component. It includes all living components like plants, animals, decomposers, etc.
(b) A pond is a self sufficient or independent unit in nature. It contains all the components of the ecosystem. In this ecosystem, producers (hydrophytes) trap the solar energy and then provide the basic food or energy for all other life in the pond. When the producers and consumers die, the decomposers present in the pond act on their dead bodies to return the various elements back to the nutrient pool.
On the other hand, in an aquarium there are not any producers and nutrient pool to trap solar energy, therefore the fishes living in an aquarium need to be nourished. Moreover due to absence of decomposers the excreta of the fishes cannot be decomposed. Therefore the aquarium needs to be cleaned regularly.
Question 7.
State in brief two ways in which non-biodegradable substances would affect the environment. List two methods of safe disposal of the non-biodegradable waste. (2013 OD)
Answer:
Non-biodegradable wastes cannot be decomposed into simpler harmless substances by the action of micro-organisms. These substances persist in the environment and cause adverse effects on the environment.
1. The use of pesticides, insecticides has increased agricultural output but the chemicals present in them enter water and food chains. This affects the fertility of the soil and causes water and soil pollution.
2. Plastic bags have changed the modem lifestyle but cause severe problems. They cause blockages in the drainage systems and these plastic bags when eaten by stray animals cause harm to them.
Methods of safe disposal of the non-biodegradable waste. (i) Molten plastic waste mixed with asphalt can be used for making roads, (ii) Solid wastes should be buried in the urban areas as land fills.
Question 8.
“Our foodgrains such as wheat and rice, the vegetables and fruits and even meat are found to contain varying amounts of pesticide residues.” State the reason to explain how and why it happens? (2014 D)
Answer:
Pesticides are poisonous chemical substances which are sprayed over crop plants to protect them from pests and diseases. These pesticides mix up with soil and water and are then absorbed by growing plants along with water and other minerals.
Thus pesticides enter the food chain at the producer level (plant level) and in the process of transfer of food through food chains these harmful chemicals get concentrated at each trophic level. These chemicals are non-biodegradable, so they get accumulated at each trophic level. Pesticides present in wheat grains, fruits vegetables and meat cannot always be removed by washing, etc.
Question 9.
“Energy flow in a food chain is unidirectional.” Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body. (2014 OD)
Answer:
“Energy flow in a food chain is unidirectional.” In the ecosystem energy flows from one trophic level to the next trophic level of the food chain. Energy flows from producers i.e., green plants to the consumers. It does not flow from the last consumer to its previous consumer and so on. Thus the energy does not flow back from consumers to the producers. So we say that flow of energy in an ecosystem is unidirectional.
Entry of pesticides in a food chain: Some harmful chemicals like pesticides, when absorbed by the plants through soil and water, get transferred from first trophic to the last trophic level of the food chain. As these chemicals are non-degradable, their concentration in the bodies of living organisms at each trophic level progressively increases. Their increase in the concentration of harmful chemicals in the body of living organisms at each trophic level of a food chain is called biological magnification. The level of concentration of chemicals is maximum for human beings as they are at the highest trophic level.
Question 10.
After the examinations Rakesh with his friends went on a picnic to a nearby park. All friends carried cooked food packed in plastic bags or plastic cans. After eating the food some friends collected the leftover food and plastic bags etc. and planned to dispose them off by burning. Rakesh immediately checked them and suggested to segregate the leftover food and peels of fruits from the plastic materials & respectively dispose them off separately in the green and red dustbins placed in the comer of the park. In your opinion, is burning plastic an eco-friendly method of waste disposal? Why? State the advantage of the method suggested by Rakesh. (2015 D)
Answer:
Burning of plastic is not an eco-friendly method of waste disposal because it produces toxic gases which cause too much air pollution. It has an adverse effect on the health of all types of living organisms including human beings. The method of waste disposal used by Rakesh is advantageous as the leftover food and peels of fmits are biodegradable and can be used as manure. The plastic bags and cans should be disposed off in red dustbins from where they can be sent for recycling, thereby keeping the environment clean.
Question 11.
Differentiate between biodegradable and non-biodegradable substances with the help of one example each. List two changes in habit that people must adopt to dispose non-biodegradable waste, for saving the environment. (2015 OD)
Answer:
Difference between biodegradable substances and non-biodegradable substances.
Biodegradable waste:
- Wastes which can be broken down into non-poisonous substances in nature in due course of time by the action of micro-organisms are called bio-degradable wastes.
- Plastic, glass, etc.
Non-biodegradable waste:
- Wastes which cannot be broken down into non-poisonous substances in nature are called non-biodegradable wastes.
- Sewage, peals of fruits and vegetables, etc.
Habits for disposing non-biodegradable waste:
- Disposal of wastes after separating them into biodegradable and non-biodegradable wastes in separate dustbins and treating wastes properly before dumping in landfills.
- Encourage the use of gunny bags, jute bags and paper bags in place of polythene/plastic bags.
- Recycle the plastic and glass objects after use.
Question 12.
Give reason to justify the following: (2016 D)
(a) The existence of decomposers is essential in a biosphere.
(b) Flow of energy in a food chain is unidirectional.
Answer:
(a) Decomposers break down complex organic substances (dead remains and waste products of organisms) into simpler inorganic substances that can be absorbed by the plants. They are essential for the proper functioning of an ecosystem.
- Decomposers play an important role in the cycling of materials in the biosphere.
- By decomposing dead bodies of plants and animals they help in cleaning the environment.
- They replenish the soil naturally.
(b) In the ecosystem energy flows from one trophic level to the next trophic level of the food chain. Energy flows from producers, i.e., green plants to the consumers. It does not flow from the last consumers to its previous consumers and so on. The energy captured by the autotrophs does not go back to the solar input. Thus the energy does not flow back from consumers to the producers. Hence the flow of energy in a food chain is unidirectional.
Question 13.
The activities of man had adverse effects on all forms of living organisms in the biosphere. Unlimited exploitation of nature by man disturbed the delicate ecological balance between the living and non¬living components of the biosphere. The unfavourable conditions created by man himself threatened the survival not only of himself but also the entire living organisms on the mother earth. One of your classmates is an active member of ‘Eco-club’ of your school which is creating environmental awareness amongst the school students, spreading the same in the society and also working hard for preventing environmental degradation of the surroundings.
(a) Why is it necessary to conserve our environment?
(b) State the importance of green and blue dust-bins in the safe disposal of the household waste. (2016 OD)
Answer:
(a) It is necessary to conserve our environment because of the following reasons:
- To save natural resources like air, water and soil from pollution which are essential for our survival.
- To maintain ecological balance in nature.
- The environment provides us fresh air to breathe, a number of useful products such as wood, paper, medicines, etc. The ozone layer of the environment also protects us from harmful ultraviolet radiations from the sun.
(b) Green dustbins are used for biodegradable wastes and blue dustbins are used for non-biodegradable wastes.
Importance of two types of dustbins:
- Disposal of wastes after separating them into biodegradable and non-biodegradable wastes in separate dustbins and treating wastes properly before dumping in landfills.
- Segregation of biodegradable and non-biodegradable wastes occur without wasting time and energy.
Our Environment Class 10 Important Questions Long Answer Type
Question 1.
A team of Indian researchers went to Antarctica to study the ozone layer. They confirmed the presence of largest ozone hole over Antarctica and was just short of 27 million sq. km. After few days of their return, one of the scientists developed rashes, burning sensation and other skin problems which the doctors have confirmed as skin cancer.
(a) What may be the cause of cancer just after return from Antarctica?
(b) What do we learn from this incident? (2011 OD)
Answer:
(a) The scientists were exposed to harmful UV-radiations of the sunlight as there was a big hole over Antarctica and this might be the cause of skin cancer. The ozone layer acts as an ozone shield and absorbs the harmful UV-radiations. The UV-radiations have extremely harmful effects on human beings, animals as well as plants.
(b) We learn that the ozone layer is very important for the existence and survival of life on earth. Ozone layer absorbs high energy UV-radiations causing a rise in temperature of the stratosphere. The use of chemicals like CFCs has endangered the ozone layer. CFCs used as refrigerator coolants rise to the stratosphere where these molecules are broken down by UV-rays resulting in attack on the ozone molecules damaging the ozone umbrella of earth.
Due to ozone layer depletion UV-rays reaching the earth cause skin cancer, cataracts, damage immune system, etc. UV-rays also decreases crop yield and certain fish larvae which are important constituents of aquatic food chains. It may also disturb global rainfall causing ecological disturbance. In this way all on the earth would be destroyed gradually.