15. Our Environment SEBA/ASSEB Class 10 Science– Important Questions and Answers | Assam HSLC

SEBA/ASSEB Class 10 Science Chapter 15: Our Environment Important Questions and Answers | HSLC Assam

Chapter 15: Our Environment

Multiple Choose Question and Answer :

Question: Which of the following contains only biodegradable substances?

(a) Plastic, glass and aluminium (b) Glass, paper and plastic

Answer: (c) Grass, flowers and leather.

[Grass, flowers and leather can be broken down by biological processes.]

Question: The first trophic level in a food chain is occupied by:

(a) Decomposers (b) Herbivores (c) Carnivores (d) Producers

Answer: (d) Producers.

[ Green plants produce food using sunlight and occupy the first trophic level.]

Question: Which organisms break down dead plants and animals?

(a) Herbivores (b) Carnivores (c) Producers (d) Decomposers

Answer: (d) Decomposers.

[Bacteria and fungi break down dead organic matter into simpler substances.]

Question: How many oxygen atoms are present in one molecule of ozone?

(a) One (b) Two (c) Three (d) Four

Answer: (c) Three

Question: In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of

(a) heat energy (b) light energy (c) chemical energy (d) mechanical energy

Answer: (c) Chemical energy.

Question: Which type of radiation from the Sun is absorbed by the ozone layer?

(a) Infrared radiation (b) Ultraviolet radiation (c) Radio waves (d) Visible light

Answer: (b) Ultraviolet radiation

Question: What is the chemical formula of ozone?

(a) O (b) O₂ (c) O₃ (d) CO₂

Answer: (c) O₃

Question: How is ozone formed in the upper atmosphere?

(a) By the action of UV radiation on oxygen molecules (b) By the action of rainwater on oxygen

Answer: (a) By the action of UV radiation on oxygen molecules

Question: What percentage of energy is generally transferred to the next trophic level?

(a) 50% (b) 90% (c) 1% (d) 10%

Answer: (d) 10%.

[ According to the 10% law, approximately 10% of energy is transferred to the next trophic level.]

Question: Which gas protects the Earth from harmful ultraviolet radiation?

(a) Ozone (b) Carbon dioxide (c) Oxygen (d) Nitrogen

Answer: (a) Ozone.

[ Ozone in the upper atmosphere absorbs much of the Sun's harmful ultraviolet radiation.]

Question: Which chemicals are responsible for ozone-layer depletion?

(a) Oxygen (b) Nitrogen (c) CFCs (d) Hydrogen

Answer: (c) CFCs.

[ Chlorofluorocarbons (CFCs) contribute to the depletion of the ozone layer.]

Question: The accumulation of harmful chemicals at successive trophic levels is called:

(a) Biological magnification (b) Nitrogen fixation (c) Photosynthesis (d) Decomposition

Answer: (a) Biological magnification.

[Non-biodegradable chemicals accumulate progressively along the food chain.]

Question: Which of the following is a non-biodegradable substance?

(a) Vegetable peels (b) Plastic bag (c) Paper (d) Cotton cloth

Answer: (b) Plastic bag.

[ Ordinary plastic does not readily break down through biological processes.]

Question: Which of the following are environment-friendly practices?
(a) Carrying cloth bags while shopping (b) Switching off unnecessary lights and fans
(c) Walking to school instead of using a vehicle (d) All of the above
Answer: (d) All of the above

Question: The flow of energy in an ecosystem is:

(a) Multidirectional (b) Unidirectional (c) Circular (d) Reversible

Answer: (b) Unidirectional.

[ Energy flows from the Sun to producers and then to consumers; it is not recycled back.]

Question: Which of the following is an environment-friendly practice?

(a) Burning plastic waste (b) Carrying cloth bags while shopping

Answer: (b) Carrying cloth bags while shopping.

[ Cloth bags help reduce the use of disposable plastic bags. ]

Question: Which one of the following is a biodegradable waste ? [SEBA 2016]

(a) Polythene bag (b) Peeled skin of mango (c) Torn leather bag (d) Plastic bottle

Answer: (b) Peeled skin of mango

[ Biodegradable waste can be naturally broken down and decomposed by microorganisms, contributing to the recycling of nutrients in the environment.]

Question: In a food chain, the third trophic level is always occupied by
(a) Producers (b) Herbivores (c) Carnivores (d) Decomposers
Answer: (c) Carnivores

Question: The percentage of solar radiation absorbed by green plants for photosynthesis is about
(a) 1% (b) 5% (c) 8% (d) 10%
Answer: (a) 1%

Question: Ozone, at the higher levels of the atmosphere , prevents . [SEBA 2017 , 2024]

(a) infra-red radiations (b) Visible light (c) UV radiations (d) both (a) and (c)

Answer: (c) UV radiations.

[ Ozone in the stratosphere absorbs and filters out a significant portion of the Sun's harmful ultraviolet (UV) radiation, particularly the most dangerous UV-B and UV-C rays. ]

Question: Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as
(a) Eutrophication (b) Bioaccumulation (c) Biomagnification (d) Biosphere
Answer: (c) Biomagnification

Question: Ozone is a molecule made up of
(a) One oxygen atom (b) Two oxygen atoms (c) Three oxygen atoms (d) Four oxygen atoms
Answer: (c) Three oxygen atoms

Question: From the energy flow diagram, it is confirmed that the flow of energy is [2024]

(a) unidirectional (b) multidirectional (c) upward in air (d) downward in water

Answer: (a) unidirectional.

[ In an ecosystem, energy flows in one direction: from the sun → producers → consumers → decomposers, and as heat it is lost at each trophic level. It does not cycle back, so the flow is unidirectional. ]

Question: Which of the following can depleted Ozone layer ? [SEBA 2023]

(a) Chloroflourocarbon (b) Nitrogen (c) Hydrogen (d) Oxygen

Answer: (a) Chloroflourocarbon .

Question: Which of the following is an artificial ecosystem?
(a) Pond (b) Lake (c) Crop field (d) Forest
Answer: (c) Crop field

Question: If the energy available at the producer level is 10,000 J, the energy available to the tertiary consumer is approximately
(a) 10 J (b) 100 J (c) 1000 J (d) 10,000 J
Answer: (a) 10 J

[10% law: 10,000 → 1,000 → 100 → 10 J]

Question: Which group of the following waste materials can be classified as non-biodegradable ? [2025]

(a) Plant waste, used tea bags (b) Polythene bags, plastic toys

Answer: (b) Polythene bags, plastic toys.

Question: Which chemicals are mainly responsible for depletion of the ozone layer?
(a) Carbon monoxide (b) Methane (c) Chlorofluorocarbons (CFCs) (d) Sulphur dioxide
Answer: (c) Chlorofluorocarbons (CFCs)

Question: Find the correct statement from the following : [2025]

(a) Ozone is not considered as poisonous and deadly gas . (b) Ozone molecule is formed of three atoms of oxygen.

Answer: (b) Ozone molecule is formed of three atoms of oxygen.

Question: Which one of the following is a biodegradable waste ? [2016]

(a) Polythene bag (b) Peeled skin of mango (c) Torn leather bag (d) Plastic bottle

Question: The 3^rd trophic level of a food chain is . [SEBA 2023]

Answer: Secondary Consumers.

[ Secondary Consumers, which are carnivores that eat the herbivores from the second trophic level .]

Assertion and Reasoning :

Choose the correct option for each question.

(a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

(b) Both Assertion and Reason are true, but Reason does not correctly explain Assertion.

(d) Assertion is false, but Reason is true.

Question: Assertion (A): Energy flow in an ecosystem is unidirectional.

Reason (R): Energy lost as heat at one trophic level is not available to the next level.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Energy passes in one direction, with some energy dissipated as heat at each transfer. ]

Question: Assertion (A): Green plants are called producers.

Reason (R): Green plants prepare food by photosynthesis.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Plants produce organic food using sunlight, carbon dioxide and water. ]

Question: Assertion (A): The number of trophic levels in a food chain is limited.

Reason (R): Only a small fraction of energy is transferred to the next trophic level.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ The progressive loss of available energy limits the length of a food chain. ]

Question: Assertion (A): Energy flow in a food chain is always unidirectional.
Reason (R): Energy lost as heat at one trophic level is not available to the previous level.
Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

Question: Assertion (A): Autotrophs are at the first trophic level in a food chain.
Reason (R): Autotrophs fix solar energy and make it available for heterotrophs.
Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

Question: Assertion (A): Vegetarian food habit is more beneficial.
Reason (R): Only about 10% energy is available from one trophic level to the next.
Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

Question: Assertion (A): Decomposers are important for maintaining an ecosystem.

Reason (R): They break down dead organisms and release simpler substances into the environment.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Decomposers recycle materials that can be reused by producers. ]

Question: Assertion (A): Non-biodegradable substances can accumulate in food chains.

Reason (R): Many such substances are not broken down by biological processes.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Persistent chemicals may accumulate at successive trophic levels. ]

Question: Assertion (A): The concentration of certain pesticides is highest at the producer level.

Reason (R): Humans occupying the top trophic level may accumulate the highest concentration of such chemicals.

Answer: (d) Assertion is false, but Reason is true.

[ The Assertion is false; biological magnification generally causes the highest concentration at the top trophic level. ]

Question: Assertion (A): The amount of ozone in the atmosphere began to drop sharply in the 1980s.

Reason (R): Oxygen atoms combine with molecular oxygen to form ozone.

Answer: (c) Assertion is true, but Reason is false.

[A true due to CFCs; R describes ozone formation, not depletion.]

Question: Assertion (A): Ozone in the upper atmosphere is harmful because it allows UV radiation to reach Earth.

Reason (R): The ozone layer absorbs much of the harmful ultraviolet radiation.

Answer: (d) Assertion is false, but Reason is true.

[ The Assertion is false. Ozone protects Earth by absorbing much of the harmful UV radiation. ]

Question: Assertion (A): Food chains are responsible for entry of harmful chemicals into our bodies.
Reason (R): The length and complexity of food chains vary greatly.
Answer: (b) Both Assertion and Reason are true, but Reason does not correctly explain Assertion.

Question: Assertion (A): All biodegradable waste is completely harmless to the environment.

Reason (R): Large amounts of untreated biodegradable waste can pollute water bodies.

Answer: (d) Assertion is false, but Reason is true.

[ The Assertion is false; biodegradable waste can still cause pollution when not managed properly. ]

Question: Assertion (A): Ozone layer protects life on Earth.
Reason (R): It absorbs harmful ultraviolet (UV) radiations from the Sun.
Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

Question: Assertion (A): Plastic is generally considered non-biodegradable.

Reason (R): Ordinary plastic is not readily broken down by decomposers under normal environmental conditions.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Ordinary plastics may persist in the environment for a long time.]

Question: Assertion (A): A food web is more complex than a single food chain.

Reason (R): A food web consists of interconnected food chains.

Answer: (a) Both Assertion and Reason are true, and Reason correctly explains Assertion.

[ Many organisms have multiple food sources and may be eaten by different consumers. ]

Very Short Question and Answer :

Question: What is an ecosystem?
Answer: An ecosystem consists of living organisms interacting with one another and with their non-living environment.

Question: Give one example of an artificial ecosystem.
Answer: Crop field (Aquarium Or Garden.)

Question: Write a food chain showing four trophic levels.
Answer: Grass → Grasshopper → Frog → Snake (or Grass → Deer → Tiger → Vulture).

Question: What is the 10% law of energy transfer?
Answer: According to the 10% law of energy transfer, only 10% of the energy available at a trophic level is transferred to the next trophic level.

Question: Name two biodegradable substances.
Answer: Fruit peels and paper .

Question: What are trophic levels?
Answer: The various steps in a food chain at which the transfer of energy takes place are called trophic levels.

Question: If 10,000 J energy is available to producers, how much energy will be available to secondary consumers?
Answer: We have, Producers = 10,000 J

Primary consumers

and the secondary consumers

Question: Name the first trophic level in a food chain.
Answer: Producers, such as green plants.

Question: What is a food web?
Answer: A food web is a network of interconnected food chains.

Question: Name two decomposers.
Answer: Bacteria and fungi.

Question: What is biological magnification?
Answer: Biological magnification (or biomagnification) is the phenomenon in which harmful, non-biodegradable chemicals accumulate progressively at each trophic level of a food chain.

Question: Write the chemical formula of ozone.
Answer: The chemical formula of ozone is .

Question: Name one non-biodegradable waste.
Answer: Plastic.

Question: What is the approximate percentage of energy transferred to the next trophic level?
Answer: 10%.

Question: Name one chemical responsible for ozone-layer depletion.
Answer: Chlorofluorocarbons (CFCs).

Short Question and Answer :

Question: Differentiate between oxygen and ozone.

Answer: The difference between oxygen and ozone are :

Oxygen (O₂)	Ozone (O₃)
(i) Oxygen is represented by the chemical formula O₂.	(i) Ozone is represented by the chemical formula O₃.
(ii) Oxygen is essential for respiration in most living organisms.	(ii) Ozone protects the Earth from harmful ultraviolet (UV) radiation coming from the Sun.
(iii) Oxygen is present in the atmosphere.	(iii) Ozone is present in the upper atmosphere and forms a protective layer around the Earth.

Question: Differentiate between biodegradable and non-biodegradable substances.

Answer: The difference between biodegradable and non-biodegradable substances are :

Biodegradable Substances	Non-biodegradable Substances
(a) These substances can be broken down by biological processes.	(a) These substances cannot be broken down easily by biological processes.
(b) They are broken down into simpler substances by microorganisms.	(b) They may remain in the environment for a long time and accumulate.
Examples: Vegetable peels, paper and leaves.	Examples: Plastic, glass and pesticides.

Question: What is the role of producers in an ecosystem?
Answer: Producers are organisms that prepare their own food by photosynthesis using solar energy. They convert solar energy into chemical energy and form the first trophic level of a food chain. They provide food and energy to all other organisms in an ecosystem.

Question: Why are food chains generally limited to three or four consumer levels?
Answer: The flow of energy in a food chain is unidirectional. The amount of energy available decreases at successive trophic levels, as only 10% of the energy is transferred from one trophic level to the next. Thus, very little energy remains available at higher trophic levels, limiting the number of consumer levels in a food chain.

Question: What is the function of the ozone layer?
Answer: The ozone layer in the higher levels of the atmosphere shields the surface of the Earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms. For example: Ultraviolet (UV) radiation is known to cause skin cancer in human beings.

Question: Mention two harmful effects of non-biodegradable waste.
Answer: Two harmful effects of non-biodegradable waste are:

(a) They cause environmental pollution as they cannot be broken down easily by biological processes.

(b) They may enter the food chain and undergo biological magnification, causing harmful effects on living organisms.

Question: How do pesticides enter the food chain?

Answer: Pesticides used in agriculture to protect crops from pests enter the soil and water bodies. From the soil, they are absorbed by plants and enter the food chain. These chemicals are non-biodegradable and get accumulated at successive trophic levels, resulting in biological magnification.

Question: Explain in brief how ozone layer is getting depleted. [2M 2019]

Answer: The ozone layer is getting depleted due to the use of chemicals called chlorofluorocarbons (CFCs), which are used in refrigerators and fire extinguishers. These chemicals react with ozone and cause its depletion. As a result, the ozone layer becomes thinner, allowing harmful ultraviolet (UV) radiations from the Sun to reach the Earth.

Question: Give any two ways in which non-biodegradable substances would affect the environment . [2019 2M]

Answer: Non-biodegradable substances affect the environment in the following two ways:

(i) They cause pollution of the environment, as they cannot be broken down by biological processes.

(ii) They get accumulated at each trophic level in a food chain, causing an increase in their concentration in the bodies of organisms. This phenomenon is called biological magnification.

Question: Differentiate between biotic and abiotic components of an ecosystem with examples.

Answer: The difference between biotic and abiotic components of an ecosystem are :

Biotic Components	Abiotic Components
(i) These are the living components of an ecosystem.	(i) These are the non-living components of an ecosystem.
(ii) They include plants, animals and microorganisms.	(ii) They include air, water, soil, sunlight and temperature.
(iii) They depend on abiotic components for their survival.	(iii) They provide the necessary conditions for the survival of living organisms.

Question: Why can the use of non-biodegradable pesticides cause serious environmental problems?

Answer: Non-biodegradable pesticides cause serious environmental problems because they cannot be broken down by biological processes and enter the food chain. These chemicals accumulate progressively at each trophic level, a process called biological magnification. As a result, their concentration becomes maximum in human beings, causing harmful effects on health.

Question: Explain the difference between a food chain and a food web.
Answer: The difference between a food chain and a food web are:

Food Chain	Food Web
(i) A food chain is a sequence of organisms in which one organism is eaten by the next organism.	(i) A food web consists of a network of interconnected food chains.
(ii) It represents a single pathway of energy flow.	(ii) It represents multiple pathways of energy flow.
(iii) Each organism generally has one pathway shown for obtaining food.	(iii) An organism may have different food sources and predators.
For example: Grass → Deer → Tiger.	For example: Grass may be eaten by deer, rabbits and grasshoppers, which are connected to different predators.

Question: Why is damage to the ozone layer a cause for concern?
Answer: The ozone layer protects living organisms by absorbing much of the Sun's harmful UV radiation. Its depletion allows more UV radiation to reach Earth's surface, increasing the risk of skin cancer, eye damage and harmful effects on other organisms.

Question: Explain how ozone is formed in the upper atmosphere.
Answer: Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen () molecules. The higher-energy UV radiations split apart some molecular oxygen () into free oxygen (O) atoms. These oxygen atoms then combine with molecular oxygen to form ozone .

(Ozone)

Question: What will happen if we kill all the organisms in one trophic level ?

Answer: If all the organisms in one trophic level are killed, the transfer of energy to the next trophic level will be affected. The organisms at the next trophic level may not get sufficient food and their population may decrease. The organisms at the lower trophic level may increase in number, disturbing the balance of the ecosystem.

Question: How can you help in reducing the problem of waste disposal? [2020 2M]

Answer: We can help in reducing the problem of waste disposal by following the three Rs: Reduce, Reuse and Recycle. We should reduce the use of non-biodegradable materials, reuse items whenever possible and recycle materials such as paper, glass and plastic. We should also segregate biodegradable and non-biodegradable wastes and dispose of them properly.

Question: Why are some substances biodegradable and some non-biodegradable?

Answer: Some substances are biodegradable because they can be broken down into simpler substances by the action of microorganisms, whereas some substances are non-biodegradable because they cannot be broken down into simpler substances by microorganisms.

Question: State two problems caused by non-biodegradable wastes what we generate . [2020 2M]

Answer: The two main problems caused by non-biodegradable waste we generate are:

(i) Non-biodegradable wastes cause environmental pollution as they cannot be broken down by biological processes.

(ii) These wastes enter the food chain and undergo biological magnification, resulting in the accumulation of harmful chemicals in organisms at higher trophic levels.

Long Question and Answer :

Question: What is ozone layer and how it is getting depleted ? [3M 2015]

Answer: The ozone layer is a layer of ozone gas present in the stratosphere. It shields the surface of the Earth from harmful ultraviolet (UV) radiation from the Sun.

The ozone layer is getting depleted due to the use of chemicals called chlorofluorocarbons (CFCs), which are used in refrigerators and air conditioners. These chemicals cause the breakdown of ozone molecules, resulting in the depletion of the ozone layer.

Question: What is ecosystem and what are its components ? [3M 2015]

Answer: An ecosystem is a system consisting of all the interacting organisms in an area together with the non-living constituents of the environment.

The components of an ecosystem are:

(a) Biotic components: All living organisms, such as plants, animals and microorganisms.

(b) Abiotic components: Non-living components, such as air, water, soil, sunlight and temperature.

Question: Explain what are the components of an ecosystem ?Mention one non-biodegradable waste we generate . [3M 2017]

Answer: An ecosystem consists of biotic and abiotic components. The biotic components include all living organisms, such as plants, animals and microorganisms. The abiotic components include non-living things, such as air, water, soil, sunlight and temperature. These components interact with one another to maintain the balance of the ecosystem.

One non-biodegradable waste we generate: Plastic or polythene bags .

Question: What is trophic level ? Describe the trophic levels of a food chain . [3M 2017]

Answer: The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels .

The trophic levels of a food chain are:

(i) First trophic level: Producers (green plants).

(ii) Second trophic level: Primary consumers (herbivores).

(iii) Third trophic level: Secondary consumers (small carnivores).

(iv) Fourth trophic level: Tertiary consumers (large carnivores).

For example: Grass → Grasshopper → Frog → Snake.

Question: What is a food chain? Explain the trophic levels using an example.

Answer: A food chain is a sequence of organisms in which one organism is eaten by another, transferring food and energy.

Example: Grass → Grasshopper → Frog → Snake.

(i) First trophic level: Grass (producer).

(ii) Second trophic level: Grasshopper (primary consumer).

(iii) Third trophic level: Frog (secondary consumer).

(iv) Fourth trophic level: Snake (tertiary consumer).

Energy decreases at each successive trophic level because only a small fraction is transferred to the next level.

Question: What is biological magnification? Explain why humans may be affected by it.

Answer: Biological magnification is the progressive accumulation of certain non-biodegradable chemicals at successive trophic levels. Pesticides used in agriculture may enter soil and water. Plants and aquatic organisms absorb these chemicals, which are then transferred to herbivores and carnivores through feeding.

Since the chemicals are not readily broken down, their concentration may increase at higher trophic levels. Humans consuming contaminated food may therefore receive these chemicals. The concentration is generally greatest in organisms at the top of the food chain.

Question: What is the role of decomposers in the ecosystem ? Draw a diagram showing flow of energy in an ecosystem . [3M 2018]

Answer: The role of decomposers in the ecosystem is to break down the dead remains and waste products of organisms. Microorganisms, comprising bacteria and fungi, act as decomposers. They break down complex organic substances into simpler inorganic substances that go into the soil and are used up again by plants.

Question: What are the environmental problems caused by improper waste disposal? Suggest suitable measures.

Answer: Improper waste disposal can pollute soil and water, harm animals and allow non-biodegradable materials to accumulate. Untreated biodegradable waste can also pollute water bodies. Some harmful substances may enter food chains.

Suitable measures are: (i) Segregating biodegradable and non-biodegradable waste.

(ii) Reducing disposable products, especially ordinary plastics.

(iii) Reusing and recycling suitable materials.

(iv) Composting suitable biodegradable waste.

(v) Ensuring proper treatment and disposal of waste.

Question: What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem?

Answer: Biological magnification (or biomagnification) is the phenomenon in which harmful, non-biodegradable chemicals accumulate progressively at each trophic level of a food chain.

Yes, the levels of biological magnification are different at different trophic levels. The concentration of harmful chemicals increases at each successive trophic level and becomes maximum in organisms at the highest trophic level.

Question: Explain why the removal of any trophic level can disturb the ecosystem.

Answer: Each trophic level is connected to other levels through food chains and food webs. Producers provide food to primary consumers, which serve as food for higher consumers. If a trophic level is removed, the organisms above it may lose their food source, while the organisms below it may increase in number.

These changes can affect several interconnected food chains and disturb the balance of the ecosystem. Therefore, no trophic level can be removed without potentially causing ecological damage.

Question: Explain the flow of energy in an ecosystem with a suitable example.

Answer: Energy enters most ecosystems through sunlight. Green plants capture solar energy through photosynthesis and convert it into chemical energy. Herbivores obtain energy by eating plants, while carnivores obtain energy by eating other animals.

Example: Grass → Grasshopper → Frog → Snake.

Producers form the first trophic level, herbivores the second, and successive consumers occupy higher levels. Only about 10% of energy is transferred to the next trophic level. The remaining energy is used in life processes or dissipated as heat. Hence, energy flow is unidirectional and available energy decreases at higher trophic levels.

Question: Describe how the ozone layer is depleted and explain its effects.

Answer: Ozone in the upper atmosphere absorbs much of the harmful ultraviolet radiation from the Sun. The depletion of ozone has been linked to synthetic chemicals such as chlorofluorocarbons (CFCs), which have been used in refrigeration and other applications.

The depletion of the ozone layer allows more harmful UV radiation to reach Earth. This can increase the risk of skin cancer and eye damage and can harm other organisms, including phytoplankton. The release of ozone-depleting substances must be controlled to protect the ozone layer.

Question: What is ozone? How is it formed in the atmosphere? How does it affect the ecosystem?
Answer: Ozone is a molecule formed by three oxygen atoms.

Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen () molecules. The higher-energy UV radiations split apart some molecular oxygen () into free oxygen (O) atoms. These oxygen atoms then combine with molecular oxygen to form ozone .

(Ozone)

Ozone is a deadly poison at the ground level. However, at the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the Earth from ultraviolet (UV) radiation from the Sun. This radiation is highly damaging to organisms, for example, it is known to cause skin cancer in human beings.

Question: Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

Answer: Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. If all the producers are removed, there would be no food for the herbivores, and the food chain would collapse. If the herbivores are removed, the population of producers may increase, while the carnivores would not get enough food and their population may decrease. Similarly, removing the carnivores may lead to an increase in the population of herbivores, which may damage the ecosystem.

No, organisms of any trophic level cannot be removed without causing damage to the ecosystem, as all trophic levels are interconnected and depend on one another for the flow of energy.

Posted 2 weeks ago

15. Our Environment SEBA/ASSEB Class 10 Science– Important Questions and Answers | Assam HSLC

SEBA/ASSEB Class 10 Science Chapter 15: Our Environment Important Questions and Answers | HSLC Assam

Chapter 15: Our Environment

Multiple Choose Question and Answer :

Assertion and Reasoning :

Very Short Question and Answer :

Short Question and Answer :

Question: What is the role of decomposers in the ecosystem ? Draw a diagram showing flow of energy in an ecosystem . [3M 2018]

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