Important Questions Class 10 Science Chapter 15

Important Questions Class 10 Science Chapter 15- Our Environment

Class 10 Science Chapter 15, “Our Environment”, provides information about air, its components, wind, air found in soil and its value, oxygen and how vital it is for living things, the atmosphere and how vital plants are to our survival. The students will study the interactions between various elements of the environment and the effects of people and their actions on the environment. Students will comprehend the many pollutants brought to the environment and how these wastes affect the ecosystem negatively.

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Science is a practical subject and it requires that students regularly engage in problem-solving activities to enhance their understanding of each concept. To aid students with a single repository of questions our team has created a question bank of Important Questions Class 10 Science Chapter 15. We have carefully chosen questions from various sources such as NCERT textbook, exemplars, and past years’ question papers. 

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Extramarks have a wealth of other study materials apart from our Science Class 10 Chapter 15 Important Questions.  To speed up their learning and improve their academic performance, students can refer to a variety of study materials from Class 1 to Class 12.

CBSE Class 10 Science Important Questions 2022-23

CBSE Class 10 Science Important Questions are also available for the following chapters:

CBSE Class 10 Science Important Questions
Sr No. Chapters
1 Chemical Reactions and Equations
2 Acids, Bases and Salts
3 Metals and Non-metals
4 Carbon and Its Compounds
5 Periodic Classification of Elements
6 Life Processes
7 Control and Coordination
8 How do Organisms Reproduce?
9 Heredity and Evolution
10 Light Reflection and Refraction
11 Human Eye and Colourful World
12 Electricity
13 Magnetic Effects of Electric Current
14 Sources of Energy
15 Our Environment
16 Management of Natural Resources

Important Questions Class 10 Science Chapter 15 – With Solutions

Regularly practising questions has proven helpful for a lot of students. Extramarks strongly recommends students to refer to our question bank of Important Questions Class 10 Science Chapter 15. Since the questions cover a full chapter and the solutions come with detailed step-by-step instructions, students are able to revise the chapter while solving these questions. 

Below are a few questions and their answers from our question set of Important Questions Class 10 Science Chapter 15.

Question 1. Which one of the following is an artificial ecosystem?

(a) Pond


(c) Lake

(d) Crop field

Answer 1: (d) Crop field

Explanation: Crop field is an artificial ecosystem.

Question 2. An ecosystem includes

(a) non-living objects

(b) all living organisms

(c) both living organisms and non-living objects

(d) sometimes living organisms and sometimes non-living objects

Answer 2: (c) both living organisms and non-living objects

Explanation: A network of living and nonliving organisms and their interactions is referred to as an ecosystem.

Question 3. In the given food chain, suppose the amount of energy at the fourth trophic level is 5 kJ. What will be the energy available at the producer level?

Grass → Grasshopper → Frog → Snake → Hawk

(a) 5 k J

(b) 50 k J

(c) 500 k J

(d) 5000 k J

Answer 3: (d) 5000 k J


The energy availability of a given trophic level is 10 times that of the following trophic level. Therefore, 50 kJ of energy is present at the third trophic level. The energy content of the first level trophic level (Producer) is 5000 KJ, while the second level trophic level is 500 KJ.

Question 4. Accumulation of non-biodegradable pesticides in the food chain in an increasing amount at each higher trophic level is known as

(a) eutrophication

(b) pollution

(c) biomagnification

(d) accumulation

Answer 4: (c) biomagnification


When toxins that remain in the environment are indirectly absorbed by living organisms through food, this process is known as biomagnification. When a higher-order organism consumes a lower-order organism that contains such compounds, the chemicals potentially accumulate in the higher-order organism.

Question 5. Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called

(a) decomposers

(b) producers

(c) herbivores

(d) carnivores

Answer 5: (b) producers


Food is created by producers using sun energy from carbon dioxide and water. Producers include some microorganisms and plants.

Question 6. 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 6: (c) chemical energy


Food serves as a vehicle for the passage of energy from one trophic level to the next. A chemical source of energy is food.

Question 7. Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the

(a) food web

(b) ecological pyramid

(c) ecosystem

(d) food chain

Answer 7: (a) food web


A food chain is an interaction between different group of organisms through which food and energy move through an ecosystem. All of the local wildlife and the non-living elements of its habitat make up an ecosystem. Ecological pyramids visually represent the trophic organisation and energy flow in an ecosystem. The food web comprises higher trophic level species that consume various lower trophic level organisms.

Question 8. The flow of energy in an ecosystem is always

(a) unidirectional

(b) bidirectional

(c) multidirectional

(d) no specific direction

Answer 8: (a) unidirectional


Energy flows from prey to predator; it cannot travel in the opposite direction. As a result, energy only moves in one direction.

Question 9. Excessive exposure of humans to U V-rays results in

(i) damage to the immune system

(ii) damage to lungs

(iii) skin cancer

(iv) peptic ulcers

(a) (i) and (ii)

(b) (ii) and (iv)

(c) (i) and (iii)

(d) (iii) and (iv)

Answer 9: (c) (i) and (iii)


Our body’s upper surface is affected by UV radiation. As the skin is the first layer of the immune barrier, UV rays can cause skin cancer, and their effects on the skin also impact our immune systems.

Question 10. Which of the following limits the number of trophic levels in a food chain?

(a) Decrease in energy at higher trophic levels

(b) Sufficient food supply

(c) Polluted air

(d) Water

Answer 10: (a) Decrease in energy at higher trophic levels


The energy availability of a given trophic level is 10 times that of the following trophic level. When we get to the fourth trophic level, we have access to a tiny amount of producing energy.

Question 11. Which of the statement is incorrect?

(a) All green plants and blue-green algae are producers

(b) Green plants get their food from organic compounds

(c) Producers prepare their own food from inorganic compounds

(d) Plants convert solar energy into chemical energy

Answer 11: (b) Green plants get their food from organic compounds


Solar energy is used to make food from green plants. Inorganic materials CO2 and water are utilised to manufacture carbohydrates using solar energy.

Question 12. The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about

(a) 1 %

(b) 5 %

(c) 8 %

(d) 10 %

Answer 12:  (a) 1 %


Photosynthesis occurs when green plants employ 1% of the radiation that is absorbed by their leaves.

Question 13. In the given Figure 15.1, the various trophic levels are shown in a pyramid. At which trophic level is maximum energy available?

(a) T4

(b) T2

(c) T1

(d) T3

Image source: NCERT textbook

Answer 13: (c) T1

Explanation: The energy supply for producers is at its highest. At the next level, an organism uses only 10% of the energy. Therefore, T1>T2>T3>T4.

Question 14. What will happen if deer is missing in the food chain given below? Grass → Deer → Tiger

(a) The population of tigers increases

(b) The population of grass decreases

(c) Tiger will start eating grass

(d) The population of tigers decreases, and the population of grass increases

Answer 14: (d) The population of tigers decreases, and the population of grass increases.


The population of grass will rise if there are no predators. Lack of food will cause the tiger population to decline.

Question 15. If a grasshopper is eaten by a frog, then the energy transfer will be from

(a) producer to decomposer

(b) producer to primary consumer

(c) primary consumer to secondary consumer

(d) secondary consumer to primary consumer

Answer 15: (c) primary consumer to secondary consumer


A key consumer is a grasshopper since it eats grass. Suppose a frog is consuming a grasshopper. The secondary consumer will be a frog.

Question 16. Disposable plastic plates should not be used because

(a) they are made of materials with lightweight

(b) they are made of toxic materials

(c) they are made of biodegradable materials

(d) they are made of non-biodegradable materials

Answer 16: (d) they are made of non-biodegradable materials

Explanation: Since plastics cannot biodegrade, they begin to accumulate in the environment and endanger living things.

Question 17. What are the trophic levels? Give an example of a food chain and state the different trophic levels in it.

Answer 17:

The several levels in the food chain where food or energy is transferred are referred to as trophic levels.


Grass → Goat → Man

In the food chain,

  • The first trophic level in the food chain is grass.
  • The goat represents the second trophic level.
  • The third trophic level is the man.

Question 18. Why is improper disposal of waste a curse to the environment?

Answer 18:

Wastes threaten all living things by polluting our environment, including the air, land, and water.

Question 19. What is the role of decomposers in the ecosystem?

Answer 19:

The function of a decomposer in the ecosystem

 is as follows:

  • They purify the environment by rotting the corpses of animals and plants.
  • They aid in nutrient recycling.
  • By rotting the dead, they provide room in the environment for new life.
  • They assist in recycling different components back into the water, soil, and air for use by producers like crop plants.

Question 20. Write the food chain of a pond ecosystem.

Answer 20:


Small aquatic animals larvae, shrimps, Insects



Question 21. Why are some substances biodegradable and some are non-biodegradable?

Answer 21:

As microbes like bacteria and decomposers like saprophytes have distinct roles to play, certain chemicals are biodegradable, and some are not at all. They may only break down natural materials like paper, wood, etc.; synthetic materials like plastics cannot be broken down. On the basis of this, some compounds are biodegradable, and others are not.

Question 22. What are the advantages of cloth bags over plastic bags during shopping?

Answer 22:

The following are some benefits of using cloth bags instead of plastic ones when shopping.

  • They can support heavier loads than plastic bags.
  • They decompose naturally.
  • They are reusable.
  • They do cause any harm to the environment.

Question 23. Why are crop fields known as artificial ecosystems?

Answer 23:

Crop fields tend to contain altered biotic and abiotic components and thus they are referred to as artificial ecosystems.

Question 24. Give any two ways in which non-biodegradable substances would affect the environment.

Answer 24:

The following are some effects that non-biodegradable materials might have on the environment:

  • They pollute the air, the soil and the water.
  • They might make the food chain bio-magnified, which would put humans at the bottom.

Question 25. Differentiate between biodegradable and non-biodegradable substances. Cite examples.

Answer 25:

Biodegradable substances are those that can disintegrate through a biological process. Examples: fruits and vegetable wastes, wood, paper etc.

Non-biodegradable substances are those that a biological process cannot break down. Examples: glass, plastic, metals, and toxic chemicals.

Question 26. What is ozone, and how does it affect the ecosystem?

Answer 26:

Three oxygen atoms combine to form the molecule known as ozone, which is an isotope of oxygen. The primary purpose of the ozone layer is to shield the surface of the planet from the sun’s harmful UV rays. These rays can cause skin cancer and are dangerous to living things.

Question 27. What help can we offer to reduce the problem of waste disposal? Give any two methods.

Answer 27:

The following are some strategies to lessen the issue of waste disposal:

  • 3 R’s: One can lessen the issue of waste disposal by adhering to the three Rs. Reduce, reuse and recycle are the three R’s. Air pollution can be decreased by people using public transportation more frequently and driving less. Plastic recycling and reuse are other options to reduce trash disposal.
  • Getting compost ready: You can compost all biodegradable garbage, including kitchen waste.

Question 28. Explain the role of decomposers in the environment.

Answer 28:

Decomposers aid in the recycling of nutrients by breaking down dead and decaying living stuff. As the dead matter is removed, the environment will be cleaned.

Question 29. What will happen if we kill all the organisms at one trophic level?

Answer 29:

If we eradicate every organism at one trophic level, the food chain will collapse, and the ecosystem will become unbalanced. Animals in the upper trophic levels will therefore perish, greatly accelerating the growth of those in the lower trophic level. All these will have an impact on the ecosystem’s general balance.

Question 30. People do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

Answer 30:

Compared to a pond or lake, a natural and full ecosystem, an aquarium is an artificial ecology that is insufficient. Hence it needs to be cleaned.

Question 31. Will the impact of removing all the organisms in the 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 31:

Yes, the effects of eliminating every organism at a trophic level will vary depending on the trophic level. For instance, removing all the producers could result in the principal consumers dying off or migrating, upsetting the trophic levels. This applies to all levels. As a result, the food chain disruption caused by the removal of creatures at any level would disrupt the ecosystem as a whole. The lower-level creatures are very necessary for the higher-level animals to survive.

Question 32. Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify.

Answer 32:

The energy flow in an ecosystem can be indicated as follows:

The green plants in an ecosystem capture around 1% of the energy of sunlight that is trapped by the leaves and converts it into food energy.

When primary consumers eat green plants, a great amount of energy is lost into the environment as heat; some amount goes into digestion and doing other works, and the rest goes for growth and reproduction. Around 10% of the food consumed is stored into the body for the next level of consumers below.

Therefore, 10% is mostly  taken as the average value for the amount of organic matter present at each step and reaching the subsequent level of consumers.

Since this little energy is available for the next level of consumers, food chains thus generally consist of only three or four steps. The loss of such amount of energy at each step is so great that little usable energy remains after four trophic levels for others.

There are generally more number of individuals at the lower trophic levels of an ecosystem; the highest number is of the producers, green plants.

The extent and complexity of food chains vary greatly in any ecosystem. Each organism in general is eaten by two or more other types of organisms, which in turn are consumed by several other organisms. So there is no straight line food chain, the relationship can be shown as a series of branching lines called a food web.

Image source: NCERT textbook

The energy flow is unidirectional because the energy captured by the autotrophs does not revert to the solar input, and the energy that passes to the herbivores does not return to the autotrophs. As it passes through the various trophic levels, it is no longer available at the former level. Secondly, the energy available at each of the trophic levels gets reduced progressively due to the loss of energy at each level.

Question 33. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Answer 33:

The gradual increase in the concentration of non-biodegradable pollutants in the food chain is known as biological magnification. All of the remaining trophic levels of ecosystems are impacted by the rise in magnification at the subsequent levels, and the concentration may differ from the first level as a result.

Question 34. What are decomposers? What will happen in their absence from the ecosystem?

Answer 34:

Bacteria and fungi, which are microorganisms, decompose the corpses and waste products of other creatures. These bacteria are the decomposers because they convert complex organic materials into straightforward inorganic ones that are then assimilated by plants once more in the soil.

Suppose there are no decomposers in the ecosystem. In that case, there won’t be any recycling of materials in the biosphere, which would result in a buildup of dead plants and animals in the environment. The environment would also finally be bereft of all the resources required to support and preserve life.

Question 35. What problems are caused by the non-biodegradable wastes that we generate?

Answer 35:

Following are the problems caused by non-biodegradable wastes:

  • Microorganisms cannot decompose these substances.
  • As the quantity keeps on increasing, dumping becomes a major problem.
  • Non-biodegradable wastes like heavy metals often enter the food chain mostly in the upper trophic levels.
  • They may percolate to the groundwater, which causes soil infertility and disturbance in the pH of the soil.

Question 36. If all the waste we produce/generates is biodegradable, will this have no impact on the environment?

Answer 36:

Microorganisms break down biodegradable waste into simpler materials that companies can use as raw materials. The consequences of a surplus of biodegradable wastes,

However, it is as follows:

  • The biodegradable wastes emit a foul stench that can be dangerous to people when inhaled because of how slowly they decompose.
  • The dumping sites may serve as a breeding ground for dangerous organisms that can harm plants, animals and humans.
  • Depletion of oxygen could occur as aquatic organism populations grow.

Question 37. Give differences between a food chain and a food web.

Answer 37:

Food Chain Food web
The food chain is the distinct, singular path by which energy moves through various species of organisms in an environment. The term “food web” refers to the complex or intricate pathway via which energy flows in an ecosystem and is made up of several food chains at various trophic levels.
The food chain is an imaginary situation The Food web is a more real situation.
Higher trophic level organisms eat only one type of lower trophic level organism as food. Higher trophic level species can consume lower trophic level organisms in another food chain.

Question 38. Why is ozone layer depletion a cause for concern? What are the steps being taken to reduce this damage?

Answer 38:

The ozone layer shields the planet. It blocks harmful UV rays from entering the Earth since they could lead to skin cancer. But air pollutants like chlorofluorocarbons are the main culprit behind the ozone layer deterioration (CFCs). Overexposure to UV radiation harms plants because it prevents photosynthesis and kills plankton and destroyers. These are the reasons why the ozone layer is deteriorating.

The steps being taken to reduce this damage are as follows:

  • Avoid using and buying aerosol sprays that contain chlorofluorocarbons (CFCs).
  •  Avoid using fire extinguishers that contain halogenated hydrocarbons, which are extremely harmful to the ozone layer.
  • Refrain from purchasing insulation produced with CFCs.

Question 39. Suggest suitable mechanisms for waste management in the fertiliser industries.

Answer 39:

The following actions must be done to manage waste in the fertiliser industry.

  • Combustion equipment that may be oxidised is used to reduce gaseous emissions. The technique involves heating the pollutants to a high temperature. Air pollutants, such as certain gases, vapours and flammable compounds are controlled by adsorption equipment. A significant quantity of solid surface area is necessary for the surface phenomenon known as adsorption. The removal of offensive and odorous compounds is accomplished with this procedure.

There are three ways to manage effluents.

  • Control can occur inside the factory at the site of generation; 
  • Wastewater can be pre-treated before being discharged to municipal treatment 


  • At the factory, wastewater can be treated entirely before being recycled or discharged directly into receiving water.

Question 40. What are the by-products of fertiliser industries? How do they affect the environment?

Answer 40:

Nitrogen and sulphur oxides are the most frequent by-products of the fertiliser industries. They enter the atmosphere and disseminate to all neighbouring locations. In addition to being dangerous for living things, gases have a corrosive effect on many different things. Acid rain is another effect they have. Forests, crops and aquatic biota are all severely harmed by acid rain.

The two most frequent by-products of the fertiliser industry are nitrous oxides and sulphur oxides. These oxides disperse over the surrounding areas after entering the atmosphere. In addition to being hazardous to living things, sulphur and nitrogen oxides have a corrosive effect on a variety of materials. Acid rain caused by sulphate oxides affects aquatic biota, agriculture and forests.

Question 41. Explain some harmful effects of agricultural practices that have an effect on the environment.

Answer 41:

The following are negative environmental implications of agricultural operations.

Soil degradation Significant cropping reduces soil fertility. Additionally, it can eventually cause desertification by causing soil erosion.

Pollution: The use of artificial fertilisers and pesticides results in pollution of the soil, water and air.

Water shortage: Excessive groundwater use for agriculture causes the water table to drop. This causes a severe water shortage in many locations.

Biomagnification: Chemical pesticides that are non-biodegradable accumulate in organisms at each trophic level

 in ever-increasing concentrations.

Deforestation: Wildlife habitat has been lost as a result of 

careless tree cutting for agricultural purposes. As a result, the natural ecology is also harmed.

Question 42. Give one method which could be applied to reduce our intake of pesticides through food to some extent.

Answer 42:

Our consumption of pesticides through food may be somewhat reduced by utilising biological ways for managing insects in crop fields and by washing fruits and vegetables before eating.

Question 43. What is an ecosystem?

Answer 43:

A biosphere’s structural and functional unit is known as an ecosystem. It is made up of living things and those around them that aren’t alive. These things interact with one another through food chains and biogeochemical cycles to provide energy flow, biotic diversity, and material cycling to create a stable, self-supporting system.

Question 44. Why is a lake considered to be a natural ecosystem?

Answer 44:

The lake is an ecosystem where living things develop, reproduce, interact with abiotic elements and engage in other natural processes unaided by humans. As a result, the lake is referred to as a natural ecosystem.

Question 45. In the following food chain, plants provide 500 J of energy to rats. How much energy will be available to hawks from snakes?

Plants → Rats → Snakes → Hawks

Answer 45:

Only 10% of the energy in an ecosystem, or 10% law, is transmitted from one trophic level to the next; the remaining 90% is lost to the environment. As a result, if plants (which are producers at the first trophic level) send 500 J of energy to rats at the second trophic level, rats will then transfer 50 J of energy to snakes at the third trophic level, who will then only pass 5 J of energy to hawks at the fourth or last trophic level.

Plants →           Rats →                 Snakes →        Hawks

5000J 500J 50J 5J 

Question 46. In the given food chain, 100 J of energy is available to the lion alone. How much energy was available to the producers?

Plants → Deer → Lion 

Answer 46:

The next trophic level receives only 10% of the energy according to the 10% law of energy flow in an ecosystem. As a result, if a lion has access to 100 J of energy in the given food chain, plants or producers have 10,000 J at their disposal.

Plants → Deer → Lion 

10,000J 1000J 100J

Question 47. List two biotic components of a biosphere. 

Answer 47:

Two biotic components of a biosphere are:

(i) Producers – Include species like all-green plants and blue-green algae (cyanobacteria) that can produce their own food from basic inorganic substances.

(ii) Consumers – Include species that cannot synthesise their food and must instead use the resources and energy that the producers have stored or eat other organisms, such as all animals.

Question 48. Why are green plants called producers?

Answer 48:

As the plants make their own food using CO2 and water in the presence of sunlight and chlorophyll, they are known as producers.

Question 49. In a food chain of frog, insect grass and snake, assign a trophic level to the frog.

Answer 49:

In the given food chain, the frog belongs to the third trophic level, as shown here:

Grass  Insect Frog Snake

T1 T2 T3 T4

Question 50. Why do producers always occupy the first trophic level in every food chain?

Answer 50:

The green plants known as producers are autotrophs or plants that can produce food using CO2 and water in the presence of sunlight. They provide all non-producers or consumers with food, either directly or indirectly. As a result, producers are found at the top of the food chain.

Question 51. We often use the word environment. What does it mean?

Answer 51:

The environment is the physical or biological environment in which an organism exists. An organism’s immediate surroundings, which comprise biotic and abiotic elements, literally make up its habitat.

Question 52. List two examples of the natural ecosystem.

Answer 52:

The two examples of the natural ecosystem are:

  • Forest ecosystem
  • River ecosystem

Question 53. What is meant by the term ‘biomass’?

Answer 53:

The entire amount of organic or living materials in an environment is known as its biomass.

Question 54. Bacteria and fungi are called decomposers. Why?

Answer 54:

Since these microbes convert the complex organic matter found in dead plants and animals into simpler components, bacteria and fungi are referred to as decomposers.

Question 55. If in a food chain, 10,000 joules of energy are available to the producer, how much energy will then be available to the secondary consumer to transfer it to the tertiary consumer?

Answer 55:

According to the 10% law, 10% of the energy produced by the producer will be made available to primary consumers, 10% to secondary consumers, and so on.

Producer Primary consumer Secondary Consumer

10,000 J 1,000 J 100 J

As a result, the secondary consumer will have 100 J of energy available to transfer to the tertiary consumer.

Question 56. Considering the following food chain that occurs in a forest:

Grass → Deer → Lion

If 10000 J of solar energy is available to grasses, how much energy would be available to the deers to transfer it to the lions?

Answer 56:

The deer has 1000 J of energy ready to transfer to the lion. The following is a picture of this:

Grass →  Deer → Lion

10,000 J 1000 J 100 J

Question 57. What is meant by biological magnification?

Answer 57:

The process of accumulating non-biodegradable substances (pesticides, etc.) into the bodies of creatures along the food chain, which continue to increase in concentration at each trophic level, is known as biological magnification or biomagnification.

Question 58. Give example to illustrate that indiscriminate use of pesticides may result in the degradation of the environment.

Answer 58:

Chemicals known as pesticides are employed to eradicate plant and animal pests. They are poisonous and non-biodegradable. For instance, overuse of DDT reduces the number of fish-eating bird species. Such birds collect DDT as they moved up the food chain. The development of the eggshell gets hampered. Due to the shell being thin and the weight of the bird during incubation, it shatters. Consequently, their population shrinks.

Question 59. List two reasons to show that the existence of decomposers is essential in an ecosystem.

Answer 59:

The presence of decomposers in an ecosystem is crucial because:

  1. i) Without them, dead plants and animals would remain on the ground, and their constituent parts, such as soil, air, and water, would never be returned to their natural habitats. In this scenario, the organic waste would continue to build up, and the cycle of life and death would be disturbed.

(ii) Decomposers are an essential component of the ecosystem because they renew or supply the nutrients that make the soil fruitful.

Question 60. State with reasons any two possible consequences of the elimination of decomposers from the Earth. 

Answer 60:

The removal of decomposers would have the following effects: 

  1. i) Producers would not have access to raw materials for food production since there would be no recycling of nutrients. The food chains will suffer as a result.

(ii) In the absence of decomposition, dead plants and animals will continue accumulating, polluting the ecosystem.

Question 61.

What does a trophic level signify in a food chain? State the significant position of autotrophs and herbivores in a food chain. 

Answer 61:

Each of the various hierarchical levels of a food chain operating in an ecosystem is represented by a trophic level. These levels are comprised of organisms that share the same role in the food chain and the same nutritional link to the main energy sources.

The first trophic level is represented by the location of producers (or autotrophs) in a food chain. They clean up solar energy and put it at the disposal of customers. The second trophic level in a particular food chain comprises the primary consumers, often known as herbivores, who eat only plants.

Question 62.

(a) From the given group of organisms, create a food chain most advantageous for humans with regard to energy.

Hawk, Snake, Rat, Goat, Cereal plant, Human being

(b) State the possible disadvantages if any cereal plant is growing in soil rich in pesticides.

(c) draw a food web using the organisms mentioned above.

Answer 62:

(a) The food chain with the greatest energy benefits for people is:

Cereal plant → Human being

(b) When the cereal plant is growing in pesticides-rich soil, the pesticides are absorbed by the developing plant together with water and minerals. When animals consume these cereal plants, the animals consume these harmful chemical pesticides. Biological amplification refers to the rise in the concentration of dangerous pesticides in the bodies of living things at each trophic level of a food chain. Pesticides can kill non-target species as well. The microbial community of the soil can alter due to widespread pesticide use in agriculture.

Image Source:

Question 63.

(a) What is an ecosystem?

(b) name two natural ecosystems.

(c) We do not need clean ponds or lakes, but an aquarium needs to be cleaned regularly. Why it is so?

Answer 63:

(a) The term “ecosystem” refers to a biological system’s structural and functional unit made up of both living things and their non-living surroundings.

(b) Pond ecosystems and grassland ecosystems are two examples of natural ecosystems.

(c) Ponds and lakes are self-sufficient natural ecosystems. Thus they don’t require routine maintenance. However, aquariums are artificial ecosystems and contain mostly living fish rather than real ecosystems, which depend on the presence of other species to maintain balance, so they must be routinely cleaned and maintained. Additionally, since there are no producers or decomposers in an aquarium, fish waste or excretory products, such as ammonia, could transform into hazardous chemicals and build up to lethal amounts, killing the fish. As a result, artificial ecosystems like aquariums require routine cleaning.

Question 64.

What is meant by the trophic level in a food chain? Illustrate a terrestrial food chain with different trophic levels. The energy flow in a food chain is always unidirectional. Why it is so?

Answer 64:

Trophic levels are the many stages that correspond to the organisms in a food chain where the exchange of food and energy occurs.

Four trophic levels in the given terrestrial food chain:

Grass → Rabbit → Wild cat → Tiger

Energy flow is unidirectional from the sun to producers and then to a variety of subsequent consumers, i.e.,

Solar radiations → Producers → Herbivores → Carnivores

It cannot pass in a reverse direction; there is always a decrease in energy flow and content with rising trophic levels. A greater amount of energy is lost at every step in the form of heat and is later used up in various metabolic activities.

Question 65.

Define an ecosystem. Draw a block diagram showing the flow of energy in an ecosystem.

Answer 65:

An ecosystem is structural and functional until the biosphere. It comprises living organisms and their non-living environment that interact by means of food chains and biogeochemical cycles resulting in energy flow, biotic diversity and material cycling to form a stable, self-sustaining system.

Green plants retain about 1% of the solar energy incident on the Earth to carry out the process of photosynthesis. Plants, in performing their metabolic activities, use a part of this trapped energy, and some portion of the energy is released as heat into the atmosphere. The remaining part of the energy is chemical energy stored in the plants as photosynthetic products and by-products. When these green plants are eaten by herbivores, the chemical energy stored in the plants gets transferred to these animals. These animals (herbivores) utilise some of the energy for metabolic activities, and some energy is released as heat while the rest of the energy is stored in their body. This process of energy transfer is repeated up to the top carnivores. In an ecosystem, the transfer of energy follows the 10 percent law, i.e., only 10 percent of the energy is transferred to each trophic level from the lower trophic level. Nearly 90 percent of energy is lost when it moves from one trophic level to the next.

The given block diagram shows a unidirectional flow of energy at different trophic levels in a freshwater ecosystem:

Image Source:

Question 66.

Explain how pesticides make their way into a food chain and subsequently get into our bodies. 

Answer 66:

Pesticides like DDT and other toxic non-biodegradable compounds enter species’ bodies through food chains, where they get concentrated at each trophic level. Biomagnification, also known as biological magnification, is this phenomenon. For instance, in a food chain working in a pond, river, or lake, the water includes negligible toxic pesticides, such as DDT, 0.02 ppb (parts per billion). The concentration of these compounds rises to 5 ppm when phytoplanktons and zooplanktons ingest this water. Fish that consume them build up 240 ppm. 1600 ppm of these compounds were identified in humans and birds that consumed this fish. As a result, the chemical concentrations at each trophic level grow.

Question 67.

“Our food grains such as rice and wheat, the vegetables and fruits and meat are found to contain comparable amounts of pesticide traces.” State the reasons to explain how and why it happens.

Answer 67:

To keep crop plants safe from pests and diseases, pesticides are harmful chemicals sprayed on them. These chemicals combine with the soil and the water. These pesticides are absorbed by the developing plants together with water and other minerals from the soil and water. Poisonous pesticides are ingested by herbivorous animals through the food chain when they eat these plants. Similar to this, pesticides enter the bodies of carnivorous animals when they eat these herbivores. As a result, depending on the trophic level they occupy in a food chain, different amounts of pesticide residues can be found in plant items such as food grains, vegetables, fruits and animal meat.

Question 68.

What is meant by a food chain? 

“The actual number of trophic levels in a food chain is quite limited.” Give a reason to justify this statement.

Answer 68:

A food chain is the arrangement of living organisms in a community in which one organism eats or feeds upon another to transfer food and energy. Trophic levels refer to the numerous points along a food chain when food (or energy) is transferred. In actuality, a trophic level is formed by each link in a food chain that represents an organism.

Since only 10% of the energy is used at each trophic level to maintain the organisms that exist there, and the majority of the remaining energy is lost as heat, the number of trophic levels in a food chain is constrained. Because of this, organisms at each trophic level transfer less energy to the one below them than they do to the one above. The ultimate member of the food chain has less energy available to it the longer the food chain is. Because the energy available to the following organism will be too tiny and insufficient to sustain that organism’s life, food chains often have three to four trophic levels.

Question 69.

State two ways of effective plastic waste collection in the school.

Answer 69:

There are two efficient ways to collect plastic waste: 

  1. i) using special dust-bins for collecting plastic; (ii) using reusable containers for cafeteria and school events; and (iii) promoting the use of less plastic in packed lunches.

Question 70.

Name any two uses of ‘single-use plastic’ in daily life.

Answer 70:

Single-use plastic, also known as throwaway plastic, is frequently used for plastic packaging and refers to goods that are meant to be used just once before being discarded or recycled. Grocery bags, bottles, straws, food packaging, containers, cups and silverware are a few of these.

Question 71.

If we discontinue the use of plastics, how can an environment-friendly substitute be provided?

Answer 71:

Best alternatives can be the use of glass, stainless steel, silicone containers and platinum. Cloth bags can easily replace plastic bags. Use wooden cleaning brushes, kitchen utensils and cutting boards, pottery and other ceramics products, etc.

Question 72.

Do you think microbes shall work similarly in landfill sites as they work in the laboratory? Justify your answer.

Answer 72:

Given that it is challenging to duplicate the precise ambient conditions needed for the microorganisms to grow in these two environments, germs may not behave the same way in landfill sites as in laboratories. However, they will function similarly in landfill sites because of the same downstream processing and other mechanisms.

Question 73.

The ozone layer depletion is a cause of concern. Why?

Answer 73:

The stratospheric layer of the atmosphere’s ozone layer, which is ozone rich, serves as a shield to keep damaging UV rays from reaching the Earth’s surface. As a result, it is important to be concerned about the ozone layer.

Question 74.

Write one negative effect of the affluent lifestyle of a few persons of society on the environment. 

Answer 74:

The affluent lifestyle of a select few people leads to the exploitation and excessive use of resources, which makes them scarce and increases waste production, which upsets the equilibrium of the ecosystem.

Question 75.

Why is the excessive use of CFCs a cause of concern? 

Answer 75:

Chlorofluorocarbons, sometimes known as CFCs, are strong chemicals that emit active chlorine into the atmosphere, where it combines with ozone molecules to turn them into oxygen. The ozone layer thins as a result. Therefore, excessive CFC consumption is a problem.

Question 76.

What is the role of ozone in the upper atmosphere?

Answer 76:

The protective shell of ozone (O3) in the upper atmosphere absorbs the majority of the sun’s harmful UV light, which can be hazardous to people, animals and plants. It safeguards us from several health risks.

Question 77.

Why we should discard biodegradable and non-biodegradable wastes in two separate dust bins? 

Answer 77:

Biodegradable wastes are naturally broken down by bacteria, which reduce them to their simplest components. This allows the nutrients to be recycled throughout the biotic and abiotic ecosystem components. Non-biodegradable trash cannot be disposed of organically since bacteria cannot break them down. Such wastes are recycled, burned or dumped in landfills among other options. Disposing of the two types of waste in separate dustbins is best because their disposal methods are different.

Question 78.

Why did the United Nations act to control the production of chlorofluorocarbons (CFCs) used in refrigerators?

Answer 78:

Since CFCs are the primary compounds contributing to ozone depletion, the United Nations has taken action to regulate their manufacture.

Question 79.

“Industrialisation has severely deteriorated the environment.” Give four reasons to support this statement.

Answer 79:

Our ecology has become worse as a result of industrialisation in the following ways:

  • The need for an additional land area to construct new enterprises has increased due to rapid industrialisation. The clearance of forest land satisfies this desire. One of the main causes of ecological unbalance, biodiversity loss, and unstable ecosystems are deforestation.
  • Industries degrade the environment by releasing a variety of toxic gases. People nearby who breathe these fumes can get a number of respiratory conditions as a result.
  • Many different sectors release large amounts of effluent and liquid waste, much of which is thrown into adjacent bodies of water. This pollutes the water. Diverse aquatic creatures perish in dirty water, and humans contract a variety of ailments from drinking it.
  • The appropriate breakdown of the solid waste discharged from factories is not ensured and is just dumped on open ground. Ibis contributes to land contamination, which lowers soil quality and brings on a variety of human and animal ailments.

Question 80.

Why has the Government of India imposed 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.

Answer 80:

Due to the fact that polythene bags are non-biodegradable and do not affect bacteria, the Indian government has banned their use. As a result, they cannot break down and remain in the environment for a long time, harming the ecology. These bags clog drains, causing water logging and mosquito breeding, which in turn causes numerous ailments like malaria and dengue. The alternatives to polythene bags are jute bags and cloth bags.

Question 81.

“Affluent lifestyle has negatively affected the environment.” Justify the given statement with the help of an example. 

Answer 81:

The way of life of humans has improved as technology has developed over time. People’s attitudes have altered as a result of these changes in their life. When individuals have more resources at their disposal, they often abuse and overuse them, which leads to the production of vast amounts of waste material. For instance, the disposable lifestyle has compelled people to use more items like plastic cups, bags and other items that accumulate in the environment and do not degrade, harming the ecosystem.

Similar to how excessive use of air conditioners, refrigerators, plastic foams, etc. emits large amounts of CFCs, which are to blame for ozone depletion.

Question 82.

“To segregate the household waste, we should have two separate dustbins, one for the biodegradable waste and the other for the non-biodegradable waste.” Justify this statement by suggesting the proper way of disposal of these wastes. 

Answer 82:

In order to dispose of household waste, two distinct dustbins should be used, one for biodegradable waste and the other for non-biodegradable waste. It is crucial to separate biodegradable trash from non-biodegradable waste before disposing of them properly. Biodegradable waste can be composted, whilst non-biodegradable garbage can be recycled, burnt or dumped.

Question 83.

We often observe domestic waste being decomposed in the by-lanes of residential colonies. Suggest ways to make the fellow residents realise that improper waste disposal is harmful to the environment. 

Answer 83:

Making people aware of the negative effects of garbage disposal is one way to get them to understand that incorrect waste disposal

 is bad for the environment.

(i) By holding seminars on the harmful impacts of waste on the environment, they can be made aware.

(ii) Using flyers and posters to spread awareness.

(iii) Establishing an eco-club in the community to raise awareness of the negative impacts that garbage has on the environment, such as: 

  • Improper trash disposal releases hazardous gases into the environment, making it dirty and unhealthy for living things.
  • The waste will enter water bodies with rainwater and contaminate the water, endangering aquatic life.
  • It gives mosquitoes a place to nest, which causes the spread of diseases, including dengue, malaria and filariasis.
  • Hazardous substances from waste contaminate the soil and can harm plants when their roots ingest them. This will surely have a negative/detrimental effect on the ecosystem and the health of humans and other creatures.

Question 84.

(a) Write two negative effects of used plastic bags on the natural environment. Suggest alternatives that can be used instead of plastic bags.

(b) List any two suitable practices that can be followed to dispose of the waste produced in our homes.

Answer 84:

(a) There are two negative effects of plastic bag use on the environment:

(i) Plastic bags are non-biodegradable materials that bacteria do not break down. As a result, they cannot disintegrate and remain in the ecosystem for a long time, harming the fertility and quality of the soil.

(ii) Plastic bags clog drains, which causes water logging and mosquito breeding, which spreads a number of diseases.

The alternatives to polyethene bags are jute and cloth bags.

(a) Techniques for getting rid of the waste generated in our homes:

  • Sorting of garbage into biodegradable and non-biodegradable categories.
  • Manure can be made from biodegradable waste.
  • Non-biodegradable garbage needs to be dumped in places where municipal authorities may pick them up and properly and scientifically dispose of them.
  • Utilise empty bottles and jars to store food and other stuff.

Question 85.

How and where is ozone formed in the atmosphere? Explain how it affects an ecosystem.

Answer 85:

Ozone levels in the stratosphere are kept constant because the two reactions are in equilibrium. 

Image source: NCERT textbook

Ozone blanket is another name for the ozone layer. It serves as a shield to guard against the damaging effects of UV radiation on all forms of life. Due to the admission of high-energy UV radiations into the Earth’s surface caused by any thinning or depletion of the ozone layer, adverse impacts on plants, animals and people result.

Following are some negative effects of ozone depletion on people, animals and plants:

  • Herpes and skin cancer incidence.
  • Damage to vision, photo burning and an increase in eye cataracts are all potential side effects.
  • Immune system dysfunction lowers the body’s ability to resist illness.
  • Increased mortality of embryos.
  • Plant photosynthesis is declining by 10 to 25%.
  • Global warming

Benefits of Solving Important Questions Class 10 Science Chapter 15

Below is a list of a few benefits of solving questions from our Important Questions Class 10 Science Chapter 15:

  • Our question bank of Important Questions Class 10 Science Chapter 15 is based on the latest CBSE syllabus and adheres to the NCERT exam-guidelines and format. So it covers questions of different formats including MCQs, fill in the blanks, short-form / medium-form and long-form answers. So students can be exposed to actual board exam-type paper patterns. This helps students to boost their confidence during the actual exams and score higher marks.
  • The answers are prepared by experienced Science teachers with decades of experience. Additionally, there is a separate team to constantly review and revise the answers. So all our solutions are as per the latest CBSE syllabus and students can confidently rely on our solutions.
  • By practising different advanced level questions provided in the Important Questions Class 10 Science Chapter 15, students can thoroughly brush up on the concepts given in the chapter. This will help them revise the concepts again and give them a chance to analyse their shortcomings and overcome them before they face the final examinations. Additionally, stick to a study schedule and follow it religiously to come out with flying colours. 

The answers given to all questions in our Class 10 Science Chapter 15 Important Questions adequately cover all of the key points with explanations. 

With its unique learning platform, Extramarks gives students a unique learning experience. Students can find various other study materials which they can refer to based on their requirements:

Q.1 A solenoid is 1 m long and 2 cm in diameter and has 50 turns/cm. A current of 5 A is flowing through it. Calculate the magnetic induction:

a) Inside the solenoid.
b) At one end on the axis of solenoid.


a) Inside the solenoid:
B = µ0NI
length = 1m = 100cm
Where, Number of turns, N = 50 /cm x 100cm = 5000
µ0 = 4 x 10-7
Current flowing through solenoid, I = 5 A.
B = (5000 x 4 x 107 x 5) T
B = x 102 T.

b) At one end on the axis of solenoid: Let B0 be the magnetic induction at the axis of solenoid. Now at the end of the axis of solenoid, the magnetic induction is,
B0 = B/2
where, B is magnetic induction inside the solenoid.
B0 = /2 102 T

Q.2 What is the principle behind the working of electric generator? Explain its working with the help of well labeled diagram.


Principle of working(Electric generator): The electric generator works on the principle that when a conductor is moved in a magnetic field then current is induced in the conductor. The direction of the induced current is given by Flemings left hand rule.

Construction and Working: The construction of a simple electric generator is shown in the figure below:

It has a rectangular coil which is placed between two strong horse-shoe magnets. On the periphery of coil large turns of insulated copper wire is wound.
Here the ends A and D of the coil are connected to slip rings R1 and R2. They rotate along with the coil, while two carbon brushes B1 and B2 keep contact with them.

Suppose coil starts rotating in the clockwise direction than current is induced in the coil, which flows from points ABCD. The direction of current is given according to the Flemings left hand rule.

After half rotation of the coil, arm CD starts moving up while AB starts moving down. Now the flow current induced is reversed, that is current flows through DCBA.
Hence we may say that after every half cycle direction of flow of current is reversed. Because of this reason the current produced by the generator is also called as alternating current.

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FAQs (Frequently Asked Questions)

1. Is Chapter 15 an important chapter from the exam perspective for Class 10?

Yes, it is definitely important from the exam perspective for Class 10 as it contains a weightage of around 3%. Apart from that, one should not skip this chapter as it is important for the students to learn about the environment, its components, factors that affect it, and how you can preserve it for a better tomorrow. 

2. What environmental factors affect the student's learning?

When students positively perceive their classroom environment, they are more likely to learn. Students will be motivated enough to learn if their academic environment promotes a sense of community and competence and allows them autonomy.