our environment assignment class 10

Our Environment Notes And Questions | Chapter 15 Class 10

Our environment notes and questions.

Below are some of the very important NCERT Class 10 Science chapter 15 our environment notes and questions. These Class 10 our environment notes and questions have been prepared by expert teachers and subject experts based on the latest syllabus and pattern of term 2. Questions with Answers to help students understand the concept.

These Questions for Class 10 Science our environment notes and questions are very important for the latest CBSE term 2 pattern. These class 10 notes and Q and A are very important for students who want to score high in CBSE Board.

We have put together these NCERT  Questions of Class 10 Science chapter 15 our environment notes and questions for practice on a regular basis to score high in exams. Refer to these Questions with Answers here along with a detailed explanation.

All those things and set of conditions that influence the life of an organism like their growth, survival, development and reproduction, constitute the environment.

It is composed of physical surroundings (e.g. air, water), living beings (e.g. plants, animals) and climatic conditions (e.g. rainfall, temperature) of the region.

It is the structural and functional unit of the biosphere. It is a stable ecological unit where regular input of energy and circulation of matter takes place. The term ecosystem was coined by AG Tansley (in 1935).

All the interacting or living organisms (biotic components) in an area together with the non-living constituents (abiotic components) of the environment form an ecosystem, e.g. a lake, a field or a forest.  

Types of Ecosystem

There are two types of ecosystem, i.e. natural and artificial ecosystem,

1. Natural Ecosystem

The naturally existing ecosystem without any human support is called a natural ecosystem. Depending upon the habitats, natural ecosystems may be terrestrial (desert, grassland and forest) and aquatic (ponds, lakes, estuaries and marine).

2. Artificial Ecosystem

An ecosystem which is created and maintained by humans is called an artificial or man-made ecosystem. It relies on human efforts to sustain. It does not possess a self-regulating mechanism.

e.g. Aquariums, botanical gardens, field crops, etc. Agro-ecosystem is the largest man-made ecosystem.

Components of Ecosystem  

The ecosystem encompasses both living (biotic) and non-living (abiotic) components of the earth.

1.Biotic Components

These include all the living organisms present in the ecosystem, i.e. plants, animals and microorganisms.

On the basis of food, the different living organisms can be categorized into three groups. These are as follows

(i) Producers . All green plants and certain blue-green algae which can produce food by the process of photosynthesis are producers. These are also called autotrophs. These are the source of nutrition for the rest Of ecosystem.

(ii) Consumers . These are dependent on producers for their nutritional requirement and consume food prepared by producers. These are also called heterotrophs.

Consumers can be further divided into the following three categories:

Herbivores . These are primary consumers which feed directly on the producers, i.e. plants. e.g. Grazing animals.

Carnivores . The carnivores which feed on herbivores are called secondary consumers.

Some are predators which attack and kill their prey and feed on their bodies. Some are scavengers that feed on dead animals that they find. These are called tertiary consumers.

Omnivores . These are animals that feed on both plants and animals, e.g. humans and bears.

(iii) Decomposers . These are microorganisms which feed on decaying and dead organic matter. They break down the remains of dead animals and plants, to release simpler inorganic materials, making nutrients available to producers. 

e.g. Bacteria and fungi.

2. Abiotic Components 

The abiotic components of an ecosystem are the non-living components on which living organisms depends. These components are light, temperature, water, atmospheric gases, wind, etc. 

It is a linear network of living organisms in a community through which energy is transferred in the form of food.

It describes the relationship between organisms about ‘who eats whom’.

On the basis of choice of habitat, food    chains are of two  

(i) Terrestrial food chain. It is the (bod chain present ou land,

e.g. Grass — Insects — Snake — Hawk.

(ii) Aquatic food chain. It is the chain present in different water bodies.

e.g. Phytoplankton — Zooplankton — Fish — Shark

Trophic Levels

The transfer of food or energy takes place through various steps or levels in the food chain known as trophic levels. 

The producers (autotrophs) are present at the first trophic level. They fix solar energy, making it available for consumers (heterotrophs). The herbivores or 9the primary consumers are found at the second trophic level.

Small carnivores or secondary consumers are present at the third trophic level. The large or the tertiary consumers form the fourth trophic level.

Energy Flow

• The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight (light energy). They convert  it into food (chemical energy).
• When green plants are eaten by primary consumers, a great deal of energy is lost as heat and an average of 10%  of the energy of food eaten by an organism is turned back into its own body and made available for the next level of consumers. This is known as the 10% law (Lindemann in 1942).

Therefore, 10% can be taken as the average value for the  amount of organic matter that is present at each step and reaches to the next trophic level.

• The loss of energy at each step is very large. Only a little energy is available for the next level of consumers, food chains generally consist of three or four steps.

• The flow of energy is unidirectional, i.e. the energy which passes to the next trophic level, does not come back to the lower trophic level.

Click Below To Learn Term 2 Syllabus All Chapters

• Chapter 4: Carbon And Its Compounds Notes / Questions 
• Chapter 5 : Periodic Classification of Elements Notes / Questions
• Chapter 8 : How Do Organism Reproduce  Notes / Questions
• Chapter 9 : Heredity And Evolution Notes / Questions
• Chapter 12 : Electricity Notes / Questions
• Chapter13 : Magnetic Effects of Electric Current Notes / Questions
• Chapter15 : Our Environment Notes / Questions 

It is the interconnection of different food chains, which correlate at various trophic levels operating in an ecosystem, Each organism is generally eaten by two or more other kinds of organisms. They in turn are eaten by several other organisms.

Environmental Problems

Human are an integral part of the environment. Various human activities pollute the environment in various ways. Serious environmental problems such as biomagnification, ozone layer depletion, waste accumulation are as follows:

Biological Magnification or Biomagnification

It is the phenomenon of progressive increase in the concentration of non-biodegradable toxicants in organisms at each successive trophic level. It is also called bioconcentration. These toxic chemicals enter the food chain through pesticides like DDT.

The maximum concentration of these chemicals gets accumulated in humans as they occupy the topmost place in any food chain.

Depletion of Ozone Layer

Ozone (O3 ) is a molecule formed by three atoms of oxygen. It is found in the stratosphere. It shields the surface of the Earth fli)m harmful ultraviolet (UV) radiations of the Sun.

Formation of Ozone Layer

Ozone is a product of UV radiations acting on oxygen (0 2 ) molecules. The high energy UV radiations split apart some tuoleeulav oxygen (0 2) into free oxygen (O) atoms. These are very reactive and combine with the molecular oxygen to form ozone.

Ozone Depleting Substance

The increasing use of synthetic chemicals like Chlorofluorocarbons (CFCs) which are used in refrigerants as coolant and in fire extinguishers are responsible for ozone layer depletion.

In the atmosphere UV radiation break down CFCs molecules and release chlorine atom these atoms on reacting with Ozone, disassociate Ozone molecule into oxygen. 

Thus, it leads to depletion of Ozone layer

Managing the garbage we produce

The household waste is called garbage.  Every household produces a lot of garbage on a daily basis. Improvement in our Lifestyle have resulted in Greater amount of waste material generation. 

These way substances can be divided into two main groups:

(i) Biodegradable substances . The substances which can be disposed off naturally by the action of

micro organizations1 like bacteria, fungi, etc., arc called biodegradable substances.

e.g. Tea leaves, waste paper, left over food, etc.

(ii) Non-Biodegradable substances . The substances that cannot be converted into harmless simpler forms by the action of Microorganisms are called non-biodegradable substances. These are toxic, harmful, may be inert and accumulate in the environment or food chain.

e.g. Plastics, insecticides, heavy metals, etc.

Methods of Waste Disposal

Various methods of waste disposal are as given below

(i) Recycling. It is the processing of waste materials to form new products.

(ii) Composting. Biodegradable domestic wastes can be buried in a pit, dug into ground and are converted into compost and used as manure.

(iii) Incineration. It is the burning of a substance at high temperature to form ash. It is commonly used to dispose hospital waste.

(iv) Landfills . Solid waste is dumped into a low lying area and covered with soil.

(v) Sewage treatment . Organic ‘material in the sewage is allowed to settle down and decompose in large tanks. The water from these tanks is cleaned and is released into water bodies.

(vi) Biogas production . In some places, sewage is decomposed anaerobically to yield biogas and manure.

Note: Disposable paper cups which are biodegradable in nature are now being used in trains instead of plastic cups and kulhads.

As the production of kulhads at a large scale resulted in the loss of top fertile layer of soil which leads to soil erosion, whereas, plastic cups are non-biodegradable in nature, therefore cause environmental problems.

Frequently Asked Questions

Short answer type questions.

1. Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.    (CBSE 2019)

2. (i) What do you understand about the term ecosystem?

(ii) Autotrophs are at the first level of the food chain. Give a reason.

(iii) In a food chain of frogs, grass, insects and snakes, assign trophic level to frogs. To which category of consumers do they belong to? (CBSE 2020) 

3. What is the role of decomposers in the ecosystem? (NCERT)

4. Natural water bodies are not regularly cleaned whereas an aquarium needs regular cleaning. hv? (CBSE 21)19)

5. How does studying the food chain in an area or habitat help us? Give an example of four steps of a food chain operating in a large lake.

6. Based on their feeding habits, differentiate between parasites and decomposers. 

7. What are trophic levels? Give an example of a food chain and state the different trophic levels in it, (NCERT)

8. Number of trophic levels is limited to 3-4 in a chain. Give a reason.

9. What will happen if we kill all the organisms in one trophic level?

10. State 10% law. Explain with an example how energy flows through different trophic levels.

11. Indicate the flow of energy in an ecosystem. Why is it unidirectional? (NCERT Exemplar) 

12. What do you mean by biological magnification?

13. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem? (NCERT Exemplar)

14. Write the major cause of ozone depletion. What steps should be taken to limit the damage to the ozone layer?

15. Explain how ozone being a deadly poison can still perform an essential function for our environment. (CBSE 2020)

16. Give a reason why a food chain cannot have more than four trophic levels? (CBSE 2020)

17. (i) Explain the role of UV radiation in producing ozone layer.

(ii) Mention the reaction involved.

(iii) Why is excessive use of CFCs a cause of concern?

18. How is ozone formed in the upper atmosphere? State its importance. What is responsible for its depletion? Write one harmful effect of ozone depletion. (CBSE 2019)

19. Give some Diethocls that could be applied to reduce accumulation of pesticides in our.

20. How can you help in reducing Ille prol)letn ol’ waste disposal? Give any two methods.

21. If all the waste we generate is biodegradable, will this have no impact on the environment?

22. Give any two ways ‘in which non-biodegradable substances would aflbet the environment.

23. Why should non-biodegradable wastes be discarded in two separate dustbins?

24. ‘Effective segregation of wastes at the point of generation is very important’. Justify this statement.

25. Sheenu went to a picnic where she saw a pond. Her teacher gives her an assignment to draw the pond ecosystem and show its different components. Help her to complete the assignment.

26. Name the wastes which are generated in your house daily. What measures would you take for their disposal?  (NCERT Exemplar)

27. A modern insecticide has been introduced with  certain new properties like accumulation in the bodies  of predators, broken down by soil bacteria, easily  washed into lakes and rivers and taken up by plant roots. Among all these properties, which one will help in reducing or keeping the level of environment pollution  to lowest?

28. Mona eats curd and yogurt and follows a vegetarian diet. For this food intake, what should be the trophic level occupied by her in a food chain ? 

Long Answer Type Questions

29. What are decomposers? What will be the consequence of their absence in an ecosystem?    (NCERT Exemplar)

30. (i) What are consumers? What will be the consequence of the absence of primary consumers in an ecosystem?

(ii) What will be the direction of energy transfer in each of the following cases?

• Grasshopper eaten by a frog
• Deer feeds on grass
• Deer eaten by a lion

31. (i) Will the impact of removing all the organisms in a trophic level be different for different trophic  levels ?

(ii) Can the organisms of any trophic level be removed  without causing any damage to the ecosystem? (NCERT Exemplar)

32. (i) ‘Energy flow in a food chain is unidirectional’. Justify this statement.

(ii) Explain how the pesticides enter a food chain and subsequently get into our body. (CBSE 2014)

33. (i) How do food chains get shortened? How does the shortening of food chain aflöct the biosphere?

(ii) How will you justify that vegetarian food habits give us more calories?  

34. Explain some harmful effects of agricultural pracåces on the environment. (NCERT Exemplar)

35. What is Ozone and how does it affect any ecosystem? (NCERT Exemplar) 

36. i) What is environmental pollution ?

(ii) Distinguish between biodegradable and non-biodegradable pollutants.

(iii) Choose the non-biodegradable pollutants from the list given below

Paper, DDT, Radioactive waste, Plastic, Insecticides.

37. Suggest any five activities in daily life, which are eco-friendly. (NCERT Exemplar)

38. What are the reasons for the shift from plastic to kulhads and then finally to paper cups? (CBSE 2020)

Case Based Questions

39. Read the following and answer the questions from (i) to (v) given below

Food web is the interconnection of different food chains, which correlate at various trophic levels operating in an ecosystem.

(i) How many food chains are present in the  food web?

(ii) Name the primary consumer in the given food web.

(iii) How much percentage of energy is less at each trophic level?

(iv) If all the foxes are killed due to a disease, what will be your observations about food sveb?

(v) Name the organism in which accumulation of toxic Non Biodegradable substances is the lowest.

40. Read the following and answer the questions from (i) to (v) given below

Food chains are very important for the survival of most species. When only one element is removed from the food chain it can result in extinction of a species in some cases.

The foundation of the food chain consists of primary producers. Primary producers or autotrophs can use either solar energy or chemical energy to create complex organic compounds, whereas species at higher trophic levels cannot and so must consume producers or other life that itself consumes producers.

Because the Sun’s light is necessary for photosynthesis, most life could not exist if the Sun disappeared.

Even so, it has recently been discovered that there are some forms of life, chemotrophs that appear to gain all their metabolic energy from chemosynthesis driven by hydrothermal vents, thus showing that some life may not require solar energy to thrive.

(i) If 10,000 J solar energy falls on green plants in a terrestrial ecosystem, what percentage of solar energy will be converted into food energy?

(ii) Why are decomposers not included in the food chain?

(iii) How are primary consumers different from primary carnivores?

(iv) State one reason that limits the number of trophic levels in a food chain.

(v) In the given food web, name the organism in which the highest accumulation of toxic substances is found.

41. Read the following and answer the questions from (i) to (v) given below

Each organism is generally eaten by two or more other lands of organisms. They in turn are eaten by several other organisms.

Study the figure which shows the similar relationship between various organisms of the ecosystem through a food web.

Analyze the populations and their effects on each other.

(i) How many trophic levels are there in the longest food chain?

(ii) What is the role of rabbits in the given food web?

(iii) Give the significance of the food web.

(iv) Why do all food chains start with plants?

(v) What leads an organism to increase in number? 

42. Read the following and answer the questions from (i) to (v) given below

To study the ozone layer depletion, Mrs. Sharma, a science teacher, drew the given flow chart on the blackboard. She asked students to fill the bubbles labeled as 1-5 in the flow chart.

(i) What are ozone depleting substances?

(ji) How is ozone formed?

(iii) Ravi wants to draw an ozone ‘layer in a diagram showing different layers of atmosphere, where should he label it?

(iv) What is the difference between good ozone and bad ozone?

(v) What could be the effect of ozone depletion?

1. Ecosystem is defined as the structural and functional unit of the biosphere. It is a stable ecological unit where continuous input of energy and circulation of matter occurs.

2. (i) Ecosystem is the structural and functional unit of the biosphere and is a stable ecological unit where regular input of energy  and circulation matter takes place. 

(ii) Autotrophs can make their own food in the presence of sunlight. They are the ultimate source of energy for each and every organism of a food chain. Hence, every chain always starts with producers (autotrophs) that is why they are placed at the first trophic level of the food chain. 

(iii) In given food chain, Grass — Insects — Frogs — Snakes

Frogs assign at third trophic level. They acts as secondary consumers who feeds of primary consumers (i.e. insects).

3. Organisms that feed on dead plants and animals are called decomposers, e.g. bacteria, fungi, etc. They break down the complex organic compounds present in the dead remains into simpler substances and obtain nutrition from them. These substances are released into the soil and to the atmosphere.

Thus, they play the following roles

(i) They help in recycling of materials, replenishment of the soil’s nutrients, etc.

(ii) They clean our surroundings by decomposing dead organisms and organic wastes,

4. Natural water bodies are examples of natural ecosystems. They  exist naturally without any human support, whereas an aquarium is an artificial ecosystem which is created and maintained by humans. It rely on human efforts to sustain. It does not possess a self-regulating mechanism.

5. The study of food chain in an area or habitat helps in

(i) understanding the energy transfor through organisms

(ii) understanding the ecological balance in a habitat or ecosystem.

(iii) understanding harmful human activities and disruption of ecological balance, if any.

An example of four steps of food chain operating in a large lake is as follows

Algae —Protozoa —Small fish—Big fish.

6. Parasites are organisms (animals or plants) that live in or an  other organism (host) and take benefits by deriving nutrients from it, i.e. they get food or protection from host organism, e.g. Cuscuta

On the other hands, decomposers are organisms that break down dead or decaying organisms into simple inorganic substances. e.g.  Fungi

7. The transfer of food or energy takes place through various levels in the food chain, which are known as trophic levels. e.g.

8. In a food chain, about 80-90% of the energy available at a trophic level is lost during its transfer to the next trophic level. Hence, the amount of energy available goes on decreasing at each successive trophic level.

If a plant fixes 4000 J energy, then the next three successive trophic levels will get 400 J, 40 J and 4 J, respectively (according to 10% law). If another level is added in a food chain then it will get only 0.4 J energy. Thus, usually food chains remain shorter and limited to 3-4 trophic levels only.

9. If we kill all the organisms in one trophic level, the lower trophic level will grow more in number and the higher trophic level will not survive.

Hence, flow of energy from one trophic level to another will not take place.

10. According to 10% law, only 10% of the energy entering a particular trophic level of organisms is available for transfer to the next higher trophic level.

The flow of energy through a food chain is unidirectional and it moves progressively through various trophic levels as follows

(i) Green plants capture 1% of energy of the sunlight that falls on their leaves and convert it into food energy.

(ii) When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment. On an average only 10% of food eaten is turned into its own body and made available for the next level of consumers,

(iii) Thus, 10% can be taken as average value of the amount of organic matter present at each step and reaches the next level of consumers.

11. The flow of energy in an ecosystem occurs in the following sequence 

Sun — Producer— Herbivore—Carnivore 

                            (Primary)   (Secondary)       

The flow of energy is unidirectional because of the reasons given below

(i) Energy flows progressively from one trophic level to another and cannot revert back. Energy given out as heat is lost to the environment and does not return to be used again.

(ii) The available energy decreases at higher trophic level. Out of the total energy available at a particular trophic level, only 10% is passed on to the next trophic level, making it impossible for energy to flow in the reverse direction.

12. Biological magnification also known as biomagnification is the phenomenon of progressive increase in the concentration of non-biodegradable toxicants in organisms at each successive trophic level.

13. Biological magnification refers to the increase in the concentration of certain toxicants at each successive trophic level.

No, the levels of magnification will not be the same in all trophic levels. When the chemicals do not degrade and accumulate progressively at each trophic level, it leads to biomagnification. Biomagnification is more in organisms of higher trophic levels.

14. Depletion of ozone is mainly caused due to the excessive use of Chlorofluorocarbons (CFCs). These are synthetic chemicals which are used as refrigerants and in fire extinguishers. Steps which should be taken to limit the damage to ozone layer include

(a) Minimizing the use of aerosol spray propellants containing fluorocarbons and chlorofluorocarbons.

(b) Exercising control over large scale nuclear explosions and limited use of supersonic planes.

15. Ozone layers filter the Sun’s ultraviolet radiation (UV-B), thereby protecting the environment from its harmful effects and also play a key role in regulating temperature.

16. The energy and biomass decrease from lower to higher trophic levels, so the length of food chain is restricted and cannot have more than four trophic levels,

17. (i) UV radiation acts on the O2 molecule. Higher energy of UV split apart O2.

(iii) CFCs rise up in the stratosphere where UV radiation splits them releasing molecular chlorine (CI‐). It reacts with O3 and releases oxygen, so O3 gets depleted.

18. Ozone at the higher levels of the atmosphere is a product of UV radiations acting on oxygen (O2 ) molecules. The high energy UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms. These atoms are very reactive and combine with the molecular oxygen to form ozone.

It shields the surface of the Earth from harmful ultraviolet (UV) radiations of the Sun.

Due to environmental pollution, the ozone layer began to deplete in the 1980s.

This was mainly due to the increasing use of synthetic chemicals like Chlorofluorocarbons (CFCs). 

These are used in refrigerants as coolant and in fire extinguishers. Due to depletion of the ozone layer, harmful UV rays can penetrate or enter our atmosphere.

These radiations are highly damaging to organisms. They can cause skin cancer in human beings, damage eyes (cause disease called cataract), decrease crop yield, disturb global rainfall, etc.

19. Following methods could be applied to reduce the accumulation of pesticides in our body.

(i) Minimize the use of pesticides 

(ii) Consuming washed fruits and vegetables

(iii) Developing vegetarian feeding habits

(i.e. feed upon plants as plants belong to lower trophic level so, they have less accumulation of insecticides, whereas organisms of higher trophic level have higher concentration of insecticides and pesticides).

20. We can reduce the problem of waste disposal by the following methods

• Recycling . The solid wastes such as paper, plastics, glass and metals, etc., are recyclable. So, waste paper can be sent to paper mills for reprocessing to form newspapers. The plastic articles can be melted and remolded again to make new articles.
• Biodegradable waste . The waste such as leftover food, fruits, animal dung, peels of vegetables can be converted into compost by burying them in a pit dug in ground and can be used as manure.

21. If all the waste is biodegradable, then there will be no accumulation of waste on the Earth and it would be a cleaner place to live.

But if this biodegradable waste is too large in amount then its slow degradation may lead to air pollution (due to release of gasses) as well as water and land pollution.

22. The two ways in which non-biodegradable substances would affect the environment are

(i) They make the environment poisonous and unfit for survival of living ol’ life.

(ii) They block the transfer of energy and minerals in the ecosystem.

23. Biodegradable materials are broken down by microorganisms present in nature into simple harmless substances. Non-biodegradable materials need a different treatment like heat and temperature for disposal and hence, both should be discarded in two different dustbins.

24. Effective segregation of waste as biodegradable and non-biodegradable is much easier to recycle. Biodegradable waste used to make manure can be made out of compost, whereas non-biodegradable waste could be recycled and reused for various purposes. Also effective segregation of wastes means that less waste goes to landfill, which makes it cheaper and better for people and the environment.

25. A pond ecosystem refers to a freshwater ecosystem where there are various organisms dependent on each other with the prevailing water environment for their nutrients and survival.

Phytoplankton—Zooplankton —Small fish—Big fish

There are two components of the pond ecosystem

(i) Abiotic . It includes water, dissolved minerals, oxygen and carbon dioxide. Sunlight is the main source of energy.

(ii) Biotic . It consists of phytoplanktons, zooplanktons, aquatic insects, fishes and other aquatic animals. These organisms are classified as producers, consumers and decomposers.

26. The waste generated in our house and measures for its disposal are given in the table below

27. Insecticides are non-biodegradable chemicals added to crop fields to stop the growth of insects infecting the crops. Modern insecticides are being developed keeping in mind the harm they cause to the environment and its components.

Biodegradable insecticides can be decomposed into harmless substances, which will subsequently be dispersed in their specific pathways and cause no pollution.

Non-biodegradable insecticides build up in the fat tissues of the body and pass on to organisms that feed on them. 

Hence, they accumulate along the chain resulting in significant amounts in the tissues of consumers at the highest trophic level.

The property of newly developed insecticide includes that it can easily get decomposed into simpler components by soil bacteria.

28. Mona follows a vegetarian diet along with milk products. She should be considered as occupying the third trophic level because the curd is prepared by the Milk cow/buffalo  by the action of bacteria, but the energy of the milk is getting transferred from cow to Mona, so Mona is at the third trophic level.

Grass      —— Cow (milk)  —— Human 

(First trophic) (Second trophic) (Third trophic)

29. Organisms which break down the complex organic compounds present in dead and decaying matter into simpler inorganic materials are called decomposers, e.g. certain bacteria and fungi.

Decomposers act as cleaning agents of the environment by decomposing dead bodies of plants and animals. They also help in recycling of materials, replenishment of soil’s nutrients, etc.

The consequence of their absence in an ecosystem can be disastrous. The dead bodies would persist for long, leading to their accumulation and thus, polluting the environment. The biogenetic nutrients associated with these remains will not be returned back to the environment.

As a result, all the nutrients present in soil, air and water would soon be exhausted and the whole life cycle of organisms would be disrupted. 

30. (i) Consumers are the organisms who derive energy by eating plants or other organisms as they cannot produce food on their own. Absence of primary consumers in nature would lead to enormous growth of plants and decline in the population of carnivore animals, who eat them. Hence, the whole food web will get distrupted.

(ii) The direction of energy transfer in following cases are as follows

• Primary consumer (grasshopper) to secondary consumer (frog).
• Producer (grass) to primary constnuer (deer).
• Primary consumer (deer) to secondary consumer (lion) 

31. (i) Yes, the impact of removing all the organisms in a  trophic level will be different [or dillörent trophie lex els. The lower trophic level ol’ an ecosystem has a greater number of individuals than the higher trophic levels. 

Removal of producers will affect all the organisms of successive trophic levels and it will threaten their survival. The removal of higher trophic level will lead to increase in organisms’ lower trophic level and the organisms at higher trophic level will die due to  shortage of food. 

(ii) No, removal of all organisms of a trophic   level will disturb the ecosystem. Killing of higher trophic level organisms will cause explosion in the population of lower

trophic level organism. This will adversely affect the ecosystem and the environment.

32. (i) The producers convert solar energy into chemical energy in the form of organic compounds. The primary consumers (herbivores) derive their nutrition from the producers. According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other.

So, the energy that is captured by the producer does not revert back to the Sun and the energy transferred to the herbivores does not come back to the producers. It  just keeps on moving to the next trophic level in one direction. That is why the flow of energy in the food chain is always unidirectional 

(ii) A large number of pesticides and chemicals are used to protect our crops     pests and diseases. Sorne of these chemicals are washed clown from the soil, while some enter the water bodies. 

From the soil, they are absorbed by plants along with water and minerals and from the  water bodies, they are taken up by aquatic plants and animals. This is how these chemicals enter the food chain.

As these chemicals cannot decompose, they accumulate progressively at each trophic level. This increase in the concentration of harmful chemicals with each step of the food chain is called biomagnification. As human beings occupy the top level in any food chain, these chemicals get accumulated in our bodies in considerably high amounts causing diseases.

33. (i) Undesirable activities of man eliminate growth of organisms belonging to one or more trophic levels in a food chain. Thus, the food chain gets shortened, e.g. hunting tigers for their skin, etc. 

It causes imbalance in the functioning of the ecosystem and biosphere. If organisms of one trophic level are eliminated, the organisms prior to that trophic level will flourish and increase in number. Also, the organisms of the subsequent trophic level will sharply decrease, thereby creating an imbalance.

(ii) Vegetarian food chain is advantageous in terms of energy because it has less number of trophic levels. As we know, only 10% of the energy is transferred to the next trophie level in a food chain, so if a person is vegetarian then, he would have a maximum amount of energy by consuming producers or plants in a food chain.

34. Some harmful effects of agricultural practices on the environment are as follows

(i) Soil degradation . Extensive cropping causes loss of soil fertility. Also, over time it can lead to soil erosion and finally to desertification.

(ii) Pollution . Use of synthetic chemical fertilizers and nucl  pesticides leads to soil, water and air pollution.

(iii) Water shortage . Excess use of groundwater for agriculture lowers the water level. This results in acute water shortage at many places.

(iv) Biomagnification . The chemical pesticides, being  accumulate in organisms in increasing amount of each trophic level 

(v) Deforestation . Indiscriminate cutting of trees of agriculture has resulted in loss of habitat for wildlife.

Thus, it also causes damage to natural ecosystem.

35. Ozone is a triatomic molecule, i.e. made up of three atoms of oxygen joined together. Its molecular formula is O3. It can affect any ecosystem in the following ways

(i) It protects against ultraviolet rays if present in the stratosphere.

(ii) Ozone dissipates the energy of UV rays by undergoing dissociation followed by reassociation.

(iii) In the atmosphere, it is highly toxic and causes injury to mucous membranes, eye irritation and internal hemorrhages in animals and humans.

36, (i) Environmental pollution is an undesirable change in the physical, chemical or biological characteristics of the natural environment, brought about by man’s activities. This pollution may affect the soil, water or air. 

(ii) Differences between biodegradable and non-biodegradable pollutants are as follows:

37. Some daily life eco-friendly activities are

(i) Save a tree, use less paper . You can buy ‘tree-free’ 100% post-consumer recycled paper for everything from greeting cards to toilet paper. Paper with a high post-consumer waste content uses less pulp and keeps more waste paper out of landfills.

(ii) Opt bamboo for hardwood floors Bamboo is considered as an environmentally-friendly flooring material due to its high yield and the relatively fast rate at which it replenishes itself. It takes just 4-6 years for bamboo to mature, compared to 50-100 years for typical hardwoods. Also look for sources that use formaldehyde-free glues.

(iii) Reduce plastics, reduce global warming Unfortunately, plastics are made from petroleum, the processing and burning of which is considered one of (he main contributors to global warming, according to the EPA. In addition, sending plastics to the landfill also increases greenhouse gasses. 

Reduce, reuse and recycle our plastics are one of the best ways to combat global warming.

(iv) Use healthier paints Conventional paints contain solvents, toxic metals and Volatile organic compounds (VOCs) that can cause smog, ozone pollution and indoor air quality problems with negative health effects, according to the EPA. These unhealthy ingredients are released into the air, while we are painting, drying of paint and even after the paints are completely dry.

(v) Use compost Instead of using synthetic fertilizers, compost provides a full complement of soil organisms and the balance of nutrients needed to maintain the soil’s health. Healthy soil mininii.ses the population of  weeds.

38. Materials that retain for a long time in the environment, without getting by any natural agents, also causing harm to the environment are called non-biodegradable. 

Plastic cups are non-biodegradable and raised the concern towards hygiene, thus they were replaced by kulhads.

Kulhads are made up of clay on a large scale resulting in the loss of top fertile soil. It is replaced by disposable paper cups because the paper can be recycled, it is biodegradable and is eco-friendly material which does not cause environment pollution.

39. (i) There are 6 food chains that constitute the given food web. These are as follows

• Seeds— Mice — Foxes  
• Young trees — Mice — Foxes 
• Young trees — Rabbits — Foxes
• Grass — Rabbits — Foxes
• Grass — Rabbits — Snake
• Young trees — Rabbits — Snake

(ii) The primary consumers are the organisms who directly feed on the producers. In the given food web, rabbits and mice are the primary consumers, whereas foxes and snakes are the secondary consumers.

(iii) About 90% of energy is loss at each trophic level.

(iv) The foxes feed on the rabbits and mice. If all the foxes are killed then there will be no direct predator of rabbits and mice, hence the number of rabbits and mice (i.e. both are primary consumers) will increase in the given ecosystem, which will disturb its balance.

(v) Accumulation of toxic non-biodegradable substances increases at each trophic level. It is least in organisms of first trophic level (i.e. seeds), young trees and grass and highest in organisms of third trophic level (i.e. foxes and snakes).

40. (i) The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight (light energy). They convert it into food energy (chemical energy).

Therefore, if 10,000 J solar energy falls on green plants in a terrestrial ecosystem, only 1% of solar energy, i.e. 100 J will be converted into energy.

(ii) Decomposers are not included in the food chain as they act at every trophic level of the food chain.

(iii) Primary consumer are those organisms who directly feed on plants; e.g. herbivores 

Primary carnivores are those organisms who feed on plant-eating animals e.g. snakes.

(iv) Decrease in energy at higher trophic levels (according to 10% law) is one of the reasons that limits the trophic levels in a food chain.

(v) Owl is placed at the highest trophic level in the given food web, therefore the accumulation of non-biodegradable toxic materials are found to be highest in them due to biomagnification.

41. (i) The longest food chain consists of a maximum five trophic levels.     

(ii) Rabbit is a herbivore as it feeds on plants directly. Its role in the given food web is to transfer the energy from  producers to carnivores.

(iii) The significance of food web is as follows 

• Food chains provide pathways for availability of food. 
• It allows endangered populations to grow in size. 

(iv) Sun or solar energy is the ultimate source of energy for the Earth. Only plants can utilize this energy to make their on food.

(v) When a predator for a particular organism decreases in number, the organisms start increasing in number.

As the animals which used to feed on them decrease in number, therefore, the population of those organisms increases.

42. (i) Substances that are responsible for depletion of the ozone layer or breakdown of ozone molecules are known as ozone depleting substances.

e.g. CFCs, halogens, nitrous oxide, CCl4 and CH4 are ozone depleting substances responsible for ozone layer depletion.

(ii) Atomic oxygen is highly reactive. It combines with molecular oxygen to form ozone.

(iii) Ozone layer is found in the stratosphere around 15-30 km above the Earth’s surface.

(iv) Ozone is a triatomic molecule made up of three atoms of oxygen (03). It is present in the atmosphere as an ozone layer shield that protects us from high energy UV radiations. 

So, it is known as good ozone whereas near the surface of earth ozone act as a highly poisonous gas. Hence,  bad ozone.

(v) Cancers, mutations, effects on eyesight, global warming, weakening of the immune system, etc., are some adverse effects of ozone depletion.

Final Words

From the above article, you have practiced Class 10 chapter 15 our environment notes and questions. We hope that the above-mentioned notes and Q & A for term 2 will surely help you in your exam. 

If you have any doubts or queries regarding Class 10 chapter 15 our environment notes and questions, feel free to reach us and we will get back to you as early as possible.

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Chapter 15 Class 10 - Our Environment

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Get Notes, NCERT Questions, Extra Questions (with answers) of Chapter 15 Class 10 Science - Our Environment.

We at Teachoo have solved the NCERT Back Questions, as well as the questions from inside the chapter and provided Revision Notes as well.

This chapter comes under Class 10 Biology.

The chapter's name is - Environment.

But, what does environment mean?

The Environment includes our physical surroundings like air, water, soil and all the living organisms around us - like animal, human beings, microorganisms like bacteria, fungi.

In this chapter, we will learn

• What is an Ecosystem
• Types of Ecosystem - Natural and Man-made, and their examples
• What are the Functions of an Ecosystem
• What are the Components of Ecosystem
• What are Producers, Consumers and Decomposers
• Different types of Consumers - Herbivores, Carnivores, Omnivores
• What are Food Chains , with Examples
• What are Food Webs
• Difference between Food Chain and Food Web
• What is the meaning of Trophic Level
• What are Autotrophs and Heterotrophs
• Difference between Autotrophs and Heterotrophs
• How does Flow of Energy take place in a Trophic Level
• Why is so much energy lost when going from one trophic level to another?
• What is Biological Magnification ?
• What is Ozone ?
• How is Ozone formed ?
• How is Ozone Layer depleted ?
• How can we segregate Waste
• How can we manage waste properly

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NCERT Solutions for Class 10 Science Chapter 15 Our Environment

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NCERT Solutions For Class 10 Science Chapter 15 Our Environment : Students searching for NCERT solutions for class 10 science chapter 15 notes can refer to this article. Also, students can find our environment class 10 extra questions and answers. Solving these NCERT Solutions For Class 10 Science Chapter 15 Our Environment will not only help students to secure good marks in board exams but also helps in cracking the competitive exams like JEE Main, NEET, JEE Advanced, etc.,

So students are advised to go through this detailed NCERT Solutions For Class 10 Science Chapter 15 Our Environment to build a strong foundation in the subject Science. Read on to find out everything about cbse class 10 biology our environment NCERT Solutions.

Before getting into the details of our environment class 10 extra questions and answers, let’s have an overview of topics and subtopics under Class 10 Science Chapter 15 Our Environment:

NCERT Solutions for Class 10 Science Chapter 15 Intext Questions

Page Number: 260

• Grass represents first trophic level.
• Grasshopper represents second trophic level.
• Frog represents third trophic level.
• Eagle represents fourth tropic level.

Question 2 What is the role of decomposers in the ecosystem ? Answer: (i) Decomposers help in decomposing the dead bodies of plants and animals and hence act as cleansing agents of the environment. (ii) Decomposers also help in putting back the various elements of which dead plants and animals are made, back into the soil, air and water for reuse by the producers like crop plants. (iii) They help in recycling of the nutrients. (iv) They decompose dead remains thereby providing space for new life to settle in the biosphere.

Page Number: 262

Question 1 Why are some substances biodegradable and some non-biodegradable ? Answer: The microorganism like bacteria and other decomposer organisms (called saprophytes) present in our environment are specific in their action. They break down the materials or products made from natural materials (say, paper) but do not break down man-made materials such as plastics. So, it is due to the property of decomposer organisms of being specific in their action that some waste materials are biodegradable, whereas others are non-biodegradable.

Question 2 Give any two ways in which biodegradable substances would affect the environment. Answer: (i) Biodegradable substances are decomposed by the action of microorganisms and decomposed materials are recycled through geo-chemical cycle. (ii) These substances keep the environment clean.

Question 3 Give any two ways in which non-biodegradable substances would effect the environment. Answer: (i) They cause air, water and soil pollution. (ii) They may cause bio-magnification in the food chain and end up in humans.

Page Number: 264

Question 1 What is ozone and how does it affect any ecosystem ? Answer: Ozone (O 3 ) is an isotope of oxygen, i.e., it is a molecule formed by three atoms of oxygen. At the higher levels of the atmosphere, ozone performs an essential function. It shields the surface of the earth from ultraviolet (UV) radiations from the sun. These radiations are highly damaging to organisms. Ultraviolet rays can cause skin cancer.

Question 2 How can you help in reducing the problem of waste disposal ? Give any two methods. Answer: (i) Recycling : The solid wastes like paper, plastics and metals, etc. are recycled. (ii) Preparation of Compost: Biodegradable domestic wastes such as left over food, fruit and vegetable peels and leaves of potted plants, etc. can be converted into compost by burying in a pit dug into ground.

NCERT Solutions for Class 10 Science Chapter 15 Textbook Chapter End Questions

Question 1 Which of the following groups contain only biodegradable item ? (a) Grass, flowers and leather (b) Grass, wood and plastic (c) Fruit peels, cake and lime juice (d) Cake, wood and grass Answer: (a) Grass, flowers and leather.

Question 2 Which of the following constitutes a food-chain ? (a) Grass, wheat and mango (b) Grass, goat and human (c) Goat, cow and elephant (d) Grass, fish and goat Answer: (b) Grass, goat and human.

Question 3 Which of the following are environment friendly practices ? (a) Carrying cloth-bags to put purchases in while shopping (b) Switching off unnecessary lights and fans (c) Walking to school instead of getting your mother to drop on her scooter (d) All of the above Answer: (d) All of the above.

Question 4 What will happen if we kill all the organisms in one trophic level ? Answer: The food chain would end and ecological balance would be affected.

• If the herbivores are killed, then the carnivores would not be able to get food and would die.
• If carnivores are killed, then the population of herbivores would increase to unsustainable level.
• If producers are killed, then the nutrient cycle in that area would not be completed.

Question 5 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. For example, on removing producers; herbivores would not be able to survive or they would migrate and ecosystem would collapse. If herbivores are removed, producers would grow unchecked and carnivores would not get food. If carnivores are removed, herbivores would increase to unsustainable levels and could destroy the producers. If decomposers are removed, the dead animals would pile up due to which the environment would become polluted. In addition to this, if dead animals will not decompose, the recycling of nutrients in the soil will be stopped and its fertility will be reduced. As a result the green cover of the earth will be lost. Thus to maintain the balance of the ecosystem the presence of organisms is necessary at each trophic level.

Question 6 What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ? Answer: Biological magnification : The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at each trophic level of a food chain is called biological magnification. Yes, levels of bio-magnification would increase as the trophic level increases and would be the highest for topmost trophic level. It would affect their biological process such as growth, reproduction, etc.

Question 7 What are the problems caused by the non-biodegradable wastes that we generate ? Answer: The problems caused by the non-biodegradable wastes are :

• If the quantity of non-biodegradable matter increases in the nature then bio-magnification of poisonous chemicals in our body increases.
• If the non-biodegradal waste keeps on increasing there will not be left any substance for new organisms.
• The increasing quantity of non-biodegradable waste will cause imbalance of ecosystem.

Question 8 If all the waste we generate is biodegradable, will this have no impact on the environment ? [CBSE 2011, 2013] Answer: If all the waste we generate is biodegradable, it will also have impact on the environment. If it is disposed off properly, the problem of air, water and soil pollution can be lessened to an extent. There would be less health problems and humans would be disease-free. But if it is not disposed off properly, it will affect the environment adversely.

Question 9 Why is damage to the ozone layer a cause for concern ? What steps are being taken to limit this damage ? Answer: The damage to the ozone layer is a cause for concern because if the ozone layer in the atmosphere disappears completely, then all the extremely harmful ultraviolet radiations 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. In an attempt to protect the ozone layer, the United Nations Environment Programme (UNEP) unanimously forged an agreement among its member countries to freeze CFC production at 1986 levels.

Our environment: Eco-system, Environmental problems, Ozone depletion, waste production and their solutions. Biodegradable and non-biodegradable substances.

Question 1. Why are some substances biodegradable and some non-biodegradable ? Answer: Substances that are broken down by biological processes are said to be biodegradable. In our environment, many of the substances are broken easily by decomposers (bacteria and fungi) as they possess specific enzymes for such activity. However, there are other substances also which are not broken down in this manner and are known as non-biodegradable substances. Since these substances are not degraded by bacteria and fungi, so they persist for a long time. These non-biodegradable substances will be acted upon by physical processes like heat and pressure.

Question 2. Give any two ways in which biodegradable substances would affect the environment. Answer:

• They may produce foul smell during decomposition process.
• They may produce some harmful gases such as ammonia, methane, carbon dioxide, etc., which can further-cause global warming.

Question 3. Give any two ways in which non-biodegradable substances would affect the environment. Answer:

• These inert substances simply persist in the environment. This means that these substances require land area for dumping.
• Excess of fertilizers, pesticides and other chemicals changes soil chemistry and also affects aquatic life.
• Most of these chemicals and heavy metal are easily absorbed by the organisms. This causes biological magnification.

Question 1. What are trophic levels? Give an example of a food chain and state the different trophic levels in it. Answer: Each step or level of the food chain forms a trophic level. Consider the following food chain:

Question 2. What is the role of decomposers in the ecosystem? Answer: Role of decomposers in the ecosystem :

• They help in breaking down the complex organic into simple inorganic that go into the soil and are used up by the plants.
• They the nutrient pool of the putting In this way, ad as cleansing agents of nature.
• They help in maintaining the fertility of by adding humus content to it.

Question 1. What is ozone and how does it affect any ecosystem? Answer: Ozone (O 3 ) is a molecule formed by three atoms of oxygen. At the higher of the atmosphere, it shields the surface of the earth from ultraviolet (UV) radiation from the Sun. It may affect any ecosystem in the following ways :

• At the surface of the earth, it is a deadly poison for all lower forms of life.
• If this layer gets depleted, then it may cause cancer in human beings including other plants and animals.

Question 2. How can you help in reducing the problem of waste disposal? Give any two methods? Answer:

• By changing our lifestyle and change in attitude will reduce disposable waste.
• Reducing packaging.
• Recycling of waste.
• Preparing compost of biodegradable waste.

Question 1. Which of the following groups contain only biodegradable items? (a) Grass, flowers and leather (b) Grass, wood and plastic (c) Fruit-peels, cake and lime-juice (d) Cake, wood and grass Answer: (c) Fruit-peels, cake and lime-juice and (d) Cake, wood and grass

Question 2. Which of the following constitute a food-chain? (a) Grass, wheat and mango (b) Grass, goat and human (c) Goat, cow and elephant (d) Grass, fish and goat Answer: (b) Grass, goat and human

Question 3. Which of the following are environment-friendly practices? (a) Carrying cloth-bags to put purchases in while shopping (b) Switching off unnecessary lights and fans (c) Walking to school instead of getting your mother to drop you on her scooter (d) All of the above Answer: (d) All of the above

Question 4. What will happen if we kill all the organisms in one trophic level? Answer: If we kill all the organisms in one trophic level, then transfer of energy as well as matter to next higher level will stop. It will lead to over- population at one particular level causing amongst the individuals. This would seriously disturb the food chain and can cause the collapse of an ecosystem even.

Question 5. 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. It will not be possible to remove any organism in any trophic level without causing damage to the ecosystem.

Question 6. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem? Answer: The accumulation of harmful chemicals in the body of living organisms at different trophic levels in a food chain is called biological magnification. Yes, the concentration of these harmful chemicals will be different at different trophic levels. It will be maximum at the last trophic levels which is mostly of the top carnivores (quaternary consumers).

Question 7. What are the problems caused by the non-biodegradable wastes that we generate? Answer: (i) Non-biodegradable wastes persist in the environment for a long time and cause greater harm to the various members of the ecosystem by causing biological magnification. (ii) Non-biodegradable waste such as fertilizers, pesticides, weedicides, etc., changes the soil chemistry. in turn affects the fertility of soil and subsequently reduces the crop yield.

Question 8. If all the waste we generate is biodegradable, will this have no impact on the environment? Answer: Biodegradable waste will be recycled easily by the decomposers such as bacteria and fungi. It will have only this bad impact on our environment that, many Of the gases released during decomposition process may result in global warming.

Question 9. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage? Answer: The ozone shields the surface of the earth from ultraviolet (UV) radiation from the sun. These radiations are highly damaging as they can cause cancer in both plants and animals, damage to eyes and immune system. They can also lead to variations in global rainfall, ecological disturbances and dwindling of global food supplies. Due to these reasons, damage to the ozone layer is a major cause for concern. Steps which are taken to limit this damage :

• To decrease the use of synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.
• In 1987, the United Nations Environment Programme (UNEP) succeeded in reaching an agreement to freeze CFC production at 1986

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1. Identify the original source of the energy which flows through a food chain? (a) Carbon dioxide (b) Glucose (c) Oxygen (d) Sunlight Answer: (d) All the living organisms get energy directly or indirectly from the sunlight reaching the surface of Earth.

Question 3. Which of the following groups contains only biodegradable items? [NCERT] (a) Grass, flowers and leather (b) Grass, wood and plastic (c) Fruit-peels, cake and lime-juice (d) Cake, wood and grass Answer: (a), (c) and (d) substances that are broken down (decomposed) by the biological processes are said to be biodegradable e.g. fruit-peels, cake, lime-juice, wood, grass, leather, flowers, etc.

Question 4. Which of the following constitutes a food-chain? [NCERT] (a) Grass, wheat and mango (b) Grass, goat and human (c) Goat, cow and elephant (d) Grass, fish and goat Answer: (b) Each step of food chain form a trophic level. Producers (grass) forms the first trophic level, herbivore (goat) the second and carnivore (human) the third trophic level.

Question 5. Which of the following are environment- friendly practices? [NCERT] (a) Carrying cloth-bags to put purchases ‘ while shopping . (b) Switching off unnecessary light and fans (c) Walking to school instead of getting your mother to drop you on her scooter (d) All of the above Answer: (d) Cloth-bags are biodegradable, switching off unnecessary light and fans conserves electricity and limited use of petrol/diesel causes less pollution. Hence, all these practices are considered as environment friendly.

Question 6. Which of the following statements about food chain are correct? (a) It includes repeated eating, i.e. each group eats the other and is subsequently eaten by some other group of organisms. (b) It shows a series of branching lines and unidirectional flow of energy. (c) It shows the unidirectional flow of energy and proceeds in a progressive straight line. (d) Both (a) and (c) Answer: (d) A food chain is a series of organisms in an environment through which energy transfer occurs starting with a producer. It proceeds in straight line. Food chain does not consist of branching lines.

Question 8. An ecosystem includes (a) all living organisms (b) non-living objects , (c) both living organisms and non-living objects (d) sometimes living organisms and sometimes non-living objects Answer: (c) All the interacting organisms in an area taken together with the non-living constituents of the environment form an ecosystem. Thus, an ecosystem consists of biotic components including all living organisms and abiotic components constituting physical factors like temperature, rainfall, wind, soil and minerals.

Question 9. In the following groups of materials, which group (s) contains only non-biodegradable items? (i) Wood, paper, leather (ii) Polythene, detergent, PVC (iii) Plastic, detergent, grass (iv) Plastic, bakelitC DDT (a) (iii) (b) (iv) (c) (i) and (iii) (d) (ii) and (iv) Answer: (d) Substances that cannot be broken down by biological processes in nature are non-biodegradable. e.g. polythene, detergent, PVC, plastics, bakelite, DDT, etc. On the other hand, substances that are broken down (decomposed) by biological processes are said to be biodegradable, e.g. wood, paper, leather, grass, animal bones, etc.

Question 10. Which of the following 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: (b) Green plants prepare their food from inorganic compounds using radiant energy of the sun in the presence of chlorophyll. All green plants and blue-green algae are called producers as they can prepare food from inorganic substances by photosynthesis. Producers capture the solar energy and convert it into chemical energy.

Question 11. What will happen if deer is missing in the food chain given below? Grass → Deer → Tiger (a) The population of tiger increases. (b) The population of grass decreases. (c) Tiger will start eating grass. (d) The population of tiger decreases and the population of grass increases. Answer: (d) If deer is missing in the given food chain, there will not be sufficient food for the tigers. Some of the tigers will die because of starvation and hence, the population of tigers will decrease. Since, grass is eaten by deers, the population of grass will also increase whefl deer is missing.

Question 12. In a class activity, two students were asked to collect different items from their fellow mates and classify them as biodegradable and non- biodegradable. All the items have been identified except three. Find out which one is non-biodegradable among these? (a) Jute crafted bag (b) A sharpner (c) Empty fevistick (d) Both (b) and (c) Answer: (d) Both (b) and (c), i.e. the sharpener and the empty fevistick container. These products are made from plastic and hence are non-biodegradable.

Question 14. Which of the following limits the number of trophic levels in a food chain? (a) Decrease in energy at higher trophic levels (b) Deficient food supply (c) Polluted air (d) Water Answer: (a) Decrease in energy at higher trophic levels limits the number of trophic levels in a food chain. At each trophic level, a large portion of energy is utilised for the maintenance of organisms that occur at that trophic level. So, organisms at higher level gets less and less energy at successive levels. The. number of trophic levels are limited to 3-4 because after that, the energy available for the next level will be too small, i.e. it will be insufficient to sustain life of the organisms.

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: (c) In a food chain, if a grasshopper is eaten by a frog, then the energy transfer will be from primary consumer to secondary consumer. Grasshopper feeds on producers i.e. the grass/plants. So, it occupies the level of primary consumer. Frogs, eating grasshopper thus become the secondary consumer.

Now that you are provided all the detailed information regarding NCERT Solutions For Class 10 Science Chapter 15 Our Environment and we hope this detailed article on class 10 science chapter 15 NCERT solutions is helpful. If you have any questions regarding this article or  NCERT Solutions For Class 10 Science Chapter 15 Our Environment, drop your comments in the comment box below and we will get back to you as soon a possible.

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Our Environment CBSE Class 10 Science Revision Notes Chapter 15

Things around us is known as Environment . It consists of living component also known as biotic component and non-living component also known as Abiotic Component.

The interaction between abiotic and biotic components is defined as ecosystem.  It is a self sustaining and functional unit of biosphere. The term ecosystem was coined by Sir Arthur Tansley (OLYMPIAD)

Types of Ecosystem

There are two types of ecosystem- natural ecosystem and artificial ecosystem. The ecosystem present naturally is known as Natural Ecosystem. Example of Natural Ecosystem are forests, grasslands, deserts, ponds, lakes, rivers, estuaries, sea. The ecosystem which is man-made is known as Artificial Ecosystem . For Example Gardens, Aquariums and Agro ecosystem which is the largest manmade ecosystem.

Fig.1. Components of ecosystem

Abiotic Factors Include  - Climatic factors such as rain, temperature, wind etc. Another abiotic factor is edaphic factors such as soil, pH, minerals etc.

Biotic Factors Include -

Producers which can make their own food, such as plants, blue green algae etc.

Consumers feed on producers. Such as herbivores. In consumers there are- primary consumers, secondary consumers, tertiary consumers etc.

Carnivores are flesh eating animals.

Omnivores consume both plants and animals.

Parasites live inside and depend upon living host.

Saprophytes feed on dead remains of plants and animals.

Food Chain is defined as series of organisms in order in which organisms feeds on another organism. There are various steps in food chain in which energy is transferred, each level is known as trophic level. Energy is always transferred unidirectionally.

Characteristics of food chain

There is a unidirectional flow of energy from producers to consumers.

There are generally 3 to 4 trophic levels.

It is always straight

Organism can occupy different trophic levels in different food chain.

A 10 percent law is followed in energy transfer which was given by Raymond Lindeman. This law states that “only 10 percent of energy is transferred from one trophic level to another trophic level”. The remaining 90 percent will be used by the present trophic level in different processes. Therefore there are usually 3-4 trophic levels in a food chain.

Fig.2. Energy transfer in trophic level

Interconnection of food chain is known as Food Web . It shows how food chain are interdependent.

Characteristic of Food Web

Food webs are never straight as they are formed by interlinking of food chains.

Food web provides alternative pathways of food availability. If a particular species is destroyed, the predator can feed on an alternative species.

Food webs increase ecosystem stability.

Fig.3. Food web

Ecological Pyramids

Ecological Pyramid is a graphical representation to show biomass or bioproductivity. There are different ecological pyramids such as pyramid of biomass, pyramid of number and pyramid of energy. Pyramid of number indicates number of individuals at different trophic levels. Pyramid of biomass indicates biomass of the members of the food chain present at different trophic levels. Pyramid of energy indicates energy at different trophic levels.

Fig.4. Upright Pyramids

Pyramid of number and pyramid of biomass can be inverted also . In aquatic ecosystem pyramid of biomass is inverted.

Fig.5. Inverted pyramid

Impact of Human Activities

Biological magnification.

The concentration of harmful substances increases with every trophic level. This is known as Biomagnification . Addition of pesticides in one trophic level increases the concentration of pesticides in other trophic level.

Fig.6. Biomagnification

Ozone Layer

High UV radiation break down oxygen into oxygen atoms. These oxygen atoms when combine with oxygen, they form ozone.

Depletion of Ozone Layer

The thickness of the ozone layer over Antarctica was found to be decreased in the year 1985. This is defined as ozone depletion. This is due to excessive use of chlorofluorocarbons in refrigerators, ACs, aerosols, etc. Thinning of ozone would allow penetration of Ultraviolet rays into earth’s atmosphere causing blindness, skin cancers and mutations.

In 1987 United Nations Environment Programme (UNEP) signed an agreement to limit the usage of CFCS. This is known as Montreal Protocol .

Fig.7. Reaction of CFC with ozone

Consequences of Ozone Depletion

Exposure of UV rays causes skin cancer. UV-rays damage the eyes also. It affects humans, plants as well as animals.

Garbage Disposal

Waste materials are known as garbage. There are two types garbage - Biodegradable Garbage and Non-biodegradable Garbage.

Garbage that can be completely decomposed by the microorganism are called Biodegradable Garbage ., such as fruit and vegetable peel, sewage.

Substances which cannot be decomposed through microorganisms are known as Non-biodegradable Garbage , For Example, Plastic, Glass, Pesticide, Metals, Radioactive Elements etc.

Methods of Waste Management

Waste disposal is a very important part of day to day life. There are different methods of waste disposal management- sewage treatment plant, biogas plant, land fillings, recycling, incineration, composting and reuse.

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• Important Questions for CBSE Class 10 Science Chapter 15 - Our Environment 2024-25

CBSE Class 10 Science Chapter-15 Important Questions with Answers - Free PDF Download

Class 10 is a very important year for students as it is the first time students are attempting to write their board examinations. Their 10th board examination marks play a very important role in determining their future grades as well. In this article, we will take a detailed look into class 10 science chapter 15 important questions so that students can prepare better for their examinations. It is very important that students must utilize this time to study hard and these important questions will help students to revise better and go over the main points in the chapter. It is of importance that students be conscious of the important questions which have a high potential of coming within the exams. Students who don’t understand the topic alright must study these questions of sophistication for class 10 so that students can have a better understanding of the chapter and also know what are the important topics to specialize in.

Vedantu is a platform that provides free CBSE Solutions (NCERT) and other study materials for students. You can download Class 10 Maths NCERT Solutions to help you to revise complete syllabus and score more marks in your examinations.

Download CBSE Class 10 Science Important Questions 2024-25 PDF

Also, check CBSE Class 10 Science Important Questions for other chapters:

Related Chapters

Study Important Questions for Class 10 Chapter 15- Our Environment

Very Short Answer Questions (1 Mark)

1. A food chain always starts with

respiration 

photosynthesis 

decay 

nitrogen fixation

Ans: Photosynthesis

2. Ozone layer is damaged by- 

methane 

carbon-dioxide 

Sulphur-dioxide 

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

water 

polluted air 

deficient food supply 

decrease in energy at higher trophic levels

Ans: Decrease in energy at higher energy levels.

4. Name the main source of energy in self-sustaining ecosystem?

5. Write an aquatic food chain.

Ans: An aquatic food chain is as follows:

Phytoplankton $\to $ Zooplankton $\to $ Small fish$\to $ large fish.

6.  Which of the following is non-biodegradable-?

paper 

cloth 

Ans: plastic

7. Which of the following is not a terrestrial ecosystem-?

forest 

desert 

aquarium 

Ans: Aquarium

8. What will happen if deer is missing in the given food chain? 

Grass $\to $ Deer $\to $ Tiger

The population of tiger decreases and the population of grass increases 

The population of grass decreases 

Tiger will start eating grass 

The population of tiger increases

Ans: Population of tiger decreases and population of grass increases.

9. What is trophic level?

Ans: The position that an organism occupied in a food chain is called trophic level.

10. Write a fresh water food chain?

Ans: Phytoplankton $\to $ zooplankton $\to $ small fish $\to $ large fish.

11. The decomposers in an ecosystem-

convert organic material to inorganic forms 

convert inorganic material to simpler forms 

convert inorganic material into organic compound 

do not break down organic compound

Ans: Convert organic material to inorganic forms.

12. The second trophic level is always of-

herbivores 

autotrophs 

carnivores 

Ans: Herbivores

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

 5% 

14. Which of the following belong to the same trophic level: grasshopper, spider, grass, hawk, and lizard?

Ans: Grasshoppers and spider

15. What is acid rain?

Ans: Any form of precipitation that contains high levels of nitric and sulfuric acids is called acid rain. It can also occur in the form of snow, fog, and tiny bits of dry material that settle to Earth.

16. The ecosystem of earth is known as-

biome 

community 

biosphere 

association

Ans: Biosphere

17. Which of the following constitute a food chain?

Grass, goat and human 

Goat, cow and elephant 

Grass fish and goat 

Grass, wheat and mango

Ans: Grass, goat, human.

18. Flow of energy in an ecosystem is always-

Unidirectional 

bidirectional 

multidirectional 

no specific direction.

Ans: Unidirectional

19. Name the main source of energy in any self-sustaining system.

20. Which of the following in not a part of biotic component of an ecosystem: water, algae, fish, bacteria?

21. Which of the following limits the of trophic levels in a food chain-

polluted 

Ans: Decrease in energy at higher trophic levels.

22. In natural ecosystems, decomposers include-

only bacteria and fungi 

only microscopic animals

herbivores and carnivores 

both (b) and (c)

Ans: Only bacteria and fungi

23. All living organisms of the earth constitute a-

biotic community 

24. What are the various steps of food chains called?

Ans: Trophic levels

25. Which one is not biodegradable: paper, plastic, sewage?

Ans: Plastic

26. Which of the following groups contain only biodegradable items?

Grass, flowers and leather 

Grass, wood and plastic 

Fruit peels, cake and lime-juice

Cake, wood and grass

Ans: Groups (a), (c) and (d).

27. Which of the following constitute a food chain?

Grass, wheat and mango 

Grass, fish and goat.

Ans: Grass, goat, human

28. Which of the following are environment-friendly practices?

Carrying cloth-bag to put purchases in while shopping. 

Switching off unnecessary lights and fans. 

Walking to school instead of getting your mother to drop you on her scooter. 

All of the above.

Ans: All of the above.

29. Construct a food chain composing the following Snake, Hawk, Rats, Plants.

Ans: Plants $\to $ Rats $\to $ Snake $\to $ Hawks

30. Name the process that is a direct outcome of excessive burning of fossil fuels?

Ans: Global warming is a direct outcome of excessive burning of fossil fuels.

31. Using Kulhads as disposable cups to serve tea in trains, proved to be a bad idea. Why?

Ans:  Yes, because making Kulhads on large scales leads to the loss of top soil.

32. Why is plastic not degraded by bacteria?

Ans: Plastic is not degraded by bacteria because they do not have enzymes which is used to degrade plastic.

Short Answer Questions (2 Marks)

1. Give scientific terms for the following-

(a) The process of eating and being eaten

Ans: Food chain

(b) The relationship between abiotic and biotic component

Ans: Ecosystem

2. What is meant by environment? Name its components.

Ans: All the surroundings which have an impact on human lives is called an environment. It has two components-

(a) Abiotic component (non-living)

(b) Biotic component (living)

3. What is 10% law? Give an example

Ans: Only 10% of energy is available at the next trophic level in 10% law. For example-Suppose 1000 Joules of light energy emitted by the sun falls on the plants. Then the plants or first trophic level has 10 joules of energy in it. Now according to 10 percent law, only 10% of 10 joules of energy (which is 1 joule) will be available for transfer to the next trophic level, so that the herbivore will have only 1 joule of energy stored as food at the second trophic level. 10% of the remaining 1 joule will be transferred to third trophic level of carnivore. So, the energy available in the lion as food will be only 0.1 joule.

4. What is artificial ecosystem? Give two examples.

Ans: Ecosystem which are made by humans are known as artificial ecosystem. For example- Dams, parks.

5. Energy transfer is said to be unidirectional whereas biochemical transfer is said to be cyclic. Why?

Ans: Energy transfer is unidirectional because when the energy is absorbed by autotrophs from the sun, it is never reabsorbed by it. And when consumers eat up the producers directly or indirectly the energy transferred in this process can never be reversed in the food chain. In biogeochemical transfer is cyclic because chemical elements move from environment to organism and back to the environment.

6. Why is there a need to ban the use of polythene bags?

Ans: Polythene bags need to be banned because-

They are non-biodegradable.

Cannot be able to decompose them. 

One of the cause of land pollution.

7. What is the significance of food chain?

Ans: Significance of food chain is-

It is used to transmit energy from one organism to the next.

It is the method by which a particular organism collects its food.

It is a way of depicting the flow of energy.

8. How would you dispose the following wastes?

(a) domestic wastes like vegetables peels

Ans: Domestic wastes should be disposed off in a pit.

(b) industrial wastes

Ans: Industrial wastes should be treated first to remove poisonous chemicals and then disposed off in water resources.

9. Why vegetarian food habit helps us in getting more energy?

Ans: Vegetarians obtain food directly from plants so due to 10 percent rule only 10% of energy is available at the successive level than previous level thus, vegetarian food habit helps us in getting more energy.

10. Write a food chain having two trophic levels.

Ans: Grass $\to $ deer 

11. Diagrammatically represent the transfer of energy in a food chain.

12. Consider the following food chains-

Plants $\to $ mice $\to $ hawks

If energy available at the producer level in both the food chains is 100J. In which case will hawks get more energy and how much?

Ans: Hawk get more energy in food chain having three trophic levels.

Plants $(100J)$ $\to $ mice $(10J)$ $\to $ hawks $(1J)$

Thus, Energy available to hawk is $\text{1J}$.

13. Why is there a need to ban the use of polythene bags?

14. What are the two functions of ecosystem?

Ans: The two functions of ecosystem are-

Ecosystem regulates essential ecological processes and life support systems and renders stability. 

It regulates and maintains itself and resists any stresses or disturbances upto a certain limit. This is known as cybernetic system.

15. What percentage of solar energy is trapped and utilized by plants?

Ans: 1% of solar energy is trapped and utilized by plants.

16. What are the harmful effects of acid rain?

Ans: The harmful effects of acid rain are-

It effects human nervous system, respiratory system and digestive system.

It can also leach aluminium from the soil.

It affects soil fauna and lead to reduced forest productivity.

It may cause extensive damage to materials and terrestrial ecosystems such as water, fish, vegetation, soils, building etc.

17. Differentiate between abiotic and biotic components of ecosystem.

Ans : The difference between abiotic and biotic components of ecosystem is as follows:

18. Give any two methods reducing the problem of waste disposal.

Ans: The two methods reducing the problem of waste disposal are-

Practicing the 3 R's: Reduce, Reuse and Recycle.

By throwing biodegradable and non-biodegradable waste into separate dustbins so that recycling can be done easily.

19. Give reason: “Life on earth depends on the sun.”

Ans: All living beings needs energy to be alive and they get energy in the form of food. And the food directly or indirectly comes from green plants. Sun plays an important role to produce food in the process of photosynthesis.

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

Ans: The position that an organism occupied in a food chain is called trophic level. An example of a food chain and state the different trophic level in it is as follows:

Plants (Producer) $\to $ Deer (Primary consumer)  $\to $ Lion (Secondary consumer)

21. What is the role of decomposers in the ecosystem?

Ans: Decomposers play a critical role in the flow of energy through an ecosystem. They break apart dead organisms into simpler inorganic materials, making nutrients available to primary producers.

22. What is ozone and how does it affect any ecosystem?

Ans: Ozone is a gas composed of three atoms of oxygen. Its molecular formula is ${{O}_{3}}$ . It f orms a layer in the upper atmosphere. It is very essential for the life on this planet. It shields the surface of the earth from ultraviolet radiation (UV) coming from sun as these radiations are very harmful causing skin cancer and cataract in humans. It also does harm to the crops.

23. How can you help in reducing the problems of waste disposal? Give any two methods.

24. What will happen if we kill all the organisms in one trophic level?

Ans: If all the organisms of one trophic level are killed, the food chain will become completely imbalanced. The organisms in the immediate higher trophic level will die out due to unavailability of food. Thus, the whole food chain will collapse. 

25. 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?

Ans: Yes, the impact of removing all the organisms in a trophic level will be different for different trophic levels. It will not be possible to remove any organism in any trophic level without causing damage to the ecosystem.

26. If all the wastes we generate is biodegradable, will this have no impact on the environment?

Ans: If all the wastes we generate is biodegradable, it will have impact on the environment-

The production of harmful gases causes pollution.

Microbes will not be able to decompose all the biodegradable waste.

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

Ans:  The problems caused by non-biodegradable wastes that we generate are-

Since, waste cannot be broken down into simpler forms hence they keep on accumulating which leads to pollution.

They cause diseases.

It also causes biological magnification. 

28. What limits the number of trophic levels in a food chain.

Ans: The loss of energy from one trophic level to the next limits the number of trophic levels in a food chain.

29. What is the harm of clay cups?

Ans: The c lay cups contain a chemical known as styrene that causes side effects such as fatigue, irritation and many more health problems. It causes depletion of top fertile soil.

30. State one reason to justify the position of man at the apex of most food chains?

Ans:  As humans are an intelligent organism so they can take advantage of position by manipulation. This is the main reason the position of man at the apex of most food chains.

31. Which food chains are advantageous in terms of energy?

Ans: Short food chains i.e two step chains  are more efficient in terms of energy.

32. If all the wastes we generate is bio-degradable what impact may this have on the environment?

Ans:   If all the wastes we generate is biodegradable, it will have impact on the environment-

33. Write the harmful effect of ozone depletion.

Ans: The harmful effects of ozone depletion are-

Causes skin cancers

Causes eye cataracts

Leads to immune deficiency disorders. 

Affect plant growth

Reduces agricultural productivity.

34. Which of the following will have the maximum concentration of harmful chemicals in its body? Peacock, frog, Grass, Snake, Grasshopper

Ans: Peacock will have maximum concentration of harmful chemicals in its body among Peacock, frog, Grass, Snake, Grasshopper.

35. Why energy of herbivores never come back to the autographs?

Ans: Energy of herbivorous never comes back to autographs because flow of energy is always unidirectional in food chain.

36. Give the correct sequence of various & trophic levels in a food chain.

Ans: The correct sequence of various & trophic levels in a food chain is as follows:

37. What is biological magnification and give its causes?

Ans: Gathering of various unimportant and harmful substances by organisms at different levels of a food chain is known as biological magnification. Its causes are the excessive use of pesticides which enter our food chain. As The bottom feeders of a food chain consume these and gradually it is carried to the top of that particular food chain.

38. DDT has entered food chain. Which food habit is safer- vegetarian or non-vegetarian?

Ans: Vegetarian habit is safer. Because less DDT will accumulate in our body. And due to Bio magnification higher level of DDT in higher trophic levels is found.

39. Aquarium requires regular cleaning whereas lakes normally do not. Why?

Ans: Lake has more diverse forms of life due to that they have larger number of food chains which leads to natural cleaning. Thus, the ecosystem is more stable. The aquarium has a very limited number of food chains and unable to sustain itself. That’s why Aquarium requires regular cleaning whereas lakes normally do not.

40. How will accumulation of bio degradable waste effect our environment?

Ans: The accumulation of bio degradable waste effect our environment because-

Short Answer Questions (3 Marks)

1. DDT that was sprayed in minute amount on food plants was detected in high concentration in man? How did it happen? Explain.

Ans:  The phenomenon behind this is biological magnification because when DDT are used to protect crops from diseases and pests. They enter the soil. From soil these are absorbed by plants. And then consumed by organisms. They get accumulated at different trophic levels. As the human beings occupy the top position in any food chain, maximum concentration of such harmful chemicals get accumulated in the bodies of man.

2. Describe how ozone layer is formed?

Ans: Formation of the ozone layer is as follows-

During the origin of life Earth, some of underwater micro-organisms were to photosynthesize due to molecular oxygen was released in atmosphere. 

This oxygen is released to stratosphere where it began to react with ultraviolet radiations from sun to form free oxygen (O). 

Free oxygen combines with molecular oxygen to form ozone the reaction is given as-

${{\text{O}}_{\text{2}}}\text{+u}\text{.v light O+O}$

$\text{2O+2}{{\text{O}}_{\text{2}}}\text{2}{{\text{O}}_{\text{3}}}\text{(ozone)}$

3. What are the major components of environment?

Ans: The major components of environment are as follows-

Lithosphere - It is the solid outer section of Earth which includes Earth's crust. It extends from the surface of Earth to a depth of about $70-100km$  .The main component of lithosphere is earth’s tectonic plates.

Hydrosphere- It comprises of all forms of water bodies on earth including marine (oceans, seas) freshwater (rivers, lakes, ponds, streams) and groundwater resources etc. It covers $71\%$ of earth’s surface. $97\%$ of water found on Earth is in the oceans in the form of salt water. Only $3\%$ of water on Earth is freshwater. Out of this, $30.8\%$ is available as groundwater and $68.9\%$ is in frozen forms as in glaciers. Amount of $0.3\%$ is available in rivers, reservoirs and lakes and is easily accessible to man.

Atmosphere – It is gaseous layer enveloping the Earth. The atmosphere with oxygen in abundance is unique to Earth and sustains life. . It mainly comprises $78.08\%$ nitrogen, $20.95\%$ oxygen, $0.93\%$ argon, $0.039\%$ carbon dioxide, and traces of hydrogen, helium, and noble gases. The amount of water vapor present is variable $\left( 0-3 \right)\%$ Earth's atmosphere has a series of layers, each with its own specific traits.

Biosphere- It refers to all the regions on Earth where life exists. The ecosystems that support life could be in soil, air, water or land.

4. Why are some substances biodegradables and some non-biodegradable?

Ans: Some substances are biodegradable and some non-biodegradable because some substances can be decomposed by microorganisms and some cannot as he micro-organisms like bacteria and other decomposers organisms (called saprophytes) present in our environment specific in their action. They break down the materials or products made from natural materials (paper) as they have some peculiar enzymes for this process. But as enzymes are specific in their action, these cannot break down many man-made materials likes plastic. These can be acted upon by physical processes but not by biological processes. Therefore, these types of substances persist for long time and cannot be decomposed into simpler substances.

5. Explain why a food chain consists of few steps only? Write a food chain having five steps.

Ans: This is because of 10% law as only 10% of energy is available at the next trophic level. As If a food chain has six or more than six steps, energy is not sufficient for the survival of organism at that trophic level. A food chain having five steps is as follows:

Grass $\to $ insects $\to $ frog $\to $ snake $\to $ eagle

6. What is the difference between food chain and food web?

Ans:   Food chain- The food chain describes which organism in the environment eats another organism. In ecology, the food chain is the series of transfer of matter and energy from organisms to organisms in the form of food. It is the sequence of events in an environment or ecosystem in which one living organism eats another living organism and another larger organism eats that organism later. It is a part of food web.

Food web- Food web means, mutually, many food chains via which energy flows into the ecosystem. The Food web is an interconnection of the various food web. A food web is just like the food chain except that the food web is larger than the food chain. Rarely, one organism is eaten by multiple predators, or it consumes many other organisms. The food webs are more complex.

7. What is biological magnification? Illustrate with the help of example.

Ans: Biological magnification refers to the process where toxic substances move up the food chain and become more concentrated at each level. For example-

Water                  $\to $       Phytoplankton       $\to $     Fish            $\to $       Bird 

$ \text{(0}\text{.02 ppm}\text{of harmful chemical)}$   $\left( 5.0ppm \right)$      $\left( \text{240ppm} \right)$        $\left( \text{1600ppm} \right)$

8. What are the ill effects of ozone layer depletion?

Ans: The ill effects of ozone layer depletion are-

Human health: -

Agriculture and plant life: -

Marine environment

Photosynthesizing phytoplankton presents in the sea which also help in reducing the 

global warming.

The lives of many plastics have been found to be shortened due to exposure to UV radiations.

9. What is the significance of food chains?

Ans: The significance of food chains is-

It is a means of transfer of food from one trophic level to another. 

It provides information about the living component of an ecosystem. 

It helps us in understanding the interactions and interdependence amongst different organism in an ecosystem. 

It is a pathway for the flow of energy in any ecosystem.

10. How Garbage pollution can be controlled?

Ans: Garbage pollution can be controlled as-

By practicing 3 R’s .

By recycling of certain wastes products like plastic and paper. 

By making use of biodegradable products as much as we can. 

By producing biogas from the organic wastes. 

Proper separation of biodegradable and non-bio-degradable waste during disposal. 

By making the compost of biodegradable wastes by burying them under soil.

11. What are the components of an ecosystem? Explain with examples

Ans: An ecosystem has two major components-

Biotic Components- It includes producers (plants), consumers (animals) and decomposers (bacteria and fungi). 

Producers- Organisms which are able to photosynthesis are called producers. It includes all green plants. 

Consumers- Organisms which depends upon other are called consumers. It is of few types- 

Herbivores- Animals which directly depends upon plants. 

Carnivores- These animals eat herbivores.

Secondary carnivores- Animals which depends upon carnivores. 

Tertiary carnivores- Largest animals which depends upon secondary carnivores. 

Decomposers- These organisms depend upon dead plants and animals. They change complex organic substances into simple inorganic substances. 

Abiotic components- Non-living components. It include physical and chemical factors such as light, water, soil, air temperature, oxygen, carbon, nitrogen and other nutrients.

12. Write any three activities which are eco-friendly.

Ans: The three activities which are eco-friendly.

S eparation of biodegradable and non-biodegradable substances.

Rainwater harvesting.

13. Energy transfer is said to be unidirectional whereas biochemical transfer is said be cyclic. Why?

14. Give difference between producers and consumers. Mention one example of each.

Ans: The difference between producers and consumers is as follows:

15. There are no predators for tiger or lion. Why?

Ans: Lions and tigers are at the highest trophic level. They are largest animals which feed upon the secondary carnivores like wolves etc. they are not killed and eaten by other animals.

16. What are the measures to protect ozone depletion?

Ans: The measures to protect ozone depletion are-

Avoid the consumption of gases dangerous to the ozone layer, due to their content or manufacturing process. Some of the most dangerous gases are CFCs (chlorofluorocarbons), halogenated hydrocarbon, methyl bromide and nitrous oxide.

Minimize the use of cars. The best transport option is urban, bicycle, or walking. If you use a car to a destination, try to carpool with others to decrease the use of cars in order to pollute less and save.

Do not use cleaning products that are harmful to the environment and to us. Many cleaning products contain solvents and substances corrosive, but you can replace these dangerous substances with non-toxic products such as vinegar or bicarbonate.

Buy local products. In this way, you not only get fresh products but you avoid consuming food that has travelled long distances. As the more distance travelled, the more nitrous oxide is produced due to the medium used to transport that product.

Maintain air conditioners, as their malfunctions cause CFC to escape into the atmosphere.

17. Describe three biotic components of ecosystem. Also give examples.

Ans: The three biotic components of ecosystem are-

Producers- All the green plants have a unique capability to synthesis organic substance such as sugar and starch by the process of photosynthesis. Therefore, they are called producers. 

Consumers- These are the living organisms which depend directly or indirectly on plants for their food. Consumers may be herbivore, carnivores, and omnivores. Example- Lion, tiger.

Decomposers- Decomposers are the organisms which depend upon the dead and decaying organisms their waste material. They form important link between living and non-living components. Example-algae.

18. What is the role of decomposers in an ecosystem?

Ans: Decomposers play a critical role in the flow of energy through an ecosystem. They break apart dead organisms into simpler inorganic materials, making nutrients available to primary producers. they are the important link between living and non-living components of environments. 

19. What will happen if we kill all the organisms in one trophic level?

Ans: If all the organisms of one trophic level are killed, the food chain will become completely imbalanced. The organisms in the immediate higher trophic level will die out due to unavailability of food. 

If the herbivores are killed, then the carnivores would not able be to get food and would die. 

If carnivores are killed, then the population of herbivores would increase to unsustainable level. 

If producers are killed, then the nutrient cycle in the area would not be completed.

Thus, the whole food chain will collapse. 

20. What is Ozone? How does it affect any ecosystem?

Ans: Ozone is a gas composed of three atoms of oxygen. Its molecular formula is ${{O}_{3}}$ . It f orms a layer in the upper atmosphere. It is very essential for the life on this planet. It shields the surface of the earth from ultra-violet radiation (UV) coming from sun as these radiations are very harmful causing skin cancer and cataract in humans. It also does harm to the crops.

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

22. Give any two ways in which biodegradable substances would affect the environment.

(a) They will serve as breeding ground for flies and mosquitoes which are carriers of 3disease like cholera, malaria etc. Give any two ways in which non-biodegradable substances would affect the environment.

Ans: Excess use of non-biodegradable pesticide and fertilizers run off with rain water to water bodies cause water pollution.

(b) They produce foul smell, thus causing air pollution.

Ans: They may choke the sever system of city or town that may overflow over roads.

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

Ans: Biological magnification refers to the process where toxic substances move up the food chain and become more concentrated at each level. The concentration of harmful chemicals will be different at different trophic levels. It will be lowest in the first trophic level and highest in the last trophic level of the food chain.

24. Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Ans: Ozone layer stops ultraviolet radiations from the Sun from reaching the earth. Ultraviolet rays cause cancer, cataract and damage to the immune system of human beings.

To limit this damage following steps should be taken-

We should minimize the use of vehicles.

We should not encourage the burning of fossil fuels. 

It is now mandatory for all the manufacturing companies to make CFC- free refrigerators throughout the world.

In $1987$, United Nations Environment Programme (UNEP) succeeded I forging an agreement between nations to freeze chlorofluorocarbons (CFCs) production to $1986$ levels. CFCs are the main cause of ozone layer depletion.

25. Why some substances are degraded and others not?

Ans: Some substances are degraded and others not because different components of food are changed to simpler substances by digestive enzymes and these enzymes are very much specific in nature and action. Similarly, substances are broken down by bacteria and saprophytes. They are also very specific in action and breakdown of the particular substance. Therefore, some substances are biodegradable and other are non-biodegradable.

25. What will happen if all the carnivores are removed from the earth?

Ans: If all the carnivores are removed from the earth, the population of herbivores will increase. Large population of herbivores will overgraze. And all plants will disappear from the earth surface and ultimately the earth may become a desert. The biosphere will get disturbed which will lead to end of life on earth.

26. What will happen to grasslands if all the grazers are removed from there?

Ans: If all the grazers are removed from grassland, then because carnivores keep the populations of other carnivores and herbivores in check. If there were no carnivores, the herbivore populations would explode and they will rapidly consume large amounts of plants and fungi, growing until there is not enough food to sustain them. Eventually, the herbivores would starve, leaving only those plants that were distasteful or poisonous to them. Species diversity would, therefore, drop dramatically.

27. The number of malarial patients in a village increase tremendously, when a large number of frogs were exported from the village. What could be the cause for it? Explain the help of food chain.

Ans: Phytoplankton $\to $Zooplankton  $\to $ Mosquito larva $\to $ Frog 

In the absence of frog, more mosquito larva survives, giving rise to large number of mosquitoes which cause increase incidence of malaria.

28. What are decomposers and what is the importance of them in the ecosystem?

Ans: Decomposers are the organisms which depend upon the dead and decaying organisms their waste material. They form important link between living and non-living components. They are important because Decomposers decompose the complex substances into simple ones so that plants can use it again.

29. Why food chains consist of three or four steps only?

Ans: Food chains consist of three or four steps only is because of 10% law as only 10% of energy is available at the next trophic level. As If a food chain has six or more than six steps, energy is not sufficient for the survival of organism at that trophic level.

30. What will happen if decomposers are not there in the environment?

Ans:  If decomposers are not there in the environment, then dead leaves, dead insects, and dead animals would pile up everywhere. So, presence of decomposers is essential for the replenishment of soil and biogeochemical cycle of elements or substances.

31. Are plants actually producers of energy?

Ans: No, plants are not actually producers of energy, they can trap the energy of sun and can convert solar energy into chemical energy in the form of carbohydrates and other food materials so they are called transducers.

32. Look at the following figures. Choose the correct one and give reason for your Choice.

Ans: Figure A is correct.

In an ecosystem, the number of individuals at producer level is maximum. This number reduces at each successive level. Therefore, the shape is a pyramid with broader base and tapering apex. 

On an average 10% of the food changes into body mass and is available for the next level of consumers.

33. It is the responsibility of the government to arrange for the management and disposal of waste. As an individual you have no role to play. Do you agree? Support your answers with two reasons.

Ans: I do not agree. As an individual, I also have the responsibility and can contribute in the following ways:

Practising 3 R’s.

Make compost pit for bio degradable waste.

Disposal of garbage only at appropriate places.

Cut down waste generation.

Recycle non-biodegradable waste.

Important Question of Our Environment Class 10 - Free PDF Download

The chapter on our environment is a very crucial chapter for students as it gives students insight into how the environment serves every organism in the animal kingdom. Students need to understand the chapter as it shows students the functioning of the food chain system in the environment. Students will also learn about the various functions of the ecosystem and how it serves various organisms. The differentiation between biotic and abiotic components of the ecosystem. Students will learn how to define an environment and all of its components. Chapter 15 of class 10 science can be found easily on the Vedantu website. The website allows for easy access to its important questions and also it is easily downloadable. Students will find these notes to be helpful during the preparation of their examinations, these important questions are easily downloadable in a pdf format. Students who find it difficult to study on the screen can also print this material so they don't waste too much time on the internet.

Chapter 15 Class 10 Science Important Concepts 

This chapter on “our environment” holds importance in various aspects as it can help students understand the chapter as it shows students the functioning of the food chain system in the environment. There are some important concepts students should be familiar with when studying this subject and this includes the following

Photosynthesis

The process where green plants convert solar energy into chemical energy is known as photosynthesis. Inorganic molecules like carbon dioxide and water are used to synthesize food like starch. The process starts with the trapping of sunlight which is done by the chlorophyll present in green plants. Raw materials such as water and carbon dioxide are the prime ingredients for photosynthesis. Water is absorbed from the soil and carbon dioxide is taken from the atmosphere. The sunlight is the catalyst here in this process which converts the carbon dioxide and water into starch and oxygen. Starch is used up by the plant whereas the oxygen is left out to the atmosphere for other organisms to utilize.

Ozone Layer 

The ozone layer is a layer that protects us from the extremely harmful rays of the sun. The ozone layer is a layer that is invisible in the atmosphere but can protect us from the harmful UV rays that the sun puts out. This chapter focuses on how the ozone layer protects us and what damages it. CFCs damage the ozone layer and create holes in the layer, this can only be avoided if we start taking better care of the environment and stop polluting so much. The more carbon dioxide there in the air the more it gets affected. 

Energy Transfer is Said to Unidirectional

Energy transfer is said to be unidirectional because any energy that is lost to heat is said to the environment can’t be reutilized by plants for photosynthesis. Energy decreases from each trophic level by around 10 percent and thus it cannot be used again. 

Significance of Food Chain

It means the transfer of food from one trophic level to another. It provides information about the various living components in our ecosystem. we can get a better understanding of the relation of different organisms that are present in our ecosystem. It is a pathway of flow from one ecosystem to another. 

Harmful Effects of Acid Rain 

It affects historical monuments and old buildings especially those made from marble. For example the taj mahal 

There are certain bacteria that are good for maintaining soil fertility and this can be killed in acid rain. 

It makes the water in lakes, ponds, and other water bodies bad for aquatic life.

Acid rain destroys the fertility of the soil which makes it hard to grow cereal crops and trees. 

Life on Earth Depends on the Sun 

For the earth, the sun is the ultimate source of energy. On various trophic levels, the plants convert the solar energy into chemical energy which is also transferred to various organisms. The energy that is also stored in various fossil fuels is basically transferred to solar energy because fossil fuel is made up of different plants and animals. Therefore we can see how solar energy is transferred into various forms of energy to consume. 

Energy Received from Vegetarian Meals 

Any organism that consumes vegetarian food is close to the product level that gets the maximum level of energy as compared to an organism of a higher trophic level because only 10 percent of the energy available is available at successive levels than any previous level. 

Class 10 Science Chapter 15 Important Questions

Why do vegetarian food habits help us get more energy?

Write a food chain that has two trophic levels.

What percentage of solar energy is trapped and utilized by plants?

What are the harmful effects of acid rain?

Differentiate between biotic and abiotic components of the ecosystem.

Name the process that is a direct outcome of excessive burning of fuel.

Why is plastic not degraded by bacteria?

What is meant by the environment? Nam its components.

What is the 10% law? Name its components.

What is an artificial ecosystem? Name its components.

Why is there a need to ban polythene bags?

Diagrammatically represent the transfer of food chains 

What are the two functions of the ecosystem?

Benefits of Important Question of Our Environment Class 10

Science is a very vast subject and can be quite difficult. So by using the right guide material like the ones found in Vedantu students can utilize it to their maximum and score the best marks possible. 

Students studying this chapter on the environment will find that it helps in higher studies and help them understand the basics in any bio-based subject in the future.

Students can utilize and practice the important questions so that they can ace their examinations. 

This is a fundamental subject for high school kids and plays an important role in higher studies

.It provides students with a structure with which they will study for his or her upcoming examinations.

Students don’t need to worry about the relevance of these questions as they're all cross-checked and updated consistently with the newest CBSE guidelines and rules . therefore the information in Vedantu is genuine and reliable.

Students can use this text to use their time wisely, it helps boost their confidence after consistent practice and students can plan their preparation accordingly.

Conclusion 

This chapter takes into account various components of the ecosystem. It starts from how the food chain works and how the various organisms in the environment help each other, the chapter talks about all the harms in the environment and all the energy that can be consumed from the sun. This article on chapter 15 class 10 science important questions will help guide students through their preparations. Students will be able to study more efficiently by using these important questions. These questions will help students to understand the topics that have more weightage than others and thus students will find that they don't have to waste time studying irrelevant topics. This article is important for students to understand the various concepts in the chapter. Students can work more diligently towards their goals and strive for higher marks as well. These important questions make sure that students are aware of the various topics in the chapter and with constant practice students will learn to tackle the difficult questions in the examinations.

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FAQs on Important Questions for CBSE Class 10 Science Chapter 15 - Our Environment 2024-25

Q1. How can we protect our environment according to Chapter 15 of Class 10 Science?

Ans: We disturb and destroy our environment by adding waste to it. Everything that we do or don't do affects our environment. We share our environment with thousands of other living and non-living organisms. To protect our environment, we can reduce the amount of waste that we produce. We can reduce the usage of products that have a short shelf life and produce waste after their disposal such as plastics. We can recycle various products such as paper and use them again. We can limit the usage of products that emit CFCs into the environment such as refrigerators and air conditioners.

Q2. What is the environment as mentioned in Chapter 15 of Class 10 Science?

Ans: The environment is a very broad term. It includes human beings, plants, animals, books around us, the soil and everything else around us. The environment provides us with the land on which we live, the air we breathe, the food we eat and the clothes we wear. Environment makes life possible on Earth. It contains various essential nutrients such as oxygen, carbon dioxide and nitrogen. Water circulates in the environment, thereby, replenishing our rivers and groundwater and providing sufficient water and moisture to our crops.

Q3. What are the types of consumers mentioned in Chapter 15 of Class 10 Science?

Ans: The food we eat provides us with the energy to function. The three categories of consumers are primary consumers, secondary consumers and tertiary consumers. Primary consumers are animals that feed on the producers (the green plants). They are called herbivores, for example, deer. The secondary consumers are those that feed on primary consumers and are called carnivores. The third level of the food chain is occupied by tertiary consumers. Primary and secondary consumers are their source of food such as vultures and pythons. To read more about this chapter visit Vedantu’s official website (vedantu.com) and download the study materials free of cost.

Q4. Why did the United Nations act to control the production of chlorofluorocarbons (CFC) used in refrigerators according to Chapter 15 of Class 10 Science?

Ans: UNEP reached an agreement in 1987 to freeze the production of CFCs at the 1986 level. Three atoms of oxygen combine to form a molecule of the zone. The presence of the ozone layer hundreds of kilometres above the surface protects us from the harmful ultraviolet rays of the sun. If these rays reach us they can cause serious damage to organisms including skin cancer in humans. The layer of ozone in the atmosphere had been depleting because of the increase in the concentration of CFCs in the environment. Acknowledging the seriousness of the issue, the UN finalized the agreement.

Q5. What role does our environment play according to Chapter 15 of Class 10 Science?

Ans: Earth has a unique place in our solar system because it has elements that make life possible. Everything that surrounds us is our environment. The resources we need to live- oxygen and water- are provided by the environment. The same environment recycles life-giving resources as they are not present in unlimited quantities. The environment protects us from the harmful rays of the sun. The sunrays that reach us after travelling through various layers of the environment enable plants to make food and produce oxygen.

CBSE Class 10 Science Important Questions

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Our Environment of Class 10

Our environment .

Man has always inhabited two worlds. One is the natural world of plants, animals soil, air and water,of which we are also a component while, the other is the world of society that we have created ourselves using science, technology and political organization. Both of these are essential for our survival but integrating them sometimes causes alterations in the environment. Thus, to ensure a sustainable future for ourselves and future generations. We need to know about out environment, its working and our role in its working, protection and management.

Environment

Environment is defined as the surroundings in which the organism lives.

Environmental science is the systematic, scientific study of our environment as well as our place in it. This study gives us the scientific foundations to understand certain important areas of economic importance that are essential for the existence, such as agriculture, forestry and fisheries. This study also gives us a basis for predicting, preventing and finding remedial measures to minimize pollution. It helps us to understand the consequences of the human intervention in the natural processes, such as construction of dams on rivers, diversion of rivers, cutting of forests, etc.

The environment may be the physical environment, the chemical environment or the biological environment. Thus, the environment has two components

Biotic component: It is the living component of the environment. All the living organisms are included in it.

Abiotic component: It is the non-living component of the environment. The abiotic components are the physical factors such as:

• Climatic factors like light, wind, humidity, temperature, precipitation etc.
• Edaphic factors like soil texture, minerals, pH, topography etc.

At the time of its origin, earth was a fire ball having a temperature of 5000-6000°C at its outer surface. As it cooled, the simple molecules like water (in the form of vapours), methane, helium and ammonia came into existence. At that time these gases were very hot and the molecules were moving at a very high speed. Lighter gases such as hydrogen and helium escaped into the atmosphere. No oxygen was present at that time. As the autotrophs were developed, the oxygen was added to atmosphere by their photosynthetic activity. Due to the volcanic eruptions, most of the minor constituents rich in sulphurous gases entered into atmosphere.

The planet earth along with the atmosphere i.e., air, land (lithosphere) and water (hydrosphere) that sustains life is called biosphere.

It extends downward into the oceans to depth of about 10.67 km and vertically into the air to about 10km where life is found to exist.

At a height between 15 to 60 km in the upper atmosphere, a layer of ozone (O3) gas exists. This ozone layer surrounds the earth as an umbrella and absorbs the ultraviolet radiations coming from the sun to the earth as they are very harmful for living organism surviving on earth. An ionic layer is also present above this ozone layer which reflects the radio waves.

THE CONTENT OF PRESENT ATMOSPHERE

Nitrogen 78 per cent

Oxygen 21 per cent

Carbon dioxide 0.032 to 0.047 per cent

Other gases 0.07 per cent

Water vapours A very less amount and its percentage is variable.

• Structure And Functions Of Biosphere
• Types Of Ecosystem
• Components Of Ecosystem
• Trophic Level
• Flow Of Energy
• Ecological Pyramids
• Biogeochemical Cycles
• Biodiversity
• Ozone Layer And Its Depletion
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Assignments Class 10 Science Our Environment

Please refer to Assignments Class 10 Science Our Environment Chapter 15 with solved questions and answers. We have provided Class 10 Science Assignments for all chapters on our website. These problems and solutions for Chapter 15 Our Environment Class 10 Science have been prepared as per the latest syllabus and books issued for the current academic year. Learn these solved important questions to get more marks in your class tests and examinations.

Our Environment Assignments Class 10 Science

Very Short Answer Type Questions 

Question. Name two natural ecosystem. Answer : Pond ecosystem and forest ecosystem.

Question. Which component of sunlight is used for the formation of ozone? Answer : Ultra violet radiation.

Question. What is bad Ozone? Answer : Ozone at ground level is deadly poisonous and is called as bad Ozone.

Question. Name 4 abiotic components of any ecosystem. Answer : Temperature, rainfall, wind, soil.

Question. Name two artificial ecosystem. Answer : Garden and crop-field.

Question. Name the natural cleansing agent in an ecosystem. Answer : Decomposers, scavengers

Short Answer Type Questions 

Question. Minimum energy is available at highest trophic level while maximum energy is at lowest level. Explain. Answer : Since non-biodegradable substances cannot be broken down into simpler forms hence they keep on accumulating in nature causing ecological imbalance. 

Question. Give one advantage and one disadvantage of Ozone. Answer : Advantage of Ozone–When it is in the stratosphere it does not allow the ultraviolet radiations to reach the earth, as UV radiations cause skin cancer and cataract. Disadvantage of ozone: On ground level ozone is poisonous gas.

Question. Aquarium requires regular cleaning whereas lakes normally do not. Why? Answer: Normally a lake has more diverse forms of life and hence a larger number of food chains. This leads to natural cleaning. Thus, the ecosystem is more stable. The aquarium has a very limited number of food chains and unable to sustain itself. But, sometimes there is excessive growth of algae in lake. Then it also needs to be cleaned.

Question. Why is plastic not degraded by bacteria? Answer: Plastic is not degraded by bacteria because they do not have enzymes to degrade plastic.

Question. Using Kulhads as disposable cups to serve tea in trains, proved to be a bad idea. Why? Answer: Making Kulhads on large scales leads to the loss of top soil. 

Question. DDT has entered food chain. Which food habit is safer- vegetarian or nonvegetarian? Answer: Vegetarian habit is safer. Being closer to producers, less DDT will accumulate in our body. Bio magnification leads to higher level of DDT in higher trophic levels.

Question. Why are green plants called producers?  Answer : Green plants can prepare complex organic matter as food from simple inorganic substances like CO 2 , H 2 O in presence of sunlight and chlorophyll. They produce food and hence called producers.

Question. What is biological magnification? Answer : The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification. As human beings occupy highest trophic level its maximum concentration was found in human beings only, which resulted in neurological disorders due to damaging of CNS (Central Nervous System).

Question. What are the problems caused by the non-biodegradable waste that we generate? Answer : Non-biodegradable waste doesn’t decompose under the action of bacteria and other microorganisms. • When these substances, e.g., polythene, plastics are buried under soil render that area barren and leads to soil pollution. • These wastes don’t burn completely in presence of oxygen and release toxic gases which causes air pollution. • The substances may be harmful on accumulating in food chain like DDT due to biomagnification.

Question. Why is damage to ozone layer a cause for concern? What steps are being taken to limit this damage? Answer : Ozone layer doesn’t allow harmful ultra violet rays of the sun to reach the earth’s surface. In order to stop further depletion of ozone layer we must scale down the use of CFC’s in form of aerosols, refrigerants etc and check their release in the atmosphere. Moreover stress should be laid on using eco-friendly techniques and proper disposal of toxic material.

Question. Why are bacteria and fungi called decomposers? List any two advantages of decomposers to the environment. Answer : Bacteria and fungi are called decomposers as they break down the dead remains and waste of organisms. They convert the organic complex substance into simple inorganic substances that go into the soil and are used up by plants. Two advantages of decomposers: 1. They return the components back to nature and creates balance in the environment. 2. They act as cleansing agents of the atmosphere.

Question. (a) Distinguish between producers and decomposers. (b) Classify the following as producers and decomposers. Green plants, bacteria, fungi, blue-green algae.

Answer : (a)

Question. Why decomposers are necessary in environment? Answer : Decomposers act on all biodegradable substances and break them into simple inorganic materials and maintain the balance of materials in the ecosystem and cleanse the environment.

Question. Why is the ozone layer getting depleted at the higher levels of the atmosphere?  Answer : Ozone is present at higher levels of the atmosphere where CFC – Cholorofluorocarbons reach, chlorine separates and acts on O 3 to split it into O 2 and (O). The conditions required to do this are available at higher levels i.e., clouds and sunlight.

Question. Give one example of grassland ecosystem and one example of pond ecosystem. Answer : Grass land Ecosystem: Grass → grasshopper → frog → snake → peacock. Pond Ecosystem : Blue-green algae → small fish → big fish → birds

Question. Energy flow in a food chain is unidirectional. Explain. Answer : The energy from the sun flows into autotrophs and it passes to herbivores and then to carnivores. The energy does not revert from autotrophs to the solar input or from herbivores back to autotrophs. Hence the flow is unidirectional.

Question. Name any two abiotic components of an environment.  Answer : Water, air.

Long Answer Type Questions 

Question. What is ozone and how does it affect any ecosystem? Answer : Ozone is a molecule of oxygen with 3 atoms its formula is O3. The ultra violet radiations split oxygen into free oxygen atoms, these atoms combine with oxygen molecules to form ozone.

O 2  —→UV rays  O + O

O 2 + O ⎯⎯→ O 3 (Ozone)

Ozone in Ecosystem: At ground level ozone is poisonous but at higher level it is very useful as it protects all living organisms from harmful UV radiations of the sun. It doesn’t allow the ultra violet radiations to enter the surface of earth. The UV radiations cause ionizing effect that leads to skin cancer in human beings.

Question. It is the responsibility of the government to arrange for the management and disposal of waste. As an individual you have no role to play. Do you agree? Support your answers with two reasons. Answer: I do not agree. As an individual, I also have the responsibility and can contribute in the following ways:- (i) Cut down waste generation. (ii)Make compost pit for bio degradable waste. (iii) Recycle non biodegradable waste.

Question. Look at the following figures. Choose the correct one and give reason for your answer.

Answer: Fig. “A” is correct. • In an ecosystem, the number of individuals at producer level is maximum. This number reduces at each successive level. Therefore, the shape is a pyramid with broader base and tapering apex. • On an average 10% of the food changes into body mass and is available for the next level of consumers . 

Question. How will accumulation of bio degradable waste effect our environment? Answer: Accumulation of bio degradable waste will: (a) Not let minerals return to mineral pool. (b) Become site of pest breeding.

Question. How can you help in reducing the problem of waste disposal? Give any two methods. Answer : To reduce the problem of waste disposal we can (i) Segregate the bio-degradable waste from non-biodegradable waste before dumping it. (ii) Remove all materials which can be recycled and send it for recycling. e.g., paper, glass, metal, rubber.

Question. Enlist various categories of consumers giving examples of each. Answer : The various categories of consumers are: Herbivores — Grass eating animals, e.g., deer, rabbit. Carnivores — Flesh eating animals, e.g., tiger, lion. Omnivores — Animals that eat both plants and other small animals i.e., flesh e.g., crow, human being. Parasites — Those organisms which depend on other living organisms and harm them for food, e.g., lice, tapeworm. Saprophytes — Organisms that depend on dead and decaying matter for their food, e.g., fungi, bacteria.

Question. What three informations are obtained from the energy flow diagrams? Answer : The information we get are: (i) The energy flow is unidirectional, it flows from sun → autotrophs → herbivores → carnivores → decomposers (ii) The flow of energy is 10% i.e., 90% of the energy is used by a given level of food chain for metabolic activities. (iii) The unwanted chemicals like pesticides gets accumulated in the highest organism in the food chain.

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 then all the organisms of next trophic level which are dependent on these are killed. Next trophic levels will not get food to eat and the entire food chain gets disturbed. At the same time the organisms at the lower trophic level will reproduce and the population will increase in abundance there by disturbing the ecosystem.

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 : The impact of removing all the organisms in a trophic level will be same. If the organisms of any trophic level be removed it will certainly damage the ecosystem. For example, Grass → Grass hopper → Frog → Snake → Peacock In this if all grasshoppers are killed/removed frogs will strive and grass will reproduce in abundance. If snakes are removed then the number of frogs will increase which will disturb the entire ecosystem.

Question. What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem? Answer : The pesticides and chemicals are absorbed by plants from the soil and enter the food chain. Being non-biodegradable they accumulate progressively at each trophic level. As human occupy the top level of any food chain, the maximum concentration of chemicals is found in our bodies. This is called biological magnification. The level of magnification will be different at different trophic levels, the maximum concentrations will be at the highest trophic level and the chemical will be less at lower trophic levels.

Question. Explain the interlink of biotic and abiotic factors in any ecosystem. Answer : In an ecosystem biotic and abiotic factors are interdependent and interlinked. For example: The grass in grassland will grow only if it gets soil which can hold water and gets sunlight with proper temperature hence the grass grows in a place which has all abiotic factors responsible for its growth but in desert these abiotic factors are not available for the growth of grass.

Question. Why are some substances biodegradable and some non-biodegradable? Answer : Substances which can be decomposed and broken down to simpler substances by micro-organisms acting on it is called bio-degradable and those substances which cannot be acted upon by micro-organisms and are not broken down into simpler substances are called non-biodegradable substances.

Question. Give any two ways in which bio-degradable substances would affect the environment. Answer : Two ways in which bio-degradable substances would affect the environment are: (i) During decomposition of the substances lot of foul smell spreads in the surrounding areas. (ii) The place where these bio-degradable substance are present with some moisture becomes breeding ground for insects like mosquitoes, housefly which are vectors in carrying parasites that cause different diseases.

Question. Give any two ways in which non-biodegradable substances would affect the environment. Answer : (i) The non-biodegradable substances get accumulated and doesn’t get decomposed hence it remains in the ecosystem and causes pollution, chokes the system of many animals and kill them. (ii) These substances due to accumulation cause water and soil pollution e.g.,pesticides, detergents, polythene.

Question. Explain the formation of ozone layer and its importance. Answer : Ozone is formed when high energy ultra violet radiations split oxygen molecule into oxygen atoms. The oxygen atom combines with oxygen molecules to form a new molecules with three oxygen atoms named ozone.

O 2  + O ⎯⎯→ O 3 (Ozone)

Importance of Ozone: It is very protective when present in stratosphere it does not allow the harmful ultra violet radiations to enter the earth’s surface which can cause skin cancer in human beings.

Value Based Question

Question. All eco-club students collect the vegetable peels from canteen and use them in compost pit made in their school. (a) Name items that can be added in compost pit other than vegetable peels. (b) What type of reaction is seen in the pit? (c) State the values seen among eco-club members. Answer : (a) Students can use leftover food and fruit peels, dried leaves. (b) Fermentation i.e., anaerobic decomposition. (c) The eco-club students show team work, collaborative work and good behaviour.

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excell up Class 10 Science

Our Environment

These notes are based on the chapter Our Environment from class 10 science NCERT book and CBSE syllabus.

Our surrounding is called environment. The clasroom, playground and garden in your school make the environment of your school. Even your teachers and fellow students are part of that environment. Similarly, the houses in your neighbourhood, neighbours, stray animals, trees, park, etc. make the environment of your neighbourhood.

• Components of ecosystem
• Food chain and food web
• Ozone layer and its depletion
• Problem of waste disposal

This is a system of interdependencies among various living beings and non-living things in a given habitat. Every component of an ecosystem is dependent on each other.

To understand this, you can take the example of a garden. The plants in the garden depend on soil, air and water. Soil, in turn, depends on decomposition of plants to get back nutrients. Many creatures depend on plants for food and shelter. Many of these creatures help plants in pollination and dispersal of seeds.

Components of Ecosystem

An ecosystem has two types of components, viz. biotic component and abiotic component.

Abiotic Component

All the non-living things make the abiotic component of an ecosystem. Air, water and soil are abiotic components.

• Air provides oxygen ( for respiration ), carbon dioxide ( for photosynthesis ) and other gases for various needs of living beings.
• Water is essential for all living beings because all the metabolic activities happen in the presence of water.
• Soil is the reservoir of various nutrients which are utilised by plants. Through plants, these nutrients reach other living beings.

Biotic Component

All living beings make the biotic component of an ecosystem. Different types of biotic components are as follows:

Producer: Green plants play the role of producers because they prepare their own food.

Consumer: Animals and other living beings play the role of consumers because they take food (directly or indirectly) from plants.

Decomposer: Bacteria and fungi play the role of decomposers, as they decompose dead remains of plants and animals so that raw materials of organisms can be channelized back to the environment.

A food chain is a simple representation of transfer of energy from the sun to different biotic components of an ecosystem. Sun is the ultimate source of energy, because most of the sources of energy on earth have got energy from sun. Green plants convert solar energy into chemical energy during photosynthesis. When an animal takes food, this energy is supplied to the animal and the process goes on. A simple food chain can be shown as follows:

Producer → Primary Consumer → Secondary Consumer

Real life cannot be as simple as a food chain shown above. For a given prey, there can be many predators. For example, grass is eaten by many animals. A goat is eaten by many carnivores. In any ecosystem, there can be many food chains which are interlinked at various levels. Thus, many food chains form a network which is called food web.

Transfer of Energy through a food chain

Different levels in the food chain are called trophic level . Out of the energy consumed by an organism at a particular trophic level, 90% is utilised for its own need and rest 10% is left for the organism of the next trophic level. So, very little energy is left for the organism which is at the tertiary level.

Let us assume that a green plant makes 100% energy in the form of chemical energy. 90% of this energy would be utilised for its own purpose. This would leave just 10% energy for the primary consumer.

Now, primary consumer shall also utilize 90% of energy which was consumed by it. This would leave just 1% energy for (10% of 10 = 1) for the secondary consumer.

By this logic, the tertiary consumer would get just 0.1% of energy which was originally made by the green plant. This is the reason, there can be just one or two organisms at the top of the food pyramid.

This explains why the population of producers is always the largest in an ecosystem, followed by the population of herbivores and then that of carnivores. Moreover, an herbivore needs to eat many plants in its lifetime to fulfill its energy need. Similarly, a carnivore needs to eat many herbivores in its lifetime.

Balance in the Ecosystem

There is a delicate balance in an ecosystem, as far as number of organisms at a particular trophic level is concerned. An increase or decrease in population of any organism can disturb this balance.

What will happen if all the deer are killed in a jungle?

Let us take a hypothetical example to understand this. If all the deer are killed in a jungle, the lions would be left with no food. This would endanger the existence of lions. Once the lions and deer would be finished, it would result in population explosion of green plants.

What will happen if all the lions are killed in a jungle?

If all the lions die in a jungle, it would create another problem. Since no lion would be left to kill the deer, the population of deer would increase substantially. This will finish off all the green plants and finally even the deer would be left with no food for them.

Biodegradable Substance: Substances which can be decomposed by microorganisms are called biodegradable substances. All the organic substances are biodegradable.

Non-biodegradable: Substances which cannot be decomposed by microorganisms are non-biodegradable. All inorganic substances are non-biodegradable. Many synthetic substances are also non-biodegradable.

Ozone Layer Depletion

Ozone layer.

The stratosphere is composed of ozone and is also called ozone layer. It prevents ultraviolet radiations from entering the earth's surface.

Chlorofluorocarbons

Fully or partly halogenated form of hydrocarbons is called chlorofluorocarbon. They contain only carbon, hydrogen, chlorine and fluorine. They are used in refrigerants and aerosols. They damage the ozone layer.

Ozone layer is also known as stratosphere. When ultraviolet radiations act on oxygen, the oxygen gets converted into ozone.

Ozone layer works like a protective shield for living beings. The ozone layers wards off harmful ultraviolet radiations from the sun.

Effect of CFCs

Use of CFCs ( Chlorofluorocarbon ) has damaged the ozone layer. As a result, the ozone layer has become thinner at certain parts.

Tackling ozone layer depletion

In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an agreement among different nations to freeze the CFC production at 1986 level. Later, an agreement was signed among different nations to phase out CFCs. It is important to note that CFC is used in refrigerators and aerosol spray. India is also a signatory of that agreement and thanks to the efforts by the United Nations and different environmentalists, the CFC emission has been put under some control.

Problems of Waste Disposal

During our day to day activities, we produce lot of waste. While some of the waste is biodegradable, a large chunk is composed of non-biodegradable substances. Plastic waste is a serious concern because plastic is non-biodegradable. We need to respect our environment and find out ways to reduce the burden on our environment.

• Ecosystem: System of interdependence among living and non-living in a given habitat.
• Biotic Components: All the living things in a given habitat comprise biotic component of ecosystem
• Abiotic Components: All the non-living things in a given habitat comprise abiotic component of ecosystem
• Environment
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Our Environment | Class 10 | Activity 15.1 with Solution

Our environment | activities in text book with solution.

• Activity 15.1
• Activity 15.2
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