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NCERT Exemplar Class 10 Science Chapter 15 Our Environment Solutions

NCERT Exemplar Solutions for Class 10 Science Chapter 15 Our Environment covers all the important questions and answers as well as advanced level questions. It helps in learning about the Ecosystem and its Components, biotic Components include living organisms like plants, animals, microbes, etc., Abiotic components include non-living organisms like soil, water, etc., food chain and food web.

The NCERT Exemplar solutions for class 10 science is very important for board exams. NCERT Exemplar Solutions for Class 10 Science Chapter 15 Our Environment is provided by our experts. They prepared the best solutions which help the students in understanding the solutions in an easy way. This chapters also covers the other topics like Trophic levels, producers, primary consumers, secondary consumers, tertiary consumers, herbivores, carnivores, decomposers, Pyramid of Trophic Levels, Ozone Layer and its Depletion, Garbage Management, Biodegradable Waste, Biodegradation and Non-biodegradable Waste.


Chapter Name

Chapter 15 Our Environment

Book Title

NCERT Exemplar for Class 10 Science

Related Study

  • NCERT Solutions for Class 10 Science Chapter 15 Our Environment
  • Revision Notes for Class 10 Science Chapter 15 Our Environment
  • MCQ for Class 10 Science Chapter 15 Our Environment
  • Important Questions for Class 10 Science Chapter 15 Our Environment

Topics Covered

  • MCQ
  • Short Answers Questions
  • Long Answers Questions

NCERT Exemplar Solutions for Chapter 15 Our Environment Class 10 Science

Multiple Choice Questions

1. Which one of the following is an artificial ecosystem?
(a) Pond
(b) Crop field
(c) Lake
(d) Forest

Solution
(b) Crop field

Crop field is a man made ecosystem.


2. In a food chain, the third trophic level is always occupied by
(a) carnivores
(b) herbivores
(c) decomposers
(d) producers

Solution
(a) carnivores

First trophic level is producers, second tropic level is herbivores and the third trophic level is occupied by carnivores.


3. 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

Solution
(c) both living organisms and non-living objects

An ecosystem includes living and nonliving organisms along with their interactions.


4. In the given food chain, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level?
Grass → Grasshopper → Frog → Snake → Hawk
(a) 5 k J
(b) 50 k J
(c) 500 k J
(d) 5000 k J

Solution
(d) 5000 k J

The available energy at a particular trophic level is 10 times that of the energy available at the next tropic level. Hence, energy at third level trophic level is 50kJ that at the second level trophic is500 kJ and at first level trophic level (Producer) is5000 kJ.


5. Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as
(a) eutrophication
(b) pollution
(c) biomagnification
(d) accumulation

Solution
(c) biomagnification

  • Eutrophication is richness of nutrient beyond optimum level. Eutrophication occurs due to run off from land.
  • Introduction of an undesired substance into environment. Pollution leads to harmful effects on living organisms.

6. Depletion of ozone is mainly due to
(a) chlorofluorocarbon compounds
(b) carbon monoxide
(c) methane
(d) pesticides
Solution
(a) chlorofluorocarbon compounds

7.  Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called
(a) decomposers
(b) producers
(c) herbivores
(d) carnivores
Solution
(b) producers
Producers synthesize food from water and carbon dioxide in the presence of sunlight. Plants and few micro-organisms are the producers. Decomposers decompose the organic materials. Herbivores are the organisms that feed on plant and its products. Carnivores feed on other organisms.

8. In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of
(a) heat energy
(b) light energy
(c) chemical energy
(d) mechanical energy
Solution
(c) chemical energy
Energy is transferred from one trophic level to the next in the form of food. Food is a chemical form of energy.

9. Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the
(a) food web
(b) ecological pyramid
(c) ecosystem
(d) food chain
Solution
(a) Food Web
In an ecological pyramid, number of organisms at the higher tropic level is always less than the number of organisms at the lower tropic level. An organism at the higher tropic level usually feeds on more than one type of organism from the lower tropic level.

10. Flow of energy in an ecosystem is always
(a) unidirectional
(b) bidirectional
(c) multi directional
(d) no specific direction
Solution
(a) unidirectional
Flow of energy takes place from the prey to the predator and it cannot be in reversed. Hence flow of energy is a unidirectional process.

11. Excessive exposure of humans to U V-rays results in
(i) damage to immune system
(ii) damage to lungs
(iii) skin cancer
(iv) peptic ulcers 
(a) (i) and (ii)
(b) (ii) and (iv)
(c) (i) and (iii)
(d) (iii) and (iv)
Solution
(c) (i) and (iii)
The upper surface of the body is affected by the UV rays. UV rays lead to skin cancer affect the immune system. This is because skin is considered as primary level of immune barrier.

12. 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, bakelite, DDT 
(a) (iii)
(b) (iv)
(c) (i) and (iii)
(d) (ii) and (iv)
Solution
(d) (ii) and (iv)
Wood and leather are biodegradable. Grass is biodegradable too.

13. Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher trophic levels
(b) Sufficient food supply
(c) Polluted air
(d) Water
Solution
(a) Decrease in energy at higher trophic levels
At a particular tropic level, the available energy is 10 times the energy level available at the next tropic level. Therefore, a minute portion of energy from the producer is available when we reach the fourth trophic level.

14. Which of the statement is incorrect?
(a) All green plants and blue green algae are producers
(b) Green plants get their food from organic compounds
(c) Producers prepare their own food from inorganic compounds
(d) Plants convert solar energy into chemical energy
Solution
(b) Green plants get their food from organic compounds 
Green plants harness the solar energy and produce their food. Solar energy is used to prepare carbohydrate with the help of CO2 and water which are inorganic substances.

15. Which group of organisms are not constituents of a food chain?
(i) Grass, lion, rabbit, wolf
(ii) Plankton, man, fish, grasshopper
(iii) Wolf, grass, snake, tiger
(iv) Frog, snake, eagle, grass, grasshopper 
(a) (i) and (iii)
(b) (iii) and (iv)
(c) (ii) and (iii)
(d) (i) and (iv)
Solution
(c) (ii) and (iii)
In option (i) plankton does not eat grass. In option iii) none of them eat grass hence option c) is the right answer.

16. The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about
(a) 1 %
(b) 5 %
(c) 8 %
(d) 10 %
Solution
(a) 1%
Green plants utilize 1% of radiation absorbed by leaf and use it for photosynthesis.

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

(a) T4
(b) T2
(c) T1
(d) T3
Solution
(c) T1

Maximum energy is available for the producers. Only 10% of the energy is consumed by an organism at next level. Hence T1>T2>T3>T4.


18. 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

Solution
(d) The population of tiger decreases and the population of grass increases

Lack of predators will increase population of grass. Due to lack of food, the population of tigerswill reduce.


19. The decomposers in an ecosystem
(a) convert inorganic material, to simpler forms
(b) convert organic material to inorganic forms
(c) convert inorganic materials into organic compounds
(d) do not breakdown organic compounds

Solution
(b) convert organic material to inorganic forms


20. If a grass hopper 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

Solution
(c) primary consumer to secondary consumer

As the grass hopper feeds on grass, it is a primary consumer. If the grasshopper is being eaten by a frog then the frog will be a secondary consumer.


21. Disposable plastic plates should not be used because
(a) they are made of materials with light weight
(b) they are made of toxic materials
(c) they are made of biodegradable materials
(d) they are made of non-biodegradable materials

Solution
(d) they are made of non-biodegradable materials

Plastics start accumulating in nature, thereby harming living organisms as they are non-biodegradable.


Short Answer Questions 

22. Why is improper disposal of waste a curse to environment? 

Solution
Wastes pollute the environment and cause harmful effects on all living organisms.


23. Write the common food chain of a pond ecosystem.

Solution

Phyto planktons and aquatic plants → small aquatic animals larvae, insects etc. → fish → bird


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

Solution
Advantages of cloth bags are:

  • capable of carrying more things
  • made of biodegradable material
  • do not pollute our environment
  • can be reused


25. Why are crop fields known as artificial ecosystems?

Solution
Crop fields are man-made. Therefore, the biotic and abiotic components are manipulated by humans.


26. Differentiate between biodegradable and non-biodegradable substances. Cite examples. 

Solution

Biodegradable substances

Non-biodegradable substances

Substances which can be broken down into simpler substances by biological processes are known as biodegradable substances.

Substances that cannot be broken down into simpler substances by biological processes are said to be non-biodegradable.

Example –wood, paper, etc.

Example –plastic, DDT, etc.


27. Suggest one word for each of the following statements/ definitions
(a) The physical and biological world where we live in
(b) Each level of food chain where transfer of energy takes place
(c) The physical factors like temperature, rainfall, wind and soil of an ecosystem
(d) Organisms which depend on the producers either directly or indirectly for food

Solution

(a) Environment 
(b) Trophic level 
(c) Abiotic factors 
(d) Consumers or heterotrophs 


28. Explain the role of decomposers in the environment?

Solution

Decomposers break down the dead and decaying organic matter and return the nutrients to the soil. Thus, they play a very important role in the nutrient recycling in the environment.


29. Select the mis-matched pair in the following and correct it.
(a) Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain (b) Ecosystem — Biotic components of environment
(c) Aquarium — A man-made ecosystem
(d) Parasites — Organisms which obtain food from other living organisms

Solution
(b) Ecosystem — Biotic components of environment 

Both biotic and abiotic components of environment constitute an ecosystem.


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

Solution
An aquarium is an artificial ecosystem which is incomplete ecosystem when compared to pond or lake which is natural and complete ecosystem. The abiotic components are not supplied naturally to the aquarium.


Long Answer Questions 

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

Solution

  1. In a terrestrial ecosystem, the green plants capture about 1% of the energy of sunlight and convert it into food energy.
  2. When primary consumers eat these green plants, a great deal of energy is lost as heat to the environment. But some amount of energy goes into digestion and in doing work. The rest goes towards growth and reproduction of the primary consumer.
  3. Approximately 10% of the food eaten by the primary consumer is turned into its own body and made available for the next level of consumers.
  4. Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.
  5. As very little energy is available for the next level of consumers, the food chains generally consist of only three or four steps.
  6. Generally, there are a greater number of individuals at the lower trophic levels.
  7. The length and complexity of food chains vary greatly.
  8. Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.
  9. So instead of a straight line food chain, the relationship can be shown as a series of branching lines called a food web.

The energy captured by the autotrophs does not revert back to the sun hencethe flow of energy is unidirectional. The energy is no longer available to the previous level as it moves progressively through the various trophic levels. Secondly, due to loss of energy at each level the energy available at each trophic level gets diminished progressively.


32. What are decomposers? What will be the consequence of their absence in an ecosystem?

Solution
Decomposers are microorganisms like bacteria and fungi which break-down the dead remains and waste products of organisms. They break-down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants.

Recycling of material in the biosphere will not take place if the decomposers are absent in the ecosystem. This in turn will lead to accumulation of dead plants and animals in the environment. Moreover, the environment will be completely devoid of all its resources needed to maintain and sustain life.


33. Suggest any four activities in daily life which are eco-friendly

Solution
The following activities in daily life are eco-friendly:

  • Use of bicycles and electrical bikes instead of vehicles running on fossil fuels.
  • Avoid use plastic bags.
  • Plant trees in our surroundings.
  • Recycle old items and use them.


34. Give two differences between food chain and food web.
Solution 

Food Chain

Food web

The food chain is the straight and single pathway for the flow of energy in an ecosystem, through different species of organisms.

Food web is defined as the convoluted or complicated pathway of an ecosystem consist of numerous food chains of the different trophic level, through which the energy flow.

Food chain is hypothetical situation

Food web is a real life situation.

Members of higher trophic level feed on single type of organism of lower trophic level

Members of higher trophic level can feed upon organisms of the lower trophic levels of other food chain.


35. Name the wastes which are generated in your house daily. What measures would you take for their disposal?

Solution
The following wastes are generated in our house daily:

  • Kitchen wastes
  • Paper wastes like newspapers, bags, envelopes
  • Plastic bags

Measures to be taken in order to dispose house waste areas follows:

  • Segregation of biodegradable and non-biodegradable wastes.
  • Safe disposal of plastic bags.
  • Vegetable/fruit peels can be placed near trees/plants, which on decomposition will enrich the soil with nutrients.
  • Give paper wastes for recycling.
  • Prepare a compost pit for kitchen wastes.


36. Suggest suitable mechanism (s) for waste management in fertiliser industries.

Solution
The following steps must be taken in order to manage the waste in fertiliser industry:

  • Use of catalytic converters in chimneys: Catalytic converters help in minimizing the release of harmful gases and suspended particulate matter.
  • Use of electrostatic precipitators in chimneys: These help in minimizing the release of SPMs, thereby reducing air pollution.
  • Effluent treatment: An effluent treatment plant should be installed in the factory. The plant should have a proper facility for physical, chemical and biological treatment of effluent.


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

Solution
The major by-products of fertilizer industry are ammonia, nitrates, urea, acids and alkalis, oil, arsenic, MEA, cyanides, sulphides, phosphates, etc.

The effects of these by-products on the environment are as follows:

  • Suspended solid and ash increase the air pollution.
  • Arsenic and cyanides may enter the food chain and cause bio magnification.
  • Fluorides in drinking water may be harmful for the teeth.
  • The pH of water is altered if the by-products reach the water bodies. This harms the aquatic ecosystem.


38. Explain some harmful effects of agricultural practices on the environment.

Solution
Some harmful effects of agricultural practices on the environment are as follows:

  • The chemistry of the soil changes because of excessive use of chemical fertilizers which kills useful microbes.
  • Bio-magnification is caused due to excessive use of non-biodegradable chemical pesticides.
  • Extensive cropping causes loss of soil fertility.
  • The ground water table lowers because of excessive use of ground water for agriculture.
  • Natural ecosystem/habitat is damaged.

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