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Exemplar Problem and Solution (NCERT) –

MCQs – 1 

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

  1. Pond
  2. Crop field
  3. Lake
  4. Forest

Answer:-(b) Crop field

Question: 2 :- In a food chain, the third trophic level is always occupied by

  1. Carnivores
  2. Herbivores
  3. Decomposers
  4. Producers

Answer:- (a) Carnivores

Question: 3 :- An ecosystem includes

  1. All living organisms
  2. Non-living objects
  3. Both living organisms and non-living objects
  4. Sometimes living organisms and sometimes non-living objects

Answer: (c) Both living organisms and non-living objects

Question: 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 

  1. 5 k J
  2. 50 k J
  3. 500 k J
  4. 5000 k J

Answer: (d) 5000 kJ

Question: 5 – Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as

  1. Eutrophication
  2. Pollution
  3. Biomagnification
  4. Accumulation

Answer: (c) Biomagnification

Question: 6 – Depletion of ozone is mainly due to 

  1. Chlorofluorocarbon compounds
  2. Carbon monoxide
  3. Methane
  4. Pesticides

Answer: (a) Chlorofluorocarbon compounds

Question: 7 – Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called

  1. Decomposers
  2. Producers
  3. Herbivores
  4. Carnivores

Answer: (b) Producers

Question: 8 – In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of

  1. Heat energy
  2. Light energy
  3. Chemical energy
  4. Mechanical energy

Answer: (c) Chemical energy

Question: 9 – Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the

  1. Food web
  2. Ecological pyramid
  3. Ecosystem
  4. Food chain

Answer: (b) Ecological pyramid

Question: 10 – Flow of energy in an ecosystem is always

  1. Unidirectional
  2. Bidirectional
  3. Multi directional
  4. No specific direction

Answer: (a) Unidirectional

MCQs – 2

Question: 11 :- Excessive exposure of humans to U V-rays results in

  1. damage to immune system 
  2. damage to lungs
  3. skin cancer
  4. peptic ulcers
    1. (i) and (ii)
    2. (ii) and (iv)
    3. (i) and (iii)
    4. (iii) and (iv)

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

Question: 12 :- In the following groups of materials, which group (s) contains only non-biodegradable items?

  1. Wood, paper, leather
  2. Polythene, detergent, PVC
  3. Plastic, detergent, grass
  4. Plastic, bakelite, DDT
    1. (iii)
    2. (iv)
    3. (i) and (iii)
    4. (ii) and (iv)

Answer:- (d) (ii) and (iv)

Question: 13 :- Which of the following limits the number of trophic levels in a food chain?

  1. Decrease in energy at higher trophic levels
  2. Defficient food supply
  3. Polluted air
  4. Water

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

Question: 14 :- Which of the statement is incorrect?

  1. All green plants and blue green algae are producers
  2. Green plants get their food from organic compounds
  3. Producers prepare their own food from inorganic compounds
  4. Plants convert solar energy into chemical energy

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

Question: 15 :- Which group of organisms are not constituents of a food chain?

  1. Grass, lion, rabbit, wolf
  2. Plankton, man, fish, grasshopper
  3. Wolf, grass, snake, tiger
  4. Frog, snake, eagle, grass, grasshopper
    1. (i) and (iii)
    2. (iii) and (iv)
    3. (ii) and (iii)
    4. (i) and (iv)

Answer: (c) (ii) and (iii)

Question: 16 – The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about

  1. 1 %
  2. 5 %
  3. 8 %
  4. 10 %

Answer: (a) 1%

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

  1. T4
  2. T2
  3. T1
  4. T3

Answer: (c) T1

Question: 18 – What will happen if deer is missing in the food chain given below?

Grass → Deer → Tiger

  1. The population of tiger increases
  2. The population of grass decreases
  3. Tiger will start eating grass
  4. The population of tiger decreases and the population of grass increases

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

Question: 19 – The decomposers in an ecosystem

  1. Convert inorganic material, to simpler forms
  2. Convert organic material to inorganic forms
  3. Convert inorganic materials into organic compounds
  4. Do not breakdown organic compounds

Answer: (b) Convert organic materials to inorganic forms

Question: 20 – If a grass hopper is eaten by a frog, then the energy transfer will be from

  1. Producer to decomposer
  2. Producer to primary consumer
  3. Primary consumer to secondary consumer
  4. Secondary consumer to primary consumer

Answer: (c) Primary consumer to secondary consumer

Question: 21 – Disposable plastic plates should not be used because

  1. They are made of materials with light weight
  2. They are made of toxic materials
  3. They are made of biodegradable materials
  4. They are made of non-biodegradable materials

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

Exemplar Problem and Solution (NCERT)

Short Answer Type

Question: 22 :- Why is improper disposal of waste a curse to environment?

Answer: Improper disposal of waste can be a curse to the environment because it leads to many problems. Let us take example of non-segregation of waste into biodegradable and non-biodegradable. If waste is not properly segregated, it can hamper the process of decomposition. If the waste is disposed off near a residential area and is not covered properly, it can create a problem of stench in the surrounding. This can also cause many epidemics.

Question: 23 :- Write the common food chain of a pond ecosystem.

Answer: Example of a food chain in the pond ecosysem:

Algae → Small Fish/shrimp → Medium Fish → Large fish/crane/duck

Question: 24 :- What are the advantages of cloth bags over plastic bags during shopping?

Answer: Cloth bags are biodegradable, while plastic bags are non-biodegradable. In most of the cases, a cloth bag is more durable than a plastic bag.

Question: 25 :- Why are crop fields known as artificial ecosystems?

Answer: In a crop field, plants do not grow naturally rather most of the plants are grown by humans. An ecosystem is nevertheless present in a crop field, but it is an artificial ecosystem as a major component of the ecosystem comes into origin because of human intervention.

Question: 26 – Differentiate between biodegradable and non-biodegradable substances. Cite examples.


Question: 27 – Suggest one word for each of the following statements/


  1. The physical and biological world where we live in Answer: Ecosystem
  2. Each level of food chain where transfer of energy takes place Answer: Trophic level
  3. The physical factors like temperature, rainfall, wind and soil of an ecosystem Answer: Abiotic factors
  4. Organisms which depend on the producers either directly or indirectly for food Answer: Consumers

Question: 28 – Explain the role of decomposers in the environment?

Answer: Decomposers decompose dead remains of plants and animals. By doing so, they serve two purposes. One; they reduce the burden on the environment by clearing dead remains. Two; they channelize the raw materials back to the environment.

Question: 29 – Select the mis-matched pair in the following and correct it.

  1. Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain
  2. Ecosystem — Biotic components of environment
  3. Aquarium — A man-made ecosystem
  4. Parasites — Organisms which obtain food from other living organisms

Answer: (b) Ecosystem: The system of interdependency among living beings and non-living things; in a given habitat.

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

Answer: A pond or a lake has its own natural system of cleaning the waste materials to maintain its ecosystem. Due to this, ponds are lakes normally do not need to be cleaned. An aquarium is a man-made ecosystem which has a very small space. The abiotic components are not supplied naturally to the aquarium. So, an aquarium needs frequent cleaning so that the living beings in it can survive

Exemplar Problem and Solution (NCERT)

Long Answer Type

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

Answer: The flow of energy in an ecosystem happens in following sequence:

Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer

The flow of energy is unidirectional in the food chain due to two reasons. A predator always eats its prey but other way round is not possible. Moreover, out of the total energy consumed by an organism at a particular trophic level; 90% is utilised for its own need and just 10% is left for the organism of next trophic level. Thus, the availability of energy gets reduced at subsequent trophic level. Due to this, the flow of energy is unidirectional in a food chain.

Question: 32 :- What are decomposers? What will be the consequence of their absence in an ecosystem?

Answer: Organisms which decompose the dead remains of plants and animals are called decomposers. Bacteria and fungi play the role of decomposers.

Decomposers decompose dead remains of plants and animals. By doing so, they serve two purposes. One; they reduce the burden on the environment by clearing dead remains. Two; they channelize the raw materials back to the environment.

Hence, if there were no decomposers in the environment it would lead to accumulation of dead plants and animals in the environment. Additionally, the environment would be finally sapped of all its resources which are needed to maintain and sustain life.

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

Answer: Four eco-friendly activities in daily life:

  1. Walking and cycling for commute.
  2. Using jute/cloth shopping bag.
  3. Using public transport.
  4. Switching off light/fans in unoccupied rooms.

Question: 34 :- Give two differences between food chain and food web.



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



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

Answer: Effluents and harmful gases are the main wastes which are produced in a fertiliser factory.

Treatment of Polluting Gases: For reducing the amount of gaseous pollutants, catalytic converters should be fitted in the chimneys.

Effluent Treatment: Effluent from the factory should be sent to effluent treatment plant. Sedimentation, flocculation, filtration and chlorination are the various steps of effluent treatment. Once effluent is treated, the clean water can then be sent to the nearest water bodies. The sludge can be allowed to decompose which can later be used as manure.

Question: 37 :- Explain some harmful effects of agricultural practices on the environment.

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

Climate Change: As farming means growing a selected number of species on a large tract of land, it promotes monoculture. Thus farming affects the biodiversity of a region in a negative way.

Deforestation: Clearing of forests for agriculture has resulted in loss of habitat to wildlife. Deforestation has also affected the natural recharge process of groundwater.

Soil degradation: Intensive farming robs off the soil of its nutrients. In the long run, it can lead to soil erosion and finally to desertification.

Water shortage: Overexploitation of groundwater for irrigation has resulted in acute water shortage at many places.

Pollution: Use of synthetic fertilisers and pesticides creates soil pollution, water pollution and air pollution.