CBSE Class 10 Biology Our Environment Important Questions and Answers for 2023

CBSE Class 10 Biology Our Environment Important Questions and Answers: In this article, we will cover all major important question and answers of the Unit V Chapter 13 Our Environment from CBSE Class 10 Science.

CBSE Class 10 Biology Our Environment Important Questions and Answers for 2023
CBSE Class 10 Biology Our Environment Important Questions and Answers for 2023

CBSE Class 10 Biology Our Environment Important Questions and Answers: In this article, we will cover various types of important question and answers of the Chapter Our Environment in CBSE Class 10 Science. It comes under the fifth unit Natural Resources as the 13th chapter. Our Environment is the last unit and the last chapter in the curriculum of Class 10th Science. Before the latest updates in the syllabus, Our Environment was the fifteenth chapter. Therefore, in some materials and resources related to the subject, you might still see it as the fifteenth chapter. 

To avoid such confusions, visit the revised CBSE Class 10 Science syllabus and refer to the latest resources for preparing for the examination.

CBSE Class 10 Science Syllabus 2022-23

Although, in brief, the topics covered under Chapter 13 Our Environment are: Eco-system, Environmental problems, Ozone depletion, waste production and their solutions. Biodegradable and non-biodegradable substances.

CBSE Class 10 Biology Our Environment Important Questions


Q.1. In a given food chain if the amount of energy at the fourth trophic level is 6 kJ, what will be the energy available at the producer level?

(a) 6000 kJ 

(b) 20 kJ 

(c) 60 kJ 

(d) 600 kJ

Q.2. Environment includes:

(a) Land, air, water 

(b) Light, temperature, rainfall

(c) Plants, animals, microbes 

(d) All of these

Q.3. Which of the following is a biodegradable waste ?

(a) DDT 

(b) Aluminum can

(c) Plastic bag 

(d) Cow dung

Q.4. Which of the following is the best way for disposal of vegetable and fruit peels?

(a) Landfill 

(b) Recycling 

(c) Composting 

(d) Burning

Q.5. Which group of waste materials can be classified as Non biodegradable ?

(a) Plant waste, used tea bags 

(b) Polyethene bags, plastic toys

(c) Used tea bags, paper straw 

(d) Old clothes, broken footwear

Q.6. 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

Q.7. The % of solar radiation absorbed by all green plants for photosynthesis is about ———–.

(a) 1% 

(b) 5% 

(c) 8% 

(d) 10%

Q.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

Q.9. Which of the statements is incorrect?

(а) 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

Q.10.  If a grasshopper is eaten by frog, then the energy transfer will be from:

(a) producers to decomposers

(b) producer to primary consumer

(c) primary consumer to secondary consumer

(d) secondary consumer to primary consumer

Q.11. What will happen if Deer is missing in the food chain given below?

Grass → Deer → Tiger

(а) 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

Q.12. The transfer of Energy in a food chain is always:

(a) Unidirectional 

(b) Methane

(c) Bi-directional 

(d) Random

Q.13. When is the World Environment Day celebrated?

(a) 16 June 

(b) 5 December 

(c) 5 June 

(d) 5 July

Q.14. Which of these is a greenhouse gas?

(a) Hydrogen Sulphide 

(b) Methane 

(c) Ozone 

(d) Carbon monoxide

Q.15. The decomposers are not included in the food chain. The correct reason for the same is because decomposers:

(a) Act at every trophic level of the food chain

(b) Do not breakdown organic compounds

(c) Convert organic material to inorganic forms

(d) Release enzymes outside their body to convert organic material to inorganic forms


(a) If both Assertion and reason are true and Reason is the correct explanation of assertion

(b) If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion

(c) If Assertion is true but the Reason is false

(d) If both Assertion and Reason are false

Q.1. Assertion (A) : Garden is an artificial ecosystem.

Reason(R) : Biotic and abiotic components are manipulated by humans.

Q.2.  Assertion (A) : Food chain is responsible for the entry of harmful chemicals in our bodies.

Reason(R) : The length and complexity of food chain vary greatly.

3. Assertion (A) : Biotic components of ecosystem continuously require energy to carry on life processes.

Reason(R) : Abiotic components are non-living factors of ecosystem.


Q.1. Ganga river has been severely polluted. All the towns along its length contribute to the pollution load. It has been assessed that more than 80 per cent of the total pollution load (in terms of organic pollution expressed as biochemical oxygen demand (BOD)) arises from domestic sources, i.e., from the settlements along the river course. Due to over-abstraction of water for irrigation in the upper regions of the river, the dry weather flow has been reduced to a trickle. Rampant deforestation in the last few decades, resulting in topsoil erosion in the catchment area, has increased silt deposits which, in turn, raise the river bed and lead to devastating floods in the rainy season and stagnant flow in the dry season. Along the main river course there are 25 towns with a population of more than 100,000 and about another 23 towns with populations above 50,000. In addition, there are 50 smaller towns with populations above 20,000. There are also about 100 identified major industries located directly on the river, of which 68 are considered as grossly polluting. Fifty-five of these industrial units have complied with the regulations and installed effluent treatment plants (ETPs) and legal proceedings are in progress for the remaining units. The natural assimilative capacity of the river is severely stressed. The principal sources of pollution of the Ganga River can be characterized as follows:

  1. Which of the following activities may pollute the river water more?

(a) Bathing using detergent and soap 

(b) Discharging animals excreta

(c) Deposit flowers and leaves as the part of puja 

(d) Bathing without soap and detergent

  1. Which of the following organisms grow abundant in water when the water get mixed with nutrients like sulphates, phosphates etc.?

(a) Algae 

(b) Zooplankton 

(c) Small fishes 

(d) Large fishes

  1. When toxic chemicals and nutrients get deposited in the water bodies, which of the following gases get depleted in the water bodies?

(a) Oxygen 

(b)Carbon dioxide 

(c) Both oxygen and carbon dioxide 


  1. Accumulation of toxic substances at higher trophic levels of an ecosystem through the food chain in water bodies affects which of the following organisms more?

(a) Phytoplankton 

(b) Zooplankton 

(c) Small fishes 

(d) Large fishes

  1. Green Algae and Diatoms are the major producers of Aquatic ecosystem. Which of the following will be more in the aquatic ecosystem:

(a) Small fishes 

(b) Large fishes 

(c) Algae and phytoplankton 

(d) Tadpole

Q.2. The atmosphere is a blanket of air and a precious natural resource for sustaining life on the Earth. Unfortunately, human activities based on national/personal interests are causing harm to this common resource, notably by depleting the fragile ozone layer, which acts as a protective shield for life on the Earth. Ozone molecules consist of three oxygen atoms, Ozone molecules are exceeding rare: fewer than ten in every million molecules of air. However, for nearly a billion years, their presence in the atmosphere has played a vital role in safeguarding life on Earth. The ozone in the troposphere (up to 110 kilometres above the Earth's surface) is 'bad' ozone which can damage lung tissues and plants. But about 90 per cent of ozone found in the stratosphere (between 10 and 40 kilometres above the Earth's surface) is "good" ozone which plays a beneficial role by absorbing dangerous ultraviolet (UV-B) radiations from the Sun. Without this beneficial ozone layer, humans would be more susceptible to certain diseases due to the increased incidence of ultraviolet rays from the Sun.

  1. Ozone holes are more pronounced at the :

(a) Equator 

(b) Tropic of cancer 

(c) Tropic of Capricorn 

(d) Poles

  1. Ozone molecules consists of:

(a) Three oxygen atoms only 

(b) two oxygen atoms only

(c) Only one atom of oxygen 

(d) None of the above

  1. U-V rays can cause diseases in humans like

(a) Skin cancer only 

(b) Cataract only 

(c) Lung cancer 

(d) Both (a) and (b)

  1. Which of the following is an ozone depleting substance?

(a) Sulphur dioxide 

(b) Methyl chloride

(c) Carbon dioxide 

(d) Methane

  1. Depletion of ozone layer is mainly due to

(a) Use of CFC’s 

(b) Use of halogens 

(c) Both (a) and (b) 

(d) None of the above


Q1- Give any two ways in which biodegradable substances would affect the environment.

Q 2- In a food chain, 10,000 joules of energy is available to the producer. How much energy will be available to the secondary consumer to transfer it to the tertiary consumer?

Q 3- The flow of energy in the food chain is unidirectional. Why?

Q 4 - Name any two abiotic components of an environment.

Q 5- Producers always occupy the first trophic level in any food chain. Why?

Q 6- What is the full form of CFCs and UNEP?


Q 1 - Differentiate between biodegradable and non-biodegradable substances with the help of one example each. List two changes in habit that people must adapt to dispose non-biodegradable waste for saving the environment.

Q 2 - What will happen if we kill all the organisms in one trophic level?

Q 3 - In a certain study conducted on the occurrence of DDT along food chains in an ecosystem, the concentration of DDT in grass was found to be 0-5 ppm. In sheep, it was 2 ppm and in man it was 10 ppm. Name the phenomenon and define?

Q 4 - How can we help in reducing the problem of waste disposal? List two ways.

Q 5 -  Why is a lake considered to be a natural ecosystem?

Q 6 -Which gas shield the surface of earth from harmful radiation of the sun. why these radiations are supposed to be harmful for us?


Q1- Why bacteria and fungi are called decomposers? List any two advantages of decomposers to the environment.

Q2- “Energy flow in a food chain is unidirectional”. Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

Q3- Answer the following: i- What is ozone? How is it formed in the atmosphere?

ii- How ozone layer is useful

iii- Name the substances responsible for the depletion of ozone layer.

Q4- (a) Write two harmful effects of using plastic bags on the environment. Suggest alternatives to the usage of plastic bags.

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

Q5- In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?

Q.6. In a food chain, if 10000 Joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer?

Download Answers to CBSE Class 10 Biology Our Environment Important Questions

ALSO CHECK: CBSE Class 10 Science Sample Paper 2022-23

Biology is a subject liked by many students in class 10th who opt for it in their senior Secondary levels well. Pursuing Biology in senior secondary level and university level enables students  make exciting careers in the field of Medicine, Pharmacy, Biotechnology, Biochemistry, Microbiology, etc

All the best!

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