Questions of Assertion Reason Chapter 13 Our Environment Science CBSE Class 10 are very simple to understand as this chapter deals with our environment means our surroundings which every student is very much familiar with. To solve assertion reason type questions of science, deeper understanding of concept about our environment is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.

How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.

How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.

In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:

(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.

Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:

Assertion (A)Reason (R)MCQ Options (Fixed for all questions)
If TrueTrue(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
If TrueTrue(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
If TrueFalse(c) Assertion (A) is true but reason (R) is false.
If FalseTrue(d) Assertion (A) is false but reason (R) is true.
If FalseFalse(e) Both Assertion and Reason are false.

Now, lets practice some Assertion Reason Questions of Science Chapter: 15 Our environment.

For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.

Question.1.
Assertion: Plastic, glass and metal wastes keep accumulating in our surrounding and their amount never reduces with time.
Reason: Plastic, glass and metal wastes are non-biodegradable and they cannot be decomposed by microorganisms.

Ans.1. (a)
The waste material which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable wastes. This is because decomposer microbes cannot act upon them, e.g., plastic, glass and metal objects.

Question.2.
Assertion: DDT can pass along food chain from crops to man or other animals and harm them.
Reason: DDT is non-biodegradable and cannot be metabolised within bodies of living organisms and accumulates in their bodies.

Ans.2. (a)

Question.3.
Assertion: Using jute bags while shopping is more environment friendly as compared to polythene bags.

Ans.3. (a)
Jute bags can be reused repeatedly for shopping and get decomposed when discarded, Polybags on the other hand keep on accumulating as solid waste and harm our environment. They can clog drainage, pollute river bodies and are extremely dangerous to grazing animals who chew them mistakenly. So, jute bags are more environment friendly than polybags.

Question.4.
Assertion: An ecosystem consists of living biological community and its non-living environment.
Reason: Ecosystem functions as self sufficient or independent unit in nature.

Ans.4. (b)

Question.5.
Assertion: A food chain comprises of producers and consumers.
Reason: Consumers can be herbivores, carnivores and omnivores.

Ans.5. (b)
A food chain always starts with producers or green plants who synthesise food. All consumers depend on green plants for food and energy directly or indirectly.

Question.6.
Assertion: Decomposers help in recycling of nutrients between living and non-living components of ecosystem.
Reason: Decomposers help in decomposing dead bodies of organisms and return various nutrient elements to their source viz soil, water and air.

Ans.6. (a)

Question.7.
Assertion: The second trophic level of a food chain operating in a grassland is mostly occupied by a carnivore.
Reason: Carnivores feed upon herbivores and are secondary consumers.

Ans.7. (d)
The second trophic level of a food chain is occupied by herbivores that feed on plants or producers that are present in first trophic level.

Question.8.
Assertion: A food chain can have maximum of three trophic levels.
Reason: Energy available at each trophic level keeps on decreasing as we move higher up the food chain.

Ans.8. (d)
A food chain can have a maximum of five to six trophic levels, this is because a lot of energy is lost as heat at each trophic level on account of metabolism. So, a small amount of energy becomes available to the next trophic level. This limits the number of trophic level in a food chain.

Question.9.
Assertion: The flow of energy in a food chain operating in an ecosystem is always unidirectional.
Reason: Lots of energy is lost as heat from living organisms at each trophic level of a food chain.

Ans.9. (b)

Question.10.
Assertion: The energy available to deer in a food chain is more as compared to that available to lion.
Reason: Deer occupies second trophic level whereas lion occupies first trophic level in a food chain operating in grassland ecosystem.

Ans.10. (c)
Deer occupies second trophic level in a food chain as it is primary consumer and directly feeds on plants. Lion occupies higher trophic level as it is a top carnivore and acts as secondary or tertiary consumers. Energy available to deer will be higher as compared to lion as energy keeps on decreasing from one trophic level to another due to loss as heat.

Question.11.
Assertion: If pesticide is present in water bodies then fish eating birds accumulate maximum amount of DDT in their bodies.
Reason: Pesticides are not metabolised within bodies of living organisms and get concentrated at each trophic level leading to bioaccumulation.

Ans.11. (a)

Question.12.
Assertion: Gases used in cooling devices can lead to depletion of ozone layer of atmosphere.
Reason: Carbon monoxide which is widely used as coolant in refrigerator reacts with ozone and destroys it.

Ans.12. (c)
Chlorofluorocarbon which is widely used as coolant in refrigerator reacts with ozone and destroys it.

Question.13.
Assertion: The burning of substances at higher temperature to form ash is called incineration.
Reason: Incineration greatly reduces the volume of waste.

Ans.13. (b)

Question.14.
Assertion: Recycling is the way of managing plastic waste.
Reason: Broken plastic articles are sent to plastic processing units where they are melted and remoulded to make new plastic articles.

Ans.14. (b)
Plastics are non-biodegradable. They cannot be decomposed by the action of microbes. Recycling them can manage them effectively.

Question.15.
Assertion: Food waste can be converted to compost by burying in a pit dug into ground and used as manure.
Reason: Non-biodegradable wastes like fruit and vegetable peels, tea leaves, broken glass jar are ideal for composting.

Ans.15. (c)
Biodegradable domestic waste such as left over food, fruit and vegetables peels, leaves of potted plants can be converted into compost.

Question.16.
Assertion: Hospital wastes like used syringes, urine bags, etc. can be incinerated.
Reason: Incineration burns the waste at very high temperature and converts it to ashes.

Ans.16. (a)
Hospital waste contains a lots of germs so it should not be disposed openly. Burning the waste kills the germs and disposes the waste in proper way.

Question.17.
Assertion: Paper cups are better option than plastic cups for serving tea.
Reason: Paper cups are biodegradable and can even be disposed of by burning.

Ans.17. (a)

Question.18.
Assertion: Most of the solid waste in urban areas is disposed off in landfills. Reason: Landfills are high lying areas of the ground.

Ans.18. (c)
Landfills are low lying areas of ground where waste is dumped and covered with soil to the level of ground.

Question.19.
Assertion: Ozone depletion can be reduced by limiting the use of air conditioners and refrigerators.
Reason: Air conditioner and refrigerators release chlorofluorocarbons in the atmosphere that destroy ozone.

Ans.19. (a)

Question.20.
Assertion: Ozone is very important layer of atmosphere.
Reason: Ozone protects the living organisms from harmful UV radiations of sun.

Ans.20. (a)