# Assertion Reason Science CBSE 10th Chapter 15: Our Environment

Assertion Reason Science CBSE Class 10 Chapter 15 Our Environment 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.

In assertion reason type of questions, all 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:

Directions: Mark the option which is most suitable :
(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 the correct explanation of assertion.
(c) If assertion is true but reason is false.
(d) If both assertion and reason are false.

Question.1.
Assertion : Aquatic food chain is the food chain present in water bodies.
Reason : The example of aquatic food chain is phytoplankton → zooplankton → fish → shark.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Aquatic food chain is the food chain present in water bodies, e.g. phytoplankton → zooplankron → fish → shark.

Question.2.
Assertion : Decomposers keep the environment clean.
Reason : They recycle matter by breaking down the organic remains and waste products of plants and animals.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.
Explanation: Decomposers keep the environment clean by decomposing or consuming the dead remains of other organisms.

Question.3.
Assertion : Ozone is both beneficial and damaging.
Reason : Stop the release of chlorofluorocarbons to protect the ozone.

(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
Explanation: Ozone is damaging as it is a deadly poison. It is beneficial as it shields the surface of the earth from UV radiations of the Sun. We should stop the release of Chlorofluorocarbons (CFCs) to protect the ozone.

Question.4.
Assertion : Garden is an artificial ecosystem.
Reason : Biotic and abiotic components are manipulated by humans.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.5.
Assertion : Supersonic jets cause pollution as they thin out ozone.
Reason : Depletion of ozone cause green house effect.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.6.
Assertion : Biotic components of ecosystem continuously require energy to carry on life processes.
Reason : Abiotic components are the non-living factors of the ecosystem.

(b) Both assertion and reason are true but reason is not the correct explanation of assertion.

Question.7.
Assertion : Decomposers act as cleaning agents of the environment.
Reason : The decomposers recycle waste material in the hydrosphere.

(c) Assertion is true but reason is false.

Question.8.
Assertion : We live in troposphere.
Reason : Our atmosphere extends beyond troposphere also.

(b) : Both assertion and reason are true, but reason is not the correct explanation of the assertion.

Explanation: Troposphere is the part of atmosphere which extends from the surface of the earth to an altitude of 10 km. Life supporting conditions are found in troposphere. Besides troposphere, atmosphere consists of three other layers – stratosphere (10-60 km), mesosphere (60-100 km) and thermosphere (100 km and above).

Question.9.
Assertion : A food chain comprises of producers and consumers.
Reason : Consumers can be herbivores, carnivores and omnivores.

(b) : Both assertion and reason are true, but reason is not the correct explanation of the assertion.

Explanation: 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.10.
Assertion : Using jute bags while shopping is more environment friendly as compared to polythene bags.

(a) : Both assertion and reason are true, and reason is correct explanation of the assertion.

Explanation: 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.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.

(a) Both assertion and reason are true, and reason is correct explanation of the assertion.

Question.12.
Assertion : The burning of substances at higher temperature to form ash is called incineration.
Reason : Incineration greatly reduces the volume of waste.

(b) Both assertion and reason are true, but reason is not the correct explanation of the assertion.

Question.13.
Assertion : Paper cups are better option than plastic cups for serving tea.
Reason : Paper cups are biodegradable and can even be disposed off by burning.

(a) Both assertion and reason are true, and reason is correct explanation of the assertion.

Question.14.
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.

(a) Both assertion and reason are true, and reason is correct explanation of the assertion.

Question.15.
Assertion : Man is a social and cultured animal.
Reason : He developed socio-cultural environment and lives in it.

(a) : Both assertion and reason are true, and reason is correct explanation of the assertion.

Explanation: Man has developed the socio-cultural environment, in which he develops certain things through his efforts, skills, social institutions and tools. It results in the growth of society and advanced development of human powers.

Question.16.
Assertion : Pyramid of biomass may be upright or inverted.
Reason : Pyramid showing total biomass produced per unit time is always upright.

(b) : Both assertion and reason are true, but reason is not the correct explanation of the assertion.

Explanation: Pyramid of biomass is upright for terrestrial habitats. Maximum biomass occurs in producers. Inverted or spindle-shaped pyramids are obtained in aquatic habitats. The biomass of phytoplankton may be smaller than that of primary carnivores. However, if total biomass produced per unit time is calculated, maximum biomass occurs in producers. There is a progressive reduction of biomass found in herbivores, primary carnivores, secondary carnivores, etc. Therefore, if total biomass produced per unit time is calculated, the pyramid of biomass shall always be upright.

Question.17.
Assertion : There is always an interaction between neighbouring or distant ecosystems.
Reason : An ecosystem is recognised as self – regulating and self – sustaining entity.

(b) : Both assertion and reason are true, but reason is not the correct explanation of the assertion.

Explanation: A biotic community cannot live in isolation. The biotic community together with the physical environment forms an interacting system called the ecosystem. Ecosystems are self-regulating and self-sustaining units. An ecosystem is an area in which the inputs and outputs can be studied across its boundaries. For convenience, it is considered as a separate entity, but, it is important to recognise that the boundaries of ecosystem are indistinct and over- lapping. Some movement always occurs from one ecosystem to another in terms of energy and materials. All ecosystems are interconnected by flow of energy and transfer of materials with the neighbouring ecosystems, or even with distant ecosystems. For example, leaves of riverbank trees dropping in river water represent transfer of energy and material from terrestrial to aquatic ecosystem.

Question.18.
Assertion: The flow of energy is unidirectional.
Reason: Energy as it progresses through the various trophic levels is no longer available to the previous level.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation : The flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is nolonger available to the previous level. Moreover, the energy available at each trophic level gets diminished progressively due to loss of energy at each level. Thus, both assertion and reason are true and reason is the correct explanation of the assertion.

Question.19.
Assertion: Energy available at each trophic level gets diminished progressively.
Reason: Little usable energy remains after four trophic levels.

(c) Assertion is true, but reason is false.

Explanation : The energy available at each trophic level gets diminished progressively due to loss of energy at each level. The usable energy available at each trophic level gets diministed progressively due to loss of energy at each level. Thus, assertion is true but reason is false.

Question.20.
Assertion: Chemicals and toxins accumulate more and more as we move up the food chain.
Reason: Anything that gets into biological tissue, that is not normally there, has the potential to accumulate and magnify.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation : Biomagnification is the increase in concentration of toxins up the food chain. Chemicals and toxins accumulate more and more as we move up the food chain, because they do not get broken down in the body. Anything that gets into biological tissue, that is not normally there, has the potential to accumulate and magnify as it moves up the food chain. Thus, both assertion and reason are true and reason is the correct explanation of the assertion.

Question.21.
Assertion: Green plants of the ecosystem are the transducers.
Reason: Producers trap the radiant energy of the sun and change it into chemical energy.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation : Green plants of the ecosystem are the transducers because producers trap the radiant energy of the sun and change it into chemical energy. Thus both assertion and the reason arecorrect and reason is the correct explanation of the assertion.

Question.22.
Assertion: Arctic’s ozone depletion tends to be milder and short lived than the Antarctic’s.
Reason: CFCs, Frigid temperatures and sunlight are not present at the Arctic at the same time.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation : It is necessary to have all three at the same time for ozone layer to deplete. Thus, both assertion and reason are true and reason is the correct explanation of the assertion.

Question.23.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation : Substances which cannot be decomposed by the action of microorganisms are known as non-biodegradable substances. Mircroorganisms release enzymes which decompose the materials but these enzymes are specific in their action that is why enzymes cannot decompose all the materials. Thus, both assertion and reason are true and, reason is the correct explanation of the assertion.

Question.24.
Assertion : Aquariums are known as the man-made ecosystems.
Reason : Aquariums are created and maintained by humans.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Aquariums are known as the man-made ecosystems because these are created and maintained by humans.

Question.25.
Assertion : Flow of energy in a food chain is unidirectional.
Reason : Energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: The flow of energy through different steps in the food chain is unidirectional. This means that energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores.

Question.26.
Assertion : Biomagnification is caused due to the accumulation of biodegradable toxicants in organisms at each successive trophic level.
Reason : Biomagnification leads to the maximum accumulation of chemicals in small fishes.

(e) Both Assertion and Reason are false.

Explanation: Biomagnification is caused due to the accumulation of non-biodegradable toxicants in organisms at each successive trophic level. The maximum concentration of these chemicals gets accumulated in human body because they occupy the topmost place in any food chain.

Question.27.
Assertion : Animals adopt different strategies to survive in hostile environment.
Reason : Praying mantis is green in colour which merges with plant foliage.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Animals blend with the surroundings or background to remain unnoticed for protection and aggression.

Question.28.
Assertion : A network of food chains existing together in an ecosystem is known as food web.
Reason : An animal like kite cannot be a part of a food web.

(c) Assertion is true but reason is false.

Explanation: In the food web different food chains are interconnected. Each chain consists of different trophic levels i.e., producers, consumers and detrivoroes. So, kite can also be a part of food web

Question.29.
Assertion : CFCs deplete the ozone layer.
Reason : CFCs are used as refrigerants and in fire extinguishers.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Ozone layer is getting depleted at the higher levels of the atmosphere due to effect of chlorofluorocarbons (CFCs) which are used as refrigerants and in fire extinguishers.

Question.30.
Assertion : The concentration of harmful chemicals is more in human beings.
Reason : Man is at the apex of the food chain.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Harmful chemicals accumulate progressively at each trophic level. Since the man is at the apex of all the food chains, the concentration of harmful chemicals may be more in human beings. The phenomenon involved is known as biomagnification.

Question.31.
Assertion : The crown fires are most destructive as they burn the tree top.
Reason : Due to crown fire the temperature of that area may rise upto 700°C.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.32.
Assertion : Tropical rain forests are disappearing fast from developing countries such as India.
Reason : No value is attached to these forests because these are poor in biodiversity.

(c) Assertion is true but reason is false.

Explanation: Tropical rain forests have disappeared mainly due to man’s activities. Due to over population in countries like India, rain forests are cut to make place available for man to live and build houses. To build buildings and factories man has incessantly cut down trees. This has caused the depletion of rain forests.

Question.33.
Assertion : Abiotic component of an ecosystem involves cycling of material and flow of energy.
Reason : This is essential to keep biotic factors alive.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.34.
Assertion : First trophic level in a food chain is always a green plant.
Reason : Green plants are called producers.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation: Green plants are producers. The first trophic level in a food chain is a producers i.e. those organisms which produce food by photosynthesis.

Question.35.
Assertion : Man is a herbivore.
Reason : Omnivores eat both plant food and meat of animals.

(d) Assertion is false but reason is true.

Question.36.
Assertion : In an ecosystem, the function of producers is to convert organic compounds into inorganic compounds.
Reason : Green plants, the producers, transduce solar energy.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.37.
Assertion : Trophic levels are formed by only plants.
Reason : Food chains and webs are formed due to linked organisms on the basis of their nutrition.

(d) Assertion is false but reason is true.

Question.38.
Assertion : Herbivores are called first order consumers.
Reason : Tiger is a top carnivore.

(b) Both assertion and reason are true but reason is not the correct explanation of assertion.

Explanation: Herbivores obtain their food from plants. Hence, are known as first order carnivores. The carnivores like tiger cannot be preyed upon further, lie at the top of food chain and hence termed as top carnivores.

Question.39.
Assertion : Ecology is study of relationship between living organisms and their environment.
Reason : The biotic community and non-living environment of an area function together to form an ecosystem.

(a) Both assertion and reason are true and reason is the correct explanation of assertion.

Question.40.
Assertion : Polythene bags and plastic containers are non-biodegradable substance.
Reason : They can be broken down by micro-organisms in natural simple harmless substances.

(c) Assertion is true but reason is false.

Explanation: Substances like polythene bags and plastics are nonbiodegradable because they cannot be broken down by micro-organisms into simpler harmless substance in nature. Substance that can be broken down by microorganisms in natural simple harmless susbstances are biodegradable substances.

Question.41.
Assertion : Consumers are present at the first trophic level.
Reason : Consumers or heterotrophs fix energy making it available for autotrophs.

(e) Both Assertion and Reason are false.

Explanation: Autotrophs are present at the first trophic level because they fix solar energy, making it available for consumers or heterotrophs.

error: Content is protected !!