Science Objective Questions and Answers: Chapter 13 Our Environment
Access targeted multiple-choice questions for Chapter 13 Our Environment designed to align with the latest CBSE academic syllabus for Class 10 Science. These objective practice sets help students evaluate their conceptual understanding and improve exam readiness.
Download Chapter 13 Our Environment MCQs with Answers
Access the complete set of multiple-choice questions for Chapter 13 Our Environment below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.
Thirty MCQs on the chapter Our Environment for CBSE Class 10 Science are given below with full explanations. The set focuses on food webs, energy flow, waste segregation, biodegradable and non-biodegradable materials and CFC related ozone depletion.
Multiple Choice Questions
(a) mouse
(b) snake
(c) hawk
(d) frog
Show Answer & Explanation
Answer: (a) mouse
Explanation:
1. Grass is eaten by the mouse, so its energy supply falls first.
2. Grass is the producer and the mouse is a primary consumer feeding directly on it, so it is hit most immediately; snake, hawk and frog depend on it only indirectly.
Teacher's Note:
1. Energy always passes step by step along the chain.
2. The level directly above the producer feels a change first.
(a) Herbivores
(b) Carnivores
(c) Producers
(d) Omnivores.
Show Answer & Explanation
Answer: (c) Producers
Explanation:
1. Producers are the most numerous organisms in an ecosystem.
2. Numbers decrease at each higher level because less energy is available, so the base level of producers is the largest.
Teacher's Note:
1. Many producers support fewer herbivores.
2. Fewer carnivores sit at the top.
(a) convert inorganic material, to simpler forms.
(b) convert organic material to inorganic forms.
(c) convert inorganic materials into organic compounds.
(d) do not break-down organic compounds.
Show Answer & Explanation
Answer: (b) convert organic material to inorganic forms.
Explanation:
1. Decomposers break organic matter down into inorganic substances.
2. Bacteria and fungi break down dead remains and wastes into simple inorganic nutrients that plants reuse.
Teacher's Note:
1. Decomposers recycle nutrients.
2. Without them dead matter would pile up.
(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.
Show Answer & Explanation
Answer: (b) Green plants get their food from organic compounds.
Explanation:
1. Green plants make food from inorganic compounds, not organic ones.
2. Statement (b) is wrong because green plants make their food from inorganic compounds (CO2 and water).
Teacher's Note:
1. Read for the word 'incorrect' in the stem.
2. Plants are autotrophs.
Assertion (A): Trophic levels are formed by only plants.
Reason (R): Food chains and webs are formed due to linked organisms on the basis of their nutrition.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (d) A is false, but R is true.
Explanation:
1. Trophic levels include consumers and decomposers too.
2. Assertion is false because trophic levels include producers, consumers and others; the reason is true.
Teacher's Note:
1. Trophic levels are steps in a food chain.
2. All feeding groups are part of it.
(a) natural
(b) artificial
(c) indigenous
(d) none of these
Show Answer & Explanation
Answer: (b) artificial
Explanation:
1. A crop field is man-made, so the fish there are in an artificial ecosystem.
2. Crop fields are maintained by humans, so even fish in a flooded field belong to an artificial ecosystem.
Teacher's Note:
1. Man-made means artificial.
2. Natural ecosystems need no human help.
(a) giving more opportunity of survival to the prey of the secondary consumer
(b) giving more opportunity of survival to the predators of the secondary consumer
(c) disturbing the food chain of which the secondary consumer is a part
(d) decreasing the population of the producers
Show Answer & Explanation
Answer: (c) disturbing the food chain of which the secondary consumer is a part
Explanation:
1. Disease in secondary consumers disturbs the food chain.
2. Any change at one level affects the other levels, so the chain is disturbed.
Teacher's Note:
1. Every level is linked.
2. Balance depends on all of them.
(a) the accumulation of harmful chemicals at each trophic level of the food chain.
(b) the accumulation of organic matter at the first trophic level of the food chain.
(c) the reduction of energy at each trophic level of the food chain.
(d) an increase in the population of a species at each trophic level of the food chain.
Show Answer & Explanation
Answer: (a) the accumulation of harmful chemicals at each trophic level of the food chain.
Explanation:
1. Biological magnification means harmful chemicals accumulate at each trophic level.
2. The chemicals do not break down, so their concentration rises up the chain.
Teacher's Note:
1. Learn this definition.
2. It applies to non-biodegradable chemicals.
(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.
Show Answer & Explanation
Answer: (d) they are made of non-biodegradable materials.
Explanation:
1. Plastic plates are non-biodegradable.
2. Microbes cannot break them down, so they stay in the environment for a long time.
Teacher's Note:
1. Use cloth or leaf plates when possible.
2. Reduce plastic.
(a) Blue green algae
(b) Cactus
(c) Fungi
(d) Spinach
Show Answer & Explanation
Answer: (c) Fungi
Explanation:
1. Fungi are decomposers, not producers.
2. Blue green algae, cactus and spinach make their own food; fungi do not.
Teacher's Note:
1. Producers photosynthesise.
2. Fungi feed on dead matter.
(a) oxygen
(b) ozone
(c) carbon monoxide
(d) all of these
Show Answer & Explanation
Answer: (b) ozone
Explanation:
1. UV rays turn oxygen molecules into ozone.
2. UV splits O2 and atoms join O2 to make O3.
Teacher's Note:
1. The product is O3.
2. It is not carbon monoxide.
(a) Unpleasant odours
(b) Ground water pollution
(c) Fires and explosions
(d) Infrared radiation
Show Answer & Explanation
Answer: (d) Infrared radiation
Explanation:
1. Infrared radiation is not a landfill problem.
2. Landfills cause odour, ground water pollution and fires, but not infrared radiation.
Teacher's Note:
1. Pick the odd one out.
2. Learn landfill problems.
Assertion (A): Certain pesticides and other chemicals used to protect our crops from diseases and pests are non-biodegradable.
Reason (R): They do not get accumulated at various trophic levels.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (c) A is true, but R is false.
Explanation:
1. Pesticides are non-biodegradable and do accumulate at trophic levels.
2. The assertion is true but the reason is false.
Teacher's Note:
1. Biomagnification contradicts the reason.
2. They do accumulate.
(a) 90%
(b) 10%
(c) 50%
(d) 25%
Show Answer & Explanation
Answer: (b) 10%
Explanation:
1. Only 10% of the energy passes to the next level.
2. The snake gets about 10% of what the rabbit has.
Teacher's Note:
1. Apply the 10% law.
2. Do not use 90% or 50%.
(I) All food chains are of equal length and complexity.
(II) Food chains generally consist of only three to four steps.
(III) The greatest number of organisms in a food chain is of the producers.
(IV) Relationships between organisms can be shown only by straight lines.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) (II), (III) and (IV)
Show Answer & Explanation
Answer: (b) Both (II) and (III)
Explanation:
1. Statements II and III are correct.
2. Food chains vary in length and are not straight-line only; most have 3-4 steps with producers most numerous.
Teacher's Note:
1. Check each statement.
2. Food chains are not all equal.
(I) The functional unit of the environment comprises only biotic components.
(II) The functional unit of the environment comprises both biotic and abiotic components.
(III) The functional unit of the environment comprises both living and non-living components.
(IV) The functional unit of the environment comprises only living components.
(a) (I) and (II)
(b) (I) and (III)
(c) (II) and (III)
(d) (III) and (IV)
Show Answer & Explanation
Answer: (c) (II) and (III)
Explanation:
1. Both biotic and abiotic components make up the unit.
2. Statements II and III say the same thing in other words.
Teacher's Note:
1. Living plus non-living.
2. Environment includes both.
Assertion (A): The green plants in a terrestrial ecosystem capture about 1% of the sunlight energy that falls on their leaves and convert it into food energy.
Reason (R): The producers make the energy from the sunlight and make it available to the rest of the ecosystem.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Explanation:
1. Plants capture about 1% of sunlight, and producers make it available to the ecosystem.
2. Both statements are true, but the reason does not explain the 1% figure.
Teacher's Note:
1. Two true facts need not be linked.
2. Learn each fact.
Assertion (A): CFCs (Chloro fluorocarbons) deplete ozone layer.
Reason (R): NO also depletes ozone layer which is generated by jet aeroplanes in stratosphere.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Explanation:
1. CFCs deplete ozone and NO from jets also does, but this does not explain CFCs' effect.
2. Both are true; the reason is not the explanation.
Teacher's Note:
1. Different substances.
2. Both damage ozone.
(a) Crop field – Natural ecosystem
(b) Garden – Man made ecosystem
(c) Temperature – Abiotic factor
(d) Grass – Transducer
Show Answer & Explanation
Answer: (a) Crop field – Natural ecosystem
Explanation:
1. A crop field is man-made, not natural.
2. The other pairs are correctly matched.
Teacher's Note:
1. Crop fields are artificial.
2. Garden is man-made.
Assertion (A): Paper cups are better option than plastic cups for serving tea.
Reason (R): Paper cups are biodegradable and can even be disposed off by burning.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (a) Both A and R are true, and R is the correct explanation of A.
Explanation:
1. Paper cups are biodegradable and burnable.
2. Both statements are true and the reason explains the assertion.
Teacher's Note:
1. Paper is better than plastic.
2. Biodegradable means safe.
(a) producer
(b) herbivore
(c) carnivore
(d) none of the above
Show Answer & Explanation
Answer: (b) herbivore
Explanation:
1. A grasshopper feeds on plants, so it is a herbivore.
2. It is not a producer or carnivore.
Teacher's Note:
1. Grass eaters are herbivores.
2. Insects can be primary consumers.
Assertion (A): CFCs deplete the ozone layer.
Reason (R): CFCs are used as refrigerants and in fire extinguishers.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Explanation:
1. CFCs deplete ozone, and are used in refrigerants and extinguishers.
2. Both are true; the use is not the explanation.
Teacher's Note:
1. Use is not cause.
2. CFCs release chlorine.
(a) can be broken down by the action of bacteria or other decomposers.
(b) cannot be acted upon by physical processes like heat and pressure.
(c) persist in the environment for a long time.
(d) may harm the various members of the ecosystem.
Show Answer & Explanation
Answer: (a) can be broken down by the action of bacteria or other decomposers.
Explanation:
1. Biodegradable substances are broken down by bacteria and other decomposers.
2. The other options describe non-biodegradable substances.
Teacher's Note:
1. Biodegradable decays.
2. Non-biodegradable persists.
Assertion (A): Autotrophs can produce food on its own.
Reason (R): Green plants can absorb 1% energy of sunlight that fall on the leaves.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (b) Both A and R are true, but R is not the correct explanation of A.
Explanation:
1. Autotrophs make food; plants absorb 1% sunlight.
2. Both true but R does not explain A.
Teacher's Note:
1. Separate facts.
2. Learn both.
I. They decompose into soil.
II. They are degraded by microorganisms such as bacteria and fungi.
III. They are not biologically magnified.
(a) Non-biodegradable substances
(b) Biodegradable materials
(c) Biomedical wastes
(d) Domestic wastes
Show Answer & Explanation
Answer: (b) Biodegradable materials
Explanation:
1. They decompose into soil and are not magnified, so they are biodegradable.
2. Non-biodegradable materials magnify.
Teacher's Note:
1. Biodegradable decays.
2. It is not magnified.
Sun → Grass → Rabbit → Snake
The food chain is incomplete due to:
(a) Absence of tertiary consumer
(b) Absence of decomposers
(c) Absence of quaternary consumer
(d) Absence of parasitic component
Show Answer & Explanation
Answer: (b) Absence of decomposers
Explanation:
1. Decomposers are absent from the chain shown.
2. The chain has producer and consumers only.
Teacher's Note:
1. Decomposers complete the chain.
2. They recycle matter.
(a) Biodegradable
(b) Non-Biodegradable
(c) Degradable
(d) None of these
Show Answer & Explanation
Answer: (b) Non-Biodegradable
Explanation:
1. Non-biodegradable substances cannot be broken down by bacteria.
2. They persist.
Teacher's Note:
1. Learn it.
2. Plastics.
(a) Gamma radiations
(b) Infra red Radiation
(c) Ultra violet radiations
(d) Nuclear radiations
Show Answer & Explanation
Answer: (c) Ultra violet radiations
Explanation:
1. Ozone shields us from ultraviolet radiation.
2. Not gamma, infrared or nuclear.
Teacher's Note:
1. UV is blocked.
2. Ozone is the shield.
Assertion (A): Increase in temperature of earth is due to green house gases.
Reason (R): Ozone increase due to chlorofluoro carbon used in refrigerants and in fire extinguishers.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Show Answer & Explanation
Answer: (c) A is true, but R is false.
Explanation:
1. Greenhouse gases warm the earth, but ozone does not increase because of CFCs.
2. A is true, R false (CFCs reduce ozone).
Teacher's Note:
1. CFCs reduce ozone.
2. Check R.
(a) Vegetable waste
(b) Fruit peel
(c) Plastics
(d) none of these
Show Answer & Explanation
Answer: (c) Plastics
Explanation:
1. Plastics are non-degradable waste.
2. Vegetable waste and peel are biodegradable.
Teacher's Note:
1. Plastics persist.
2. Learn it.
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Practice MCQs for Class 10 Science Chapter 13 Our Environment
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FAQs
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