Bihar Board Class 10 · Science · Matric exam 2027
Chapter 15: Our Environment
This chapter’s questions from Bihar Board (BSEB)’s real papers of 2021–2026 — the 14 asked most often, 3 with the full model answer, 11 with how the answer begins — and objective questions with the board’s key.
- marks a year (about)
- 4
- questions a year (about)
- 5
- rank in Science
- #9
From 6 years of papers, 2021–2026 · full chapter-wise marks
VVI questions — the ones the board asked most (14)
- Q1Long answer5 marksAsked: 2021, 2024
What is the effect of deforestation on wildlife ?
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Model answer · effect of deforestation on wildlife
- 1.Deforestation leads to the destruction of the natural habitats of wild animals. When forests are cut down, the trees, plants and other vegetation that make up the natural habitat of wild animals are removed, so the animals lose the place where they naturally live.1 mark
- 2.Lack of habitat creates a crisis of food and shelter for wild animals. Without the forest as their habitat, wild animals do not get their natural food from plants and other organisms of the forest, and they also lose the shelter that protected them from weather and predators.1 mark
- 3.Many species of wild animals reach the verge of extinction. As their habitat and food and shelter are destroyed, a large number of wild animal species become endangered and move closer to extinction.1 mark
- 4.A situation of conflict arises between wild animals and humans. As forests are destroyed, wild animals are forced to move out into human settlements and agricultural fields in search of food and shelter, and this brings them into conflict with humans, further endangering these animals.1 mark
- 5.The balance of the ecosystem is disturbed, leading to a decrease in biodiversity. The forest ecosystem depends on the interaction of its biotic and abiotic components, and removal of trees disturbs this balance; as more species become endangered or extinct, the biodiversity of the ecosystem decreases.1 mark
- Use the exact words 'natural habitats' and 'habitat' in the first two paragraphs.
- Mention both 'extinction' and 'endangered' for the species decline point.
- End with 'ecosystem' and 'biodiversity' linked together in the last paragraph.
Marks split from a structure derived from past papers (checked twice); not Bihar Board’s official scheme
- Q2Long answer5 marksAsked: 2022, 2024
What is a food chain ? Explain it with an example.
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Model answer · food chain, example
- 1.The process of transfer of energy from one organism to another is called a food chain. The series of organisms taking part at various biotic levels, each feeding upon the one before it, forms this food chain. Each step or level of the food chain forms a trophic level, and the flow of energy from one trophic level to the next, through the organisms of the food chain, is what we call a food chain.2 marks
- 2.The example of grass, deer, and lion illustrates a food chain. In this food chain, grass is eaten by the deer, and the deer is in turn eaten by the lion. In this way, the energy fixed by the grass passes on to the deer and then to the lion, forming a simple food chain of three steps.1.5 marks
- 3.In this food chain, grass is the producer, deer is the primary consumer, and lion is the secondary consumer. The producers, being autotrophs, fix up the solar energy and make it available to the heterotrophs or consumers. The deer, being a herbivore, is the primary consumer which feeds directly on the producer, grass, while the lion, being a carnivore that feeds on the deer, is the secondary consumer.1.5 marks
Diagram: Draw a straight line food chain with arrows showing the direction of energy flow: Grass → Deer → Lion, labelling Grass as "Producer", Deer as "Primary consumer", and Lion as "Secondary consumer".
- Write the exact words 'food chain' and 'transfer of energy' in the first paragraph.
- Name grass, deer and lion in that order as the example food chain.
- Label grass as producer, deer as primary consumer, and lion as secondary consumer.
Marks split from a structure derived from past papers (checked twice); not Bihar Board’s official scheme
- Q3Long answer6 marksAsked: 2026
What steps have been taken to limit ozone depletion ?
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Model answer · steps to limit ozone depletion
- 1.In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to freeze CFC production at 1986 levels. This agreement, known as the Montreal Protocol, was adopted to prevent the depletion of the ozone layer, which had begun to drop sharply in the 1980s.2 marks
- 2.The production and use of chlorofluorocarbons (CFCs), the synthetic chemicals used as refrigerants and in fire extinguishers that were linked to the sharp decrease in the amount of ozone in the atmosphere, have been completely banned or restricted under the agreement reached in 1987.2 marks
- 3.Environmentally friendly alternatives are now being used in place of chlorofluorocarbons (CFCs) in refrigerators and fire extinguishers, so that the use of these harmful chemicals, which endangered the ozone layer, is reduced and the ozone layer is protected from further damage.2 marks
- Write '1987' and 'United Nations Environment Programme (UNEP)' together with 'Montreal Protocol' in the first paragraph.
- State clearly that 'chlorofluorocarbons (CFCs)' have been 'banned or restricted' in the second paragraph.
- Name 'refrigerators' and 'fire extinguishers' with 'alternatives' in the third paragraph.
Marks split from a structure derived from past papers (checked twice); not Bihar Board’s official scheme
- Q4Short answer2 marksAsked: 2024
What is bio-magnification ?
How the model answer begins
1. The increase in the concentration of harmful chemicals or pollutants at each trophic level in a food chain is called biological magnification. As human beings occupy the top level in any food chain, the maximum…
The full answer from Medha Ma’am → - Q5Short answer2 marksAsked: 2025
What are the harmful effects of aerosol chemicals ?
How the model answer begins
1. Aerosol chemicals such as chlorofluorocarbons (CFCs) destroy the ozone layer present at the higher levels of the atmosphere. The ozone layer shields the surface of the earth from ultraviolet (UV) radiation from the Sun,…
The full answer from Medha Ma’am → - Q6Short answer2 marksAsked: 2025
What is the role of decomposers in the ecosystem?
How the model answer begins
1. Decomposers are the microorganisms, comprising bacteria and fungi, that break-down the dead remains and waste products of organisms. They break-down the complex organic substances into simple inorganic substances that…
The full answer from Medha Ma’am → - Q7Short answer2 marksAsked: 2026
What is an ecosystem ?
How the model answer begins
1. An ecosystem is formed by all the interacting organisms in an area together with the non-living constituents of the environment. Thus an ecosystem consists of biotic components comprising living organisms and abiotic…
The full answer from Medha Ma’am → - Q8Short answer2 marksAsked: 2026
What are the functions of producers in the ecosystem ?
How the model answer begins
1. Producers synthesize food by converting solar energy into chemical energy. All green plants and certain blue-green algae which can produce food by photosynthesis are called the producers, and they capture the energy…
The full answer from Medha Ma’am → - Q9Short answer2 marksAsked: 2023
What is greenhouse effect ?
How the model answer begins
1. The greenhouse effect is the process by which the atmosphere of the earth traps the heat coming from the sun and keeps the earth warm.
The full answer from Medha Ma’am → - Q10Short answer2 marksAsked: 2022
What is environment?
How the model answer begins
1. The environment is the sum total of physical, chemical, and biological factors surrounding an organism.
The full answer from Medha Ma’am → - Q11Short answer2 marksAsked: 2022
Who are known as consumers?
How the model answer begins
1. Organisms that consume the food produced, either directly from producers or indirectly by feeding on other consumers, are called consumers. They depend on the producers either directly or indirectly for their…
The full answer from Medha Ma’am → - Q12Short answer2 marksAsked: 2022
How can the environment be protected?
How the model answer begins
1. The environment can be protected by stopping deforestation and increasing afforestation, that is, planting more trees. This helps maintain the natural balance and reduces damage caused by human activities to the…
The full answer from Medha Ma’am → - Q13Short answer2 marksAsked: 2021
What is pollution?
How the model answer begins
1. Pollution is the undesirable change in the natural balance due to the entry of harmful substances into the environment.
The full answer from Medha Ma’am → - Q14Short answer2 marksAsked: 2025
What are the harmful effects of aerosol chemicals ?
How the model answer begins
1. Chemicals used in aerosols such as chlorofluorocarbons (CFCs) damage the ozone layer. The ozone layer shields the surface of the earth from ultraviolet radiation from the Sun, and its depletion allows greater amounts of…
The full answer from Medha Ma’am →
Objective questions with the board’s key (10)
- 1. Bihar Board 2026
The chemical which shows biomagnification is
- (A) CFC
- (B) DDT ✓
- (C) NADP
- (D) ATP
Answer: (B)
- 2. Bihar Board 2026
The molecular formula of ozone is
- (A) O4
- (B) O2
- (C) O3 ✓
- (D) O5
Answer: (C)
- 3. Bihar Board 2026
Which of the following is responsible for imbalance in environment ?
- (A) Due to increasing human population ✓
- (B) Through afforestation
- (C) Due to growth of more green plants
- (D) Biodiversity
Answer: (A)
- 4. Bihar Board 2026
Bacteria are called
- (A) producer
- (B) decomposer ✓
- (C) consumer
- (D) none of these
Answer: (B)
- 5. Bihar Board 2026
What type of ecosystem is a pond?
- (A) Artificial
- (B) Natural ✓
- (C) Abiotic
- (D) None of these
Answer: (B)
- 6. Bihar Board 2026
Which gas is responsible for global warming ?
- (A) O_2
- (B) NH_3
- (C) N_2
- (D) CO_2 ✓
Answer: (D)
- 7. Bihar Board 2026
Which of the following is a non-biodegradable substance?
- (A) DDT ✓
- (B) Paper
- (C) Sewage
- (D) None of these
Answer: (A)
- 8. Bihar Board 2026
Tiger is a consumer of
- (A) First trophic level
- (B) Second trophic level
- (C) Third trophic level ✓
- (D) None of these
Answer: (C)
- 9. Bihar Board 2026
Which of the following is a decomposer?
- (A) Algae
- (B) Round worm
- (C) Bacteria ✓
- (D) Amarbel
Answer: (C)
- 10. Bihar Board 2025
Primary consumers are called
- (A) Decomposer
- (B) Omnivorous
- (C) Carnivorous
- (D) Vegetarian ✓
Answer: (D)
Questions parents and students ask
- How many marks does "Our Environment" carry in Bihar Board Class 10 Science?
- In the Bihar Board papers of 2021–2026, this chapter carried about 4 marks and about 5 questions a year; by marks it ranks 9 in Science.
- Which are the most important (VVI) questions of "Our Environment"?
- The 14 questions above are from the board’s real papers, each with the years it was asked; the most-asked come first with their full model answers. All 14 written questions of this chapter, with answers, are in the AskMedha app.
- Do the answers follow the board’s marking scheme?
- BSEB does not publish a marking scheme. Each answer is written point by point on a structure derived from past papers and checked by a second, independent model; it is never called the board’s official scheme.
The same preparation, with Medha Ma’am — on your phone
Every question of every chapter with its model answer, practice questions in the board’s own shapes, 60 minutes of class a day, written answers marked, a test every Sunday and a WhatsApp report to parents.
Medha Ma’am is an AI teacher, not a live tutor. Every answer is checked twice; a person takes responsibility.