There is a great concern all over the world to conserve biodiversity for maintaining ecological balance in nat

Question

Q. There is a great concern all over the world to conserve biodiversity for maintaining ecological balance in nature. Explain giving three reasons. Write different ways that have helped in increasing tiger population in our country.

(OR)

What is integrated organic farming ? How did Ramesh Chandra Dagar, a farmer from Sonepat, Haryana effectively use this procedure and succeed with zero waste ?

CBSECBSE Class XII Board 2020Subjective· 5mImportance★★★★★

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Part (a)Concept understanding — Biodiversity Explanation

Biodiversity: The Web of Life Around You

Imagine walking into a kitchen garden. You see a few tomato plants, some mint, maybe a rose bush. Now imagine walking into a forest — hundreds of tree species, birds calling from every direction, insects crawling under leaves, fungi on the bark, and a stream with tiny fish. That staggering variety of living things — from the tallest tree to the invisible bacteria in the soil — is what we call biodiversity.

The Simple Intuition

Biodiversity is short for biological diversity. Think of it as the "variety of life" on Earth. Just as a library with only one kind of book is boring and limited, an ecosystem with only one kind of plant or animal is fragile and poor. Biodiversity is nature's library — the more species, the richer and more stable the system.

The Precise Meaning

The NCERT textbook defines biodiversity as:

The variety of living organisms present on Earth, including the different plants, animals, fungi, and microorganisms, their genes, and the ecosystems they form.

This definition has three layers, and each matters:

Genetic diversity — variation within a species. For example, all humans are one species, but we have different eye colours, heights, and resistance to diseases. In crops, genetic diversity means some wheat varieties resist drought while others resist pests.
Species diversity — the number of different species in a region. A tropical rainforest has thousands of species; a cold desert has very few.
Ecological diversity — the variety of habitats, ecosystems, and communities. A forest, a grassland, a coral reef, and a pond are all different ecosystems.

Important

Biodiversity is not just about counting species. It includes the genes inside each species and the ecosystems they create together. Lose one layer, and the others suffer.

Why Does Biodiversity Matter?

For a commerce or humanities student, the question is natural: why should I care about how many beetles live in a forest? The answer is that biodiversity is the foundation of everything we use and consume.

Direct economic value — We depend on biodiversity for food (crops, fish, livestock), medicine (many drugs come from plants and fungi), raw materials (timber, cotton, rubber), and tourism (wildlife sanctuaries, national parks).

Indirect value — This is harder to see but more critical. Forests clean the air, wetlands purify water, bees pollinate crops, and soil microbes recycle nutrients. These are called ecosystem services. If biodiversity collapses, these services stop — and no technology can replace them at scale.

Ethical and cultural value — Every species has a right to exist, regardless of its usefulness to humans. Many cultures, especially in India, revere certain trees, animals, and rivers as sacred. Biodiversity is also a source of beauty, inspiration, and knowledge.

Note

The NCERT textbook emphasises that biodiversity is our life insurance. It gives us resilience — when one species fails due to disease or climate change, another can take its place. A system with low biodiversity (like a wheat monoculture) is one disease away from collapse.

A Quick Look at India's Biodiversity

India is one of the world's mega-diverse countries. Though it has only 2.4% of the world's land area, it contains about 8% of all known species. This includes:

Over 45,000 plant species
More than 90,000 animal species
10 biogeographic zones — from the Himalayas to the Western Ghats to the Andaman Islands

This richness is not accidental. India's varied climate, geography, and ancient landmass have allowed many species to evolve and survive here.

The Threat: Why We Talk About It …

Part (b)Concept understanding — Biofertilizers Biopesticides

Imagine you have a garden. You want your plants to grow strong and healthy, and you also want to keep pests away. There are two main ways to do this: one is with harsh chemicals (chemical fertilizers and pesticides), and the other is with living things or natural substances. Biofertilizers and biopesticides are the second way — they are nature’s own tools for farming.

Let’s start with biofertilizers. Think of them as "living manure." A chemical fertilizer is like giving a plant a direct shot of nutrients — it works fast but can burn the soil over time. A biofertilizer, on the other hand, is a preparation containing live microorganisms (like bacteria, fungi, or algae) that help the plant get nutrients from the soil or air. For example, certain bacteria can take nitrogen from the air and convert it into a form the plant can use. The plant doesn’t get fed directly; instead, the biofertilizer helps the soil become richer and more fertile naturally.

Note

The NCERT textbook (Class 12 Biology, Chapter 10) defines biofertilizers as organisms that enrich the nutrient quality of the soil. The main examples are Rhizobium (a bacterium that lives in root nodules of legumes and fixes nitrogen), Azospirillum and Azotobacter (free-living nitrogen-fixing bacteria), and blue-green algae (like Anabaena) which also fix nitrogen.

Now, biopesticides. These are living organisms or natural substances that control pests — insects, fungi, weeds, etc. — without using synthetic chemicals. Instead of spraying a poison that kills everything (good and bad bugs alike), a biopesticide might use a specific bacterium that only harms a particular caterpillar, or a fungus that attacks a weed. The most famous example is Bacillus thuringiensis (often called Bt), a bacterium that produces a protein toxic to certain insect larvae but harmless to humans, animals, and most other insects.

Important

The key difference between chemical and biological agents: Biofertilizers and biopesticides are renewable, eco-friendly, and do not leave toxic residues in the soil or water. They are a cornerstone of sustainable agriculture — farming that can continue for generations without destroying the land.

Why does this matter for a commerce or humanities student? Because agriculture is not just about biology — it’s about economics, policy, and human health. Chemical fertilizers and pesticides are expensive to produce, can pollute groundwater, and their overuse leads to "superpests" that become resistant. Biofertilizers and biopesticides are often cheaper in the long run, safer for farm workers, and help maintain soil health. Governments around the world (including India) promote them through subsidies and organic farming schemes. Understanding them helps you see why "organic" food costs more, why some farmers switch to natural methods, and how environmental regulations work.

Here’s a quick summary of the main types you should know (from NCERT):

Biofertilizers:
- Rhizobium (symbiotic with legumes) …

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Part (a): Biodiversity should be conserved for narrowly utilitarian (products), broadly utilitarian (ecosystem services) and ethical reasons; India's tiger numbers rose through Project Tiger, tiger reserves, anti-poaching laws, habitat/prey protection, corridors and community participation. Part (b): Integrated organic farming is a chemical-free, zero-waste cyclical system - Ramesh Chandra Dagar of Sonepat combined cattle, biogas, composting, water harvesting and bee-keeping so that no by-product was wasted.

Part (a)

Three reasons to conserve biodiversity.

Narrowly utilitarian: humans draw countless direct economic benefits from biodiversity - food (cereals, pulses, fruit), firewood, fibre, and industrial products, as well as many medicines (a large fraction of drugs are derived from plants and other organisms).
Broadly utilitarian: biodiversity provides essential ecosystem services - forests and other plants produce the oxygen we breathe through photosynthesis, pollinators enable fruit/seed set, and ecosystems regulate climate, floods and water cycles.
Ethical/moral: every species has intrinsic worth; we have a moral responsibility to care for them and to pass on this biological legacy in good health to future generations.

Ways that increased the tiger population in India.

Launch of Project Tiger (1973) and setting up of dedicated tiger reserves with strictly protected core areas.
Strict anti-poaching measures and enforcement of the Wildlife Protection Act.
Protection and restoration of habitat and prey base so tigers have enough food and space.
Wildlife corridors linking reserves to prevent inbreeding and allow movement. …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

Showing the 12 most recent of 80 on this concept.

CBSE 2026Set A1 markMCQ
$Q. How many mega-biodiversity countries are there in the world?$
(a) 25
(b) 34
(c) 14
(d) 17
›Reveal solutionSolution

The world has 17 megadiverse countries that together hold most of the Earth's species; India is one of them.

A small number of countries lying largely within the tropics harbour a very large share of the world's biodiversity. These are termed megadiverse (mega-biodiversity) countries and number 17, including …

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CBSE 2026Set A1 markMCQ
$Q. Which region got comparatively shorter span of time for species evolution and diversification due to frequent glaciation?$
(a) temperate region
(b) tropical region
(c) polar region
(d) glaciation occurred in all regions
›Reveal solutionSolution

Tropics stayed relatively undisturbed and had more evolutionary time; temperate regions faced frequent glaciations, giving less time for diversification.

One explanation for the greater species richness of the tropics is time: tropical latitudes have remained relatively undisturbed for millions of years, providing a long, stable period for species to evolve and diversify. Temperate regions, in contrast, were subj …

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CBSE 2026Set A1 markMCQ
$Q. Which of the following cyanobacteria fixes atmospheric nitrogen?$
(a) Nostoc
(b) Anabaena
(c) Oscillatoria
(d) All of these
›Reveal solutionSolution

All the listed cyanobacteria are nitrogen fixers; the correct option is (d).

Cyanobacteria (blue-green algae) are autotrophic aquatic and terrestrial microbes that can fix atmospheric nitrogen and are used as biofertilizers, especially in paddy fields. Nostoc, Anabaena and Oscillatoria are all exa …

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CBSE 2026Set A1 markMCQ
$Q. With the help of what are butterfly caterpillars controlled?$
(a) Pseudomonas
(b) Trichoderma
(c) Bacillus thuringiensis
(d) Baculovirus
›Reveal solutionSolution

Bacillus thuringiensis is used to control butterfly caterpillars; the correct option is (c).

Bacillus thuringiensis (Bt) is a bacterium used as a biocontrol agent against insect pests. Dried Bt spores are mixed with water and sprayed onto crops. When eaten by the larvae (caterpillars) of butterflies and moths, the toxin (crystal protein) is released in their gut and kills them, while being harmless to other …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. Microbes (micro-organism) found in the form of biofertilizer is$
(a) Agrobacterium
(b) Bacillus thuringiensis
(c) Baculoviruses
(d) Rhizobium
›Reveal solutionSolution

Biofertilisers are living organisms that enrich soil nutrient quality; Rhizobium (a symbiotic N2-fixer in legume root nodules) is a classic bacterial biofertiliser.

Rhizobium lives symbiotically in the root nodules of leguminous plants and fixes atmospheric nitrogen into a usable form, enriching soil fertility - hence it is used as a biofertiliser. Agrobacterium is used as …

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CBSE 2026Set ANNUAL1 mark
$Q. Which fungus is used as biological control in the treatment of plant diseases?$
›Reveal solutionSolution

Trichoderma species are free-living fungi widely used as biological control agents to protect plant roots from fungal pathogens.

Trichoderma is a genus of free-living fungi commonly found in root ecosystems, and several species act as effective biocontrol agents against a number of plant pathogens, reducing the need for chemical fungicides. This is one of th …

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$Q. Cyanobacteria are useful biofertilizers in the field of$
(a) Wheat
(b) Paddy
(c) Maize
(d) Sugarcane
›Reveal solutionSolution

Cyanobacteria (blue-green algae) are nitrogen-fixing biofertilizers especially valuable in flooded paddy fields.

Cyanobacteria such as Nostoc, Anabaena, and Oscillatoria are photosynthetic, nitrogen-fixing prokaryotes that enrich soil with organic matter and fix atmospheric nitrogen into forms plants can use, increasing soil fertility.

…

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CBSE 2026Set ANNUAL1 markMCQ
$Q. Which bacterial species acts as an bio-insecticide ?$
(a) LAB
(b) Bacillus thuringiensis
(c) Acetobacter aceti
(d) Streptococcus
›Reveal solutionSolution

Bacillus thuringiensis (Bt) produces crystal (Cry) proteins toxic to insect larvae and is widely used as a biological insecticide.

Bacillus thuringiensis forms proteinaceous crystals during a particular phase of its growth that contain a toxic insecticidal protein. When ingested by an insect larva, the toxin is activated in the alkaline gut environment, damaging the gut lining and killing the insect — this is used commercially as Bt-based bio-insecticide (dried spore-crystal formulations) and is also the …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. Assertion (A): Rhizobium leguminosorum is a symbiotic bacterium found in the root nodules of leguminous plants. Reason (R): This bacterium has the ability to fix atmospheric sulphur into sulphur dioxide.$
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true but Reason is false.
(d) Assertion is false but Reason is true.
›Reveal solutionSolution

Rhizobium leguminosorum is indeed a symbiotic bacterium in leguminous root nodules (Assertion true), but it fixes atmospheric NITROGEN into ammonia — not sulphur into sulphur dioxide (Reason false).

Assertion: Rhizobium species live symbiotically in the root nodules of leguminous plants (like pea, gram, beans) — true; this is a classic example of a biofertilizer relationship.

…

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CBSE 2026Set ANNUAL1 mark
$Q. Fill in the blank: When a species become extinct, the plant and animal species associated with an obligatory way also become extinct. It is called ______.$
›Reveal solutionSolution

The linked extinction of dependent species along with the species they rely on is called co-extinction.

Many species are so closely dependent on another species (for food, host or partner) that they cannot survive without it. When such a host or partner species becomes extinct, the plants and animals that were obligately associated with it also die out. This linked loss is called co-extinction, for exa …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. The possible reason for extinction of Steller's sea cow is due to -$
(a) Alien species invasion
(b) Over exploitation
(c) Habitat Loss
(d) Co-extinction
›Reveal solutionSolution

Steller's sea cow became extinct because humans hunted it excessively — an example of over-exploitation.

Over-exploitation is one of the major causes of biodiversity loss ("The Evil Quartet"): when a resource is harvested by humans faster than it can replenish, the species declines to extinction. Steller's sea cow (Hydrodamalis gigas) was a large, docile marine mammal that was kill …

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CBSE 2026Set ANNUAL1 markMCQ
$Q. Which one of the following is commonly found in root ecosystem and control several plant pathogens?$
(a) Rhizobium
(b) Bacillus thuringiensis
(c) Trichoderma
(d) Azospirillum
›Reveal solutionSolution

Trichoderma is a soil fungus of the root ecosystem used as a biocontrol agent against many plant pathogens.

Biocontrol agents are living organisms used to control plant diseases and pests instead of chemicals. Trichoderma species are free-living fungi very common in the root ecosystems (rhizosphere) and are effective biocontrol agents against several soil-borne plant pathogens.

…

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Q.There is a great concern all over the world to conserve biodiversity for maintaining ecological balance in nature. Explain giving three reasons. Write different ways that have helped in increasing tiger population in our country.

Part (a)

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