Biodiversity and Conservation Class 12: Concepts, Patterns and Board Answers

What Biodiversity and Conservation is about

Weightage: This chapter is part of Unit X, Ecology and Environment, which carries 10 of the 70 theory marks together with Organisms and Populations and Ecosystem.Source: CBSE Biology (044) syllabus 2026-27, course structure, Unit X Ecology and Environment

In real board papers: asked in 8 of the 8 board papers we hold (2023 to 2026), on average 4.8 marks per paper. See the questions

Key concepts

Levels of biodiversity

NCERT section 13.1 Biodiversity

Diversity exists at all levels of biological organisation. The three most important:

1. Genetic diversity: variation within a species over its range.

• The medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges varies in the potency and concentration of reserpine it makes.
• India grows over 50,000 genetically distinct rice strains and about 1,000 mango varieties.

2. Species diversity: variety of species.

• The Western Ghats have greater amphibian species diversity than the Eastern Ghats.

3. Ecological diversity: variety of ecosystems.

• India (deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, alpine meadows) has greater ecosystem diversity than a Scandinavian country like Norway.

Why it matters now: this diversity took millions of years to accumulate, but could be lost in less than two centuries at present rates of species loss. Biodiversity and its conservation are vital environmental issues of international concern.

Worked example

Classify each as genetic, species or ecological diversity: (a) over 50,000 strains of rice in India, (b) more amphibian species in the Western Ghats than the Eastern Ghats, (c) India having deserts, mangroves and coral reefs, (d) reserpine content of Rauwolfia varying across the Himalayas. (2 marks)

Try it first, then show the solutionSolution

1. (a) Genetic diversity (variation within one species). (b) Species diversity. (1)
2. (c) Ecological diversity (variety of ecosystems). (d) Genetic diversity (within Rauwolfia vomitoria). (1)

Answer: (a) genetic (b) species (c) ecological (d) genetic.

How many species: the world and India

NCERT section 13.1.1 How Many Species are there on Earth and How Many in India?

Recorded versus actual: according to the IUCN (2004), slightly more than 1.5 million plant and animal species have been described, but how many remain is unclear.

How ecologists estimate the total: species inventories are more complete in temperate than tropical countries, and most undiscovered species are in the tropics. Biologists compare the temperate–tropical species richness of an exhaustively studied insect group and extrapolate this ratio to other groups. Extreme estimates range from 20 to 50 million; a more conservative, scientifically sound estimate by Robert May is about 7 million.

Composition of recorded species:

• Animals: more than 70%; plants (including algae, fungi, bryophytes, gymnosperms, angiosperms): no more than 22%.
• Insects: more than 70% of animals, so 7 out of every 10 animals are insects.
• Fungi have more species than fishes, amphibians, reptiles and mammals combined.
• Prokaryotes are not included: conventional taxonomy does not suit them and many cannot be cultured; by biochemical or molecular criteria they may number in millions.
• Examples of richness: more than 20,000 ant species, 3,00,000 beetles, 28,000 fishes, nearly 20,000 orchids.

India:

• Only 2.4% of the world's land area but 8.1% of global species diversity: one of the 12 mega diversity countries.
• About 45,000 plant species and twice as many animals recorded.
• If only about 22% of all species are recorded (May's estimate), India probably has more than 1,00,000 plant and more than 3,00,000 animal species still to be discovered.
• Many may go extinct before they are found: 'nature's biological library is burning' before the titles are catalogued.

Worked example

India has recorded about 45,000 plant species. If only 22% of all species have been recorded, estimate the total number of plant species in India and how many remain undiscovered. (2 marks)

Try it first, then show the solutionSolution

1. Total ≈ 45,000 ÷ 0.22 ≈ 2,04,500 plant species. (1)
2. Undiscovered ≈ 2,04,500 − 45,000 ≈ 1,59,500, i.e. more than 1,00,000 as NCERT states. Check: 22% of 2,04,500 ≈ 45,000. (1)

Answer: About 2 lakh plant species in all; roughly 1.6 lakh (more than 1 lakh) still undiscovered.

Latitudinal gradient in diversity

NCERT section 13.1.2 Patterns of Biodiversity (latitudinal gradients)

Pattern: species diversity generally decreases from the equator towards the poles. With very few exceptions, the tropics (23.5° N to 23.5° S) have more species than temperate or polar areas.

NCERT examples:

• Birds: Colombia (near the equator) nearly 1,400 species; New York (41° N) 105; Greenland (71° N) only 56. India, mostly tropical, has more than 1,200 bird species.
• A tropical forest in Ecuador has up to 10 times as many vascular plant species as an equal area of temperate forest in the Midwest of the USA.
• The Amazonian rain forest has the greatest biodiversity on earth: more than 40,000 plant species, 3,000 fishes, 1,300 birds, 427 mammals, 427 amphibians, 378 reptiles and more than 1,25,000 invertebrates; there may be at least two million insect species yet to be named.

Three hypotheses for tropical richness:
1. More evolutionary time: speciation is a function of time; temperate regions had frequent glaciations, whereas the tropics remained relatively undisturbed for millions of years, allowing long diversification.
2. Constant environment: tropical environments are less seasonal, more constant and predictable, which promotes niche specialisation and greater diversity.
3. More solar energy: higher energy input gives higher productivity, which might indirectly support greater diversity.

Worked example

Colombia has about 1,400 bird species, New York 105 and Greenland 56. How many times more bird species does Colombia have than Greenland? Give two reasons for this pattern. (3 marks)

Try it first, then show the solutionSolution

1. 1,400 ÷ 56 = 25 times. Check: 56 × 25 = 1,400. (1)
2. The tropics were not subjected to frequent glaciations and have had a long undisturbed evolutionary time for speciation. (1)
3. Tropical environments are less seasonal and more predictable (niche specialisation), and receive more solar energy, raising productivity (any one more). (1)

Answer: 25 times; more evolutionary time, constant environment and more solar energy (any two).

Species–area relationship

NCERT section 13.1.2 Patterns of Biodiversity (species–area relationships)

Observation: Alexander von Humboldt, exploring South American jungles, saw that within a region species richness increases with explored area, but only up to a limit.

Shape: for many taxa (angiosperms, birds, bats, freshwater fishes), the relationship between species richness and area is a rectangular hyperbola. On a logarithmic scale it becomes a straight line:

log S = log C + Z log A (equivalently S = CA^Z)

• S: number of species (richness); A: area;
• C: the intercept on the Y-axis;
• Z: the slope, also called the regression coefficient.

Values of Z:

• For areas within a region, Z is usually 0.1 to 0.2, whatever the taxonomic group or region (plants in Britain, birds in California, molluscs in New York state give amazingly similar slopes).
• For very large areas such as whole continents, Z is much steeper: 0.6 to 1.2. For frugivorous birds and mammals in tropical forests of different continents, Z = 1.15.

Meaning of a steeper slope: species richness rises much faster with area, because different continents hold largely different sets of species; it also means that losing area causes a bigger loss of species.

Use in conservation: the equation predicts how many species are lost when habitat shrinks: S_new/S_old = (A_new/A_old)^Z.

Worked example

For a region, C = 10 and Z = 0.2. Calculate the species richness for an area of 1000 km² using log S = log C + Z log A. (2 marks)

Try it first, then show the solutionSolution

1. log S = log 10 + 0.2 × log 1000 = 1 + 0.2 × 3 = 1.6; S = 10^1.6 ≈ 39.8 ≈ 40 species. (1)
2. Check with S = CA^Z: 1000^0.2 = 10^0.6 ≈ 3.98; S = 10 × 3.98 ≈ 39.8. (1)

Answer: About 40 species.

Importance of species diversity to the ecosystem

NCERT section 13.1.3 The Importance of Species Diversity to the Ecosystem

Does species number matter? Ecologists have no definitive answer, but for decades they believed communities with more species are more stable.

A stable community:

• does not vary too much in productivity from year to year;
• is resistant or resilient to occasional natural or man-made disturbances;
• resists invasions by alien species.

David Tilman's long-term outdoor plot experiments:

• Plots with more species showed less year-to-year variation in total biomass.
• Increased diversity contributed to higher productivity.

Rich biodiversity is essential for ecosystem health and imperative for the survival of the human race.

Rivet popper hypothesis (Paul Ehrlich, Stanford):

• An airplane = ecosystem; its rivets = species.
• If passengers each pop a rivet (a species goes extinct), flight safety (ecosystem functioning) may not suffer at first, but as more rivets go, the plane becomes dangerously weak.
• Which rivet is lost also matters: rivets on the wings (key species that drive major ecosystem functions) are far more critical than those on seats or windows.

Worked example

Explain the rivet popper hypothesis and what the 'wing rivets' represent. (2 marks)

Try it first, then show the solutionSolution

1. Paul Ehrlich compared an ecosystem to an airplane held together by rivets (species); removing rivets one by one (extinctions) may not cause failure at first, but the plane weakens dangerously as more are lost. (1)
2. Wing rivets represent key species that drive major ecosystem functions; losing them is much more serious than losing less important species. (1)

Answer: Species are rivets; gradual loss weakens the ecosystem; key species are like wing rivets.

Loss of biodiversity

NCERT section 13.1.4 Loss of Biodiversity

New species are hardly being added by speciation, but losses continue, driven mainly by human activities.

Evidence:

• Human colonisation of tropical Pacific islands led to the extinction of more than 2,000 native bird species.
• The IUCN Red List (2004) documents 784 extinctions in the last 500 years: 338 vertebrates, 359 invertebrates and 87 plants.
• Recent extinctions: dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller's sea cow (Russia), and three subspecies of tiger (Bali, Javan, Caspian). 27 species disappeared in the last twenty years alone.
• Extinctions are not random: amphibians seem more vulnerable.
• More than 15,500 species face the threat of extinction: 12% of birds, 23% of mammals, 32% of amphibians and 31% of gymnosperms.

The 'Sixth Extinction': fossils show five mass extinctions in over 3 billion years before humans. The present one differs in rate: current extinction rates are 100 to 1,000 times faster than in pre-human times, because of human activities. If trends continue, nearly half of all species might be wiped out in the next 100 years.

Consequences of biodiversity loss in a region:
1. Decline in plant production.
2. Lower resistance to environmental perturbations such as drought.
3. Greater variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles.

Endangered organisms and the Red Data Book (syllabus terms): species whose chance of dying out in the wild soon is very high are called endangered or threatened. The IUCN records threatened species and their status in its Red List; the printed volumes of these records are called the Red Data Book.

Worked example

How does the present 'Sixth Extinction' differ from the five earlier mass extinctions? State two consequences of biodiversity loss in a region. (3 marks)

Try it first, then show the solutionSolution

1. Earlier mass extinctions happened before humans; the present one is driven by human activities. (1)
2. Species are now being lost an estimated 100 to 1,000 times faster than before humans existed. (1)
3. Consequences: decline in plant production; lower resistance to perturbations like drought; increased variability in productivity, water use, and pest and disease cycles (any two). (1)

Answer: Human-caused and 100–1,000 times faster; e.g. falling plant production and lower drought resistance.

Causes of biodiversity loss: the Evil Quartet

NCERT section 13.1.4 Loss of Biodiversity (causes)

Four major human-caused drivers, nicknamed 'The Evil Quartet':

1. Habitat loss and fragmentation (the most important cause):

• Tropical rain forests once covered more than 14% of the earth's land surface; now no more than 6%. About 1000 hectares are lost in the time it takes to read this chapter.
• The Amazon ('lungs of the planet'), with probably millions of species, is cleared for soya beans and for grasslands to raise beef cattle.
• Pollution degrades many habitats.
• Fragmentation of large habitats badly affects mammals and birds needing large territories and migratory animals, causing population declines.

2. Over-exploitation ('need' turning into 'greed'):

• Steller's sea cow and the passenger pigeon went extinct in the last 500 years from over-exploitation.
• Many marine fish populations are over-harvested, endangering commercially important species.

3. Alien species invasions:

• Introduced species (accidentally or deliberately) may become invasive and cause decline or extinction of native species.
• The Nile perch introduced into Lake Victoria (East Africa) led to the extinction of more than 200 species of cichlid fish.
• Invasive weeds in India: carrot grass (Parthenium), Lantana, water hyacinth (Eichhornia).
• The illegal introduction of the African catfish Clarias gariepinus for aquaculture threatens indigenous catfishes in Indian rivers.

4. Co-extinctions:

• When a species goes extinct, species associated with it obligatorily also go extinct.
• A host fish going extinct takes its unique parasites with it.
• In a co-evolved plant–pollinator mutualism, the extinction of one invariably leads to the extinction of the other.

Worked example

Name the four causes of biodiversity loss (the Evil Quartet) and give one NCERT example for each. (2 marks)

Try it first, then show the solutionSolution

1. Habitat loss and fragmentation: tropical rain forests reduced from over 14% to no more than 6% of land; Amazon cleared for soya and cattle. Over-exploitation: Steller's sea cow, passenger pigeon. (1)
2. Alien species invasions: Nile perch in Lake Victoria wiping out over 200 cichlid species (or Parthenium, Lantana, water hyacinth, Clarias gariepinus). Co-extinctions: parasites of an extinct host fish; partners in plant–pollinator mutualism. (1)

Answer: Habitat loss and fragmentation, over-exploitation, alien invasions and co-extinctions, each with an example.

Why conserve biodiversity

NCERT section 13.2.1 Why Should We Conserve Biodiversity?

Reasons fall into three categories:

1. Narrowly utilitarian (direct economic benefits):

• Food such as cereals, pulses and fruits; also fibre, firewood and building material.
• Industrial products such as dyes, resins, tannins, perfumes and lubricants.
• Medicines: more than 25% of drugs sold worldwide come from plants; 25,000 plant species are used in traditional medicines by native peoples. Many more medicinal plants may await discovery in tropical rain forests.
• Bioprospecting: exploring molecular, genetic and species diversity for products of economic importance; biodiversity-rich nations can benefit enormously.

2. Broadly utilitarian (ecosystem services):

• The Amazon forest is estimated to produce, through photosynthesis, 20% of the total oxygen in the earth's atmosphere.
• Pollination by bees, bumblebees, birds and bats, without which plants would not give fruits or seeds.
• Intangible benefits: aesthetic pleasure of walking in woods, spring flowers, a bulbul's song.
• (NCERT's summary also mentions pest control, climate moderation and flood control.)

3. Ethical:

• We owe care to the millions of plant, animal and microbe species that share the planet.
• Every species has an intrinsic value, even with no economic value to us.
• We have a moral duty to care for them and pass our biological legacy on in good order to future generations.

Worked example

Classify these reasons for conservation as narrowly utilitarian, broadly utilitarian or ethical: (a) the Amazon producing about 20% of atmospheric oxygen, (b) plants providing more than 25% of marketed drugs, (c) every species having intrinsic value, (d) bees pollinating crops. (2 marks)

Try it first, then show the solutionSolution

1. (a) Broadly utilitarian (ecosystem service). (b) Narrowly utilitarian (direct product). (1)
2. (c) Ethical. (d) Broadly utilitarian (pollination service). (1)

Answer: (a) broadly utilitarian (b) narrowly utilitarian (c) ethical (d) broadly utilitarian.

In situ conservation

NCERT section 13.2.2 How do we conserve Biodiversity? (in situ conservation)

In situ (on site) conservation: protecting the whole ecosystem, so biodiversity at all levels is protected: 'save the entire forest to save the tiger'.

Biodiversity hotspots: since nations cannot afford to save everything, conservationists identified regions for maximum protection with:

• very high species richness, and
• a high degree of endemism (species found nowhere else).
• Initially 25, then 9 more: 34 hotspots worldwide. They are also regions of accelerated habitat loss.
• Three cover India's richest regions: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
• All hotspots together cover less than 2% of the earth's land, yet hold an extremely high number of species; strictly protecting them could reduce ongoing mass extinctions by almost 30%.

Protected areas in India: ecologically unique, biodiversity-rich regions are legally protected as biosphere reserves, national parks and wildlife sanctuaries. NCERT's figures: 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries.

Sacred groves: tracts of forest set aside by religious and cultural traditions, in which all trees and wildlife are venerated and fully protected. Found in:

• Khasi and Jaintia Hills, Meghalaya (the last refuges for many rare and threatened plants);
• Aravalli Hills, Rajasthan;
• Western Ghats of Karnataka and Maharashtra;
• Sarguja, Chanda and Bastar areas of Madhya Pradesh.

Ramsar sites (syllabus term): wetlands designated as being of international importance under the Ramsar Convention, an international treaty for the conservation and wise use of wetlands (signed at Ramsar, Iran, in 1971). Protecting them is a form of in situ conservation of wetland ecosystems.

Worked example

What are biodiversity hotspots? Name the three that include parts of India, and state why protecting hotspots is effective. (3 marks)

Try it first, then show the solutionSolution

1. Hotspots are regions with very high species richness and a high degree of endemism (species found nowhere else); 34 are recognised worldwide. (1)
2. Indian ones: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya. (1)
3. Together they cover less than 2% of the earth's land but hold a very large number of species; strict protection could cut ongoing mass extinctions by almost 30%. (1)

Answer: High-richness, high-endemism regions; Western Ghats–Sri Lanka, Indo-Burma, Himalaya; small area, huge species share, ~30% fewer extinctions if protected.

Ex situ conservation and international efforts

NCERT section 13.2.2 How do we conserve Biodiversity? (ex situ conservation)

Ex situ (off site) conservation: when a plant or animal is endangered or threatened and needs urgent help, it is taken out of its natural habitat and kept in a special setting with protection and care.

Methods:

• Zoological parks, botanical gardens and wildlife safari parks. Many animals extinct in the wild survive in zoos.
• Cryopreservation: gametes of threatened species stored in a viable, fertile state for long periods.
• In vitro fertilisation of eggs.
• Tissue culture propagation of plants.
• Seed banks: seeds of different genetic strains of commercially important plants stored for long periods.

In situ versus ex situ:

• In situ: in the natural habitat; protects the whole ecosystem and all levels of diversity; e.g. national parks, sanctuaries, biosphere reserves, sacred groves, hotspots.
• Ex situ: outside the habitat; for urgent rescue of particular species; e.g. zoos, botanical gardens, seed banks, cryopreservation.

International efforts (biodiversity knows no political boundaries):

• Convention on Biological Diversity ('The Earth Summit'), Rio de Janeiro, 1992: called on all nations to conserve biodiversity and use its benefits sustainably.
• World Summit on Sustainable Development, Johannesburg, South Africa, 2002: 190 countries pledged to achieve by 2010 a significant reduction in the rate of biodiversity loss at global, regional and local levels.

Worked example

Distinguish between in situ and ex situ conservation with two examples each. When is ex situ conservation preferred? (3 marks)

Try it first, then show the solutionSolution

1. In situ: conserving species in their natural habitat by protecting the whole ecosystem, e.g. national parks, wildlife sanctuaries, biosphere reserves, sacred groves. (1)
2. Ex situ: protecting threatened species outside their habitat, e.g. zoos, botanical gardens, seed banks, cryopreserved gametes. (1)
3. Ex situ is preferred when a species is endangered or threatened and needs urgent measures to avoid extinction. (1)

Answer: In situ protects habitats (national parks, sacred groves); ex situ protects species off-site (zoos, seed banks); ex situ for urgent rescue of threatened species.

Biodiversity and Conservation in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Patterns of Biodiversity
• Loss of Biodiversity and Its Causes
• In Situ and Ex Situ Conservation

Biodiversity and Conservation: key facts

Species–area relationship

$\log S=\log C+Z\log A;S=C{A}^Z$

S species richness, A area, Z slope, C intercept.

Typical Z values

$Z=0.1\text{–}0.2(\text{within regions});Z=0.6\text{–}1.2(\text{continents});Z=1.15(\text{frugivorous birds and mammals})$

Steeper slope: richness rises faster with area.

Species lost when area shrinks

$\frac{S_{\text{new}}}{S_{\text{old}}}={\left(\frac{A_{\text{new}}}{A_{\text{old}}}\right)}^Z$

Derived from S = CA^Z with the same C.

India's share

$\text{land}=2.4\%;\text{species}=8.1\%;\text{plants}\approx 45,000;\text{animals}\approx 90,000$

One of 12 mega diversity countries.

Global counts

$\text{described}>1.5\text{million};\text{May’s estimate}\approx 7\text{million};\text{recorded share}\approx 22\%$

Animals > 70% of recorded species; insects > 70% of animals.

Protected areas and hotspots (NCERT)

$34\text{hotspots (3 in India)};14\text{biosphere reserves};90\text{national parks};448\text{sanctuaries}$

Hotspots: < 2% of land; protection could cut extinctions by almost 30%.

Biodiversity and Conservation: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

How the board asks Biodiversity and Conservation

The question patterns to expect, and the method that works for each.

Tricks to remember Biodiversity and Conservation

Short memory aids. Say each one aloud once, then use it on a question the same day.

• G-S-E: 'Genes, Species, Ecosystems'

  Genetic (rice strains, Rauwolfia), Species (Western Ghats amphibians), Ecological (India versus Norway).

  Use it when: Levels of biodiversity.

• Evil Quartet: 'HOAC'

  Habitat loss and fragmentation, Over-exploitation, Alien invasions, Co-extinctions.

  Use it when: Causes of biodiversity loss.

• Tropics win by 'TCS': Time, Constancy, Sunlight

  More evolutionary Time, more Constant environment, more Solar energy.

  Use it when: Latitudinal gradient hypotheses.

• Z: 'Zero point one to two inside, point six to one-point-two across continents'

  Regional slope 0.1–0.2; continental 0.6–1.2; frugivores 1.15.

  Use it when: Species–area questions.

• Birds by latitude: 1400 → 105 → 56

  Colombia (equator) → New York (41° N) → Greenland (71° N).

  Use it when: Latitudinal gradient example.

• Indian hotspots: 'Western, Indo, Him'

  Western Ghats–Sri Lanka, Indo-Burma, Himalaya.

  Use it when: Hotspot questions.

Biodiversity and Conservation: board-level solved questions

Ordered from board level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section D style)

Read the situation, then answer every part. In the board paper this is a 4-mark question split into 1 + 2 + 1 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Biodiversity and Conservation

The slips examiners see most often, and what to write instead.

• ✗Mistake: Writing the species–area equation incorrectly

  Wrong working

  log S = log Z + C log A.

  Right working

  log S = log C + Z log A, where Z is the slope and C the intercept.

  ✓Do this: Remember: Z is the slope, so it multiplies log A.

  Usually costs: 1 mark.

• ✗Mistake: Saying plants make up most recorded species

  ✓Do this: Animals are more than 70% of recorded species; plants no more than 22%; insects are more than 70% of animals.

  Usually costs: ½ to 1 mark.

• ✗Mistake: Calling zoos in situ conservation

  ✓Do this: Zoos, botanical gardens, safari parks, seed banks and cryopreservation are ex situ; national parks, sanctuaries, biosphere reserves and sacred groves are in situ.

  Usually costs: 1 mark.

• ✗Mistake: Giving the wrong reason for the current extinction crisis

  ✓Do this: The difference from past mass extinctions is the rate (100–1,000 times faster) and the cause (human activities).

  Usually costs: 1 mark.

• ✗Mistake: Defining hotspots by species richness only

  ✓Do this: Hotspots need both very high species richness and a high degree of endemism.

  Usually costs: ½ mark.

• ✗Mistake: Mixing up broadly and narrowly utilitarian reasons

  ✓Do this: Narrowly utilitarian = direct products (food, drugs, fibre); broadly utilitarian = ecosystem services (oxygen, pollination, aesthetics).

  Usually costs: 1 mark.

NCERT exercise guide: Biodiversity and Conservation

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Biodiversity and Conservation: previous year questions

• Asked in 8 of the 8 board papers we hold (2023 to 2026), on average 4.8 marks per paper; 16 questions in all, counting OR alternatives. In 4 of 4 sample papers.

Counted from the real papers on our previous year papers page, not estimated. Average marks are over every board paper we hold, with an OR pair counted once. Chapter tags are ours.

Solved board questions from Biodiversity and Conservation

Real questions from recent papers. Try each one first, then open our step-by-step solution with marks per step.

Every Biodiversity and Conservation question, by year

Practice questions on Biodiversity and Conservation

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   The term biodiversity was popularised by:
   (a) Robert May (b) Edward Wilson (c) Paul Ehrlich (d) David Tilman

   Hint

   A sociobiologist.

   Answer

   (b) Edward Wilson

2. Q2 · 1 mark · Assertion-reasonBoard level

   Assertion (A): Species diversity decreases from the equator towards the poles.
   Reason (R): Temperate regions were subjected to frequent glaciations in the past.
   (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.

   Hint

   Evolutionary time hypothesis.

   Answer

   (a)

3. Q3 · 1 mark · MCQHarder board level

   In the species–area relationship for frugivorous birds and mammals in tropical forests of different continents, Z is about:
   (a) 0.1 (b) 0.2 (c) 0.6 (d) 1.15

   Hint

   Continental scale.

   Answer

   (d) 1.15

4. Q4 · 2 marks · Very short answerBoard level

   Give two examples each of in situ and ex situ conservation in India. (2 marks)

   Hint

   Habitat versus off-site.

   Answer

   In situ: national parks, wildlife sanctuaries, biosphere reserves, sacred groves (any two) (1). Ex situ: zoological parks, botanical gardens, seed banks, cryopreservation of gametes (any two) (1).

5. Q5 · 2 marks · Very short answerHarder board level

   Why do ecologists say 'nature's biological library is burning before we catalogue the titles'? (2 marks)

   Hint

   Undiscovered species going extinct.

   Answer

   Only about 22% of species have been recorded; India may have over 1,00,000 plant and 3,00,000 animal species still undescribed, and listing them needs huge taxonomic effort (1). Many species face extinction before they are discovered, so we lose them without knowing they existed (1).

6. Q6 · 2 marks · Very short answerBoard level

   Describe two ways in which species diversity contributes to ecosystem stability. (2 marks)

   Hint

   Tilman.

   Answer

   More diverse communities show less year-to-year variation in productivity (biomass), as in Tilman's plots (1). They tend to be more resistant or resilient to disturbances and more resistant to invasion by alien species (1).

7. Q7 · 3 marks · Short answerHarder board level

   Explain the Evil Quartet with one example of each. (3 marks)

   Hint

   HOAC.

   Answer

   Habitat loss and fragmentation: rain forests reduced from over 14% to no more than 6% of land (¾). Over-exploitation: Steller's sea cow and passenger pigeon (¾). Alien invasions: Nile perch eliminating over 200 cichlid species in Lake Victoria (¾). Co-extinctions: parasites of an extinct host fish, or partners in a plant–pollinator mutualism (¾).

8. Q8 · 3 marks · Short answerBoard level

   What are biodiversity hotspots? Why are they given priority, and what fraction of land do they cover? (3 marks)

   Hint

   Richness plus endemism.

   Answer

   Regions with very high species richness and a high degree of endemism; 34 are recognised (1). They are also regions of accelerated habitat loss, so conservation resources give the best return there (1). They cover less than 2% of the earth's land but hold an extremely high number of species; strict protection could reduce mass extinctions by almost 30% (1).

9. Q9 · 5 marks · Long answerHarder board level

   (a) Describe the latitudinal gradient in species diversity with examples. (2)
   (b) Give three hypotheses explaining it. (3) (5 marks)

   Hint

   Colombia, New York, Greenland; Amazon.

   Answer

   (a) Species diversity generally falls from the equator to the poles; the tropics (23.5° N–23.5° S) harbour more species. Colombia has nearly 1,400 bird species, New York (41° N) 105 and Greenland (71° N) 56; the Amazon rain forest is the most biodiverse place on earth (over 40,000 plant and 1,25,000 invertebrate species) (2). (b) Tropics had more evolutionary time without frequent glaciations (1); they are less seasonal, more constant and predictable, promoting niche specialisation (1); they receive more solar energy, raising productivity and indirectly diversity (1).

10. Q10 · 3 marks · Short answerHOTS / competency

    Suppose two islands in the same region have areas of 100 km² and 10,000 km², with C = 5 and Z = 0.15 for both. Calculate the expected number of species on each. (3 marks)

    Hint

    log S = log C + Z log A.

    Answer

    Island 1: log S = log 5 + 0.15 × 2 = 0.699 + 0.30 = 0.999; S ≈ 10 species (1). Island 2: log S = 0.699 + 0.15 × 4 = 0.699 + 0.60 = 1.299; S ≈ 19.9 ≈ 20 species (1). Check: a 100-fold area increase multiplies S by 100^0.15 = 10^0.3 ≈ 2.0, and 10 × 2 = 20 (1).

11. Q11 · 2 marks · Very short answerHOTS / competency

    Over-exploitation and alien invasions both reduce biodiversity. Suppose an Indian lake is over-fished for its native carp and then stocked with a fast-growing alien fish. Explain how the two causes could combine. (2 marks)

    Hint

    Weakened natives, strong invader.

    Answer

    Over-fishing reduces native carp populations, as over-harvesting threatens commercially important species (1). A fast-growing alien fish can then become invasive and out-compete or prey on the weakened natives, as the Nile perch did in Lake Victoria and Clarias gariepinus threatens Indian catfishes, possibly driving natives to extinction (1).

12. Q12 · 2 marks · Very short answerHarder board level

    Name the two international meetings on biodiversity mentioned in NCERT and state what each called for. (2 marks)

    Hint

    1992 and 2002.

    Answer

    Convention on Biological Diversity (Earth Summit), Rio de Janeiro, 1992: all nations to conserve biodiversity and use its benefits sustainably (1). World Summit on Sustainable Development, Johannesburg, 2002: 190 countries pledged a significant reduction in the rate of biodiversity loss by 2010 (1).

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Who popularised the term biodiversity?Show answer

   The sociobiologist Edward Wilson.

2. 2.What is Robert May's estimate of global species diversity?Show answer

   About 7 million species.

3. 3.What share of world land and species does India have?Show answer

   2.4% of land and 8.1% of global species diversity.

4. 4.Which group has more species than all vertebrate groups (fishes, amphibians, reptiles, mammals) combined?Show answer

   Fungi.

5. 5.Who first described the species–area relationship?Show answer

   Alexander von Humboldt.

6. 6.What did Tilman's experiments show?Show answer

   Plots with more species had less year-to-year variation in biomass, and greater diversity gave higher productivity.

7. 7.How many extinctions does the IUCN Red List (2004) record in the last 500 years?Show answer

   784 (338 vertebrates, 359 invertebrates and 87 plants).

8. 8.Name three subspecies of tiger that have gone extinct.Show answer

   Bali, Javan and Caspian tigers.

9. 9.What percentage of amphibian species face extinction?Show answer

   32%.

10. 10.What did the Nile perch do in Lake Victoria?Show answer

    Led to the extinction of more than 200 species of cichlid fish.

11. 11.What percentage of atmospheric oxygen is the Amazon estimated to produce?Show answer

    About 20%.

12. 12.When and where was the Earth Summit held?Show answer

    In Rio de Janeiro, 1992 (Convention on Biological Diversity).

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Can you define genetic, species and ecological diversity with one example each?
• ☐Can you explain how ecologists estimate the total number of species on earth?
• ☐Can you give the latitudinal bird example and three hypotheses for tropical richness?
• ☐Can you write the species–area equation, explain Z and calculate species loss?
• ☐Can you explain the rivet popper hypothesis and Tilman's findings?
• ☐Can you list the Evil Quartet with an example of each?
• ☐Can you give narrowly utilitarian, broadly utilitarian and ethical reasons for conservation?
• ☐Can you compare in situ and ex situ conservation and name India's three hotspots and four sacred grove regions?

Biodiversity and Conservation: frequently asked questions