Biodiversity and Conservation NEET: Complete Notes + 22 MCQs

1At a glance: what biodiversity means

Definition: the term biodiversity refers to the totality of genes, species and ecosystems of a region. NCERT opens the biodiversity and conservation chapter with the scale of this diversity: more than 20,000 species of ants, 3,00,000 species of beetles, 28,000 species of fishes and nearly 20,000 species of orchids.

Ecologists and evolutionary biologists try to understand this diversity by asking six questions:

1. Why are there so many species?
2. Did such great diversity exist throughout earth’s history?
3. How did this diversification come about?
4. How and why is this biodiversity important to the biosphere?
5. Would it function any differently if the diversity was much less?
6. How do humans benefit from the diversity of life?

This chapter belongs to Unit 10 (Ecology) on our NEET Biology hub. The first unit of Class 11, The Living World, introduces biodiversity as the number and types of organisms on earth.

2Levels of biodiversity

In our biosphere immense diversity (heterogeneity) exists not only at the species level but at all levels of biological organisation, from macromolecules within cells to biomes. Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation. The most important of them are genetic, species and ecological diversity.

1. Genetic diversity

A single species may show high diversity at the genetic level (variation in nucleotides, genes, chromosomes or whole genomes) over its distributional range. In other words, genetic diversity is the sum total of genetic information contained in the genes of individual plants, animals and microorganisms. A species needs it to maintain reproductive vitality, resistance to diseases and the ability to adapt to changing conditions.

Example: the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges shows variation in the potency and concentration of the active chemical reserpine that the plant produces (mainly in its roots). Reserpine is an alkaloid used to treat high blood pressure.

2. Species diversity

A species is a group of organisms so similar genetically that they can interbreed and produce fertile offspring. Species diversity is the diversity at the species level, usually measured as the total number of species within discrete geographical boundaries. The simplest measure is species richness, the number of species per unit area.

NCERT example: the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

3. Ecological diversity

At the ecosystem level, India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has a greater ecosystem diversity than a Scandinavian country like Norway. (Scandinavia is in northern Europe and includes Norway, Sweden and Denmark; these countries put strong emphasis on conservation, but their range of ecosystems is narrower than India’s.)

It has taken millions of years of evolution to accumulate this rich diversity, but we could lose all that wealth in less than two centuries if the present rates of species losses continue.

Alpha, beta and gamma diversity BEYOND NCERT

Diversity at the community and ecosystem level is often described from three perspectives. These terms are not in the NCERT chapter but appear in some reference books:

• Alpha (α) diversity, within-community diversity: the diversity of organisms sharing the same community or habitat. It combines species richness and evenness (equitability), i.e. how evenly individuals are spread among species. Example: peacocks, parrots and crows present in equal numbers in a sample area show high evenness. In nature, species are rarely evenly distributed.
• Beta (β) diversity, between-community diversity: the change (replacement) of species from one community or habitat to another, due to different microhabitats, niches and environmental conditions.
• Gamma (γ) diversity: the diversity of habitats over a total landscape or geographical area.

3How many species are there on Earth?

Published records tell us how many species have been recorded, but not how many exist. According to the International Union for Conservation of Nature and Natural Resources (IUCN) (2004), the total number of plant and animal species described so far is slightly more than 1.5 million.

For many taxonomic groups, species inventories are more complete in temperate than in tropical countries. Since most undiscovered species are in the tropics, biologists compare the temperate-tropical species richness of an exhaustively studied group of insects and extrapolate this ratio to other groups of animals and plants to estimate the total.

• Some extreme estimates range from 20 to 50 million.
• Robert May’s more conservative and scientifically sound estimate places global species diversity at about 7 million.

Earth’s biodiversity from current inventories

• More than 70 per cent of all recorded species are animals.
• Plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) are no more than 22 per cent.
• Among animals, insects are the most species-rich group, making up more than 70 per cent of all animals: out of every 10 animals, 7 are insects.
• The number of fungi species is more than the combined total of fishes, amphibians, reptiles and mammals (hook: FARM).

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Prokaryotes are not included in these estimates. Biologists are not sure how many prokaryotic species there might be: conventional taxonomic methods are not suitable for identifying microbial species, and many species cannot be cultured in the laboratory. If biochemical or molecular criteria are used, their diversity alone might run into millions.

4India’s biodiversity

• India has only 2.4 per cent of the world’s land area.
• Its share of global species diversity is an impressive 8.1 per cent.
• This makes India one of the 12 mega diversity countries of the world (NCERT).
• Nearly 45,000 species of plants and twice as many (about 90,000) animals have been recorded from India.
• If we accept May’s global estimate, only 22 per cent of all species have been recorded so far. Applied to India, there are probably more than 1,00,000 plant species and more than 3,00,000 animal species yet to be discovered and described.

Completing this inventory would need immense trained manpower (taxonomists) and time, and many species may become extinct before we discover them. In NCERT’s words, “Nature’s biological library is burning even before we catalogued the titles of all the books stocked there.”

5Patterns of biodiversity: latitudinal gradients

Diversity is not uniform across the world. The best-known pattern is the latitudinal gradient: in general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, the tropics (23.5° N to 23.5° S) harbour more species than temperate or polar areas.

• Colombia, near the equator: nearly 1,400 species of birds.
• New York (41° N): 105 species; Greenland (71° N): only 56 species.
• India, with much of its land in tropical latitudes: more than 1,200 species of birds.
• A forest in a tropical region like Ecuador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA.

A similar decrease is seen from lower to higher altitudes on a mountain. BEYOND NCERT An increase of 1,000 m in altitude lowers temperature by about 6.5 °C; this drop and the greater seasonal variability at higher altitudes reduce diversity.

Amazonian rain forest

The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth. It is home to more than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and more than 1,25,000 invertebrates. Scientists estimate there might be at least two million insect species there waiting to be discovered. (Hook from the notes: FBPRIMA.)

Why are the tropics so rich?

1. More evolutionary time: speciation is generally a function of time. Unlike temperate regions, subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and had a long evolutionary time for species diversification.
2. Constant environment: tropical environments are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to greater species diversity.
3. More solar energy: more solar energy is available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity.

6Species-area relationship

During his explorations of South American jungles, the German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit. For a wide variety of taxa (angiosperm plants, birds, bats, freshwater fishes) the relation between species richness and area is a rectangular hyperbola. On a logarithmic scale the species-area relationship becomes a straight line:

Values of Z

Ecologists have found that Z lies in the range of 0.1 to 0.2 regardless of the taxonomic group or the region: whether plants in Britain, birds in California or molluscs in New York state, the slopes of the regression lines are amazingly similar.

For very large areas like entire continents, the slope becomes much steeper, with Z values of 0.6 to 1.2. For frugivorous (fruit-eating) birds and mammals in the tropical forests of different continents, the slope is 1.15. A steeper line (more inclined towards the Y-axis) means species richness rises faster with area.

Regression coefficient in brief

In biology, regression measures how one variable (the dependent variable, on the Y-axis) changes with another (the independent variable, on the X-axis). The raw species-area data form a curve, and a straight line cannot be fitted to it. Taking logarithms turns the curve into a straight line; its slope gives Z and its intercept gives log C. Slope is “rise over run”: if every 3 extra hours of study added 2 marks, the slope would be 2/3. (The correlation coefficient r, which ranges from −1.0 to +1.0, is a different measure: it shows how closely two variables are related, with r = 0 meaning no relationship.)

Two hypotheses are often given for the relationship BEYOND NCERT: larger areas contain more kinds of habitats, and species number reflects a balance between colonisation and extinction (island biogeography).

7Importance of species diversity to the ecosystem

Does the number of species in a community really matter to the functioning of the ecosystem? Ecologists have not been able to give a definitive answer. For many decades they believed that communities with more species generally tend to be more stable than those with fewer species.

What is a stable community?

• It should not show too much variation in productivity from year to year.
• It must be either resistant or resilient to occasional disturbances (natural or man-made).
• It must be resistant to invasions by alien species.

David Tilman’s experiments

David Tilman’s long-term ecosystem experiments using outdoor plots gave some tentative answers. Plots with more species showed less year-to-year variation in total biomass, and increased diversity contributed to higher productivity. We may not understand fully how species richness contributes to the well-being of an ecosystem, but rich biodiversity is essential for ecosystem health and imperative for the survival of the human race.

Rivet popper hypothesis (Paul Ehrlich)

Would Western Ghats ecosystems be less functional if one of its tree frog species were lost forever? Would it matter if, instead of 20,000, we had only 15,000 species of ants? There are no direct answers, but the Stanford ecologist Paul Ehrlich gave an analogy:

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A rivet is a short metal pin that holds two metal plates together. Losing a few rivets may not affect flight safety at first, but as more are removed the plane becomes dangerously weak. Which rivet is removed also matters: losing rivets on the wings is far more serious than losing a few on the seats or windows.

8Loss of biodiversity

It is doubtful whether new species are being added through speciation, but there is no doubt about continuing losses. The biological wealth of our planet is declining rapidly, and the accusing finger points to human activities. The colonisation of the tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.

Types of extinction BEYOND NCERT

• Natural (background) extinction: as environmental conditions change, some species disappear and better-adapted ones take their place. In the geological past this happened at a very slow rate.
• Mass extinction: episodes in earth’s geological history when large numbers of species were lost together, because of catastrophes.
• Anthropogenic extinction: species disappearing because of human activities. This man-made extinction is a very severe depletion of biodiversity because it is happening within a short period.

Numbers to remember (IUCN Red List 2004, NCERT)

• 784 species extinct 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).
• The last 20 years alone saw the disappearance of 27 species.
• Extinctions are not random: amphibians appear more vulnerable.
• More than 15,500 species worldwide face the threat of extinction (more than 650 of them from India, per the NCERT summary).
• Threatened today: 12% of birds, 23% of mammals, 32% of amphibians and 31% of gymnosperms.

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The sixth extinction

Fossil records show that during the long period (more than 3 billion years) since the origin and diversification of life, there were five episodes of mass extinction, all before humans appeared. The “Sixth Extinction” now in progress differs in its rate: current extinction rates are estimated to be 100 to 1,000 times faster than in pre-human times, and our activities are responsible. If present trends continue, nearly half of all species on earth might be wiped out within the next 100 years.

Consequences of biodiversity loss

In general, loss of biodiversity in a region may lead to:

1. a decline in plant production;
2. lowered resistance to environmental perturbations such as drought; and
3. increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.

9IUCN Red List and Red Data Book

The NEET syllabus for biodiversity and conservation names endangered organisms, extinction and the Red Data Book. The NCERT text uses IUCN Red List data but does not list the categories, so this section is background BEYOND NCERT.

The IUCN Red List, started in 1964, is a catalogue of taxa facing a risk of extinction. It informs the public and policy makers about the urgency and scale of conservation problems. Its uses are:

• developing awareness about the importance of threatened biodiversity;
• identifying and documenting endangered species;
• providing a global index of the decline of biodiversity;
• defining conservation priorities at the local level and guiding conservation action.

The current system (IUCN Categories version 3.1) has nine categories. The notes used the older 1994 system, which had eight, with a single “Lower Risk” category.

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Threatened animals of India named in the notes: Himalayan musk deer, Great Indian Bustard, snow leopard, Kashmir stag (hangul) and Indian wild ass. Threatened plants: the medicinal plant Podophyllum and the pitcher plant Nepenthes (Nepenthes khasiana of Meghalaya).

10Causes of biodiversity loss: the Evil Quartet

The accelerated rates of species extinction today are largely due to human activities. There are four major causes; “The Evil Quartet” is the sobriquet used to describe them.

1. Habitat loss and fragmentation

This is the most important cause driving animals and plants to extinction (NEET 2019). When people cut down trees, fill a wetland, plough grassland or burn a forest, the natural habitat of a species is changed or destroyed.

• The most dramatic examples come from tropical rain forests. Once covering more than 14 per cent of the earth’s land surface, they now cover no more than 6 per cent. By the time you finish reading this chapter, 1,000 more hectares of rain forest would have been lost.
• The Amazon rain forest, called the “lungs of the planet”, harbouring probably millions of species, is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle (cattle raised for meat, unlike dairy cattle).
• Besides total loss, degradation of habitats by pollution also threatens many species.
• Fragmentation: when large habitats are broken into small fragments, mammals and birds requiring large territories and animals with migratory habits are badly affected, leading to population declines. A forest patch surrounded by croplands, orchards, plantations or urban areas is a fragmented habitat.

2. Over-exploitation

Humans have always depended on nature for food and shelter, but when “need” turns to “greed”, it leads to over-exploitation of natural resources. Many extinctions in the last 500 years, such as Steller’s sea cow and the passenger pigeon, were due to over-exploitation. Today many marine fish populations are over-harvested, endangering some commercially important species.

3. Alien species invasions

When alien species are introduced, unintentionally or deliberately, some become invasive and cause decline or extinction of indigenous species.

• Nile perch, a predatory fish introduced into Lake Victoria in east Africa, fed on cichlids and eventually caused the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish.
• Invasive weeds such as carrot grass (Parthenium), Lantana and water hyacinth (Eichhornia) damage the environment and threaten native species. (NCERT spells it Eicchornia; the accepted spelling is Eichhornia.)
• The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture threatens the indigenous catfishes of our rivers. Its high fecundity, rapid growth, wide habitat preferences, tolerance to extreme water conditions and ability to feed on a wide variety of prey can devastate native fish and aquatic invertebrates.

4. Co-extinctions

When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.

• When a host fish species becomes extinct, its unique assemblage of parasites meets the same fate.
• In a coevolved plant-pollinator mutualism, extinction of one invariably leads to extinction of the other. In such mutualism, pollinators (bees, butterflies) get pollen or nectar as food; some bees also use waxes and resins from flowers to build hives.

Obligate mutualism: a mutualism is obligate when one species relies completely on another. Yucca moths and yucca plants depend on each other: the plant cannot make seeds without the moth, which lays its eggs in the yucca flowers it pollinates, and the moth larvae reach maturity only by eating developing yucca seeds.

11Why should we conserve biodiversity?

The arguments for biodiversity and conservation are grouped into three categories: narrowly utilitarian, broadly utilitarian and ethical.

1. Narrowly utilitarian

Humans derive countless direct economic benefits from nature:

• food (cereals, pulses, fruits)
• firewood
• fibre
• construction material
• industrial products (tannins, lubricants, dyes, resins, perfumes)
• products of medicinal importance

More than 25 per cent of the drugs sold worldwide are derived from plants, and 25,000 species of plants contribute to the traditional medicines of native peoples. With increasing resources put into bioprospecting (exploring molecular, genetic and species-level diversity for products of economic importance in medicine, agriculture and industry), nations with rich biodiversity can expect enormous benefits.

2. Broadly utilitarian

Biodiversity plays a major role in many ecosystem services:

• The fast-dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth’s atmosphere.
• Pollination, without which plants cannot give us fruits or seeds, is provided by pollinators: bees, bumblebees, birds and bats.
• Intangible benefits: the aesthetic pleasure of walking through thick woods, watching spring flowers or waking up to a bulbul’s song.

3. Ethical

We share this planet with millions of plant, animal and microbe species. Every species has an intrinsic value, even if it has no current economic value to us. We have a moral duty to care for their well-being and pass on our biological legacy in good order to future generations.

12How do we conserve biodiversity? In situ conservation

When we conserve and protect the whole ecosystem, its biodiversity at all levels is protected: we save the entire forest to save the tiger. This is in situ (on site) conservation. When a species is endangered or threatened and needs urgent measures, ex situ (off site) conservation is the desirable approach. Together, in situ and ex situ conservation are the two pillars of biodiversity and conservation in NCERT.

Biodiversity hotspots

Many nations cannot afford to conserve all their biological wealth, so conservationists identified biodiversity hotspots for maximum protection: regions with very high species richness and a high degree of endemism (species confined to that region and found nowhere else). Norman Myers developed the hotspot concept in 1988 BEYOND NCERT.

• Initially 25 hotspots were identified; nine more were added, bringing the total to 34.
• Hotspots are also regions of accelerated habitat loss.
• All hotspots together cover less than 2 per cent of earth’s land area, yet harbour an extremely high number of species. Strict protection could reduce ongoing mass extinctions by almost 30 per cent.

India’s three hotspots:

1. Western Ghats and Sri Lanka, treated as one unit because of their shared biogeographical history
2. Indo-Burma
3. Himalaya

13National parks, sanctuaries and biosphere reserves

In India, ecologically unique and biodiversity-rich regions are legally protected as biosphere reserves, national parks and sanctuaries. NCERT: India has 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries (the NCERT summary says more than 450).

National parks

• A legally protected area where flora, fauna and even objects of historical significance are conserved.
• Declared by the state government by notification (the central government can also declare one) under the Wild Life (Protection) Act, 1972.
• Boundaries are well defined at the time of declaration and can be altered only on a resolution passed by the state legislature.
• Grazing is not permitted.
• A national park cannot be downgraded to a sanctuary.
• India’s first national park: Jim Corbett (1936, then Hailey National Park).

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Nagarjunsagar-Srisailam (Andhra Pradesh) is a tiger reserve, one of the largest in India, rather than a national park. Project Tiger began in 1973 BEYOND NCERT; India now has 58 tiger reserves.

Wildlife sanctuaries

• Protected areas where particular species of birds and animals are conserved; flora and fauna are both protected.
• Notified by the central or state government.
• Boundaries are less strictly fixed than those of national parks.
• A sanctuary can be upgraded to a national park.
• Grazing of livestock and some private ownership or rights may be allowed.

Examples: Indian Wild Ass Sanctuary (Little Rann of Kutch, Gujarat); Ranganathittu Bird Sanctuary (near Mysore, Karnataka).

Biosphere reserves

Biosphere reserves are a special category of protected areas of land and/or coastal environments in which people are an integral component of the system. They represent natural biomes and contain unique biological communities. They come under UNESCO’s Man and Biosphere (MAB) Programme (launched 1971; the first biosphere reserves were designated in 1976) BEYOND NCERT.

• Large protected areas for conserving wildlife, plant and animal resources and the traditional life of tribal people living there.
• Cover terrestrial and coastal ecosystems.
• Internationally recognised, nominated by national governments, and remain under the jurisdiction of the country where they are located.
• India’s biosphere reserve programme began in 1986; Nilgiri was the first biosphere reserve.

1. Core (natural) zone: an undisturbed, legally protected ecosystem; no human activity.
2. Buffer zone: surrounds the core; limited activities such as research, education and resource use.
3. Transition zone: the outermost part, where reserve managers and local people cooperate in settlement, cropping, recreation, forestry and other economic uses without disturbing the ecology. It may include a restoration region, a degraded area selected for restoration to a near-natural form.

Examples: Nilgiri, Nanda Devi, Nokrek, Manas, Dibru-Saikhowa, Dihang-Dibang, Sundarbans, Gulf of Mannar, Great Nicobar, Similipal, Khangchendzonga, Pachmarhi and Agasthyamala.

The World Conservation Union (IUCN) and the World Wide Fund for Nature (WWF) support projects worldwide to promote conservation and appropriate development of biosphere reserves.

14Sacred groves

India has a history of religious and cultural traditions that protected nature. In many cultures, tracts of forest were set aside, and all the trees and wildlife within were venerated and given total protection. These sacred groves are tracts of virgin forest with rich biodiversity, protected by local people because of beliefs, culture, religion and taboos (often because deities are believed to reside there). They are remnants of primary forest and repositories of rare and endemic species. Sacred groves show how closely biodiversity and conservation have long been linked in Indian culture.

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15Ex situ conservation

In this second half of in situ and ex situ conservation, threatened animals and plants are taken out of their natural habitat and placed in special settings where they can be protected and given special care.

• Zoological parks, botanical gardens and wildlife safari parks serve this purpose. Many animals that have become extinct in the wild continue to be maintained in zoological parks.
• Arboreta are botanical gardens where specific trees and shrubs are cultivated.
• A wildlife safari park is a zoo-like drive-in attraction where visitors observe freely roaming animals from vehicles.

Modern ex situ methods

• Cryopreservation: gametes of threatened species can be preserved in viable and fertile condition for long periods. Material is stored at ultra-low temperature, typically in liquid nitrogen at −196 °C, in compact, low-maintenance units. It is particularly useful for vegetatively propagated crops such as potato.
• In vitro fertilisation: eggs can be fertilised in vitro.
• Tissue culture: plants can be propagated using tissue culture methods.
• Seed banks: seeds of different genetic strains of commercially important plants can be kept for long periods.

16Earth Summit 1992 and WSSD 2002

Biodiversity knows no political boundaries, so its conservation is a collective responsibility of all nations. Two global meetings shaped biodiversity and conservation at the international level; the first produced the Convention on Biological Diversity.

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The CBD has three objectives BEYOND NCERT: conservation of biological diversity, sustainable use of its components, and fair and equitable sharing of benefits arising from the use of genetic resources. Brazil is often cited as the most biodiverse country in the world.

17Biodiversity and conservation: NCERT summary and exercises

• Life originated nearly 3.8 billion years ago; biodiversity is the sum total of diversity at all levels of biological organisation.
• More than 1.5 million species are recorded, but nearly 6 million more may await discovery. Over 70 per cent of named species are animals, of which 70 per cent are insects. Fungi have more species than all vertebrates combined.
• Species richness is highest in the tropics and decreases towards the poles; it is also a function of area (rectangular hyperbola).
• Diverse communities tend to be less variable, more productive and more resistant to biological invasions.
• Present extinction rates are 100 to 1,000 times higher than before humans. Nearly 700 species have become extinct in recent times and more than 15,500 (over 650 from India) face extinction.
• Reasons to conserve are narrowly utilitarian, broadly utilitarian and ethical. Conservation is in situ or ex situ.

NCERT exercises with short answers

18High-yield lines for biodiversity and conservation NEET

1. Biodiversity term popularised by sociobiologist Edward Wilson.
2. Rauwolfia vomitoria → reserpine → genetic diversity.
3. India: >50,000 rice strains, 1,000 mango varieties.
4. Western Ghats > Eastern Ghats in amphibian diversity.
5. IUCN (2004): slightly more than 1.5 million species described; Robert May: about 7 million.
6. Animals >70%; plants ≤22%; insects >70% of animals.
7. India: 2.4% of land, 8.1% of species; one of 12 mega diversity countries.
8. Colombia ~1,400, India >1,200, New York 105, Greenland 56 bird species.
9. Amazon: 40,000 plants, 3,000 fishes, 1,300 birds, 427 mammals, 427 amphibians, 378 reptiles, 1,25,000 invertebrates.
10. log S = log C + Z log A; Z = 0.1–0.2 (regions), 0.6–1.2 (continents), 1.15 frugivorous birds and mammals.
11. Tilman: more species → less year-to-year variation in biomass, higher productivity.
12. Rivet popper hypothesis: Paul Ehrlich.
13. 784 extinctions in 500 years: 338 vertebrates, 359 invertebrates, 87 plants.
14. Threatened: amphibians 32%, gymnosperms 31%, mammals 23%, birds 12%.
15. Extinction rate now 100–1,000 times pre-human; five past mass extinctions.
16. Evil Quartet: habitat loss and fragmentation (most important), over-exploitation, alien species, co-extinctions.
17. Rain forests: from 14% to 6% of land surface.
18. Nile perch → >200 cichlid species lost in Lake Victoria.
19. Amazon: 20% of atmospheric oxygen; >25% of drugs from plants; 25,000 medicinal plant species.
20. 34 hotspots, <2% of land; protection could cut mass extinctions by ~30%.
21. India (NCERT): 14 biosphere reserves, 90 national parks, 448 sanctuaries.
22. Earth Summit: Rio 1992. WSSD: Johannesburg 2002, 190 countries, target 2010.

19MCQs from the notes

These are the biodiversity and conservation questions from the chapter notes, with answers checked against NCERT.

20Practice MCQs (NCERT-based)

Biodiversity and conservation NEET-pattern questions written directly from the NCERT text.

21Common mistakes

• Writing “longitudinal gradient”. The pattern is a latitudinal gradient.
• Writing 17 mega diversity countries. NCERT says India is one of the 12.
• Saying fungi are the largest plant group. Angiosperms are; fungi come second.
• Mixing up Z values: 0.1–0.2 within regions, 0.6–1.2 for continents.
• Giving two reasons for conservation. NCERT gives three, including the ethical one.
• Calling sacred groves ex situ. They are in situ.
• Saying the Earth Summit was in Johannesburg. Rio de Janeiro was 1992; Johannesburg was WSSD 2002.
• Quoting current counts (18, 106, 574) in NEET. Use NCERT’s 14, 90, 448.
• Listing the cheetah as globally extinct. It became extinct in India only.
• Writing the rivet popper “tree” example. NCERT’s example is a Western Ghats tree frog.

22Common doubts on biodiversity and conservation