Biodiversity and Conservation is Chapter 13 of NCERT Class 12 Biology and part of Unit 10, Ecology and Environment, of the NEET UG syllabus. These notes cover the levels of biodiversity, species numbers, latitudinal and species-area patterns, loss of biodiversity and the evil quartet, reasons to conserve, hotspots, and in situ and ex situ conservation, with a free notes PDF.
Biodiversity and Conservation NEET Notes
Section-wise key points from NCERT Chapter 13, comparison tables, high-yield facts and common mistakes for NEET 2027 revision.
Biodiversity and Conservation at a Glance
| Item | Details |
|---|---|
| NEET UG syllabus unit | Unit 10: Ecology and Environment |
| NCERT textbook | Biology, Class 12, Chapter 13 (rationalised book) |
| Other chapters in the unit | Organisms and Populations (Chapter 11), Ecosystem (Chapter 12) |
| Syllabus topics | Concept, patterns and importance of biodiversity; loss of biodiversity; biodiversity conservation; hotspots, endangered organisms, extinction, Red Data Book, biosphere reserves, national parks and sanctuaries, sacred groves |
| Official chapter | NCERT Chapter 13 |
| Notes PDF | View PDF |
The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.
The syllabus lists the Red Data Book; the NCERT chapter discusses threatened and extinct species through the IUCN Red List (2004). Numbers on this page are the figures printed in NCERT, which is what NEET questions follow.
What is biodiversity and what are its levels?
Biodiversity is the combined diversity at all levels of biological organisation, from macromolecules within cells to biomes. The term was popularised by the sociobiologist Edward Wilson.
| Level | Meaning | NCERT example |
|---|---|---|
| Genetic diversity | High diversity at the genetic level within a single species over its range | Rauwolfia vomitoria in different Himalayan ranges differs in the potency and concentration of reserpine; India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango |
| Species diversity | Diversity at the species level | The Western Ghats have greater amphibian species diversity than the Eastern Ghats |
| Ecological diversity | Diversity at the ecosystem level | India, with deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has greater ecosystem diversity than Norway |
How many species are there on Earth and in India?
More than 1.5 million plant and animal species have been described (IUCN, 2004). Robert May’s conservative estimate puts global species diversity at about 7 million.
- The world has more than 20,000 species of ants, 3,00,000 of beetles, 28,000 of fishes and nearly 20,000 of orchids.
- Some extreme estimates of total species range from 20 to 50 million.
- Total species numbers are estimated by extrapolating the temperate-tropical species richness ratio of a well-studied insect group to other groups.
- More than 70 per cent of recorded species are animals; plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) are no more than 22 per cent.
- Insects make up more than 70 per cent 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 in these estimates; their diversity alone might run into millions.
India’s Share
| Item | NCERT figure |
|---|---|
| Share of world land area | 2.4 per cent |
| Share of global species diversity | 8.1 per cent |
| Status | One of the 12 mega diversity countries |
| Recorded plant species | Nearly 45,000 |
| Recorded animal species | About twice the plant number |
| Yet to be discovered (by May’s estimate) | More than 1,00,000 plant and more than 3,00,000 animal species |
What are the patterns of biodiversity?
Biodiversity is uneven. Species diversity generally decreases from the equator towards the poles, and species richness rises with area up to a limit.
Latitudinal Gradients
- With very few exceptions, the tropics (23.5° N to 23.5° S) have more species than temperate or polar areas.
- Birds: Colombia (near the equator) nearly 1,400 species; New York (41° N) 105; Greenland (71° N) only 56; India more than 1,200.
- A tropical forest in Ecuador has up to 10 times as many vascular plant species as an equal temperate forest in the Midwest of the USA.
- The Amazonian rain forest has the greatest biodiversity on Earth: 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.
| Why the tropics have more species | Explanation |
|---|---|
| More evolutionary time | Tropical latitudes stayed relatively undisturbed for millions of years, while temperate regions had frequent glaciations |
| Stable environment | Less seasonal, more constant and predictable conditions promote niche specialisation |
| More solar energy | Higher productivity, which might indirectly contribute to greater diversity |
Species-area Relationship
- Alexander von Humboldt observed that species richness increases with explored area, but only up to a limit.
- The relation is a rectangular hyperbola; on a logarithmic scale it is a straight line: log S = log C + Z log A.
- S = species richness, A = area, Z = slope of the line (regression coefficient), C = Y-intercept.
- Z lies between 0.1 and 0.2 for most taxa and regions, but is much steeper (0.6 to 1.2) for very large areas such as entire continents.
- For frugivorous birds and mammals in tropical forests of different continents, the slope is 1.15.
Why does species diversity matter to an ecosystem?
A stable community varies little in productivity from year to year, resists or recovers from disturbance, and resists invasion by alien species.
- David Tilman’s long-term outdoor plot experiments found that plots with more species showed less year-to-year variation in total biomass, and that increased diversity gave higher productivity.
- Paul Ehrlich’s ‘rivet popper hypothesis’ compares an ecosystem to an airplane and species to its rivets. Losing a few rivets may not affect flight at first, but the plane weakens as more are removed.
- Which rivet is lost also matters: rivets on the wings stand for key species that drive major ecosystem functions.
Loss of Biodiversity: Extinctions and the Evil Quartet
Biodiversity is declining rapidly, and current extinction rates are estimated to be 100 to 1,000 times faster than in pre-human times because of human activities.
- Human colonisation of tropical Pacific Islands is said to have caused 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 tiger subspecies (Bali, Javan, Caspian). The last twenty years alone saw 27 species disappear.
- Amphibians appear more vulnerable to extinction.
- More than 15,500 species worldwide face the threat of extinction, including 12 per cent of bird, 23 per cent of mammal, 32 per cent of amphibian and 31 per cent of gymnosperm species.
- There have been five earlier mass extinctions; the ‘Sixth Extinction’ differs in its much faster rate.
- Effects of biodiversity loss: decline in plant production, lower resistance to perturbations such as drought, and more variable ecosystem processes such as productivity, water use and pest and disease cycles.
| Cause (evil quartet) | Key points and examples |
|---|---|
| Habitat loss and fragmentation | The most important cause. Tropical rain forests once covered more than 14 per cent of the land surface and now no more than 6 per cent. The Amazon (‘lungs of the planet’) is cleared for soya beans and beef cattle. Fragmentation hurts animals needing large territories and migratory animals. |
| Over-exploitation | When need turns to greed. Steller’s sea cow and passenger pigeon became extinct this way; many marine fish are over-harvested. |
| Alien species invasions | Nile perch in Lake Victoria led to the extinction of more than 200 cichlid fish species. Invasive weeds: carrot grass (Parthenium), Lantana, water hyacinth (Eichhornia). The illegally introduced African catfish Clarias gariepinus threatens native catfishes. |
| Co-extinctions | When a species becomes extinct, species obligately associated with it also die out, such as the parasites of a host fish or a co-evolved plant and its pollinator. |
Why should we conserve biodiversity?
NCERT groups the reasons into three arguments: narrowly utilitarian, broadly utilitarian and ethical.
| Argument | Basis | Examples from NCERT |
|---|---|---|
| Narrowly utilitarian | Direct economic benefits | Food, firewood, fibre, construction material, industrial products and medicines. More than 25 per cent of drugs sold worldwide come from plants, and 25,000 plant species are used in traditional medicine. Bioprospecting explores diversity for economically important products. |
| Broadly utilitarian | Ecosystem services | The Amazon forest is estimated to produce 20 per cent of the oxygen in Earth’s atmosphere through photosynthesis; pollination by bees, bumblebees, birds and bats; aesthetic pleasures |
| Ethical | Intrinsic value | Every species has intrinsic value, and we have a moral duty to pass on our biological legacy in good order |
How do we conserve biodiversity?
In situ conservation protects the whole ecosystem on site (‘save the entire forest to save the tiger’); ex situ conservation takes threatened species out of their habitat for special care.
| Feature | In situ (on site) | Ex situ (off site) |
|---|---|---|
| Approach | Protect the species in its natural habitat along with the entire ecosystem | Remove threatened animals and plants to special settings for protection and care |
| Examples | Biodiversity hotspots, biosphere reserves, national parks, wildlife sanctuaries, sacred groves | Zoological parks, botanical gardens, wildlife safari parks, seed banks |
| Techniques | Legal protection of ecologically unique, biodiversity-rich regions | Cryopreservation of gametes, in vitro fertilisation, tissue culture propagation, long-term seed storage |
Biodiversity Hotspots
- Hotspots are regions with very high species richness and a high degree of endemism (species found only there). They are also regions of accelerated habitat loss.
- Initially 25 hotspots were identified; nine more were added, making 34.
- Three cover India’s high-biodiversity regions: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
- All hotspots together cover less than 2 per cent of Earth’s land area, and strict protection could reduce ongoing mass extinctions by almost 30 per cent.
Protected Areas and Sacred Groves in India
- NCERT gives India 14 biosphere reserves, 90 national parks and 448 wildlife sanctuaries.
- Sacred groves are forest tracts protected for religious and cultural reasons: Khasi and Jaintia Hills (Meghalaya), Aravalli Hills (Rajasthan), Western Ghat regions of Karnataka and Maharashtra, and the Sarguja, Chanda and Bastar areas of Madhya Pradesh.
- In Meghalaya, sacred groves are the last refuges for many rare and threatened plants.
International Efforts
- The Convention on Biological Diversity (the Earth Summit), Rio de Janeiro, 1992, called on all nations to conserve biodiversity and use its benefits sustainably.
- At the World Summit on Sustainable Development, Johannesburg, 2002, 190 countries pledged to significantly reduce the rate of biodiversity loss by 2010.
Most-asked Facts for NEET: Biodiversity and Conservation
Revise these one-line facts from the NCERT chapter just before the exam.
- The term biodiversity was popularised by Edward Wilson.
- Three levels: genetic, species and ecological diversity.
- Rauwolfia vomitoria shows genetic diversity in reserpine production.
- Robert May estimated global species diversity at about 7 million.
- Animals are more than 70 per cent of recorded species; insects are more than 70 per cent of animals.
- India: 2.4 per cent of world land, 8.1 per cent of global species diversity, one of 12 mega diversity countries.
- Species diversity decreases from the equator towards the poles.
- Species-area relation: log S = log C + Z log A; Z is 0.1 to 0.2, and 0.6 to 1.2 for whole continents.
- Species-area relationship was observed by Alexander von Humboldt.
- Rivet popper hypothesis: Paul Ehrlich. Biodiversity and stability plot experiments: David Tilman.
- Evil quartet: habitat loss and fragmentation, over-exploitation, alien species invasions, co-extinctions.
- Habitat loss and fragmentation is the most important cause of extinction.
- Nile perch in Lake Victoria caused the extinction of more than 200 cichlid species.
- Current extinction rates are 100 to 1,000 times faster than in pre-human times.
- 34 biodiversity hotspots in the world; 3 cover India.
- Sacred groves in Meghalaya are in the Khasi and Jaintia Hills.
- Earth Summit: Rio de Janeiro, 1992; World Summit on Sustainable Development: Johannesburg, 2002.
Common Mistakes to Avoid
Watch for these mix-ups when you answer questions on this chapter.
- Swapping India’s figures. India has 2.4 per cent of world land area and 8.1 per cent of global species diversity, not the other way round.
- Saying species diversity increases towards the poles. It decreases away from the equator.
- Using Z = 0.6 to 1.2 for small regions. That steeper range applies to very large areas like entire continents; within regions Z is 0.1 to 0.2.
- Calling over-exploitation the most important cause of extinction. NCERT names habitat loss and fragmentation.
- Classing seed banks or cryopreservation as in situ. They are ex situ methods; sacred groves, national parks and biosphere reserves are in situ.
- Listing the Eastern Ghats as an Indian hotspot. The three are Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
- Saying insects are 70 per cent of all species. They are more than 70 per cent of animal species.
- Mixing up the arguments for conservation: ecosystem services such as oxygen and pollination are broadly utilitarian, direct products are narrowly utilitarian.
- Saying the current ‘Sixth Extinction’ is like the five earlier ones. It differs in rate: 100 to 1,000 times faster, because of human activities.
- Treating the 25 original hotspots as the current number. Nine more were added, making 34.
Biodiversity and Conservation Notes PDF and Related Pages
Download the AglaSem notes for Biodiversity and Conservation (key notes and important questions with answers) free: View PDF
- All chapters: NEET Biology notes
- Full topic list: NEET syllabus
- Practice: NEET question papers
- Source text: NCERT Chapter 13 (NCERT, Class 12 Biology)
NEET Biology Notes: All Chapters
Botany
- The Living World
- Biological Classification
- Plant Kingdom
- Cell: The Unit of Life
- Plant Growth and Development
- Anatomy of Flowering Plants
- Cell Cycle and Cell Division
- Respiration in Plants
- Photosynthesis in Higher Plants
- Morphology of Flowering Plants
- Principles of Inheritance and Variation
- Microbes in Human Welfare
- Sexual Reproduction in Flowering Plants
- Molecular Basis of Inheritance
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
Zoology
- Animal Kingdom
- Biomolecules
- Breathing and Exchange of Gases
- Excretory Products and their Elimination
- Body Fluids and Circulation
- Structural Organisation in Animals
- Locomotion and Movement
- Reproductive Health
- Chemical Coordination and Integration
- Neural Control and Coordination
- Evolution
- Human Health and Disease
- Human Reproduction
- Biotechnology and its Applications
- Biotechnology: Principles and Processes
All chapters with their notes PDFs are on the NEET Biology notes page.
Biodiversity and Conservation NEET Notes FAQs
Which NCERT chapter is Biodiversity and Conservation?
It is Chapter 13 of the NCERT Class 12 Biology textbook (rationalised book), the last chapter of the ecology unit after Organisms and Populations (Chapter 11) and Ecosystem (Chapter 12).
Is Biodiversity and Conservation in the NEET 2027 syllabus?
It is in the latest NEET UG syllabus (2026, released by NMC on 22 December 2025) under Unit 10, Ecology and Environment. NMC is expected to release the 2027 syllabus later; check the syllabus page once it is out.
What is the evil quartet?
It is the name for the four major causes of biodiversity loss: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Habitat loss and fragmentation is the most important of them.
Which biodiversity hotspots cover India?
Three of the world’s 34 hotspots cover India’s high-biodiversity regions: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
Are these notes enough for NEET questions on biodiversity?
No. Read NCERT Chapter 13 line by line first, because NEET Biology questions closely follow the NCERT textbooks. Use these notes and the PDF for quick revision, then practise previous year questions.