What is biodiversity in simple words?

Biodiversity is the variety of all living things in a place, from tiny microbes to tigers and banyan trees. It also covers the differences in genes inside one species and the many kinds of habitats, such as forests, wetlands and coral reefs. More variety usually means a healthier, more stable ecosystem.

What are the three levels of biodiversity?

The three levels are genetic diversity, species diversity and ecosystem diversity. Genetic diversity is variation within one species, such as India's thousands of rice strains. Species diversity is the number and variety of species in an area. Ecosystem diversity is the range of habitats, like deserts, mangroves and alpine meadows.

Why is India called a megadiverse country?

India holds a much bigger share of the world's species than its share of the world's land. NCERT's Class 12 Biology textbook says India has 2.4 per cent of global land area but 8.1 per cent of recorded species diversity. That is why it is counted among the world's 12 megadiversity countries.

What are the main causes of biodiversity loss?

NCERT groups the main causes as the 'Evil Quartet': habitat loss and fragmentation, over-exploitation, invasion by alien species, and co-extinctions. Habitat loss is the most important of these. Pollution, poaching and climate change add further pressure on many plants and animals.

What is the difference between in situ and ex situ conservation?

In situ conservation protects species in their natural home, for example in national parks, wildlife sanctuaries, biosphere reserves and sacred groves. Ex situ conservation protects them outside their home, in zoos, botanical gardens, seed banks or through cryopreservation of gametes. In situ saves the whole ecosystem; ex situ is an emergency back-up.

Biodiversity: Meaning, Types, Importance and Threats

Biodiversity is the variety of life on Earth. It includes every plant, animal and microorganism, the genetic differences within each species, and the many ecosystems they form. Biodiversity keeps ecosystems stable and gives people food, medicine, clean water and fresh air, so protecting it matters for everyone.

This page is the main guide to biodiversity on this site. It covers the meaning, the levels, wildlife diversity, why biodiversity matters, India’s place as a megadiverse nation, hotspots, threats and conservation. Each section ends with a link to a detailed article on that topic.

What is biodiversity?

The word biodiversity is short for “biological diversity”. NCERT’s Class 12 Biology textbook notes that the term was popularised by the sociobiologist Edward Wilson. He used it to describe the combined diversity found at every level of biological organisation.

Put simply, biodiversity covers plants, animals, microorganisms and the ecosystems that hold them. It is not only a count of species. It also includes the genetic differences inside each species and the variety of habitats that support life.

Think of a single patch of forest in the Western Ghats. It has hundreds of tree species, insects, frogs, birds, fungi and soil bacteria. Each species also varies from one individual to the next. Together, these living things and their surroundings form an ecosystem. All of this variety, taken together, is biodiversity.

Diversity exists at many scales. It ranges from molecules inside cells to whole biomes, the large natural regions such as deserts or tropical rainforests. For exams, however, three levels matter most: genetic, species and ecosystem.

Flora and fauna: the two halves of living diversity

Two words appear in almost every biodiversity lesson. Flora means the plant life of a region, and fauna means its animal life. A list of the flora and fauna of a place is a quick way to describe its biodiversity. Our guide to flora and fauna and how they differ explains both terms with clear examples.

What are the three types of biodiversity?

Biologists describe biodiversity at three linked levels. Each level needs protection, because losing one weakens the others.

Genetic diversity

Genetic diversity is the variation in genes within a single species. Two members of a species are never exactly alike. NCERT’s Class 12 Biology textbook gives a strong Indian example: India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

Genetic variety can also change the chemistry of a plant. The medicinal plant Rauwolfia vomitoria grows in different Himalayan ranges. Its plants differ in how much reserpine, an active chemical, they produce. Genetic diversity helps a species survive disease and changing climate.

Species diversity

Species diversity is the variety of species found in an area. It depends on both the number of species and how common each one is. NCERT notes that the Western Ghats have a greater diversity of amphibian species than the Eastern Ghats.

Ecosystem diversity

Ecosystem diversity (also called ecological diversity) is the variety of habitats, communities and ecological processes in a region. India has deserts, rainforests, mangroves, coral reefs, wetlands, estuaries and alpine meadows. Because of this range, NCERT says India has greater ecosystem diversity than a Scandinavian country such as Norway.

Level	What it measures	Example from NCERT
Genetic diversity	Variation in genes within one species	Over 50,000 rice strains and 1,000 mango varieties in India
Species diversity	Variety of species in an area	Western Ghats have more amphibian species than the Eastern Ghats
Ecosystem diversity	Variety of habitats and communities	India’s deserts, mangroves, coral reefs and alpine meadows

How many species are there on Earth?

Nobody knows the exact number. Scientists have described and named a large number of species, but many more remain unknown. The figure used in NCERT’s Class 12 Biology textbook comes from the IUCN (2004). By that count, slightly more than 1.5 million species had been described. Treat 1.5 million as the textbook figure for exams, since it is an older tally. The ecologist Robert May gave a careful estimate of about 7 million species in total.

The known species are not shared equally between groups. NCERT’s Class 12 Biology textbook (Reprint 2026-27) reports that more than 70 per cent of recorded species are animals. Plants make up no more than 22 per cent. In this count NCERT groups fungi with plants, along with algae, mosses (bryophytes), gymnosperms and flowering plants (angiosperms). The same chapter adds that fungi alone have more species than fishes, amphibians, reptiles and mammals put together. Among animals, insects form more than 70 per cent of the total. In other words, about 7 out of every 10 animal species are insects.

Microbes are the biggest unknown. Bacteria and other prokaryotes (cells without a nucleus) are hard to identify with ordinary methods. Many cannot even be grown in a laboratory. Their diversity alone may run into millions of species.

Where is biodiversity highest?

Biodiversity is not spread evenly across the planet. In general, species diversity falls as you move from the equator towards the poles. This pattern is called the latitudinal gradient. NCERT compares bird species to show it: Colombia, near the equator, has nearly 1,400 bird species. New York at 41° N has 105, and Greenland at 71° N has only 56. India, which lies largely in the tropics, has more than 1,200 bird species.

Ecologists give three main reasons for rich tropical life:

More evolutionary time. Tropical regions escaped repeated ice ages, so species had longer to form.
Steady conditions. Tropical climates change less with the seasons. Steady conditions let species specialise in narrow roles, called niches.
More solar energy. Strong sunlight raises plant productivity, which can support more species.

Area matters too. The explorer Alexander von Humboldt noticed that species richness rises as the area explored grows, but only up to a limit. This is known as the species-area relationship.

What is wildlife diversity?

Wildlife means the animals that live in the wild, outside human care. NCERT’s earlier Class 8 book, Resources and Development, explains that wildlife includes animals, birds and insects as well as aquatic life forms. Wildlife diversity is the variety of these wild animals in a region, from large mammals to beetles, fish and frogs. It is the part of biodiversity most people notice first.

Why is wildlife diversity important?

Every wild animal plays a part in its ecosystem. Bees make honey and pollinate flowers. Birds eat insects and help keep their numbers in check. Vultures feed on dead animals, which makes them natural cleaners of the environment. Large or small, each species helps maintain the balance of nature.

Wildlife also supports people directly. Animals provide milk, meat, hides and wool. Many wild species are close relatives of the animals and crops we depend on. When a predator, pollinator or scavenger disappears, the effects spread through the food web.

What happened to India’s vultures?

India’s vultures show how fragile wildlife diversity can be. That earlier Class 8 book explains that vultures were dying of kidney failure soon after feeding on dead livestock. Those animals had been treated with diclofenac, a painkiller. In August 2006, the Drugs Controller General of India banned the use, sale and manufacture of veterinary diclofenac. A Rajya Sabha reply from the Environment Ministry (PIB, December 2024) adds that meloxicam and tolfenamic acid, found safe to vultures, are now widely used instead. The same reply names breeding centres, such as Pinjore in Haryana, where vultures are raised in captivity and later released into the wild.

Why is wildlife declining?

NCERT’s Class 11 geography book lists several reasons for falling wildlife numbers:

Industrial growth that sped up the use of forest resources
Clearing land for farms, settlements, roads, mines and reservoirs
Lopping trees for fodder and fuelwood
Grazing by domestic cattle, which damages habitats
Hunting for sport in the past, and commercial poaching (illegal hunting) today
Forest fires

Poachers target animals for their hides, skins, nails, teeth, horns and feathers. Tigers, elephants, rhinoceroses, snow leopards and crocodiles are among the animals at risk, as the earlier Class 8 book points out.

How is wildlife protected by law?

India passed a comprehensive Wildlife Act in 1972. NCERT’s Class 11 book calls it the main legal framework for wildlife protection. The Act has two aims. First, it shields threatened animals named in its schedules. Second, it backs protected areas such as national parks and sanctuaries with the force of law. An amendment in 1991 brought tougher punishments and covered some plant species too. The law has since changed again. According to PIB, the Wild Life (Protection) Amendment Act, 2022, has been in force since 1 April 2023.

International trade is also controlled. Governments have signed a treaty called CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora). Under it, cross-border trade in wild plants and animals must not endanger their survival.

Flora and fauna of India

India’s wildlife changes sharply from one region to the next. The Himalaya, the Thar Desert, the Western Ghats, the Sundarbans and the islands each have their own plants and animals. Learning them region by region makes revision easier. Explore the flora and fauna of India by region for a guided tour.

Why is biodiversity important?

NCERT groups the reasons for conserving biodiversity into three types of argument. Together they show that biodiversity matters for money, for survival and for moral reasons.

Narrowly utilitarian: direct products

Narrowly utilitarian reasons are about the direct goods we take from nature. These include cereals, pulses and fruits, firewood, fibre and building material. They also include industrial products such as tannins, dyes, resins and perfumes.

Medicines are a major part of this value. NCERT’s Class 12 Biology textbook (Reprint 2026-27) states that more than 25 per cent of drugs sold worldwide come from plants. It adds that 25,000 plant species are used in traditional medicines. Searching living things for useful products is called bioprospecting. Countries rich in biodiversity can gain a great deal from it.

Broadly utilitarian: ecosystem services

Broadly utilitarian reasons are about the free services that ecosystems provide. Plants release oxygen through photosynthesis. Bees, birds and bats pollinate crops, without which plants cannot give fruits or seeds. Roots hold soil and reduce flooding. Worms, fungi and microbes keep soil fertile and water clean.

Biodiversity also makes ecosystems more stable. Ecologist David Tilman ran long-term experiments on outdoor plots. Plots with more species showed less change in total biomass from year to year. They were also more productive.

Ethical: every species has value

The ethical argument says each species has value in itself, even if it earns nothing for people. Humans share the planet with millions of other species. We have a duty to care for them and to pass this living heritage on to future generations.

Importance of biodiversity in detail

Biodiversity also offers beauty, recreation, cultural meaning and scientific knowledge. Each of these deserves a closer look with examples. Our article on the importance of biodiversity sets out the reasons in an easy, exam-ready list.

Plant diversity

Plants form the base of nearly every food chain on land. They feed animals, shelter them and produce much of the oxygen we breathe. Many crops, medicines and timbers come from wild plant species. Read plant diversity: meaning, importance and conservation to see how plant variety is measured and protected.

Why is India a megadiverse country?

A megadiverse country is one that holds an unusually large share of the world’s species. According to NCERT’s Class 12 Biology textbook (Reprint 2026-27), India has only 2.4 per cent of the world’s land area. Yet its share of global species diversity is 8.1 per cent. This makes India one of the 12 megadiversity countries of the world.

The same chapter says nearly 45,000 plant species have been recorded from India. About twice as many animal species are known. Many more species are probably still waiting to be discovered and named.

India’s location and landforms explain this richness. The country spans tropical and temperate latitudes. It has high mountains, wet forests, dry deserts, long coasts and island groups. Each setting supports different communities, so India scores high at all three levels of biodiversity.

Biodiversity of India in detail

India’s biodiversity can be studied through its species, its ecosystems and its biogeographic zones. These zones are large areas that share a similar history and similar living things. For the full picture, read the biodiversity of India: megadiversity, zones and species.

What are biodiversity hotspots?

Conservation money and staff are limited. Experts therefore picked out certain regions for the highest level of protection. NCERT defines biodiversity hotspots as regions with very high species richness and a high degree of endemism. Endemism means species are confined to that region and found nowhere else. Hotspots are also places where habitats are being lost quickly.

NCERT’s Class 12 Biology textbook names the Western Ghats and Sri Lanka, Indo-Burma and the Himalaya as hotspots covering India’s richest regions. India is usually counted in four hotspots, though. The country profile on the Convention on Biological Diversity website lists the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland. Together, hotspots cover only a tiny part of Earth’s land, yet they hold a very large share of its species.

Biodiversity hotspots in India

India’s hotspots range from the snowy Himalaya to the rainforests of the Western Ghats and the north-east. Each has its own endemic plants, frogs, birds and mammals. Each also faces pressure from farming, roads and settlements. Our guide to biodiversity hotspots in India explains each one, with maps and key species.

Biodiversity hotspots of the world

India’s hotspots are part of a worldwide set of priority regions. Many of them lie in the tropics, where species richness is highest. Each was picked because it combines many endemic species with fast habitat loss. See biodiversity hotspots of the world for the global list and how it was drawn up.

Endemic species

An endemic species lives naturally in only one area. The Nilgiri tahr, a wild goat of the southern Western Ghats, is a well-known Indian example. Endemic species face high risk because they have nowhere else to go. Learn more in our article on endemic species and examples from India.

What are the main threats to biodiversity?

Species have always appeared and disappeared over Earth’s history. Fossils show five past episodes of mass extinction. Today, however, NCERT says species are disappearing 100 to 1,000 times faster than in pre-human times. Human activities are responsible for this faster rate, often called the “Sixth Extinction”.

The IUCN Red List (2004), cited by NCERT, recorded the extinction of 784 species in the last 500 years. Well-known lost species include the dodo of Mauritius, the quagga of Africa and the thylacine of Australia. Three subspecies of tiger, the Bali, Javan and Caspian tigers, have also vanished.

The Evil Quartet

NCERT calls the four major causes of biodiversity loss the Evil Quartet: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Habitat loss is the most important of the four. A co-extinction happens when a species dies out along with the host or partner it depends on. NCERT’s examples for each cause, from the Nile perch to Lantana, are covered in the detailed article linked below.

NCERT’s Class 12 Biology textbook (Reprint 2026-27) gives a striking figure for habitat loss. Tropical rainforests once covered more than 14 per cent of Earth’s land surface. They now cover no more than 6 per cent.

Other pressures

Pollution, overfishing and climate change add to the Evil Quartet. Warmer seas, for instance, bleach and weaken coral reefs that shelter countless fish. Forest fires, landslides and floods can also wipe out local populations. Loss of biodiversity can lower plant production and make ecosystems less able to cope with drought.

Loss of biodiversity in detail

Biodiversity loss has causes, effects and solutions that are often asked as long answers. A clear structure helps you score well. Read loss of biodiversity: causes, effects and solutions for a complete exam-ready treatment.

How can we conserve biodiversity?

Conservation means protecting and wisely managing living resources so that they last. There are two main approaches: protecting species where they live, and protecting them away from their natural home.

In situ conservation

In situ means “on site”. This approach protects the whole ecosystem in which a species lives. NCERT sums it up neatly: we save the entire forest to save the tiger. India protects its richest areas as biosphere reserves, national parks and wildlife sanctuaries.

Traditional culture helps too. In many communities, patches of forest were set aside as sacred groves, where all trees and animals were left untouched. NCERT mentions sacred groves in the Khasi and Jaintia Hills of Meghalaya, the Aravalli Hills of Rajasthan and the Western Ghats. In Meghalaya, they shelter many rare and threatened plants.

Ex situ conservation

Ex situ means “off site”. Threatened plants and animals are taken out of their natural habitat and cared for elsewhere. Zoos, botanical gardens and wildlife safari parks serve this purpose. Some animals now extinct in the wild survive only in zoos.

Modern methods go further. Cryopreservation stores sperm and eggs at very low temperatures for long periods. Eggs can be fertilised in the laboratory, and plants can be grown through tissue culture. Seed banks store seeds of many crop varieties for future use.

In situ vs ex situ conservation

The two methods work best together. In situ protection keeps natural processes going, while ex situ work acts as an insurance policy. Compare them side by side in our guide to in situ and ex situ conservation of biodiversity.

Biodiversity conservation methods

Conservation also includes laws, international agreements, community action and education. The Convention on Biological Diversity, signed at the 1992 Earth Summit in Rio de Janeiro, asked all nations to protect biodiversity and use it sustainably. Read biodiversity conservation: methods, importance and examples for the full set of methods.

What can students do?

Students can make a real difference close to home. Plant native trees rather than exotic ones. Avoid buying products made from wild animals. Join bird counts, nature camps or school eco-clubs. Learn the names of plants and animals around your school, because people protect what they know.

Biodiversity topics at a glance

Use this master table to revise the whole topic and find the right detailed article.

Topic	Key idea	Read more
Flora and fauna	Plant life and animal life of a region	Flora and fauna
Levels of biodiversity	Genetic, species and ecosystem diversity	Types of biodiversity
Importance	Direct goods, ecosystem services and ethics	Importance of biodiversity
Plant diversity	Plants support food chains, medicine and soil	Plant diversity
India’s biodiversity	A megadiverse country with varied ecosystems	Biodiversity of India
Regional wildlife	Plants and animals change by region	Flora and fauna of India
Hotspots in India	Species-rich regions with many endemics	Hotspots in India
World hotspots	Priority regions across the globe	Hotspots of the world
Endemic species	Species found in only one area	Endemic species
Threats	The Evil Quartet plus pollution and climate change	Loss of biodiversity
Conservation approaches	On-site and off-site protection	In situ vs ex situ
Conservation methods	Laws, protected areas, people and education	Biodiversity conservation