Biodiversity

Also called: Biological diversity · Topic: Biodiversity and its Conservation · NCERT: Class 10, Ch 2 "Forest and Wildlife Resources"; Class 11, Ch 14 "Biodiversity and Conservation"

Meaning

Biodiversity (biological diversity) is the number and variety of plants, animals and micro-organisms, the genes they carry and the ecosystems they form. It covers variety within species, between species and between ecosystems. The word comes from "bio" (life) and "diversity" (variety).

• It is the result of 2.5–3.5 billion years of evolution, and NCERT calls it our "living wealth".
• It gives us food, medicine, clean water and a steady climate. Losing it can also mean losing species forever.

Explanation

Species: the basic unit

• A species is a group of similar organisms that can breed with each other and produce fertile young (offspring that can also have young).
• How many species exist?
• Estimates run from 2 million to 100 million.
• About 10 million is the best estimate (NCERT Class 11).

• Only about 2 million have been described so far.

• New species keep being found. About 40% of South America's freshwater fishes are still not classified (NCERT).

The three levels of biodiversity

Level	What it means	Example	Why it matters
Genetic diversity	Variation of genes inside one species	Differences in human height and skin colour; the many varieties of rice or wheat	Needed for healthy breeding. It lets a species adapt to a new disease or a new climate
Species diversity	Variety of species in an area	Many tree, bird and insect species in a rainforest	Areas with very many species are called hotspots
Ecosystem diversity	Variety of ecosystem types, habitats and processes	Grasslands and sholas (stunted evergreen forest patches in high valleys) of Anamalai, Western Ghats (NCERT Fig. 14.1)	Each ecosystem gives different services to people

• Species diversity is measured in three ways:
• Richness: how many species there are.
• Abundance: how many individuals of each species there are.

• Types: what kinds of species are present.

• Ecosystem boundaries are not sharp.

• A forest slowly changes into a grassland.
• So ecosystems are hard to mark on a map.

Why biodiversity is uneven: the tropics vs the poles

• Latitudinal diversity gradient: the number of species is highest in the tropics (near the equator, about 23.5°N to 23.5°S). It falls steadily towards the poles.
• Near the poles: large populations of only a few species (for example, huge herds of reindeer and few plant types).

• In the tropics: many species, but each has smaller numbers.

• Tropical rainforests cover only a small share of the land, but hold about half of all species.

• Why the tropics are richer:
• More sunlight and more water
  • Plants grow all year.
  • So there is more food for animals.
• Deep weathering (rock breaking down into soil)
  • The warm, wet climate breaks rock down fast.
  • This gives thick soils that support dense forests.
• Stable climate over long periods
  • Ice did not cover the tropics in the Ice Ages.
  • So species had more time to evolve.
• More niches (a niche is a species' "job" and space in an ecosystem)
  • A rainforest has many layers, from the forest floor to the treetops.
  • Each layer gives room for more species.

Feature	Tropics	High latitudes (near poles)
Number of species	Very high	Low
Population of each species	Small	Large
Solar energy and rain	High, all year	Low, seasonal
Climate history	Stable for long periods	Disturbed by glaciation

The value of biodiversity (four kinds, NCERT)

• (a) Ecological value
• Species capture and store energy (plants do this through photosynthesis).
• They make organic matter and break it down (decomposers recycle dead material).
• They cycle water and nutrients. They fix gases (CO₂ into plants, nitrogen into soil) and help control climate.
• More diverse ecosystems are more stable and more productive. If one species is lost, others can take over its job.

• Forests are primary producers (they make food from sunlight), and all other life depends on them (NCERT Class 10).

• Ecosystem services (benefits people get from nature): the Millennium Ecosystem Assessment (2005) puts them in four groups [4]:

Group	Meaning	Examples
Provisioning	Products we take from ecosystems	Food, water, timber, fibre, medicines [4]
Regulating	Benefits from nature keeping processes in balance	Climate control, flood control, cleaning water, treating waste, stopping erosion [4]
Cultural	Non-material benefits	Spiritual value, recreation, beauty, learning [4]
Supporting	Needed to produce all other services	Nutrient cycling, soil formation, primary production [4]

• (b) Economic value
• Biodiversity gives us food crops, livestock, timber, fish, medicines and cosmetics.
• Agro-biodiversity is the variety of crops, livestock and their wild relatives. It is the store of genes used to breed new varieties.
• How agro-biodiversity is lost:
  • Farmers grow only a few high-yielding varieties (HYVs).
  • Old local varieties stop being grown.
  • Their genes are lost.

• Seeing biodiversity only as a resource also harms it. Over-use makes species decline. There are also fights over who owns and profits from genetic resources. The Nagoya Protocol (CBD, 2010) deals with this through access and benefit-sharing.

• (c) Scientific value: each species gives clues on how life began, how it evolved and how it keeps working.

• (d) Ethical value: every species has an intrinsic right to exist (a right of its own, not only because it is useful to people). Conservation also keeps genetic diversity for agriculture and fisheries (NCERT Class 10).

Where it occurs

• World pattern: richest in the tropics, poorest near the poles. Tropical rainforests hold about half of all species.
• Madagascar (island in the Indian Ocean, off south-east Africa): about 85% of its plants and animals are endemic (found naturally there and nowhere else in the wild).
• South America: about 40% of its freshwater fishes are still not classified (NCERT).
• India: a megadiverse country (one of a small group of countries that together hold most of the world's species):
• India has only about 2.4% of the world's land area, but 7–8% of all recorded species (PIB, 2025) [2][3].
• It has recorded over 45,500 plants and over 91,200 animals in its ten biogeographic regions (natural zones with their own typical plants and animals) [3]. PIB (2025) rounds these to 45,000 plants and 91,000 animals [2].
• India has 4 of the 34 global biodiversity hotspots [3]:
  • Himalaya
  • Indo-Burma (North-east India)
  • Western Ghats and Sri Lanka
  • Sundaland (Nicobar Islands)

• India is one of the eight Vavilovian centres (centres where crop plants first came from, named after the Russian scientist N.I. Vavilov). It has more than 300 wild ancestors and close relatives of crop plants [3].

• Western Ghats examples:

• Anamalai: grasslands and sholas, NCERT's example of ecosystem diversity.
• Nilgiri tahr: a mountain goat of the high grasslands of the Nilgiris and Anamalai hills (Tamil Nadu–Kerala).
• Lion-tailed macaque: a monkey of the Western Ghats rainforests.

• Humboldtia decurrens: a rare tree of the southern Western Ghats (NCERT Fig. 14.3).

• India's endemic animals: India ranks 10th in birds (69 endemic species), 5th in reptiles (156) and 7th in amphibians (110) [3]. Endemism is highest in amphibians (61.2%) and reptiles (47%) [3].

Don't confuse with

• Genetic diversity vs species diversity: genetic diversity is variation inside one species (for example, differences in human height or the many varieties of rice). Species diversity is the variety of different species in an area.
• Species richness vs species abundance: richness is how many species there are. Abundance is how many individuals of each species there are. The poles have high abundance of a few species but low richness.
• Endemic species vs hotspot: an endemic species is found naturally in one area only (for example, the Nilgiri tahr). A hotspot is an area with very many species. India has 4 of the 34 hotspots [3].
• Regulating vs supporting services: regulating services keep nature in balance (flood control, climate control). Supporting services are needed to make all other services, such as nutrient cycling, soil formation and primary production [4].

Prelims Hooks

• The three levels of biodiversity are genetic, species and ecosystem. Differences in human height are an example of genetic diversity, not species diversity.
• Species diversity is measured by richness, abundance and types. The sholas and grasslands of Anamalai (Western Ghats) are NCERT's example of ecosystem diversity.
• About 85% of Madagascar's plants and animals are endemic. The Nilgiri tahr, lion-tailed macaque and Humboldtia decurrens are endemic to the Western Ghats.
• India has 2.4% of world land but 7–8% of recorded species [2][3]. It has 4 of the 34 hotspots: Himalaya, Indo-Burma, Western Ghats–Sri Lanka and Sundaland (Nicobar Islands) [3].
• India's endemism is highest in amphibians (61.2%), then reptiles (47%) [3].
• The MEA (2005) groups ecosystem services as provisioning, regulating, cultural and supporting. Nutrient cycling and soil formation are supporting services, not regulating ones [4].

Mains Points

• Distribution pattern (GS-I): life is richest in the tropics.
• Causes: more sunlight and water, a stable climate over long periods (no Ice Age glaciation) and more niches in layered rainforests.

• Result: tropical regions, including India's Western Ghats and North-east, matter greatly for world conservation.

• India's responsibility (GS-III): India has 2.4% of world land but 7–8% of species, 4 of the 34 hotspots and high reptile and amphibian endemism [2][3].

• Endemic species live nowhere else, so losing their habitat here means they disappear from the whole world.

• Endemic species therefore need protection where they live (in-situ conservation).

• Agro-biodiversity, food security and ecosystem services (GS-III):

• Since the Green Revolution, a few HYVs have spread and pushed out local varieties. India is a Vavilovian centre with 300+ wild crop relatives [3]. Gene banks, community seed banks and benefit-sharing under the Nagoya Protocol can protect future crop breeding.
• The MEA (2005) shows that nature gives regulating, cultural and supporting services, not only goods [4]. Policy should count services like flood control by forests and wetlands, not only timber or crops.

Related concepts

• Species
• Genetic diversity
• Species diversity
• Ecosystem diversity
• Latitudinal diversity gradient
• Endemic species
• Importance of biodiversity
• Ecosystem services
• Agro-biodiversity

Read more

• Biodiversity: meaning, levels, distribution and value