3 Types of Biodiversity: Genetic, Species and Ecosystem (With Examples)

The three types of biodiversity are genetic diversity, species diversity and ecosystem diversity. Genetic diversity is variety within one species. Species diversity is the variety of species in a place. Ecosystem diversity is the variety of habitats in a region. Together, these three levels describe the main levels of variety of life on Earth.

This article explains each level with the examples NCERT expects in Class 12 exams. For the wider topic, including threats and conservation, start with our main guide to biodiversity: meaning, types, importance and threats.

What are the types of biodiversity?

Biodiversity means the variety of living things at every level, from genes to whole landscapes. NCERT’s Class 12 Biology textbook says the term was popularised by the sociobiologist Edward Wilson. He used it for the combined diversity at all levels of biological organisation.

Diversity exists at many levels, from molecules inside cells up to biomes. NCERT picks out three levels as the most important:

1. Genetic diversity: variety within a species
2. Species diversity: variety between species
3. Ecological (ecosystem) diversity: variety of ecosystems

The international definition says the same thing in legal language. Article 2 of the Convention on Biological Diversity (CBD) defines biological diversity as “the variability among living organisms from all sources”. It adds that this “includes diversity within species, between species and of ecosystems”. Those three phrases match the three types exactly.

What is genetic diversity?

Genetic diversity is the variation in genes among individuals of the same species. A gene is a unit of heredity passed from parents to offspring. Because genes differ, members of one species can differ in size, colour, taste, yield or chemistry.

NCERT puts it this way: a single species “might show high diversity at the genetic level over its distributional range”. The distributional range is the whole area where the species grows or lives.

Examples of genetic diversity

• Rauwolfia vomitoria. NCERT describes this medicinal plant growing in different Himalayan ranges. Its genetic variation might show up as differences in the potency and concentration of reserpine, the active chemical it produces.
• Rice. India has more than 50,000 genetically different strains of rice, according to NCERT’s Class 12 Biology book.
• Mango. The same textbook gives 1,000 varieties of mango in India.

Everyday life offers more examples. Dog breeds, local rice strains and the many kinds of brinjal in a vegetable market all belong to single species. Their differences come from genetic variation, sometimes shaped by human selection.

Why does genetic diversity matter?

Genetic variety gives a species the raw material to adapt. If a new disease or a hotter climate arrives, some individuals may carry genes that help them survive. A species with very little genetic variety has fewer such options.

Farmers and plant breeders also depend on it. Old crop strains may carry traits that breeders can use in new varieties. NCERT notes that seeds of different genetic strains of commercially important plants can be stored for long periods in seed banks. That is one form of off-site protection, compared with on-site methods in our guide to in situ and ex situ conservation.

What is species diversity?

Species diversity is the variety of species found in a particular area. For most animals and plants, a species is a group of organisms that can breed with one another and produce fertile offspring.

Ecologists look at two things when they measure it:

• Species richness: the number of different species present
• Species evenness: how evenly individuals are shared among those species

Imagine two ponds, each with five fish species. In the first pond, every species is about equally common. In the second, one species makes up nearly every fish caught. Both ponds have the same richness, but the first has higher evenness and so greater diversity.

Examples of species diversity

NCERT’s example is regional. It states that the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. Amphibians are animals such as frogs, toads and caecilians that usually begin life in water.

A wider example comes from the same chapter. Species diversity generally falls as you move from the equator towards the poles. NCERT notes that Colombia, near the equator, has nearly 1,400 bird species, while Greenland at 71° N has only 56. India, with much of its land in the tropics, has more than 1,200 bird species.

Species diversity is also where the counts of plants and animals belong. NCERT’s book, citing the IUCN (2004), says slightly more than 1.5 million species had been described. Its chapter also reports that India holds 8.1 per cent of global species diversity on only 2.4 per cent of the world’s land area. The story behind those figures is told in our article on the biodiversity of India. Some regions also hold many endemic species, found nowhere else, which is why they are named biodiversity hotspots in India.

What is ecosystem diversity?

Ecosystem diversity is the variety of ecosystems in a region. An ecosystem is a community of living things together with its non-living surroundings. The CBD’s Article 2 defines it as “a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit”. You can read more about ecosystems in our guide what is an ecosystem?

NCERT calls this level ecological diversity. Its example compares two countries. India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has greater ecosystem diversity than a Scandinavian country like Norway.

Examples of ecosystem diversity in India

Each of India’s ecosystems supports its own community of life:

• Deserts, such as the Thar, with drought-tolerant shrubs and reptiles
• Rain forests of the Western Ghats and the north-east
• Mangroves along tidal coasts, such as the Sundarbans
• Coral reefs in shallow tropical seas, such as around island groups
• Wetlands, such as marshes, lakes and floodplains inland
• Estuaries, where rivers meet the sea
• Alpine meadows high in the Himalaya, above the tree line

Each habitat favours different species, so a country with many ecosystems usually supports many species too.

How are the three types of biodiversity connected?

The three levels nest inside one another, like boxes. Genes sit inside individuals, individuals form species, and species live together in ecosystems.

A change at one level affects the others. If a forest is cleared, an ecosystem disappears. The species that lived only there may vanish with it, and so do their unique genes. This is why NCERT says conservation efforts aim to protect diversity at all three levels.

Loss can also start from the bottom. When farmers replace many local crop strains with a few, genetic diversity falls even though the crop species survives. The full set of threats, from habitat loss to alien species, is covered in loss of biodiversity: causes, effects and solutions.

Why is each type of biodiversity important?

Each level gives people something different:

• Genetic diversity provides crop and livestock varieties, and traits for breeding disease-resistant plants.
• Species diversity provides food, fibre, timber and medicines. NCERT notes that searching for useful products in molecular, genetic and species-level diversity is called bioprospecting.
• Ecosystem diversity provides services such as pollination, clean water, fertile soil and flood control.

The full list of reasons, including ethical ones, is set out in our article on why biodiversity is important.

Sources

• NCERT Class 12 Biology, Chapter 13: Biodiversity and Conservation
• Convention on Biological Diversity, Article 2: Use of Terms