Biodiversity
Definition
Biodiversity refers to the variety of life forms found in all living organisms, including those in terrestrial, marine, and other aquatic ecosystems, along with the ecological systems they are part of. It includes the diversity within species, between different species, and among ecosystem.
Biological diversity is usually considered at three different levels
A. Genetic diversity i.e. at genetic level
B. Species diversity
C. Ecosystem diversity
Genetic Diversity
Every living thing — from tiny bacteria to big animals and plants — carries a huge amount of genetic information. This information is stored in their genes, which act like instructions that control how an organism looks, grows, and survives.
Different organisms have different numbers of genes:
- Tiny bacteria like mycoplasma have about 450–700 genes.
- Common bacteria like E. coli have around 4,000 genes.
- A fruit fly has about
- 13,000 genes.
- Rice plants have between 32,000–50,000 genes.
- Humans have around 35,000–45,0
00 genes.
These genetic differences — not just in number but also in structure — help species adapt to their environment. More genetic variety means better chances of survival during changes like diseases, climate shifts, or food shortages.
But if all individuals in a species are too genetically similar (this is called genetic uniformity), they might all react the same way to a disease or drought — making them more vulnerable. That’s why diversity is important.
Genetic diversity happens naturally through:
- Mutations (small changes in genes),
- Sexual reproduction, where genes from both parents mix and form new combinations.
For example, two brothers from the same parents may look different because they inherited different versions (called alleles) of the same genes.
This variety of genes in a population is called the gene pool. Over time, natural selection (survival of the fittest) helps keep helpful genes and remove harmful ones. This process helps organisms adapt and survive better.
India is rich in genetic diversity and is known as a Vavilov Centre — a place where many important crop plants (like rice and wheat) first evolved. This idea was proposed by a Russian scientist, N.I. Vavilov, in the 1950s.
Species Diversity
Species diversity means the variety of different species (like plants, animals, insects, and microbes) living in a particular area. It tells us how rich and balanced the life forms are in that region.
We can understand species diversity in three ways:
- Species Richness – This means the number of different species present in an area. For example, a forest with 100 different types of plants has more richness than a grassland with only 10 types.
- Species Abundance – This looks at how many individuals there are in each species. For example, if one forest has equal numbers of deer, tigers, and monkeys, it’s more balanced than a forest with 90% monkeys and very few deer or tigers.
- Taxonomic (or Phylogenetic) Diversity – This checks how different or related the species are. An area with completely unrelated species (like birds, frogs, and trees) has more diversity than one with only similar species (like three types of grasses).
The type of species also matters. If the species in an area are from very different biological groups, that area has greater species diversity.
Globally, about 1.7 million species have been discovered so far, but scientists believe there may be between 5 to 50 million species in total.
Species diversity is not evenly spread across the Earth:
- It is highest near the equator (like in tropical rainforests).
- It becomes less as we move toward the poles or go to higher altitudes.
- In the ocean, continental shelves (shallow coastal areas) have more species than deep-sea regions.
Many factors like rainfall, temperature, and soil nutrients affect species diversity in both land and water ecosystems.
Ecosystem Diversity
Ecosystem diversity means the variety of different ecosystems found in a region. An ecosystem includes all the living things (plants, animals, microbes) and non-living things (like water, air, soil) interacting together in a particular area.
Different ecosystems have different types of life and environments. For example:
- Tropical forests in South India have a lot of plant and animal species.
- Deserts have fewer species and a completely different climate.
- Marine ecosystems (oceans and seas) have many kinds of fish, but they are very different from freshwater ecosystems (like rivers and lakes).
So, the differences between these ecosystems in their climate, species, and interactions are called ecosystem diversity.
India is a great example of ecosystem diversity. It has:
- Ice-covered mountains (Himalayas),
- Hot deserts (Rajasthan),
- Rainforests (Western Ghats and Northeast India),
- Grasslands, wetlands, coral reefs, and even deep-sea ecosystems.
Each of these ecosystems has its own special mix of living and non-living components. These areas also have many endemic species — which means species that are found only in India and nowhere else in the world.
For example:
- About 33% of India’s flowering plants are endemic.
- So are 53% of freshwater fish, 60% of amphibians, 36% of reptiles, and 10% of mammals.
The richest regions in ecosystem diversity and endemism in India are:
- Northeast India
- Western Ghats
- Northwest Himalayas
- Andaman and Nicobar Islands