Biodiversity
உயிரியல் பன்முகத்தன்மை
Do not confuse 'Biodiversity' with mere species count. It is the sum total of genetic, species, and ecological variation that sustains the biosphere. If you think evolution is just a timeline, you are failing the first chapter.
The idea
Biodiversity is the number and types of organisms present on Earth. Current scientific data confirms that the number of species known and described ranges between 1.7 to 1.8 million. This figure represents the global taxonomic diversity documented to date.
Why it matters
It exists because of the vast evolutionary history and adaptation of life forms to diverse ecological niches across the planet.
NEET lens
NEET expects the exact range: 1.7-1.8 million. Do not confuse 'described species' with 'estimated species'. Memorize this data point; it is a frequent 'fill in the blank' question in Section A.
Clinical significance
Loss of biodiversity triggers ecosystem collapse, leading to the emergence of zoonotic diseases. When host species diversity decreases, pathogens jump to humans more efficiently. Ecological stability is the primary defense against global pandemics.
Introduction
There are an estimated 8.7 million species on Earth. Of these, we have formally described and named only about 1.8 million. Every unnamed species is a gap in our knowledge of life history. Every species lost before it is named is a chapter of that history gone forever. Biodiversity is not just a count of species — it is the accumulated product of 3.8 billion years of evolution, and we are losing it faster than we can document it.
Core concept
Biodiversity refers to the variety and variability of life on Earth. It operates at three levels:Genetic diversity — variation in genes within a species (e.g., different varieties of rice)Species diversity — the number and variety of species in a given areaEcosystem diversity — the variety of ecosystems in a region (forests, grasslands, wetlands, etc.)India is one of the world s 17 megadiversity countries — nations that together harbour more than 70% of the world s biodiversity despite covering only a fraction of its land area.Biodiversity is highest in the tropics and decreases towards the poles. This is the latitudinal gradient in species diversity — one of ecology s most well-documented patterns.
Go deeper
The latitudinal gradient is explained by several (non-mutually exclusive) hypotheses: greater solar energy input in the tropics, longer evolutionary time, greater habitat complexity, and lower extinction rates. NEET occasionally asks for these explanations.The term endemic species — species found only in a particular region and nowhere else — is closely linked to biodiversity. Biodiversity hotspots are defined partly by their endemism. India has two major hotspots: the Western Ghats and the Eastern Himalayas.
From Class 10
In Class 10, you may have studied ecosystems and the variety of organisms within them. You probably encountered the word biodiversity as a general term for the variety of life. In Class 11, biodiversity has a more precise meaning — it has levels, it can be measured, and its loss is a scientific and ecological crisis, not just an environmental concern.