Species Diversity
சிற்றின பன்முகத்தன்மை
Do not confuse species diversity with genetic diversity. While genetic diversity measures allelic variation within a single species, species diversity measures the richness of different species within a specific region. If you fail to distinguish these, you lose four marks instantly.
The idea
Species diversity refers to the variety and abundance of species within a defined region. The NCERT explicitly cites the Western Ghats as having higher amphibian species diversity compared to the Eastern Ghats. This is a measure of taxonomic richness. It is the most common metric used to assess biodiversity at the community level.
Why it matters
It reflects the evolutionary history and specific environmental conditions of a region that allow different species to occupy distinct niches.
NEET lens
NEET expects you to memorize the Western Ghats vs. Eastern Ghats amphibian comparison as a factual anchor. Questions often present data tables or maps requiring you to identify regions of high species richness. Focus on the distinction between species richness and species evenness to avoid traps.
Clinical significance
Ecosystems with low species diversity are fragile and prone to collapse under environmental stress. When keystone species are lost due to low diversity, trophic cascades occur, leading to the total failure of ecosystem services. This is analogous to multi-organ failure in a patient; the system cannot compensate for the loss of specialized functions.
Introduction
Species diversity is the diversity at the species level — the number and variety of species in a given region.
Core concept
Example (NCERT): the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. Global numbers: IUCN (2004) — slightly more than 1.5 million species described; Robert May — about 7 million estimated. Of all recorded species, more than 70 per cent are animals and no more than 22 per cent are plants (including algae, fungi, bryophytes, gymnosperms and angiosperms); insects are the most species-rich animal group (more than 70 per cent of animals). The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals. India has 8.1 per cent of the global species diversity on 2.4 per cent of the world's land area.
Go deeper
Species diversity is not uniform: it follows latitudinal gradients and species-area relationships.
From Class 10
A rainforest has many more kinds of trees and animals than a desert — it has higher species diversity.