Biodiversity-1 for NEET

Category	Details
Introduction	An alien would be amazed by the enormous diversity of life on Earth. Humans also find this diversity astonishing, with more than 20,000 species of ants, 300,000 species of beetles, 28,000 species of fishes, and nearly 20,000 species of orchids.
Ecologists’ Key Questions	Why are there so many species? Did such great diversity exist throughout Earth’s history? How did this diversification come about? How and why is this diversity important to the biosphere? Would the biosphere function differently if the diversity was much less? How do humans benefit from the diversity of life?
Why So Many Species?	It took millions of years of evolution for the current diversity to accumulate. Various factors such as environmental change, speciation, and natural selection contribute to the high number of species.
Did This Diversity Always Exist?	No, the diversity we see today accumulated over millions of years due to evolutionary processes. The current rate of species loss is much higher than it has been in the past.
How Did Diversification Occur?	Diversification occurred through evolutionary processes, driven by adaptation to environmental changes, geographical isolation, and genetic mutations leading to new species.
Importance of Diversity	Diversity is crucial for the stability and functionality of ecosystems. It allows ecosystems to provide essential services like food, clean air, and water. Greater biodiversity leads to greater resilience against disturbances and environmental changes.
Impact of Reduced Diversity	Reduced biodiversity would lead to weaker ecosystems, making them more susceptible to diseases, climate change, and the loss of ecosystem services, impacting human survival.
Human Benefits from Biodiversity	Humans benefit from biodiversity in numerous ways, such as food, medicine, ecosystem services (e.g., pollination, water purification), and maintaining climate stability.
Definition of Biodiversity	Biodiversity, coined by Edward Wilson, refers to the combined diversity at all levels of biological organization, including genetic, species, and ecological diversity.
Levels of Biodiversity	Genetic Diversity: Variation within a species. For example, Rauwolfia vomitoria shows genetic variation in reserpine concentration across Himalayan ranges. India has over 50,000 genetically distinct rice strains and 1,000 mango varieties. Species Diversity: For example, the Western Ghats have greater amphibian species diversity than the Eastern Ghats. Ecological Diversity: India has a diverse range of ecosystems, from deserts to rainforests, coral reefs, mangroves, and alpine meadows.
Species Loss Rates	At the current rate, the world could lose much of its biodiversity in less than two centuries if the rate of species loss continues.
Global Species Count	According to IUCN (2004), 1.5 million species of plants and animals have been described. Estimates of total species range from 20 million to 50 million, with a conservative estimate by Robert May at about 7 million species globally.
Species Composition	70% of recorded species are animals. Plants, including algae, fungi, bryophytes, gymnosperms, and angiosperms, make up 22% of the total. Insects are the most species-rich group, comprising over 70% of all animal species. The number of fungi species exceeds the combined total of fishes, amphibians, reptiles, and mammals.
Prokaryotic Species	Prokaryotic species estimates are uncertain due to difficulties in culturing them in labs. However, using biochemical and molecular criteria, their diversity could run into millions.
Biodiversity in India	India occupies only 2.4% of the world’s land area but hosts 8.1% of the world’s species. 45,000 plant species and around 90,000 animal species have been recorded. Based on Robert May’s estimate, only 22% of the species have been recorded. India likely has over 100,000 plant species and 300,000 animal species yet to be discovered.
Challenges in Completing Species Inventory	Completing the species inventory in India is difficult due to the lack of sufficient trained taxonomists and the time required. Many species face extinction before being discovered.
Urgency of Biodiversity Conservation	The destruction of natural habitats is causing species extinction at an unprecedented rate, making biodiversity conservation a critical global issue for sustaining life on Earth.
Extrapolating Species Data	Explanation: The method of extrapolating species data is used by biologists to estimate the total number of species on Earth, especially when complete inventories do not exist. This approach is necessary because a majority of species, especially in the tropics, have not yet been discovered or described. Example of Extrapolation: Species inventories are more complete in temperate regions (like Europe and North America) than in tropical regions (like the Amazon or Southeast Asia), which harbor a vast amount of undiscovered biodiversity. Biologists use the species richness of an exhaustively studied group of insects (a well-studied group) in temperate areas and compare it to the species richness in tropical regions. Based on this statistical comparison, they can estimate the number of undiscovered species in tropical areas. Ratio-Based Approach: For example, if a certain insect group has a species richness ratio of 1:10 between temperate and tropical regions, and scientists have recorded 1,000 species of that insect in temperate areas, they can hypothesize that there may be around 10,000 species of that insect in tropical regions. This kind of ratio-based extrapolation can then be applied to other taxonomic groups (such as plants, fungi, or mammals) to come up with gross estimates of total species diversity. Uncertainty and Limitations: While this method is useful for producing estimates, it carries uncertainties. Factors such as habitat destruction, incomplete data, and variations between species groups may affect the accuracy of the extrapolations.