2.5.2 Biodiversity and species notes

1. 2.5.2.1Biodiversity: genetic, species and ecosystem levels; alpha, beta and gamma diversity

   Biodiversity is the variety of life at three levels — genes, species and ecosystems — and ecologists measure it within a habitat (alpha), between habitats (beta) and across a region (gamma).

   Advanced · 9 min · Full course
2. 2.5.2.2Biodiversity hotspots: world and India

   A biodiversity hotspot is a region very rich in endemic plants that has already lost most of its natural habitat; there are 36 in the world and India shares four.

   Advanced · 7 min · Full course
3. 2.5.2.3India as a megadiverse country: biogeographic zones

   India is one of the world's 17 megadiverse countries: with 2.4% of the land it holds about 7–8% of recorded species, spread over ten biogeographic zones from the Trans-Himalaya to the islands.

   Advanced · 8 min · Full course
4. 2.5.2.4Threats to biodiversity: habitat loss, invasive alien species and extinction

   Species are being lost far faster than the natural rate, mainly because of habitat loss, over-exploitation, invasive alien species and co-extinctions — the "Evil Quartet" — with climate change and pollution adding pressure.

   Advanced · 8 min · Full course
5. 2.5.2.5IUCN Red List: categories and criteria

   The IUCN Red List, kept by the International Union for Conservation of Nature, grades species by their risk of extinction into nine categories; three of them — Critically Endangered, Endangered and Vulnerable — together make up "threatened".

   Advanced · 7 min · Full course
6. 2.5.2.6Threatened mammals of India

   India's threatened mammals range from flagship big animals such as the tiger, elephant and snow leopard to little-known species such as the Malabar civet and Namdapha flying squirrel; exams test their IUCN status, where they live and the latest counts.

   Advanced · 8 min · Full course
7. 2.5.2.7Threatened birds of India

   India has over 1,300 bird species; the most threatened are grassland birds such as the great Indian bustard and Bengal florican, the vultures, and a few very rare endemics such as Jerdon's courser of Andhra Pradesh.

   Advanced · 8 min · Full course
8. 2.5.2.8Reptiles, amphibians, fish and marine species in news

   Among cold-blooded and aquatic animals, exams focus on India's three crocodilians, five sea turtles, the river dolphins, the dugong, sharks and mahseers, and amphibians — the most threatened vertebrate class in the world.

   Advanced · 8 min · Full course
9. 2.5.2.9Threatened and endemic plants of India

   India's flora is rich in endemics; the plants most often tested are red sanders and Beddome's cycad of Andhra Pradesh, medicinal Himalayan herbs such as kuth and jatamansi, and the orchids and pitcher plant protected under the Wildlife Act.

   Advanced · 7 min · Full course
10. 2.5.2.10Conservation: in situ and ex situ methods, gene banks and seed vaults

    Biodiversity is conserved either in its natural home (in situ: parks, reserves, sacred groves) or outside it (ex situ: zoos, botanical gardens, seed and gene banks, cryopreservation); in situ is the main method and ex situ is the back-up.

    Advanced · 8 min · Full course

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