Genetic diversity: Diversity shown by a single species at the genetic level. E.g., Rauwolfia vomitoria shows genetic variation in reserpine.
2
Species diversity: Diversity at the species level. E.g., Western Ghats have a greater amphibian species than Eastern Ghats.
3
Ecological diversity: Diversity at the ecosystem level. E.g., deserts, rainforests, mangroves, etc.
TOTAL NUMBER OF SPECIES ON EARTH (GLOBAL SPECIES DIVERSITY)
Biologists are not sure about the number of prokaryotic species because:
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Conventional taxonomic methods are not suitable to identify microbial species.
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In the laboratory, many species cannot be cultured.
PATTERNS OF BIODIVERSITY
i. Latitudinal gradients: Species diversity decreases from the equator to the poles. Biodiversity (species richness) is highest in the tropics because:
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It had more evolutionary time.
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Relatively constant environment.
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It receives more solar energy.
ii. Species- Area relationship: Study of Alexander von Humboldt: Within a region, species richness increases with increasing explored area, but only up to a limit. S = CAz
S = Species richness | A = Area | C = Y-intercept | Z = slope of the line (regression coefficient)
For small areas, Z value= 0.1 to 0.2.
For large areas (e.g., entire continents), Z value= 0.6 to 1.2.
IMPORTANCE OF SPECIES DIVERSITY
Rivet popper hypothesis: Proposed by Paul Ehrlich. In an airplane (ecosystem), if passengers pop a rivet (extinction of a species), it may not affect flight safety (functioning of the ecosystem). But as more rivets are removed, the plane becomes dangerously weak.
LOSS OF BIODIVERSITY
IUCN Red List (2004): E.g., Dodo, Quagga, Thylacine,ๅ ทStellar’s sea cow, etc.
Causes of Biodiversity losses ('The Evil Quartet')
1
Habitat loss & fragmentation: Most important cause.
2
Over-exploitation: Stellar’s sea cow, Passenger pigeon, etc. extinct due to over-exploitation.
3
Alien species invasions: Cause extinction of indigenous species. E.g., Nile Perch introduced in Lake Victoria caused the extinction of cichlid fish, African Catfish is a threat to indigenous catfishes in our rivers.
4
Co-extinction: When a species becomes extinct, the species associated with it also becomes extinct. E.g., Parasites – host, Plant – pollinator.
BIODIVERSITY CONSERVATION
There are 3 categories of reasons for conservation:
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Narrowly utilitarian arguments: Humans derive economic benefits from nature such as food, firewood, industrial products, and medicines.
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Broadly utilitarian arguments: Biodiversity has ecosystem services. E.g., production of O2, Pollination, Aesthetic pleasures.
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Ethical arguments: Every species has intrinsic value. We have a moral duty to care for their well-being.
Types of Biodiversity conservation:
a. In situ conservation (on site):
Conservation of organisms within natural or human-made ecosystems. E.g.,
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National Park: Reserved for the welfare of wildlife where private ownership, cultivation, grazing, etc. are prohibited. E.g., Eravikulam National Park.
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Sanctuary: Protection only to the animals. Collection of timbers, minor forest products, and private ownership are allowed. E.g., Periyar wildlife sanctuary.
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Biosphere Reserves: Areas of land or coastal ecosystems for conservation and sustainable use.
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Sacred forests (Sacred groves): Forest fragments that are communally protected based on religious beliefs.
