Biodiversity and Conservation | Plus 2 Zoology | Exam Capsule Notes (Web and PDF)

BIODIVERSITY & CONSERVATION:

CHAPTER AT A GLANCE

LEVELS OF BIODIVERSITY

1. 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

• Conventional taxonomic methods are not suitable to identify microbial species.
• 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

• It had more evolutionary time.
• Relatively constant environment.
• 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, Stellar’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.

• Narrowly utilitarian arguments: Humans derive economic benefits from nature such as food, firewood, industrial products, and medicines.
• Broadly utilitarian arguments: Biodiversity has ecosystem services. E.g., production of O2, Pollination, Aesthetic pleasures.
• 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.,

• National Park: Reserved for the welfare of wildlife where private ownership, cultivation, grazing, etc. are prohibited. E.g., Eravikulam National Park.
• Sanctuary: Protection only to the animals. Collection of timbers, minor forest products, and private ownership are allowed. E.g., Periyar wildlife sanctuary.
• Biosphere Reserves: Areas of land or coastal ecosystems for conservation and sustainable use.
• Sacred forests (Sacred groves): Forest fragments that are communally protected based on religious beliefs.

b. Ex situ conservation (off site):

• Conservation of organisms outside their habitats.
• E.g., genetic resource centres, zoological parks, wildlife safari parks, botanical gardens, gene banks, cryopreservation, etc.

Hotspots:

• The regions with very high species richness, high endemism but most threatened.
• There are 34 hotspots in the world.
• 3 hotspots cover India’s biodiversity regions- Western Ghats & Sri Lanka, Indo-Burma and Himalaya.

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