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

BIODIVERSITY & CONSERVATION: 

CHAPTER AT A GLANCE

Edward Wilson popularized the term biodiversity.

LEVELS OF BIODIVERSITY

1. Genetic diversity: Diversity shown by a single species at genetic level. E.g. Rauwolfia vomitoria shows genetic variation in reserpine.
2. Species diversity: Diversity at species level. E.g. Western Ghats have greater amphibian species than Eastern Ghats.
3. Ecological diversity: Diversity at ecosystem level. E.g. deserts, rain forests, mangroves etc.

TOTAL NUMBER OF SPECIES ON EARTH (GLOBAL SPECIES DIVERSITY)

Biologists are not sure about No. of prokaryotic species because

• Conventional taxonomic methods are not suitable to identify microbial species.
• In 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 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 co-efficient) 

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 ecosystem). But as more rivets are removed, 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 extinction of cichlid fish, African Catfish is a threat to indigenous catfishes in our rivers.
4. Co-extinction: When a species extinct, the species associated with it also extinct. E.g. Parasites – host, Plant – pollinator.

BIODIVERSITY CONSERVATION

There are 3 categories of reasons for conservation.

• Narrowly utilitarian arguments: Human 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 an 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 which 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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