NEET Biology Class 12 Biodiversity And Its Conservation Notes

Biodiversity And Its Conservation

Biodiversity:

Biodiversity is the diversity of biological organization ranging from cellular macromolecules to biomes. Edward Wilson popularized the term ‘Biodiversity’.

Levels Of Biodiversity

1. Genetic diversity: Diversity shown by a single species at the genetic level. For example, Rauwolfia vomitoria (Himalayan) shows genetic variation in the potency & concentration of the chemical reserpine. India has more than 50,000 different strains of rice and 1,000 varieties of mango.
2. Species diversity: Diversity at the species level. For example, Western Ghats have greater amphibian species than the Eastern Ghats.
3.  Ecological diversity: Diversity at the ecosystem level.

For example, In India, deserts, rainforests, mangroves, coral reefs, wetlands, estuaries & alpine meadows are seen.

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Biology Class 12 Notes For Neet

Total Number Of Species On Earth (Global Species Diversity)

• According to IUCN (2004) more than 1.5 million species described far.
• According to Robert May’s Global estimate about 7 million species would have on earth. (He considered the species to be discovered in the tropics. i.e. only 22% of the total species have been recorded so far).

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• Animals are more diverse (above 70%) than plants including Plantae and Fungi (22%).
• Among animals, insects are the most species-rich group (70%, i.e. out of every 10 animals, 7 are insects).
• Number of fungi species is more than the combined total of the species of fishes, amphibians, reptiles & mammals.

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• India has only 2.4% of the world’s land area but has 8.1% of the species diversity. India is one of the 12 mega-diversity countries of the world.
• Nearly 45,000 plant species and twice as many animals have been recorded from India.
• Applying May’s global estimates, India would have more than 1 lakh plant species and 3 lakh animal species.
• Biologists are not sure about the total number of prokaryotic species because
  • Conventional taxonomic methods are not suitable for identifying microbial species.
  • In the laboratory, many species cannot be cultured

Biology Class 12 Notes For Neet

Patterns Of Biodiversity

1. Latitudinal gradients:

• Species diversity decreases from the equator to the poles.
• Tropics (latitudinal range of 23.5° N to 23.5°) have more species than temperate or polar areas.

For example, the number of bird species in different latitudes:

• Colombia (near the equator): About 1400 species.
• India (in the tropics): > 1200 species.
• New York (41 N): 105 species.
• Greenland (71 N): 56 species.

Class 12 Biology Notes For Neet

Tropical forest region like the Equator has up to 10 times of vascular plant species as compared ta temperate forest region like the Midwest of the USA.

The tropical Amazonian rainforest (South America) is the greatest biodiversity on earth. It contains

• > 40000 species of plants
• 3000 species of fishes
• 1300 species of birds
• 427 species of mammals
• 427 species of amphibians
• 378 species of reptiles
• > 1,25,000 species of invertebrates

Biology Class 12 Notes For Neet

Biodiversity (species richness) is highest in the tropics because:

• Tropics had more evolutionary time.
• Relatively constant environment (less seasonal).
• They receive more solar energy which contributes to greater productivity.

“biodiversity class 12 notes “

2. Species Area relationship:

According to the study of Alexander von Humboldt in South American jungles, within a region, species richness increases with increasing explored area, but only up to limit. The relation between species richness and area gives a rectangular hyperbola.

S= CA^z

Where,

S= Species richness

A= Area

C= Y- Intercept

Z= Slope of the line (regression coefficient)

• On a logarithmic scale, the relationship is a straight line described in the equation Log S = log C + Z log A
• Generally, for small areas, the Z value is 0.1 to 0.2.
• But for large areas (For example, entire continents), the slope of the line is steeper (Z value: 0.6 to 1.2).
• For example, for frugivorous birds and mammals in the tropical forests of different continents, the Z value is 1.15.

Class 12 Biology Notes For Neet

Importance Of Species Diversity

According to David Tilman, plots with more species shows less year-to-year variation in total biomass. Increased diversity contributes to higher productivity. It is essential for ecosystem health and the survival of the human race.

‘Rivet popper hypothesis’:

• It is an analogy used to understand the importance of biodiversity. It is proposed by Stanford ecologist Paul Ehrlich.
• In an airplane (ecosystem), all parts are joined together using many rivets (species). If passengers pop a rivet (extinction of a species), it may not affect flight safety (functioning of the ecosystem).
• But as more and more rivets are removed, the plane becomes dangerously weak. Loss of rivets on the wings (key species that drive major ecosystem functions) is more dangerous to flight safety than the loss of a few rivets on the seats or windows inside the plane.

“class 12 biodiversity and conservation notes “

Loss Of Biodiversity

• IUCN Red List (2004) says that 784 species (338
• vertebrates, 359 invertebrates & 87 plants) were extinct in
• the last 500 years. For example, Dod (Mauritius), Quagga (Africa),
• Thylacine (Australia), Stellar’s sea cow (Russia), and 3 subspecies (Bali, Javan, Caspian) of tiger. 27 species have been disappeared in the last 20 years.
• More than 15,500 species are facing the threat of extinction. 12% of birds, 23% of mammals, 32% of amphibians, and 31% of gymnosperm species face the threat of extinction.
• The current extinction rate is 100 and 1000 times faster than in pre-human times. If this trend continues, nearly 50% of species might be extinct within the next 100 years.

Impacts of Loss of Biodiversity

• Decline in plant production.
• Environmental perturbations such as drought.
• Increased variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles.

Causes of Biodiversity losses (‘The Evil Quartet’):

1. Habitat loss and fragmentation: Most important cause:

• For example, Tropical rain forests (loss from 14% to t6%).
• Thousands of hectares of rainforests is being lost within hrs.
• The Amazon rainforest is being cut for cultivating soya beans or for the conversion of grasslands for cattle. Fragmentation badly affects animals requiring large territories and migratory animals.

2. Over-exploitation: Stellar’s sea cow, Passenger pigeon, etc. extinct due to exploitation.

3. Alien species invasions: Alien species cause the decline or extinction of indigenous species. For example,

• Nile Perch: Nile Perch introduced in Lake Victoria (East Africa) caused the extinction of more than 200 species of cichlid fish.
• Invasive weed species like Parthenon (carrot grass),
• Lantana and Einkorn (water hyacinth) caused damage to our native species.
• Illegal introduction of the African Catfish (Clarkias gariepinus) for aquaculture is posing a threat to the indigenous catfishes in our rivers.

4. Co-extinction: When a species becomes extinct, the species associated with it extinct. For example,

• Extinction of the parasites when the host is extinct.
• Co-evolved plant-pollinator mutualism is where the extinction of one leads to the extinction of the other.

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Biodiversity Conservation

There are 3 categories of reasons for conservation.

1. Narrowly utilitarian arguments:

• Human derive economic benefits from nature such as food, firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes), and medicines.
• More than 25% of the drugs are derived from plants.
• 25,000 species of plants have medicinal value.

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2. Broadly utilitarian arguments:

Biodiversity has many ecosystem services.

• For example, the Amazon forest (the ‘lung of the planet’) produces 20% of the total O₂ in the earth’s atmosphere.
• Pollination through bees, bumblebees, birds, and bats.
• Aesthetic pleasures.

“class 12 biodiversity and conservation notes “

3. Ethical arguments: Every species has an intrinsic value. We have a moral duty to care for their well-being.

Biodiversity conservation is 2 types:  In situ (on-site) conservation and Ex-situ (off-site) conservation.

1. In situ conservation (on site): It is the conservation of genetic resources within natural or human-made ecosystems in which they occur.  For example, protected areas such as National Parks, Sanctuaries, Biosphere reserves, cultural landscapes, natural monuments, etc.

• National Park: Strictly reserved for the welfare of the wildlife where private ownership, cultivation, grazing etc. are prohibited. For example, Eravikulam National Park in Kerala.
• Sanctuary: Here, protection is given only to the animals. Collection of timbers, minor forest products, and private ownership are allowed along as they do not harm the animals. For example, Periyar Wildlife Sanctuary in Kerala.
• Biosphere Reserves: Areas of land or coastal ecosystems for conservation and sustainable use.
• Sacred forests (Sacred groves): For example,
  • Sacred groves in Khaki & Jaina Hills in Meghalaya
  • Aravalli Hills of Rajasthan
  • Western Ghat regions of Karnataka & Maharashtra
  • Sarguja, Chanda & Bastar areas (Madhya Pradesh).
  • India has 14 Biosphere Reserves, 90 National Parks and
  • 448 wildlife sanctuaries.

2. Ex situ conservation (off-site):

It is the conservation of organisms outside their habitats. For example, genetic resource centres, zoological parks, wildlife safari parks, botanical gardens, gene banks, cryopreservation etc.

Class 12 Biology Notes For Neet

Hotspots

• These are the regions with very high species richness, a high degree of endemism (species confined only ta specific regions) but most threatened.
• There are 34 hotspots in the world. 3 hotspots cover India’s biodiversity regions Western
• Ghats & Sri Lanka, Indo-Burma and Himalayan.

“class 12 biodiversity and conservation notes “

International Efforts for conserving biodiversity

• The Earth Summit (Ride Janeiro, 1992) 3 objectives
• Conservation of biodiversity
• Sustainable use of biodiversity
• Sharing of benefits in the utilization of genetic resources.

The World Summit on Sustainable Development (Johannesburg, South Africa, 2002): 190 countries pledged to reduce the current rate of biodiversity loss