Revision: Class 12 >> Biodiversity and Conservation NEET (UG) Biodiversity and Conservation

Biodiversity is defined as the variety of plant and animal life in the world or in a particular habitat, a high level of which is usually considered to be important and desirable

The sum total of species richness, i.e., the number of species of plants, animals and micro-organisms inhabiting in a given habitat, is known as biodiversity.

It is a tool used to classify organisms based on their similarities and differences.

Hotspot is a biodegradable region that is both a significant reservoir of biodiversity and is threatened with destruction.

Eutrophication is the process by which a body of water becomes enriched with nutrients such as phosphates and nitrates, causing excessive algal growth and depleting dissolved oxygen.

Ramsar Sites: It is a wetland site designed of international importance under the Ramsar convention. It is an inter-governmental environmental treaty established in 1971 by UNESCO and coming into force in 1975.

Biodiversity refers to the variety and variability of life on Earth, encompassing all organisms, their genetic differences, and the ecological complexes (communities and ecosystems) they form.

Species that completely disappear from the planet are referred to as extinct.

Species that are not native to a region or locality but are unintentionally or purposefully introduced and cause harm to the native species already present are referred to as invasive species.

When a species possesses a very high risk of extinction as a result of rapid population decline of 50 to more than 70 per cent over the previous 10 years, it is said to be an endangered species.

Cryopreservation is a technique in which organisms, tissue, and cells are preserved and stored at the very low temperature of liquid nitrogen (−196°C) for years. They remain viable in the frozen state for future use.

• Biodiversity has three levels: genetic, species, and ecosystem diversity.
• The term was coined by Walter Rosen and popularised by E.O. Wilson.
• Biodiversity provides essential ecosystem services: nutrient cycling, pollination, climate regulation, and more.
• Species diversity decreases from the tropics to the poles.
• Biodiversity ≠ species count alone; genetic and ecosystem variation matter equally.
• Present biodiversity reflects billions of years of evolution and is under threat from human activity.

• Biodiversity exists at three levels — genetic, species and ecological (ecosystem) diversity.
• Genetic diversity (intraspecific) is variation in genes and chromosomes within the same species. Example: 1000 varieties of mangoes and 50,000 varieties of rice in India.
• Species diversity (interspecific) refers to the variety of plant and animal species (richness) and the number of individuals of each species (evenness) in a region. Example: India is among the 15 nations richest in species diversity.
• Ecological diversity refers to the variety of ecosystems and habitats within a geographical area. Example: India has deserts, rainforests, wetlands, grasslands, estuaries, etc.
• Diversity at all three levels is rapidly being reduced by modern human activities.

• Over 1.5 million species documented so far. Robert May estimated about 7 million species globally.
• More than 70% of recorded species are animals, plants comprise only 22%, and 70% of all animals are insects.
• Fungi species outnumber all vertebrates combined. Conventional taxonomic methods cannot identify prokaryotic species.
• India is one of 12 megadiverse nations, holding 8.1% of global biodiversity with only 2.4% of the world's land area. About 45,000 plant species and nearly double the number of animal species have been recorded.
• India has over 1,00,000 plant and 3,00,000 animal species yet to be discovered. Only 22% of India's natural wealth has been recorded so far.
• Tropical rainforests are still unexplored. The major threat is species loss due to deforestation and reclamation before they are even identified.
• A lizard from Amboli Ghat, Maharashtra, misidentified as Hemidactylus brookii, was correctly renamed Hemidactylus varadgirii using DNA profiling, in honour of Dr. Varad Giri.

Latitudinal Gradient

• Species richness is high near the equator (tropics: 23.5°N to 23.5°S) and decreases towards the poles. Example: The Amazon rainforest has 40,000 plant species, 1,300 bird species, and 427 mammal species.
• The tropics have high biodiversity due to a stable climate, reduced glaciation, abundant sunlight, higher rainfall, and greater niche specialisation.

Altitudinal Gradient

• Species diversity decreases at higher altitudes due to drastic climatic changes and seasonal variations.

Species-Area Relationship

• Observed by Alexander Von Humboldt, species richness increases with area but only up to a limit. For many species, this forms a rectangular hyperbola.
• Expressed as log⁡ S = log⁡ C + Z log⁡ A, where S = species richness, A = area, Z = slope, and C = Y-intercept. On a logarithmic scale, it gives a straight line.
• Z-value for smaller areas = 0.1-0.2. For larger areas (continents) = 0.6 to 1.2 (steeper slope – species increase faster than area explored).

1. Ecosystem Stability: High species diversity ensures a stable ecological community with consistent year-to-year biomass productivity.
2. Disturbance Resistance: Diverse ecosystems are highly resilient and recover quickly from natural or man-made disturbances.
3. Invasion Immunity: Rich species diversity provides strong natural resistance against the entry and establishment of invasive alien species.
4. Tilman's Finding: Long-term outdoor plot experiments by David Tilman proved that species-rich communities show minimal variation in total biomass.
5. Higher Productivity: Tilman's research also directly linked increased species diversity to higher overall ecosystem productivity.
6. Rivet Popper Hypothesis: Paul Ehrlich compared the ecosystem to an aeroplane and individual species to the rivets holding it together.
7. Cumulative Impact: While a few extinctions might not cause immediate damage, cumulative species loss dangerously weakens the entire ecosystem over time.
8. Critical Key Species: Losing key species (like rivets on an aeroplane's wings) poses an immediate, catastrophic threat to major ecosystem functions.
9. Human Survival: Preserving rich biodiversity is not just essential for ecosystem health, but imperative for the survival of the human race.

• Biodiversity loss involves the decline or complete disappearance of life forms, which severely disrupts ecosystem balance and drives species toward extinction.
• The current global biodiversity crisis is an ongoing, human-driven mass extinction event, with rates accelerating 100 to 1,000 times faster than historical natural background rates.
• Modern species loss is primarily caused by the "Evil Quartet": habitat loss and fragmentation, over-exploitation, alien species invasion, and co-extinction.
• Human activities like deforestation shrink natural habitats, while introduced alien species multiply rapidly without natural predators and outcompete indigenous wildlife.
• Reduced ecosystem biodiversity directly leads to lower plant productivity, altered nutrient cycling, and significantly decreased resistance to climate variations and diseases.
• The IUCN Red List systematically tracks these threats by grading species' extinction risks across defined categories, ranging from Least Concern (LC) to Critically Endangered (CR) and Extinct (EX).

• Biodiversity conservation involves protecting, managing, and restoring living organisms to maintain species, habitats, and ecological balance for the future.
• Direct economic benefits include resources such as food, fuel, fibre, timber, traditional medicines, modern drugs, and useful genes found in wild plant relatives.
• Indirect ecological services provided by nature include oxygen production, crop pollination, nutrient cycling, seed dispersal, climate regulation, and soil fertility maintenance.
• Every living organism has an inherent right to live, creating a moral responsibility for humans to preserve natural biological wealth for future generations.
• Bioprospecting explores plants, animals, and microorganisms to discover commercially important products, valuable genes, and new medicines before species disappear.