Revision: Ecology >> Biodiversity and Its Conservation Biology Science (English Medium) Class 12 CBSE

• The diversity of life forms present on Earth, including plants, animals, and microorganisms, is called biodiversity.
• Biodiversity is the occurrence of different types of genes among the individuals of species, habitats and ecosystems, both terrestrial and aquatic within a defined area.

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: The process by which a body of water enriched in dissolved nutrients (such as phosphates) that stimulates the growth of aquatic algae usually resulting in the depletion of 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 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.

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 is the variety of life on Earth - including microorganisms, fungi, plants and animals in both terrestrial and aquatic habitats.
• Diversity exists in size, shape, colour, nutrition, habitat and reproduction. It arises due to adaptations of organisms to different environmental conditions for survival.
• Biodiversity = totality of genes, species and ecosystems in a region (as per IUCN, UNEP and WRI).
• Term coined by Walter Rosen (1982), popularised by Edward Wilson to describe diversity at all levels of biological organisation.
• Today's biodiversity is the result of 3.5 billion years of evolutionary history, influenced by natural processes and human activities.

• While slightly over 1.5 million species have been officially recorded worldwide, scientifically sound estimates suggest the actual global total is around 7 million.
• Animals constitute more than 70% of all recorded species, with insects making up 7 out of every 10 animals, whereas plants account for roughly 22%.
• Prokaryotes are excluded from these standard estimates because conventional laboratory and taxonomic methods cannot accurately identify them, though their true numbers likely reach into the millions.
• Despite covering only 2.4% of the Earth's land area, India holds an impressive 8.1% of global species diversity, earning it the status of a megadiversity country.
• India has recorded nearly 45,000 plant species and twice as many animal species; however, estimates indicate hundreds of thousands of species remain undiscovered and face the severe threat of extinction before ever being catalogued.

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.