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: 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.

• 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.

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.

• 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 plants, 1300 birds and 427 mammals.
• Tropics have high diversity due to a stable climate, less 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, C = Y-intercept. On a logarithmic scale, it gives a straight line.
• Z value for smaller areas = 0.1 to 0.2. For larger areas (continents) = 0.6 to 1.2 (steeper slope — species increase faster than area explored).

• A stable community maintains constant biomass production, withstands disturbances, recovers quickly and resists invasive species.
• David Tilman proved that greater species richness maintains the stability of an ecological community. Rich diversity leads to lesser variation in biomass production — called Productivity Stability Hypothesis.
• Paul Ehrlich (Stanford) proposed the Rivet Popper Hypothesis — an ecosystem compared to an aeroplane and species to rivets. Loss of one species may not cause immediate damage, but gradual loss seriously threatens the ecosystem.
• Loss of key species causes rapid and serious damage, showing that diversity and ecosystem well-being do not share a linear relationship.
• Loss of species disturbs food chains, food webs, energy flow and natural cycles — affecting the entire balance of the ecosystem.

• Loss of biodiversity causes ecosystem imbalance and may lead to extinction of species (natural, mass, and anthropogenic).
• Natural causes include forest fires, earthquakes, and volcanic eruptions, while human causes include habitat destruction, hunting, and overexploitation.
• The present biodiversity loss is considered the 7th mass extinction, occurring 100–1000 times faster due to human activities.
• Loss of biodiversity reduces plant productivity, disturbs environmental processes, and lowers resistance to disturbances.
• The “Evil Quartet” causes biodiversity loss: habitat loss, over-exploitation, alien species invasion, and co-extinction.
• Invasive species can harm or eliminate native species due to a lack of natural predators (e.g., Parthenium, water hyacinth).
• Conservation status is maintained in the IUCN Red Data Book; endangered species have declining populations, while extinct species are completely lost.

• Conservation of biodiversity means protection and proper management of species to maintain balance and ensure benefits for the present and the future.
• Narrowly utilitarian value: biodiversity provides food, shelter, medicines, and industrial products; many species are used in traditional and modern medicine.
• Broadly utilitarian value: biodiversity supports ecological processes like oxygen production, pollination, seed dispersal, and also provides recreational benefits.
• Bioprospecting involves searching for useful biological resources like new medicines, genes, and economically important products.
• Ethical reason: all living organisms have an equal right to live, so humans should not destroy biodiversity.