Revision: Ecology and Environment >> Biodiversity and Its Conservation Biology (Theory) ISC (Science) ISC Class 12 CISCE

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.

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

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.

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

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.

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.

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.

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.

Plants occurring in a particular is called flora of that area i.e. vegetative growth forms flora. Flora deals with plants.

The animals occurring in a area form the fauna of that area. Fauna deals with animals.
Flora and fauna of an area is the plants and animals found in that area.

Regions of the Earth that are extremely rich in species, especially endemic species, and are under severe threat of habitat loss are called biodiversity hotspots.

The official document that records and provides information on rare, endangered, and threatened species of plants, animals, fungi, and local sub-species within a country or state is called the Red Data Book.

The total set of genes and alleles present in a population is known as gene pool. 

The gradual or rapid loss of genetic diversity within a species, including loss of populations, genes, or gene combinations, is called genetic erosion.

A protected area strictly reserved for the conservation of wildlife, where activities like grazing, forestry, hunting, and cultivation are prohibited.

A protected area where special protection is given to animals, and activities like timber harvesting and collection of minor forest products are allowed as long as they do not harm wildlife.

The forest conserved in the name of God and considered to be sacred is called a sacred grove.

or

The sacred groves are tracts of forest that have been completely immune from human interference on the basis of religious beliefs. 

A botanical garden is a well-tended area displaying a wide range of plants labelled with their botanical names.

A protected or designated area where wild animals roam freely in conditions similar to their natural habitat and visitors observe them safely is called a wildlife safari.

A facility where seeds are stored under controlled conditions to preserve plant genetic diversity for future use is called a seed bank.

The preservation of cells, tissues, or germplasm by cooling them to very low sub-zero temperatures, usually –196°C, to stop all biological activity is called cryopreservation.

An institution where valuable plant genetic material is preserved in a viable condition to prevent its loss or extinction is called a gene bank.

• 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.

• Global biodiversity, a term popularised by Edward Wilson, refers to the total variety of life on Earth and is studied across three fundamental levels: genetic, species, and ecological.
• While the IUCN (2004) formally records slightly over 1.5 million described species, ecologist Robert May conservatively estimates the true global total to be approximately 7 million.
• Animals dominate the documented species list, comprising over 70% of all recorded life on Earth.
• Insects are the single most diverse taxonomic group, constituting 61% of all described animal species.
• Plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) account for no more than 22% of all formally described species.
• Prokaryotic diversity remains unknown because conventional taxonomic methods cannot identify them; however, molecular and biochemical criteria suggest microbial species could number in the millions.

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).

• India is 1 of 12 mega-diverse countries, holding 60–70% of global biodiversity.
• India has 8 floristic regions, from Western Himalayan conifers to Andaman mangroves.
• India ranks 10th globally / 4th in Asia for plant diversity (~47,000 species; ~15,000 flowering plants).
• Over 35% of plant species are endemic.
• India records ~89,451 animal species, including ~390 mammal species.
• India's coastline (~7,500 km) supports mangroves, coral reefs, estuaries, and lagoons.
• Three major endemism hotspots: Northeast India, Western Ghats, and Andaman & Nicobar Islands.

• Biodiversity represents the variety of all life forms and ecosystems on Earth, forming the foundation for sustainable development and environmental health.
• It maintains crucial ecological balances and provides essential ecosystem services, such as regulating atmospheric gases and ensuring long-term ecosystem stability.
• It supplies critical resources for human survival, including food, raw materials, fuel, and the wild genetic traits needed to improve domestic agricultural crops.
• It is the primary source for many modern pharmaceuticals and traditional medicines, with a vast majority of plant-derived drugs discovered through indigenous knowledge.
• It supports global food security by providing subsistence communities with vital access to wildlife, animal protein, and traditional food plants.
• It possesses immense ethical and aesthetic value, inspiring a moral responsibility to protect nature while supporting economic growth through nature tourism.

• Proposed by ecologist Paul Ehrlich, this hypothesis uses an analogy to explain the critical role of species diversity in maintaining ecosystem stability.
• It compares an ecosystem to an airplane, and the various species living within it to the thousands of rivets holding the airplane together.
• The extinction of a species is compared to removing a rivet; initially, losing a few species may not noticeably disrupt the overall functioning of the ecosystem.
• However, the continuous and progressive loss of species over time gradually weakens the ecosystem, making it dangerously unstable.
• The specific type of species lost is crucial; the extinction of a key species that drives major ecological functions (like removing a rivet from a wing flap) can cause an immediate system collapse.
• The hypothesis concludes that while the exact consequence of losing one species is unpredictable, continuous species extinction guarantees the long-term breakdown of the ecosystem.

• 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).

• The World Conservation Union (IUCN) evaluates and categorises species at risk of extinction based on their population decline, habitat quality, and geographical distribution.
• Historically, species were classified into seven broad conservation categories: extinct, endangered, vulnerable, rare, threatened, intermediate, and out of danger.
• The modern IUCN framework evaluates extinction risk using precise quantitative criteria, such as the rate of population decline, population size, and the extent of the geographic range.
• Under the updated system, species are placed into specific risk levels, ranging from Extinct (EX) and Critically Endangered (CR) to Least Concern (LC).
• 'Endangered' species face rapid population decline and immediate survival threats, whereas 'rare' species naturally possess small populations localised in restricted geographical pockets.
• Notable examples of endangered species in India include the Asiatic lion, Indian Rhinoceros, Hornbill, and the medicinal plant Rauwolfia serpentina.
• The Great Indian Bustard is a prime example of a highly endangered species; heavy hunting for its flesh has drastically reduced the population of this large ground bird.

• Biodiversity hotspots are highly threatened regions prioritised for conservation due to their massive numbers of endemic species found nowhere else on Earth.
• Globally, 34 identified hotspots cover just 2.3% of the Earth's surface but harbor 50% of the world's plant species, and protecting them could reduce global mass extinction by nearly 30%.
• India hosts two major biodiversity hotspots, the Western Ghats and the Eastern Himalayas, which possess incredible biological wealth but are suffering from accelerated habitat loss.
• The Western Ghats are severely endangered by mining and natural gas exploration, which directly threatens the natural habitats of the Asiatic lion and wild bison.
• Major Indian heritage sites like Manas and Sunderban National Parks are under extreme pressure from dams, deforestation, and water exploitation, endangering their native tiger and rhino populations.

It is an official state or national document established to record and document rare and endangered species of animals, plants, and fungi, including local sub-species within a specific territory.

Primary Role: It serves as the central information repository for ecological research and conservation efforts.

Functions:

• Provides crucial baseline data for conducting scientific studies on threatened species.
• Facilitates active monitoring programs for endangered organisms and helps track the status of their natural habitats.

• Rapid genetic erosion and biodiversity loss are driven by destructive human activities, including habitat fragmentation, over-exploitation, pollution, and shifting cultivation.
• Biodiversity conservation is fundamentally split into two distinct frameworks: in situ (on-site within natural habitats) and ex situ (off-site within controlled human facilities).
• In situ conservation secures ecosystems dynamically, allowing threatened animal and plant populations to continue evolving within biosphere reserves, national parks, and sacred groves.
• Ex situ conservation physically isolates rare or endangered species in artificial setups like botanical gardens, zoological parks, aquaria, and wildlife safari parks to ensure survival.
• Advanced ex situ techniques preserve genetic blueprints long-term using cryogenic storage of gametes in liquid nitrogen, seed and pollen banks, tissue culture, and gene banks.
• Cultivation in botanical gardens plays a vital rescue role, as demonstrated by the ginkgo tree (Ginkgo biloba), a living fossil that avoided extinction primarily through intensive horticultural multiplication.

The complete set of genes and all their alternative forms (alleles) present within a specific, interbreeding population.

• Isolation: Populations that are geographically or reproductively separated from one another and thus do not interbreed possess distinct, separate gene pools.
• Intraspecific Variation: Even within the exact same species, the gene pools of different populations can vary significantly depending on their unique evolutionary history and local environmental conditions.
• Significance of Size: A large gene pool indicates extensive genetic diversity. This leads to robust populations that are highly capable of surviving extreme environmental challenges and intense natural selection.
• Fluctuations: A gene pool increases in size and diversity when new mutations occur and successfully survive. It decreases when a population undergoes a significant reduction in size.
• Scientific Utility: Analysing a gene pool provides a clear picture of the variety, number, and type of genes existing in a population. It is a fundamental concept used to calculate gene frequencies (the mathematical ratio of different alleles in a population).

The gradual or sudden loss of genetic diversity within a plant or animal species, leading to the diminishment or complete loss of its unique gene pool (specific alleles or gene combinations).

• Pace of Erosion: It can occur rapidly due to catastrophic events and severe land-use changes, or it can progress gradually and go unnoticed for long periods.

• Primary Causes: While a minor loss of genetic diversity occurs naturally, alarming levels of genetic erosion are driven primarily by human activities, such as natural habitat destruction and the imposition of movement restrictions on wild populations.

• Importance of Diversity: A rich genetic diversity is absolutely crucial for a species' overall fitness, its long-term viability, and its ability to successfully adapt to changing environmental conditions.

Ecological Consequences:

• It severely weakens the genetic health of an entire species, pushing it toward eventual extinction.
• The disappearance of a species triggers a domino effect, adversely impacting other dependent species and ultimately degrading the overall health and stability of the environment.

• Global conservation requires a multi-layered framework operating across international, national, regional, and local political scales to bypass geopolitical boundaries.
• International bodies like the World Conservation Union and global treaties such as CITES actively protect transboundary ecosystems by preventing the illegal trade of endangered wildlife.
• National strategies enforce statutory regulations within domestic borders, establishing national parks and using financial compensation schemes to incentivise habitat protection.
• Keystone species are prioritised in conservation management because their activities uniquely dictate the survival and persistence of numerous other species in the community.
• The extinction or removal of a single keystone species triggers a cascading failure, destabilising the entire food web and causing the secondary collapse of dependent organisms.
• The total scope of modern biodiversity conservation is deeply interdisciplinary, relying on technical sciences like biotechnology alongside socio-political factors such as economics, policy reform, and ethics.

• India has enacted Wildlife (Protection) Act, 1972 to protect endangered species and ban hunting and trade in wildlife.
• A network of national parks, wildlife sanctuaries, and biosphere reserves has been established for in-situ conservation.
• Project Tiger, Project Elephant, and Rhino Conservation Programme were launched to protect flagship species and their habitats.
• Central Zoo Authority manages zoological parks and supports captive breeding of endangered species.
• India is a signatory to CITES (1976) to regulate international trade in endangered flora and fauna.
• Habitat protection, anti-poaching measures, and eco-development programmes are promoted with central and state cooperation.
• Public awareness, legislation, pollution control, recycling, and scientific research form important components of conservation strategy.

• India's formal wildlife conservation efforts began as early as 1873 with the Madras Wild Elephant Preservation Act and culminated in the comprehensive Wildlife (Protection) Act of 1972.
• Following a severe decline from approximately 40,000 tigers in 1910 to just 268 in 1972 due to hunting and illegal trade, the government imposed a strict hunting ban in 1970.
• Project Tiger was launched on April 1, 1973, with the primary objective of protecting the Royal Bengal Tiger, its prey, and its natural habitat from human intrusion.
• The project is managed by the National Tiger Conservation Authority across 50 reserves, utilising a zoning system that strictly bans human activity in core areas while allowing sustainable use in buffer zones.
• Project Tiger has been a massive global success, aiding population recovery to 2,226 tigers by 2018 and making India home to 70% of the world’s wild tiger population.
• The initiative created an "umbrella effect", meaning the protection of tiger ecosystems indirectly secured the habitats of other endangered wildlife like rhinos, elephants, and snow leopards.

1. Geographical Extent: India covers approximately 3.2 million sq km, featuring a vast range of climates – from the arctic, snow-covered Himalayas to the torrid, tropical rainforests of the south.
2. Floral Diversity: India hosts about 45,000 plant species, which accounts for 7% of the world's total flora. The conspicuous vascular flora alone comprises over 17,000 species.
3. High Endemism: More than 35% of India's vascular plants are endemic, meaning they are native exclusively to India and are not found anywhere else in the world.
4. Faunal Diversity: The country supports a rich variety of animal life, with over 89,451 documented species, representing 6.5% of the world's total fauna.
5. Conservation Strategies: To maintain ecological balance and actively protect this vast biological diversity, the government has established a network of protected areas, including:
   → Bird Sanctuaries
   → Wildlife Sanctuaries
   → National Parks
   → Biosphere Reserves (a more recent conservation approach)

• Biosphere reserves are multi-purpose protected areas designed to conserve genetic diversity within ecosystems while uniquely permitting regulated, sustainable human activity.
• The framework was launched globally by UNESCO in 1971 under the Man and Biosphere (MAB) Programme to balance biodiversity conservation with local community livelihoods.
• These reserves are structured into three distinct sections: a strictly protected Core Zone, a regulated Buffer Zone for research and training, and a Transition Zone for sustainable community cooperation.
• Primary objectives include conserving rare and endangered species, promoting long-term ecological research, and providing facilities for environmental education.
• Each reserve represents a distinct ecological biome that is large enough to prevent genetic drift, inbreeding, and the loss of biodiversity.
• The MAB programme operates on a massive scale, encompassing over 356 reserves across 90 countries, with India officially designating 15 reserves by 2008.
• Established in 1986, the Nilgiri Biosphere Reserve (spanning 5,520 sq km across three southern states) holds the distinction of being India's first designated reserve.
• Beyond conservation, these areas offer immense scientific value for studying natural habitats, support nature-based recreation, and strengthen legal enforcement against overexploitation and poaching.

A national park is an area strictly reserved for the betterment and protection of wildlife, where human activities such as forestry, grazing, or cultivation are completely prohibited.

Indian Statistics: India has 110 national parks covering an area of over 40,501 sq km, which constitutes approximately 1.23% of the country's total geographical area.

Historical Milestones:

• World's First: Yellowstone National Park (USA).
• India's First: Jim Corbett National Park (Nainital, Uttarakhand).

Tiger Reserves in India:

• Largest: Nagarjuna Sagar Srisailam Sanctuary (Andhra Pradesh).
• Smallest: Ranthambore National Park (Rajasthan).

Specific Fauna: Nandan Kanan Zoo (Odisha) is distinctly recognised for the conservation of white tigers.

Key Legislation: The Biodiversity Act of India was officially passed by the Indian Parliament in the year 2002.

• Meaning: A protected area dedicated primarily to the conservation and protection of fauna (animal life).
• Permitted Activities: Certain operations, such as the harvesting of timber and the collection of minor forest products, are allowed, provided they do not interfere with the well-being of the animals.
• Private Rights: In direct contrast to national parks, private ownership rights are permitted within the boundaries of a sanctuary.
• Indian Statistics: India has approximately 543 wildlife sanctuaries covering an area of over 1,16,800 sq km, which constitutes nearly 4% of the country's total geographical area.

Meaning: Tracts of forest that are strictly protected and kept completely immune from human interference based on deep-rooted religious and cultural beliefs.

Key Locations in India:

• Khasi and Jaintia Hills (Meghalaya)
• Aravalli Hills (Rajasthan)
• Western Ghat regions (Karnataka and Maharashtra)
• Sarguja, Chanda, and Bastar areas (Madhya Pradesh)

Important Preserved Flora: Specific tree species commonly protected within these Indian sacred groves include Ficus religiosa, Saraca asoca, Shorea robusta, and Alstonia scholaris.

• Meaning: A well-tended, controlled area that displays a diverse range of living plants, each properly labeled with its scientific (botanical) name.
• Collections: They often house specialised, documented plant collections sourced from specific geographical regions across the world.
• Primary Objectives: Their fundamental role is to maintain these living plant collections specifically for scientific research, biodiversity conservation, public display, and environmental education.

• Meaning: A designated natural park or protected environment where hundreds of wild animals are allowed to roam freely in their natural habitat.
• Primary Purpose: They are organized primarily for eco-tourism, allowing visitors to actively observe and photograph wildlife, as well as engage in hiking and sightseeing.
• Indian Context: Safaris in India are characterised by their deeply untamed, lush rainforest environments rather than heavily managed enclosures.
• Common Indian Fauna: Visitors can observe a diverse array of free-roaming wildlife, including elephants, rhinoceroses, bears, wild dogs, and various reptiles.

• Seed bank = ex situ method storing seeds under controlled conditions
• Space-efficient, economical, supports large-scale storage
• ~1,400 seed banks and ~400 botanic gardens worldwide preserve seeds
• Cryopreservation (-196°C, liquid nitrogen) used for rare/recalcitrant species
• Distinct from botanical gardens (living plants) and gene banks (broader genetic material)

• Cryopreservation = storage at −196°C using liquid nitrogen
• Cryoprotectants (glycerol, DMSO) prevent ice-crystal cell damage
• Process order: Select → Treat → Cool (−38 °C) → Store (−196 °C) → Thaw → Regenerate
• Enables near-indefinite storage of plant/animal germplasm
• Successfully used in species like rice, tomato, tobacco, carrot, groundnut
• Distinct from seed banking and botanical gardens in method and scope

• Gene banks actively prevent plant extinction by preserving viable seeds, pollen, and tissues for future breeding and conservation.
• Standard preservation involves drying seeds to 5% moisture and storing them at –10 to –20°C.
• For rare or recalcitrant plants, cryopreservation uses liquid nitrogen at -196°C to maintain genetic stability long-term without ageing.
• Advanced techniques like tissue culture save space, reduce costs, and ensure virus-free material for global exchange.
• Habitat destruction drives genetic erosion; combating it requires protecting natural wildlife corridors, avoiding non-native species, and establishing seed banks.

• Ramsar sites are internationally significant wetlands, including natural areas like marshes and mangroves as well as man-made reservoirs, which are essential for sustaining global biological diversity.
• The Ramsar Convention is an international treaty signed in Ramsar, Iran, on February 2, 1971, aimed at the conservation and sustainable utilization of these wetland ecosystems.
• In recognition of the treaty's signing, World Wetland Day is celebrated globally every year on February 2nd.
• Wetlands are designated as Ramsar sites based on nine specific criteria – eight of which focus on biodiversity – to protect the ecosystems and the resources upon which humans depend.
• There are over 2,008 Ramsar sites across 169 countries globally, with the United Kingdom having the highest number of sites and Bolivia holding the largest total wetland area.
• India has 26 designated Ramsar sites, though these critical ecosystems face severe threats from water pollution, invasive species, and aggressive human development.

• Global Significance: Earth's biological resources are recognised as invaluable global assets that are absolutely vital for humanity's current and future economic and social development.
• The Growing Threat: Ecosystems and species face unprecedented threats today, with human activities driving species extinction at an alarming and rapid rate.
• Initial Response (November 1988): To address this crisis, the United Nations Environment Programme (UNEP) convened the Ad Hoc Working Group of Experts on Biological Diversity to explore the need for a global treaty.
• Legal Framework (May 1989): The working group successfully prepared an international legal instrument dedicated to the conservation and sustainable use of biological diversity.
• Nairobi Convention (May 22, 1992): These continuous global efforts officially culminated in the adoption of the Nairobi Convention on Biological Diversity.

• The Earth Summit (UNCED) was held at Rio de Janeiro, Brazil, from 3–14 June 1992, with participation from 172 countries to link environment and development.
• Major issues discussed included climate change, pollution, energy alternatives, water resources, and sustainable development.
• Important outcomes included Agenda 21, the Rio Declaration, the Statement of Forest Principles, and opening of the Convention on Biological Diversity (CBD) for signature.
• The summit led to global environmental actions, including formation of the Commission on Sustainable Development (CSD) and later agreements like the Kyoto Protocol and Paris Agreement.

• Event Overview: The United Nations World Summit on Sustainable Development was held in Johannesburg, South Africa, in 2002.
• Participation & Core Aim: It brought together approximately 21,000 delegates, including 104 Heads of State, with the primary goal of bridging the economic gap between rich and poor nations.
• Action-Oriented Focus: Rather than creating new global conventions or roadmaps (like Agenda-21), it functioned as a "conference of action" dedicated to implementing the environmental promises previously made at the Rio Earth Summit.
• Key Highlights: The summit's major achievement was setting strict global deadlines for critical issues, including poverty eradication, health, water and sanitation, agriculture (fisheries), energy, biodiversity, and climate change.