Tropical forests (especially tropical rainforests) have the highest species richness and ecosystem complexity due to stable warm climate, high solar input and year-round precipitation that support high primary productivity and rapid speciation.
In situ conservation refers to protecting species in their natural habitats (e.g., national parks, wildlife sanctuaries, biosphere reserves), maintaining ecological processes and genetic diversity in the wild.
Zoological parks are ex situ conservation facilities where organisms are maintained outside their natural habitats. Sanctuaries, national (natural) parks and biosphere reserves are examples of in situ conservation.
India has two global biodiversity hotspots within its boundaries: the Western Ghats and the Eastern Himalayas. These regions have high species endemism and face significant habitat loss.
The IUCN (International Union for Conservation of Nature) publishes the Red List of Threatened Species, categorizing taxa by extinction risk (e.g., Critically Endangered, Endangered, Vulnerable).
The term 'biodiversity' is generally credited to W. G. Rosen (Walter G. Rosen) in the mid-1980s; E.O. Wilson later popularized it.
The Amazon rainforest is often called the 'lungs of the Earth' because of its vast area, very high primary productivity and large-scale carbon dioxide uptake and oxygen release through photosynthesis.
Amphibians are highly vulnerable to habitat destruction because of their dependence on both aquatic and terrestrial habitats, permeable skin, and often narrow ecological requirements; many amphibian species are declining globally.
Both statements are true: stable, warm, and predictable tropical climates (stable temperature, humidity and photoperiod) promote high primary productivity, longer growing seasons and ecological niche specialization, which foster speciation and high biodiversity.
Species richness is a measure of biodiversity indicating how many species occupy an area. Endemism describes species confined to a specific area (e.g., island endemics), often vulnerable to habitat loss because of their limited range.
a. Species richness: The number of different species present in a given area or community. b. Endemism: The condition of a species being native to and restricted to a particular geographic region.
India contains two global biodiversity hotspots within its political boundaries — the Western Ghats and the Eastern Himalayas — characterized by high species endemism and significant habitat loss.
Two hotspots: Western Ghats and Eastern Himalayas.
Biodiversity is considered at three hierarchical levels: genetic diversity (variation within species), species diversity (variety of species in a region), and ecosystem diversity (variety of habitats and ecological processes).
Genetic diversity, Species diversity, Ecosystem diversity.
The alkaloid reserpine is the active compound in Rauvolfia (Rauwolfia) vomitoria. Variation in such plant secondary metabolites is part of biochemical diversity, which arises from genetic diversity within and among species.
Reserpine; it exemplifies biochemical (a facet of genetic) diversity.
The Amazon rainforest covers vast area with high net primary productivity and dense vegetation that absorbs carbon dioxide and produces oxygen through photosynthesis. It stores huge amounts of carbon in biomass and soil, influences regional and global climate and hydrological cycles, and supports immense biodiversity — hence called the "lungs of the Earth."
The Amazon has immense primary productivity and biomass, photosynthesizes large amounts of CO2 into organic matter and releases oxygen, acting as a major carbon sink and regulator of global climate.
The Red Data Book, compiled by IUCN, lists species under threat categories (e.g., Extinct, Critically Endangered, Endangered, Vulnerable). It provides baseline data on distribution, population trends and threats to help scientists, managers and policymakers prioritize conservation, design recovery plans and monitor biodiversity.
The Red Data Book (IUCN Red List) is a catalogue of taxa assessed for extinction risk; its purposes are to document species' conservation status, raise awareness, guide conservation priorities and policy, and inform management and recovery actions.
Comparison: - Objective: In situ preserves species in their natural ecosystems and ecological interactions; ex situ preserves individuals/populations outside their habitats. - Examples: In situ — national parks, wildlife sanctuaries, biosphere reserves; Ex situ — zoological parks, botanical gardens, seed gene banks, cryobanks. - Advantages: In situ maintains natural selection, behavior and ecosystem functions; Ex situ allows controlled breeding, protection from immediate threats and conservation of genetic material. - Limitations: In situ may be limited by ongoing habitat destruction and resource conflicts; Ex situ can cause loss of natural behaviours, limited genetic representation and high cost. - Use together: Both approaches are complementary — ex situ can support in situ by reintroduction, and in situ ensures long-term survival of species in nature.
In situ: conservation within natural habitats (e.g., national parks, sanctuaries, biosphere reserves); maintains ecological processes and genetic diversity in the wild. Ex situ: conservation outside natural habitats (e.g., zoos, botanical gardens, seed banks, cryopreservation); useful for captive breeding, safeguarding small populations and restoring populations.
Under IUCN categories, an Endangered species has a severely reduced population size or restricted range and meets quantitative criteria indicating imminent risk of extinction without conservation intervention. Examples include Asiatic lion (historically endangered) and many other taxa.
Endangered species are species facing a very high risk of extinction in the near future due to rapid population decline, loss of habitat, overexploitation or other threats.
Factors causing latitudinal decline in biodiversity include reduced sunlight and temperature (lower energy), shorter growing seasons, greater climatic variability, historical glaciation events, and simpler ecosystems with fewer specialized niches — all limiting species richness toward polar regions.
Because of decreasing solar energy and primary productivity, harsher and more seasonal climates, lower habitat heterogeneity and fewer ecological niches toward the poles, leading to lower speciation rates and higher extinction rates.
Human activities such as conversion of land for agriculture and urban growth, logging, mining, road building, and pollution directly destroy or fragment habitats. Climate change alters habitats; invasive species and overexploitation further degrade ecosystems, collectively driving habitat loss and biodiversity decline.
Major drivers: deforestation (agriculture expansion, logging), urbanization and infrastructure development, mining, pollution, dam construction, invasive species, overgrazing, and climate change.
Invasives can rapidly increase and dominate new ecosystems because of lack of natural enemies. They compete for resources, prey on native species, transmit novel pathogens and change habitat structure. Examples: Nile perch in Lake Victoria caused native cichlid extinctions; Lantana camara displaces native plants in India. Endemic species, being range-restricted and specialized, often cannot adapt or disperse and thus face extinction.
Alien (invasive) species outcompete, predate, introduce diseases, hybridize with, or alter habitats of endemic species; endemics with restricted ranges and low population sizes are especially vulnerable.
1. Habitat loss and fragmentation: Conversion of forests, wetlands and grasslands to agriculture, urban areas, roads and dams destroys and fragments natural habitats, reducing population sizes and isolating populations (habitat fragmentation), leading to local extinctions and loss of species richness.
2. Overexploitation: Unsustainable hunting, fishing, logging and harvesting (overfishing, poaching) reduce population sizes below recovery levels and drive species toward extinction (example: overharvesting of medicinal plants, timber species).
3. Pollution: Chemical pollutants (pesticides, heavy metals), eutrophication from fertilizers, oil spills and plastic debris degrade habitats and poison organisms, reducing survival and reproductive success.
4. Invasive alien species: Introduction of non‑native plants, animals or pathogens outcompete, prey on or bring diseases to native species (biological invasion), altering community structure and causing extinctions.
5. Climate change: Anthropogenic greenhouse gas emissions alter temperature and rainfall patterns, shift species’ ranges, disrupt phenology and increase frequency of extreme events, stressing species beyond tolerance limits.
6. Genetic erosion and reduced genetic diversity: Small, fragmented populations and selective harvesting reduce genetic variation, lowering adaptability and increasing extinction risk.
7. Other drivers: Mining, industrial development, agricultural intensification (monoculture, heavy pesticide use), infrastructure projects and human population growth indirectly amplify the above threats.
These threats often act together, producing synergistic impacts that accelerate biodiversity loss.
Major human-caused threats: habitat loss and fragmentation, overexploitation, pollution, invasive species, climate change, and genetic erosion.
Definition: - Mass extinction: A relatively short period in geological time when a very large number (typically >75% of species) across many taxa become extinct globally. Historically there have been five mass extinctions.
Are we facing one now? - Many scientists warn of a current, human‑driven (Anthropocene) biodiversity crisis — sometimes called the sixth mass extinction — due to habitat loss, overexploitation, invasive species and climate change. If current trends continue, large-scale losses are likely.
Steps to prevent or reduce a mass extinction (key measures): 1. In situ conservation: Expand and effectively manage Protected Areas (national parks, wildlife sanctuaries, biosphere reserves) including ecological corridors to reduce fragmentation. 2. Legislation and policy: Enforce and strengthen laws (e.g., CITES, national wildlife protection acts), land‑use planning and biodiversity action plans. 3. Sustainable resource use: Promote sustainable fisheries, forestry and agriculture (sustainable development, agroforestry, reduced pesticide use) to lower overexploitation and habitat conversion. 4. Ex situ conservation: Maintain seed banks, captive breeding programs, botanic gardens and gene banks to preserve genetic resources and enable reintroductions. 5. Control invasive species: Prevention, early detection and eradication/control programs for invasive alien species. 6. Climate action: Reduce greenhouse gas emissions, promote mitigation and ecosystem‑based adaptation (restoration of forests and wetlands) to buffer climate impacts. 7. Restoration ecology: Active restoration of degraded habitats (reforestation, wetland restoration) to recover ecosystem function and biodiversity. 8. Community involvement and education: Empower local communities, promote traditional knowledge, and increase public awareness to support conservation. 9. Scientific research and monitoring: Use IUCN Red List assessments, long‑term monitoring and biodiversity indicators to prioritize actions and track progress. 10. Economic incentives: Provide incentives for conservation (payments for ecosystem services, sustainable livelihoods) and reduce financial drivers of biodiversity loss.
Collectively, these measures can slow or avert large‑scale extinctions, but rapid, coordinated global action is essential.
Mass extinction is a geologically rapid, widespread loss of a large proportion of Earth's species. Evidence indicates we are entering a human‑driven (sixth) mass extinction; strong conservation actions are required to prevent or slow it.
Explanation and substantiation: - Jhum cultivation (shifting cultivation or slash‑and‑burn) involves clearing patches of forest, burning vegetation and cultivating crops for a few years, then moving to a new patch when fertility declines. - Deforestation: Primary forests and rich habitats are cleared, removing native trees and understory species that support high biodiversity and many endemic species in Northeast India. - Habitat loss and fragmentation: Small, scattered cleared plots fragment continuous forest, isolating wildlife populations and reducing habitat availability. - Soil erosion and nutrient loss: Burning and repeated cultivation expose soils to erosion and leaching, reducing productivity and inhibiting natural forest regeneration. - Reduced species richness: Many species (plants, insects, birds, mammals) dependent on mature forest are lost or decline in jhum fields; specialists and endemic species are especially vulnerable. - Successional changes and invasives: Repeated cycles may prevent recovery to original forest; secondary growth often has fewer species and may be invaded by weeds or opportunistic species. - Increased human‑wildlife conflict and hunting: Expansion of jhum frontiers increases access to remote areas, often increasing hunting and poaching pressure on wildlife.
Conclusion: While traditional shifting cultivation practiced at very low population densities could be sustainable, current shortened fallow periods and population pressures have made jhum a major threat to biodiversity in the northeastern states. Alternatives such as agroforestry, terraced agriculture, settled farming with soil-conservation measures and community forest management can reduce the threat.
Jhum (shifting or slash‑and‑burn) cultivation causes deforestation, soil erosion, loss of primary forest and species, habitat fragmentation and decreases biodiversity; repeated cycles reduce soil fertility and prevent forest recovery.
Concise list with brief notes: - Habitat destruction (deforestation, wetland drainage, urbanization): removes species’ homes and resources. - Habitat fragmentation: isolates populations, reduces gene flow and increases extinction risk. - Overexploitation: unsustainable hunting, fishing, logging and harvesting. - Pollution: chemicals, plastics, eutrophication and oil spills that degrade ecosystems. - Invasive alien species: outcompete or prey on native species and introduce diseases. - Climate change: alters ranges, phenology and community interactions, increasing stress. - Disease outbreaks: emergent pathogens can decimate wild populations. - Genetic erosion: loss of genetic diversity through small populations and selective harvesting. - Agricultural intensification and monocultures: reduce habitat heterogeneity and species richness. - Industrialization, mining and infrastructure development: direct habitat loss and fragmentation. - Human population growth and unsustainable consumption patterns: increase pressure on natural resources.
These causes often interact, producing compounded effects on biodiversity.
Causes of biodiversity loss: habitat destruction and fragmentation, overexploitation, pollution, invasive species, climate change, disease, genetic erosion, and socio‑economic drivers (population growth, unsustainable development).
Practical individual and community actions: - Reduce, reuse, recycle: Minimise resource extraction and waste; lower demand for raw materials that drive habitat loss. - Sustainable consumption: Choose sustainably sourced food, timber, fish; reduce meat consumption to lower land and water use. - Use native plants and create wildlife‑friendly gardens: Provide habitat, food and corridors for local species. - Avoid buying products from threatened species: Say no to illegal pet trade, ivory, unsustainably harvested plants. - Support and visit protected areas responsibly: Promote ecotourism that funds conservation and respects regulations. - Volunteer and participate: Join local habitat restoration, tree planting, citizen science and monitoring programs. - Advocate and educate: Raise awareness, support conservation policies and community‑based resource management. - Reduce carbon footprint: Conserve energy, use public transport and renewable energy to mitigate climate change impacts. - Encourage sustainable agriculture: Support organic, agroforestry and practices that preserve soil and biodiversity. - Financial support: Donate to reputable conservation organizations and support livelihood programs that reduce pressure on biodiversity.
These actions—combined with policy-level measures—help conserve biodiversity locally and globally.
Contribute by practicing sustainable living (reduce/reuse/recycle), supporting protected areas, using native plants, avoiding wildlife products, promoting habitat restoration, participating in community conservation, and advocating policy and education.
i) Protected areas: - Definition and purpose: Areas set aside and managed primarily for long‑term conservation of nature, biodiversity and ecosystem services (IUCN definition). They are the cornerstone of in situ conservation. - Types: National parks (strict protection, no exploitation), Wildlife Sanctuaries (less strict), Biosphere Reserves (core, buffer and transition zones combining conservation with sustainable use), Conservation Reserves, Community Reserves and other categories. - Functions: Protect habitats and species, maintain ecological processes, preserve genetic diversity, provide sites for research and education, and offer ecosystem services (water regulation, soil conservation). - Management: Involves legal protection, zoning (core/buffer), monitoring, anti‑poaching, species recovery programmes and community participation.
ii) Wildlife Sanctuaries: - Definition: Areas legally notified for the protection of wildlife where animals are safeguarded and their habitats conserved; human activities may be permitted to a limited extent compared with national parks. - Characteristics: Focus on protecting particular species or communities; regulated human use (grazing, collection of minor forest produce) may be allowed; boundaries can be modified by the government. - Difference from National Parks: National parks have stricter protection — no grazing or resource extraction and stronger restrictions on human activity; sanctuaries allow some controlled use. - Role: Provide habitat protection, conserve threatened species, act as buffer zones or corridors between stricter protected areas, and support local livelihoods under regulated use.
Examples and key terms: In India, protected areas include national parks (e.g., Jim Corbett), wildlife sanctuaries (e.g., Periyar), and biosphere reserves (e.g., Nilgiri). These implement in situ conservation and are guided by laws and international frameworks (IUCN categories, CBD).
i) Protected areas: Designated regions (national parks, sanctuaries, biosphere reserves) managed for in situ conservation of biodiversity, ecosystem services and genetic resources. ii) Wildlife Sanctuaries: Protected areas where wildlife is protected but some regulated human activities (grazing, resource use) may be allowed; primary aim is species and habitat protection.