Class 12 Biology · Chapter 13 NotesBiodiversity and Conservation

Biodiversity refers to the variety of life at all levels, from genetic differences within species to the diversity of ecosystems. It includes genetic diversity, such as the variations in the medicinal plant Rauwolfia vomitoria, species diversity, like the higher number of amphibian species in the Western Ghats compared to the Eastern Ghats, and ecological diversity, which encompasses different ecosystems such as deserts, rainforests, and wetlands. India, with its vast biological wealth, is one of the 12 megadiversity countries, hosting a significant portion of the world's species.

• Genetic diversityVariations within species
• Species diversityNumber of different species in an area
• Ecological diversityVariety of ecosystems

Biodiversity is not evenly distributed across the globe. The tropics, for example, harbor more species than temperate or polar regions. This latitudinal gradient can be attributed to factors like evolutionary time, environmental stability, and solar energy. Another key pattern is the species-area relationship, which shows that species richness increases with the area explored, but only up to a certain limit. This relationship is described by the equation log S = log C + Z log A, where S is species richness, A is area, and Z is the slope of the line.

• Latitudinal gradientMore species in the tropics
• Species-area relationshiplog S = log C + Z log A
• Factors influencing biodiversityEvolutionary time, environmental stability, solar energy

The current rates of species extinction are alarmingly high, primarily due to human activities. The main causes of biodiversity loss include habitat destruction and fragmentation, over-exploitation of species, invasion by alien species, and co-extinctions, where the loss of one species leads to the extinction of others dependent on it. For instance, the introduction of the Nile perch into Lake Victoria led to the extinction of over 200 species of cichlid fish. The accelerated rates of extinction threaten the ecological balance and the services that ecosystems provide.

• Habitat loss and fragmentationMajor cause of extinction
• Over-exploitationOver-harvesting of species
• Alien species invasionsIntroduction of non-native species
• Co-extinctionsLoss of dependent species

Conserving biodiversity is essential for maintaining ecological balance and ensuring the survival of human populations. Conservation efforts can be broadly categorized into in situ and ex situ methods. In situ conservation involves protecting species within their natural habitats, such as biosphere reserves, national parks, and wildlife sanctuaries. Ex situ conservation includes maintaining threatened species in zoological parks, botanical gardens, and using techniques like cryopreservation and tissue culture to preserve genetic material.

• In situ conservationProtecting species in their natural habitats
• Ex situ conservationMaintaining species in controlled environments
• Biosphere reserves, national parks, and wildlife sanctuaries
• Cryopreservation and tissue culture for genetic material

Biodiversity is crucial for human welfare, providing direct benefits such as food, fiber, firewood, and pharmaceuticals. It also offers indirect benefits through ecosystem services like pollination, pest control, climate moderation, and flood control. The ethical argument for conserving biodiversity emphasizes the intrinsic value of all species and our moral responsibility to preserve them for future generations. Recognizing the importance of biodiversity helps in making informed decisions about resource use and conservation.

• Direct benefitsFood, fiber, firewood, pharmaceuticals
• Indirect benefitsEcosystem services
• Ethical responsibilityPreserving biodiversity for future generations

Effective strategies for biodiversity conservation include identifying and protecting biodiversity hotspots, which are regions with high species richness and endemism. In India, efforts include the establishment of biosphere reserves, national parks, and wildlife sanctuaries. Sacred groves, which are protected areas due to cultural and religious beliefs, also play a significant role in conservation. International agreements, such as the Convention on Biological Diversity, emphasize the collective responsibility of nations to conserve biodiversity and ensure sustainable use of its benefits.

• Biodiversity hotspotsRegions with high species richness
• Biosphere reserves, national parks, and wildlife sanctuaries
• Sacred grovesProtected areas due to cultural beliefs
• International agreementsCollective responsibility for conservation