Biodiversity and Conservation Class 12 Biology Chapter Notes

Key Terms and Definitions

Biodiversity

The variety of life forms and ecosystems at all levels of biological organization, including genetic, species, and ecological diversity. Coined by sociobiologist Edward Wilson.

Endemism

The ecological state of a species being unique to a specific geographic location, such as an island, nation, country, or other defined zone.

Biodiversity Hotspot

A biogeographic region with significant levels of biodiversity that is under threat from human activities. It must have at least 1,500 species of vascular plants as endemics and have lost at least 70% of its primary vegetation.

Keystone Species

A species which has a disproportionately large effect on its natural environment relative to its abundance. Its removal causes a cascade of negative effects on the ecosystem.

In-situ Conservation

The conservation of species in their natural habitats. It is the process of protecting an endangered plant or animal species in its natural habitat, either by protecting or cleaning up the habitat itself, or by defending the species from predators.

Ex-situ Conservation

The conservation of components of biological diversity outside their natural habitats. This involves maintenance of threatened species in artificial settings like zoological parks, botanical gardens, and gene banks.

The Evil Quartet

The four major causes responsible for biodiversity loss: Habitat loss and fragmentation, Over-exploitation, Alien species invasions, and Co-extinctions.

Cryopreservation

A technique used in ex-situ conservation where gametes of threatened species are preserved in a viable and fertile condition for long periods at very low temperatures (-196°C) in liquid nitrogen.

Sacred Groves

Tracts of forest set aside by local communities for religious reasons, where all trees and wildlife within are venerated and given total protection. A form of in-situ conservation.

Levels of Biodiversity

Biodiversity is not just about the number of species; it exists at multiple levels of biological organization. Understanding these levels is fundamental to appreciating the complexity of life and the need for comprehensive conservation efforts. The three main levels are:

1. Genetic Diversity: This refers to the variation of genes within a single species. A species with high genetic diversity has a greater ability to adapt to environmental changes, resist diseases, and evolve. For example, the plant _Rauwolfia vomitoria_ growing in different Himalayan ranges shows genetic variation in the potency and concentration of the active chemical, reserpine, that it produces. Similarly, India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

1. Species Diversity: This is the variety of different species within a particular region or ecosystem. It is often measured in terms of species richness (the number of species per unit area) and species evenness (the relative abundance of different species). For instance, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. A forest with 10 different species of trees is more diverse than a plantation with only one species.

1. Ecological Diversity: This refers to the variety of ecosystems, habitats, and ecological processes in a region. It includes the diversity of communities and habitats within a geographical area. For example, India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows, has a greater ecosystem diversity than a Scandinavian country like Norway. Each ecosystem supports a unique set of species and interactions, contributing to the overall biodiversity of the planet.

Must-Remember Facts for Exams

• According to IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but the global species diversity is estimated to be about 7 million.
• More than 70% of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms, and angiosperms) comprise no more than 22% of the total. Among animals, insects are the most species-rich taxonomic group.
• India has only 2.4% of the world's land area, but its share of the global species diversity is an impressive 8.1%.
• The Species-Area relationship, proposed by Alexander von Humboldt, is given by the equation S = CA^Z. On a logarithmic scale, the relationship is a straight line described by the equation log S = log C + Z log A.
• The value of Z (slope of the regression line) generally lies in the range of 0.1 to 0.2 for small areas. For very large areas like entire continents, the slope is much steeper, with Z values in the range of 0.6 to 1.2.
• The 'Evil Quartet' are the four main causes of biodiversity loss: Habitat loss & fragmentation, Over-exploitation, Alien species invasions, and Co-extinctions.
• There are currently 36 biodiversity hotspots in the world. India has four: Himalayas, Western Ghats, Indo-Burma region, and Sundaland.
• The historic Convention on Biological Diversity ('The Earth Summit') was held in Rio de Janeiro in 1992.
• The World Summit on Sustainable Development was held in 2002 in Johannesburg, South Africa.

In-situ vs. Ex-situ Conservation

Worked Example: Species-Area Relationship

• {"item":"Understanding the Formula","description":"The formula S = CA^Z describes how the number of species (S) increases with the area explored (A). 'C' is the Y-intercept, and 'Z' is the slope of the line.\n\nScenario: A biologist is studying two islands. Island 1 has a Z-value of 0.2. Island 2, which is larger and more isolated, has a Z-value of 1.1.\n\nInterpretation:\n Island 1 (Z=0.2): This is a typical value for a smaller, less isolated area. Species richness increases at a predictable, slower rate as you explore more area.\n Island 2 (Z=1.1): This high Z-value is typical for very large areas like continents or very isolated ecosystems. It means that species richness increases very rapidly as you increase the area. This indicates a high degree of endemism and that different parts of the island have very different species compositions."}
• {"item":"Logarithmic Scale","description":"Why use the log scale log S = log C + Z log A? It converts the curvilinear relationship (rectangular hyperbola) into a straight line, making it easier to analyze and calculate the slope 'Z'. This is the graph most commonly asked about in exams."}

Exam Traps and Scoring Tips

Examiners frequently test the distinction between conservation methods. Be precise with your definitions and examples for in-situ and ex-situ conservation. A common 3-mark question asks you to name, define, and give two examples of each. Also, master the Species-Area Relationship graphs. Remember that S = CA^Z gives a rectangular hyperbola on a normal scale, while log S = log C + Z log A gives a straight line on a logarithmic scale. Label your axes correctly (Area on X-axis, Species Richness on Y-axis). Finally, when asked about arguments for conserving biodiversity, mention all three categories: Narrowly Utilitarian (economic benefits like food, medicine), Broadly Utilitarian (ecosystem services like pollination, oxygen), and Ethical (every species has an intrinsic right to exist).

Practice Questions with Solutions

• What are the two primary criteria for a region to be declared a biodiversity hotspot? A: It must have very high levels of species richness and a high degree of endemism (at least 1,500 species of vascular plants as endemics).
• Name the invasive weed that is causing environmental damage in India by choking water bodies. A: Water hyacinth (Eichhornia crassipes).
• What is the significance of the 'Z' value in the species-area relationship equation? A: The 'Z' value, or the slope of the regression line, indicates the rate at which species richness increases with an increase in area. A steeper slope (higher Z value) means species richness increases more rapidly with area.
• Differentiate between a National Park and a Wildlife Sanctuary based on the level of protection. A: National Parks have a higher degree of protection where no human activity is allowed. In Wildlife Sanctuaries, limited human activities like grazing and collection of minor forest produce are permitted as long as they don't harm the wildlife.

Frequently Asked Questions

Frequently Asked Questions