CBSE Class 12 Biology (2026–27)
Chapter 13: Biodiversity and Conservation
20 Important Questions and Answers
Q1. What is biodiversity? Explain its three levels.
Answer:
Biodiversity refers to the variety and variability of living organisms present on Earth. The term was popularized by Edward Wilson. Biodiversity exists at three levels. Genetic diversity refers to variation in genes within a species, such as thousands of rice varieties found in India. Species diversity refers to the variety of species in a region; for example, the Western Ghats have greater amphibian diversity than the Eastern Ghats. Ecological diversity refers to the diversity of ecosystems such as forests, deserts, wetlands, mangroves, and coral reefs. These three levels together maintain ecological balance and help organisms adapt to environmental changes. Biodiversity is essential for ecosystem stability and human welfare.
Q2. Why is India considered a mega-diversity nation?
Answer:
India is recognized as a mega-diversity nation because it possesses a vast variety of plants, animals, and ecosystems despite occupying only about 2.4% of the world’s land area. The country contains diverse habitats such as forests, deserts, mountains, wetlands, mangroves, and coral reefs. India has more than 50,000 genetically different rice strains and numerous endemic species. It is also home to important biodiversity hotspots like the Himalaya, Indo-Burma, and Western Ghats–Sri Lanka regions. The rich species diversity and high degree of endemism contribute significantly to India’s status as one of the world’s twelve mega-diversity countries.
Q3. Explain the latitudinal gradient in species diversity.
Answer:
The latitudinal gradient is a pattern showing that species diversity increases from the poles toward the equator. Tropical regions near the equator support a greater variety of organisms than temperate and polar regions. For example, tropical rainforests contain far more species than Arctic ecosystems. This occurs because tropical areas have remained relatively undisturbed for long periods, receive more solar energy, and provide stable environmental conditions. Such conditions promote speciation and reduce extinction rates. Consequently, biodiversity reaches its maximum in tropical ecosystems and gradually declines toward higher latitudes. This pattern is one of the most important observations in biodiversity studies.
Q4. Describe the species–area relationship.
Answer:
The species–area relationship states that species richness increases as the area explored increases. Alexander von Humboldt observed this pattern while studying plants. Within a region, the relationship is represented by the equation:
S=CA^{Z}
where S is species richness, A is area, and C and Z are constants. Initially, species increase rapidly with area, but the rate slows down later. When plotted on a logarithmic scale, the relationship appears as a straight line. This concept helps ecologists understand biodiversity distribution and design conservation strategies for protecting larger habitats that support more species.
Q5. What are the major causes of biodiversity loss?
Answer:
The major causes of biodiversity loss are collectively known as the Evil Quartet. These include habitat loss and fragmentation, over-exploitation, invasion by alien species, and co-extinctions. Habitat destruction is the most significant cause, as forests and natural ecosystems are converted into agricultural or urban areas. Over-exploitation occurs when species are excessively hunted, fished, or harvested. Alien species introduced into new habitats may outcompete native organisms. Co-extinction happens when one species becomes extinct and another species dependent on it also disappears. These factors have accelerated species extinction rates and threaten ecological stability worldwide.
Q6. What is habitat loss and fragmentation? How does it affect biodiversity?
Answer:
Habitat loss occurs when natural habitats are destroyed due to deforestation, urbanization, mining, or agriculture. Fragmentation happens when large habitats are divided into smaller isolated patches. These changes reduce available resources, breeding grounds, and shelter for organisms. Species requiring large territories, such as tigers and elephants, are severely affected. Fragmented populations become isolated, leading to reduced gene flow and increased risk of extinction. Habitat loss is considered the most important cause of biodiversity decline worldwide. Conserving large continuous habitats is therefore essential for maintaining species diversity and ecosystem health.
Q7. Explain over-exploitation as a cause of biodiversity loss.
Answer:
Over-exploitation refers to the excessive use of biological resources beyond their capacity for renewal. Humans exploit plants and animals for food, medicine, trade, and commercial purposes. Excessive hunting, fishing, logging, and wildlife trade can drastically reduce population sizes. Historical examples include the extinction of the passenger pigeon and Steller’s sea cow. Even when a species does not become completely extinct, over-exploitation may reduce its population to critically low levels, affecting ecosystem balance. Sustainable utilization and strict conservation laws are necessary to prevent species decline caused by over-exploitation and ensure long-term ecological stability.
Q8. What are alien species invasions? Give an example.
Answer:
Alien species are organisms introduced intentionally or accidentally into habitats where they do not naturally occur. These species may become invasive and outcompete native organisms for food, space, and resources. Invasive species often lack natural predators in the new environment, allowing them to spread rapidly. Examples include Parthenium (Congress grass), water hyacinth, and Lantana. Such species can disrupt food chains, alter habitats, and reduce native biodiversity. Alien species invasions are considered one of the major causes of biodiversity loss because they threaten the survival of indigenous flora and fauna.
Q9. What is co-extinction?
Answer:
Co-extinction occurs when the extinction of one species leads to the extinction of another species that depends on it. Many organisms share close ecological relationships such as pollination, parasitism, and mutualism. If one partner disappears, the associated species may also become extinct. For example, if a host fish species becomes extinct, the parasites dependent on it may also disappear. Similarly, the extinction of a plant species can threaten specialized pollinators. Co-extinction demonstrates the interconnected nature of ecosystems and highlights the importance of conserving all components of biodiversity rather than focusing on individual species alone.
Q10. Why is biodiversity important for ecosystem functioning?
Answer:
Biodiversity plays a crucial role in maintaining ecosystem functioning and stability. Diverse ecosystems are more productive and resistant to environmental disturbances. Different species perform various ecological roles such as nutrient cycling, decomposition, pollination, and energy transfer. Biodiversity enhances ecosystem resilience, allowing systems to recover from droughts, diseases, and climate fluctuations. It also supports food webs and ecological interactions. A reduction in biodiversity can disrupt ecosystem processes and decrease productivity. Therefore, preserving biodiversity is essential for sustaining ecological balance, supporting human life, and ensuring the continued availability of natural resources.
Q11. What are biodiversity hotspots?
Answer:
Biodiversity hotspots are regions with exceptionally high species richness and a large number of endemic species that are under severe threat from habitat destruction. These areas are priorities for conservation because protecting them can save many unique species. Globally, there are several recognized hotspots, and India shares three important ones: the Himalaya, Indo-Burma, and Western Ghats–Sri Lanka. These regions contain diverse ecosystems and numerous organisms found nowhere else in the world. Conservation efforts in hotspots are highly effective because a relatively small area can protect a large proportion of global biodiversity.
Q12. What is in-situ conservation? Give examples.
Answer:
In-situ conservation means protecting species within their natural habitats. This method allows organisms to continue their evolutionary processes while maintaining ecological interactions. Protected areas such as national parks, wildlife sanctuaries, biosphere reserves, and sacred groves are examples of in-situ conservation. By preserving entire ecosystems, this approach protects not only individual species but also their habitats and ecological relationships. In-situ conservation is considered the most effective strategy for maintaining biodiversity because it ensures long-term survival under natural environmental conditions and supports the conservation of genetic diversity.
Q13. What is ex-situ conservation? Mention its advantages.
Answer:
Ex-situ conservation involves protecting endangered species outside their natural habitats. Examples include zoos, botanical gardens, seed banks, tissue culture repositories, and cryopreservation facilities. This method is particularly useful for species facing immediate threats in the wild. Ex-situ conservation allows controlled breeding, genetic preservation, and scientific research. It can also facilitate the reintroduction of species into their natural habitats when conditions improve. Although it cannot completely replace habitat conservation, ex-situ conservation serves as an important backup strategy for protecting rare and endangered species from extinction.
Q14. Differentiate between in-situ and ex-situ conservation.
Answer:
In-situ conservation protects species within their natural habitats, whereas ex-situ conservation protects them outside their natural environments. National parks, wildlife sanctuaries, biosphere reserves, and sacred groves are examples of in-situ conservation. Zoos, botanical gardens, seed banks, and cryopreservation units are examples of ex-situ conservation. In-situ conservation maintains natural ecological interactions and evolutionary processes. Ex-situ conservation provides special protection for critically endangered species under controlled conditions. Both methods complement each other and are essential for effective biodiversity conservation. Together, they help prevent species extinction and preserve genetic diversity for future generations.
Q15. What are sacred groves and why are they important?
Answer:
Sacred groves are patches of natural vegetation protected by local communities due to religious or cultural beliefs. Human activities such as tree cutting and hunting are generally prohibited in these areas. Sacred groves act as reservoirs of rare, endemic, and endangered species. They help preserve biodiversity, maintain ecological balance, and protect local water resources. In India, sacred groves are commonly found in regions such as the Western Ghats, Meghalaya, and Rajasthan. These traditional conservation practices demonstrate how cultural values can contribute significantly to biodiversity protection and sustainable ecosystem management.
Q16. What is the role of IUCN in biodiversity conservation?
Answer:
The International Union for Conservation of Nature (IUCN) is a global organization dedicated to conserving nature and biodiversity. One of its major contributions is maintaining the Red List of Threatened Species, which categorizes species based on their risk of extinction. The IUCN collects scientific data, assesses conservation status, and provides recommendations for biodiversity protection. Governments and conservation organizations use these assessments to formulate policies and conservation strategies. The Red List helps identify endangered species and prioritize efforts for their protection, making IUCN a key institution in global conservation initiatives.
Q17. Explain the concept of ecosystem services.
Answer:
Ecosystem services are the benefits that humans obtain from ecosystems. These include provisioning services such as food, fuel, medicines, and raw materials. Ecosystems also provide regulating services like climate regulation, water purification, and pollination. Cultural services include recreation, spiritual values, and aesthetic enjoyment. Supporting services such as nutrient cycling and soil formation sustain life on Earth. Biodiversity is essential for maintaining these services because different species perform specialized ecological functions. Loss of biodiversity can reduce ecosystem efficiency and negatively affect human well-being, making conservation essential for sustainable development.
Q18. Why should biodiversity be conserved?
Answer:
Biodiversity should be conserved for ecological, economic, and ethical reasons. Ecologically, it maintains ecosystem stability and productivity. Economically, biodiversity provides food, medicines, fuel, fiber, and other valuable resources. Many industries depend directly on biological resources. Ethically, every species has an intrinsic right to exist and should be preserved for future generations. Biodiversity also supports ecosystem services that sustain human life. Rapid species extinction threatens ecological balance and human welfare. Therefore, conservation is necessary to protect natural heritage, ensure sustainable resource use, and maintain the health of Earth’s ecosystems.
Q19. How do national parks contribute to biodiversity conservation?
Answer:
National parks are protected areas established to conserve wildlife, natural habitats, and ecological processes. Human activities such as hunting, grazing, and resource extraction are strictly regulated or prohibited. These protected areas provide safe environments for endangered species and help maintain genetic diversity. National parks preserve entire ecosystems, allowing natural ecological interactions to continue. They also support scientific research, environmental education, and ecotourism. By safeguarding habitats from human interference, national parks play a crucial role in protecting biodiversity and preventing species extinction. They are an important component of in-situ conservation strategies.
Q20. What are biosphere reserves? State their significance.
Answer:
Biosphere reserves are large protected areas designed to conserve biodiversity while promoting sustainable use of natural resources. They include core zones for strict protection, buffer zones for research and education, and transition zones where sustainable human activities are permitted. Biosphere reserves protect ecosystems, endangered species, and genetic diversity. They also facilitate scientific studies, environmental monitoring, and conservation education. By integrating conservation with sustainable development, biosphere reserves help balance ecological protection and human needs. They serve as important models for biodiversity conservation and environmental management at regional and global levels.