NCERT Solutions for Class 12 Biology Chapter 15 - Biodiversity and its Conservation

Chapter 15 of Class 12 Biology, "Biodiversity and Conservation," is essential for understanding the variety of life on Earth and the importance of preserving it. Biodiversity refers to the diversity of organisms in different ecosystems. It is classified into three main types: genetic diversity, species diversity, and ecosystem diversity. Genetic diversity looks at the differences within species, species diversity refers to the variety of species in an area, and ecosystem diversity includes different habitats in a region.

One important pattern of biodiversity is seen in the latitudinal gradient, where species richness increases near the equator. Another key concept is the species-area relationship, which shows that larger areas support more species.

The chapter also explains how biodiversity is crucial for ecosystem stability, human welfare, and overall environmental health. However, biodiversity faces threats like habitat loss, pollution, climate change, and overexploitation, leading to extinction of species.

To protect biodiversity, two main conservation approaches are used: in-situ conservation, which involves protecting species in their natural habitats (like national parks), and ex-situ conservation, which involves preserving species outside their natural environments (like zoos or seed banks). Both are crucial in maintaining Earth's biological richness.

Q1. Name the three important components of biodiversity.

Answer: Biodiversity refers to the vast variety present among the various life forms. The three components of biodiversity are:

1. Genetic diversity

2. Species diversity

3.Ecosystem diversity

Q2. How do ecologists estimate the total number of species present in the world?

Answer: In order to estimate the number of species present on earth, ecologists statistically compare species richness of well-studied groups of insects of tropical and temperate regions and these ratios are extrapolated with other groups of plants and animals to estimate the species richness found on Earth. As per estimates, about 7 million species are present on Earth.

Q3. Give three hypotheses for explaining why tropics show the greatest levels of species richness.

Answer: Tropics show the greatest level of species richness due to the following reasons (hypotheses):

1. The climate of tropical areas is more stable as compared to temperate areas. So, the local populations continuously live in the absence of natural disturbances.

2. Tropical communities are highly productive and can support a wide range of other species. This is mainly because the tropics receive more solar energy.

3. In the tropics, there is warm temperature and high humidity. Such conditions are favorable for a number of varieties of fungi, plants, and algae.

Q4. What is the significance of the slope of regression and species-area relationship?

Answer:The slope of regression has a major role in determining the species-area relationship. In smaller areas, the slope of regression is similar regardless of the taxonomic group or region. On the other hand, in the case of larger areas, the curve is steeper. Biodiversity also increases from higher to lower altitudes.

Q5. What are the major causes of species losses in a geographical region?

Answer: The major causes of species losses in a geographical region are as follows;

1. Habitat loss and fragmentation

2. Over-exploitation

3. Alien species invasion

4. Co-extinction

Q6. How is biodiversity important for ecosystem functioning?

Answer: Importance of biodiversity in ecosystem functioning

1.Biodiversity is important for maintaining stability, productivity, resilience, alternative pathways, and the overall health of a particular ecosystem.

2. A scientist named David Tilman confirmed that higher biodiversity will be the productivity of the ecosystem as more plants are there to photosynthesize and more decomposers are there to recycle the waste of the ecosystem. He also proved that if Biodiversity an area is higher than a Year-to-year variation in total biomass will be less contributing to the overall stability of an ecosystem.

3. Rich biodiversity provides resilience against natural as well as man-made disturbances.

4. To clarify the importance of rich biodiversity on ecosystem functioning, the Rivet Popper hypothesis was proposed by Paul Ehrlich. He cited that the way in an airplane all parts are joined by thousands of rivets; Similarly, in an ecosystem, all components are joined by species. As more and more rivets of the airplane are removed and it becomes disassembled. Similarly, as species are removed the functioning of the ecosystem also gets affected. 

Q7. What are sacred groves? What is their role in conservation?

Answer: Sacred groves are the traditionally protected patches of forests around places of worship where local tribal communities actively participate to protect these regions and do not allow to cut even a single branch of the tree because of religious reasons. Sacred groves in India are found in the Western Ghats of Karnataka, Maharashtra, Khasi, and Jaintia hills in Meghalaya, Aravali hills in Rajasthan, and Sarguja, Chanda, and Bastar areas of Madhya Pradesh.

Role of sacred groves on the conservation of biodiversity

- Sacred groves help in the protection of a number of rare, endangered and endemic species.

- In these regions, deforestation is strictly prohibited and thus they are biodiversity-rich areas.

Q8. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?

Answer: Ecosystem services refer to goods or benefits that we get from the ecosystem. Prevention of soil erosion and floods comes under benefits provided by the ecosystem to us. The ecosystem includes both abiotic and biotic components. The biotic components are the living organisms present in an ecosystem. Biotic components play role in providing ecosystem services. some of these roles are as follows:

1. The roots of plants hold the soil particles very tightly. This prevents the erosion or degradation of the top layer of soil.

2. Plants increase soil fertility and biodiversity

3. The presence of plants also helps in controlling the flow of floods and leads to minimal destruction.

4. The roots of plants make the soil porous thus allowing water to seep in the soil.

5. The carbon dioxide and oxygen balance are maintained in the ecosystem via plants and animals.

Q9. The species diversity of plants (22 percent) is much less than that of animals (72 percent). What could be the explanations for how animals achieved greater diversification?

Answer: Animals have achieved greater diversification than animals due to the following reasons:

1. Animals possess a nervous system to receive stimuli and show a response against them.

2. Animals are motile and they can avoid competition thus leading to greater diversification.

3. Plants are not mobile and they require fewer evolutionary adaptations. Thus, there is higher diversity among animals than plants.

Q10. Can you think of a situation where we deliberately want to make a species extinct?

How would you justify it?

Answer: Yes, some harmful pathogens i.e., disease-causing organisms with little or no role in the ecosystem can be made extinct. Their extinction will not lead to any effect on the ecological balance. These pathogens include the smallpox virus, Poliovirus is about to get eradicated. There are efforts to make this world free from these diseases as much as possible. E.g., TB, AIDS, Malaria, etc. Since the microorganisms causing these diseases have no role to play in the environment, they can be made to get eradicated

Biodiversity and its Conservation Important Questions

Q1. What is biodiversity and why is it important?
Answer: Biodiversity refers to the variety of life forms on Earth, including plants, animals, and microorganisms. It is important because it maintains ecosystem balance, provides resources for humans, and supports life on the planet.

Q2. What are the types of biodiversity?
Answer: The three main types of biodiversity are genetic diversity, species diversity, and ecosystem diversity. These types represent variations within species, between species, and across ecosystems.

Q3. What are the main causes of biodiversity loss?
Answer: Biodiversity loss is mainly caused by habitat destruction, pollution, over-exploitation of species, climate change, and the introduction of invasive species.

Q4. How does biodiversity support ecosystem services?
Answer: Biodiversity supports essential ecosystem services like pollination, nutrient cycling, water purification, and climate regulation. These services are crucial for the survival of all living organisms, including humans.

Q5. What are some examples of biodiversity conservation efforts?
Answer: Examples of biodiversity conservation efforts include the establishment of national parks, wildlife sanctuaries, biosphere reserves, and marine protected areas. Global initiatives like the Convention on Biological Diversity (CBD) also aim to protect biodiversity through international cooperation.