Q1. Name the three important components of biodiversity.
Answer: Biodiversity describes the combined diversity at all levels of biological organisation. The three most important components are:

1. Genetic diversity: The high diversity at the genetic level shown by a single species over its distributional range. For example, India has more than 50,000 genetically different strains of rice.
2. Species diversity: The diversity at the species level. For instance, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.
3. Ecological diversity: Diversity at the ecosystem level. India, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows, has a greater ecosystem diversity than a country like Norway.

Q2. How do ecologists estimate the total number of species present in the world?
Answer: Ecologists estimate the total number of species on Earth by studying well-known groups of organisms, such as insects, in detail. They compare the number of species found in temperate regions with those in tropical regions, where biodiversity is usually higher. Using this data, they make statistical extrapolations to estimate the total number of species across all plants and animals. Based on such studies, scientist Robert May estimated that there are about 7 million species on our planet.

Q3. Give three hypotheses for explaining why tropics show greatest levels of species richness.
Answer: The high biological diversity of the tropics is explained by the following hypotheses:

1. Evolutionary Time: Speciation is generally a function of time. Tropical latitudes have remained relatively undisturbed for millions of years (unlike temperate regions subjected to frequent glaciations) and thus had a long evolutionary time for species diversification.
2. Constant Environment: Tropical environments are less seasonal, relatively more constant, and predictable. Such constant environments promote niche specialisation and lead to greater species diversity.
3. Higher Productivity: There is more solar energy available in the tropics. This greater solar energy contributes to higher productivity, which in turn might contribute indirectly to greater diversity.

Q4. What is the significance of the slope of regression in a species area relationship?
Answer: The slope of regression (Z) in the species–area relationship indicates how the number of species increases with an increase in the area explored.

The relationship is expressed by the equation:

Where:

• S = Number of species
• A = Area explored
• C = Constant (intercept)
• Z = Slope of the line (rate of increase in species with area)

For smaller areas, the Z value is generally low (0.1–0.2), showing a gradual rise in species richness. For larger areas like continents, Z becomes steeper (0.6–1.2), meaning species richness increases more rapidly with area. Hence, a higher slope indicates a faster discovery of new species as area increases.

Q5. What are the major causes of species losses in a geographical region?
Answer: The accelerated rates of species extinctions are largely due to human activities, often described as “The Evil Quartet.”

1. Habitat loss and fragmentation: The most important cause driving extinctions. Tropical rain forests are dramatic examples, being destroyed for cultivation or grazing. Fragmentation affects animals with large territories or migratory habits.
2. Over-exploitation: When “need” turns to “greed,” it leads to overuse of natural resources, causing extinctions like the Steller’s sea cow and the passenger pigeon.
3. Alien species invasions: Introduced alien species can become invasive and cause decline or extinction of native species (e.g., Nile perch causing extinction of 200+ cichlid species in Lake Victoria).
4. Co-extinctions: When one species becomes extinct, others associated with it (e.g., host-parasite or plant-pollinator pairs) also become extinct.

Q6. How is biodiversity important for ecosystem functioning?
Answer: Rich biodiversity is crucial for ecosystem functioning and human survival due to following reasons-

1. Ecosystems with a higher number of species tend to be more stable, maintaining consistent biomass and showing greater overall productivity.
2. A diverse community utilizes available resources more efficiently, reducing waste and competition among species.
3. Biodiversity increases an ecosystem’s ability to resist and recover from disturbances like diseases, droughts, or invasions by alien species.
4. Biodiversity supports key processes like oxygen production, pollination, and nutrient cycling. The Amazon rainforest produces about 20% of Earth’s oxygen, pollinators help plants bear fruits and seeds, and decomposers recycle nutrients to maintain soil fertility and ecosystem balance.

Q7. What are sacred groves? What is their role in conservation?
Answer: Sacred Groves are tracts of forest protected due to religious or cultural beliefs that emphasise nature conservation. All trees and wildlife within them are venerated and given full protection.

Role in Conservation (In situ) are:

1. Serve as examples of in situ conservation, where endangered species are protected in their natural habitats.
2. Act as refuges for rare and threatened plants.
3. Found in areas such as the Khasi and Jaintia Hills (Meghalaya), Aravalli Hills (Rajasthan), and parts of the Western Ghats.

Q8. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Answer: The biotic components of an ecosystem play a vital role in controlling floods and preventing soil erosion through the following ways:

1. Soil Erosion Control: Plant roots firmly bind soil particles, preventing the washing or blowing away of topsoil.
2. Flood Control: Forest vegetation acts like a sponge — tree canopies intercept rainfall while roots absorb and slowly release water, reducing surface runoff and flood intensity.
3. Ecosystem Conservation: These natural protections are most effective when ecosystems are preserved and maintained in their natural state.

Q9. The species diversity of plants (22%) is much less than that of animals (72%). What could be the explanations to how animals achieved greater diversification?
Answer: Animals make up more than 70% of recorded species, while plants constitute about 22%. Reasons for this include:

1. Mobility: Animals are mobile, allowing them to exploit varied habitats and niches, leading to higher speciation.
2. Complex Nervous Systems: Enable intricate adaptations for survival, feeding, and reproduction.
3. Coevolution: Particularly in insects, diversification is linked with coevolution with plants (e.g., pollination mutualisms).

Q10. Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Answer:
Situation: When an invasive alien species poses a severe threat to native biodiversity, ecosystem stability, or human health, and no effective control measures exist.

Deliberate extinction of a species may be justified when an invasive alien species causes severe harm to native biodiversity, ecosystem balance, or human health. Such species often outcompete native organisms, leading to loss of habitat and extinction of local species. For instance, Parthenium , Eichhornia, and the Nile perch in Lake Victoria have caused major ecological disruptions. In such cases, eliminating these harmful species becomes necessary to protect native ecosystems and restore ecological balance.