Chapter 13 : Biodiversity and Conservation

Class 12 Biology Chapter 13 : Biodiversity and Conservation Exercise Questions and Answers :

1. Name the three important components of biodiversity.

Answer : The three important components of biodiversity are :

(i) Genetic diversity

(ii) Species diversity

(iii) Ecological diversity

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

Answer : Estimating the total number of species on Earth is a challenging task due to the vast number of undiscovered species. While there are records of over 1.5 million described species, the total number remains uncertain. Estimates vary widely, with some extreme projections suggesting 20 to 50 million species. A more conservative estimate by Robert May places the global species diversity at around 7 million. These estimates are derived by statistically comparing temperate and tropical species richness in exhaustively studied groups of insects and extrapolating to other taxa. Prokaryotes are not included, as traditional taxonomic methods are inadequate for their identification.

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

Answer :  The high species richness observed in tropical regions can be explained by several hypotheses are :

Long Evolutionary Time Hypothesis : Tropical latitudes have experienced relative climatic stability and remained undisturbed for millions of years. This extended period of stability has provided ample time for speciation and species diversification to occur. In contrast, temperate regions have faced frequent glaciations and more variable climates, which may have limited the time available for species to evolve.

Stable and Predictable Environments Hypothesis : Tropical environments exhibit less seasonality and more constant, predictable conditions compared to temperate regions. This stability allows for niche specialization among species, as there are fewer extreme environmental fluctuations. The predictable conditions promote the coexistence of a greater number of species, each adapted to specific ecological niches.

High Productivity Hypothesis : The tropics receive more solar energy, resulting in higher primary productivity. This increased energy availability supports more abundant resources and sustains larger populations of organisms. Greater productivity can indirectly contribute to greater species diversity, as it provides the foundation for diverse ecological interactions and complex food webs.

These hypotheses collectively account for the exceptional biodiversity observed in tropical regions and highlight the role of evolutionary time, environmental stability, and high productivity in shaping the richness of life forms in the tropics.

4. What is the significance of the slope of regression in a species – area relationship?

Answer : The slope of regression in a species-area relationship (SAR) indicates the rate of change in species richness concerning changes in the surveyed area. A steeper slope signifies that larger areas support a disproportionately higher number of species. This has critical implications for biodiversity conservation, habitat fragmentation assessments, land use planning, and ecological research. It helps prioritize conservation efforts, predict species richness, and understand the scaling of biodiversity in different ecosystems.

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

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

Habitat Loss and Fragmentation: This is the primary cause of species extinctions, particularly evident in tropical rainforests. Rapid deforestation, driven by activities like logging, agriculture, and cattle ranching, drastically reduces available habitats for a wide range of species.

Over-Exploitation: Human overconsumption of natural resources, such as overfishing and hunting, can lead to the depletion and extinction of species. Commercially important marine fish populations are especially vulnerable.

Alien Species Invasions: The introduction of non-native species, either intentionally or accidentally, can result in the displacement or extinction of indigenous species. Examples include the introduction of the Nile perch in Lake Victoria and invasive weed species like Lantana.

Co-Extinctions: When one species becomes extinct, other species closely associated with it, such as parasites or mutualistic partners, also face extinction. This phenomenon underscores the interconnectedness of species in ecosystems.

These factors, driven by human activities and habitat degradation, are the main drivers of species losses and pose significant challenges for biodiversity conservation and ecosystem stability.

6. How is biodiversity important for ecosystem functioning?

Answer : Biodiversity is important for ecosystem functioning because  :

(i) Diverse ecosystems are more resilient and better able to withstand environmental changes and disturbances.

(ii) Biodiversity provides essential services such as pollination, nutrient cycling, pest control, and water purification, benefiting both ecosystems and human well-being.

(iii) Different species occupy unique ecological niches, optimizing the utilization of resources like sunlight, nutrients, and water.

(iv) Complex food webs, facilitated by biodiversity, regulate population sizes and contribute to ecosystem stability.

(v) Biodiversity, particularly in forests, helps store carbon, mitigating the impact of climate change.

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

Answer :  Sacred groves are forested areas set aside in various cultures, where all trees and wildlife are venerated and granted total protection. They are found in regions such as Khasi and Jaintia Hills in Meghalaya, Aravalli Hills of Rajasthan, Western Ghats in Karnataka and Maharashtra, and Sarguja, Chanda, and Bastar areas of Madhya Pradesh.

These groves play a crucial role in conservation, serving as the last refuges for numerous rare and threatened plant species, contributing to the preservation of biodiversity.

8. 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 ecosystems help control floods and soil erosion through their roles in maintaining ecological balance. Trees and vegetation, for example, absorb and slow down the flow of water, reducing the risk of flooding. Their root systems anchor the soil, preventing erosion by stabilizing the topsoil. Additionally, the microbial and fungal communities in the soil contribute to soil structure and stability. Together, these biotic components act as natural safeguards, regulating water flow and preventing erosion in ecosystems.

9. The species diversity of plants (22 per cent) is much less than that of animals (72 per cent). What could be the explanations to how animals achieved greater diversification?

Answer : The greater diversification of animals (72%) compared to plants (22%) in terms of species diversity can be attributed to several factors are :

(i) Animals are generally more mobile than plants, which allows them to colonize and adapt to a wider range of environments and ecological niches.

(ii) Animals often have more complex reproductive strategies, such as sexual reproduction, which can lead to greater genetic diversity and speciation.

(iii) Interactions like predator-prey relationships can drive faster evolutionary changes in animals as they adapt to their ecological roles and niches.

(iv) Animals face diverse selective pressures, such as competition for resources and sexual selection, which can drive rapid evolutionary changes and speciation.

(v) Some animal groups have diversified due to specialization in particular ecological niches or habitats, which can lead to the emergence of new species.

(vi) The ability of animals to migrate in response to environmental changes can create opportunities for diversification in new habitats.

(vii) The mutualistic relationships between animals and plants, such as pollination and seed dispersal, can lead to coevolution and diversification of both groups

10. Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?

Answer : In some cases, it may be necessary to deliberately make a species extinct for ecological or conservation reasons. Justification might include the eradication of invasive species that threaten native biodiversity, disrupt ecosystems, or harm human interests. This action can restore balance and protect native species. However, such decisions must be based on comprehensive scientific assessments and consider the potential consequences to ensure that it aligns with broader conservation goals and environmental ethics.