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NCERT Solutions for Class 12 Biology Chapter 15 Biodiversity and Conservation
Name the three important components of biodiversity
The three important components of biodiversity are : genetic diversity, species diversity and ecological diversity. These components are the basic building blocks of biodiversity. These are intimately linked and may have common elements.
How do ecologists estimate the total number of species present in the world?
Ecologists make a significant comparison of species richness of exhaustively studied groups of insects of the temperate and tropical regions and extrapolate this ratio to other groups of animals and plants to calculate gross estimate of the total number of species existing on the earth.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
The three hypotheses for higher species richness in tropical areas, are:
- Prolong evolutionary time – Temperate areas have undergone frequent glaciation in the past. It killed most of the species. No such disturbance occurred in tropics where species continued to flourish and evolve undisturbed for millions of years.
- Favourable environment – There are no unfavourable seasons in tropics. Continued favourable environment has helped tropical organisms to gain more niche specialisation and increased diversity.
- More sunlight – More solar energy is available in tropics. This promotes higher productivity and increased biodiversity.
What is the significance of the slope of regression in a species-area relationship?
When analysis of species-area relationships is done among small areas, the values of slope of regression are remarkably similar regardless of the taxonomic group or the region. However, when such analysis is done among very large areas, i.e., continents, then the slope of regression would be much steeper. Biodiversity also changes with the change in altitude. It increases from higher to lower altitudes.
What are the major causes of species losses in a geographical region?
The major causes of species losses in a geographical area are:
- Habitat loss and fragmentation
- Over exploitation
- Alien species invasion
- Disturbance and degradation
- Intensive agriculture and forestry.
How is biodiversity important for ecosystem functioning?
Biodiversity is useful in ecosystem services. Maintenance and sustainable utilisation of useful products and services of various ecosystems as well as individual species require the presence of biodiversity. The rich biodiversity is important for stability, productivity, resilience and ecosystem health. Increased biodiversity contributes to higher productivity. Forest and oceanic systems control climate and maintain gaseous composition of atmosphere through photosynthesis. Biodiversity is essential for natural pest control, maintenance of populations of various species, pollination by insects and birds, nutrient cycling, conservation and purification of water, formation and protection of soil, etc.
What are sacred groves? What is their role in conservation?
Sacred groves are forest patches around places of working. These are held in high esteem by tribal communities/state or central government. Tribals do not allow to cut even a single branch of trees in these sacred groves. Preserved over the course of many generations, sacred groves represent native vegetation in a natural or near natural state & thus are rich in biodiversity & harbour many rare species of plants & animals. This is the reason why many endemic species flourish in these regions.
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Biotic components of ecosystem include plants and animals. Floods and soil erosion are prevented by the producers especially trees present in the ecosystem. The roots of trees bind to the soil firmly thus preventing soil erosion by wind or water. Raindrops in a forest do not hit the floor directly. The canopy layer of forest intercepts the flow of raindrops so that the rainwater falls on leaves of trees and then drips slowly onto the forest floor. Thus, water does not collect and stagnate on the forest floor. This prevents flooding. Moreover trees in the forest also regulate water cycle
The species diversity of plants (22 percent) is much less than that of animals (72 percent). What could be the explanations to how animals achieved greater diversification?
Scientists recorded 22% of plant species diversity including algae, fungi, bryophytes, pteridophytes, gymnosperms and angiosperms. But they recorded 72% of animal species (including insects, molluscs, fishes, mammals, birds etc.) diversity. Plants have less adaptive capacity as compared to animals. Animals show locomotory movements and can move from one place to another to suit the environment and also in search of food. On the contrary, plants are fixed. Moreover, animals have well organised body structure with various organs to help adjust to the environment.
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Certain species are the causal organisms of a number of human diseases which are epidemic. Mostly many disease causing viruses like Varicella virus, Polio virus, HIV are harmful to human beings and have no role in ecosystem stability as decomposers. But to eradicate the diseases caused by them, these viruses should be eradicated i.e., made extinct if possible.
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