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- Species richness, as a measure of diversity, has been used by many ecologists. Species abundance and species proportional abundance based indices are some other alternative approaches to the measurement of diversity. Ans: 1 The tropical area have a...
- For a limited area like, a country, it gives a constant value of 0. It remains amazingly similar for all those small regions. On the contrary, for measuring species-area relationship over large areas like the entire continents, the slope of...
- What are sacred groves? What is their role in conservation? Ans: Sacred forests or sacred groves are forest patches around places of worship which are held in high esteem by tribal communities. They are the most undisturbed forest patches which are often surrounded by highly degraded landscapes. They are found in several parts of India, e. Temples built by tribals are found surrounded by deodar forests in Kumaon region, Jaintias and Khasjas in Meghalaya. Not a single branch is allowed to be cut from these forests. As a result many endemic species which are rare or have become extinct elsewhere can be seen to flourish here.
- Bishnois of Rajasthan protect Prosopis cineraria and Black Buck religiously. Some water bodies are also held sacred in certain places, e. Their aquatic flora and fauna are naturally preserved. Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem? Ans: Ecosystem services are products or benefits given by ecosystem processes to the environment for its purification, beauty, biodiversity, protection of natural resources, habitat to wild life and tribals, protection of soils, CO2 — O2 balance, retention of water against floods, drought and pollution.
- Plants play a vital role in the control of floods and soil erosion. Their roots bind the soil Roots of plants also make the soil porous and allow water to go into the soil. 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? Ans: Species diversity refers to the variety of species within a region which is less in plants as compared to animals.
- Most animals possess simple or complex nervous system to control and coordinate various activities. They possess receptors to receive against them. Most of their responses are adaptive and ensure their survival in changing environmental conditions. They, therefore, have evolved to reveal much higher species diversity than plants who do not possess nervous system and respond differently against environment stimuli. Can you think of a situation where we deliberately want to make a species extinct? How would you justify it? Ans: Humans can cause extinction of species through various means. We are trying to eradicate disease causing organisms e. Since such micro-organisms are harmful to the human society, such attempt is justified. Further, such micro-organisms are not essential components producers or decomposers of any ecosystem, and losing one or few such organisms would not affect the functioning of ecosystem.
- Objectives Describe the diversity of species types on Earth, relating the difference between known numbers and estimated numbers. List and describe three levels of biodiversity. Explain four ways in which biodiversity is important to ecosystems and humans. Analyze the potential value of a single species. A World Rich in Biodiversity Biodiversity, short for biological diversity, is the variety of organisms in a given area, the genetic variation within a population, the variety of species in a community, or the variety of communities in an ecosystem.
NCERT Solutions For Class 12 Biology Biodiversity And Conservation
Certain areas of the planet, such as tropical rainforests, contain an extraordinary variety of species. Humans need to understand and preserve biodiversity for our own survival. Unknown Diversity The study of biodiversity starts with the unfinished task of cataloging all the species that exist on Earth. The number of species known to science is about 1.- However, the actual number of species on Earth is unknown. Scientists accept an estimate of greater than 10 million for the total number of species. Unknown Diversity New species are considered known when they are collected and described scientifically. Unknown species exist in remote wilderness, deep oceans, and even in cities. Some types of species are harder to study and receive less attention than large, familiar species. Levels of Diversity Biodiversity can be studied and described at three levels: species diversity, ecosystem diversity, and genetic diversity. Species diversity refers to all the differences between populations of species, as well as between different species. Ecosystem diversity refers to the variety of habitats, communities, and ecological processes within and between ecosystems.
- Levels of Diversity Genetic diversity refers to all the different genes contained within all members of a population. A gene is a segment of DNA that is located in a chromosome and that codes for a specific hereditary trait. Benefits of Biodiversity Biodiversity can affect the stability of ecosystems and the sustainability of populations. We depend on healthy ecosystems to ensure a healthy biosphere that has balanced cycles of energy and nutrients. Species are part of these cycles. Species Are Connected to Ecosystems When scientists study any species closely, they find that it plays an important role in an ecosystem. Every species is probably either dependent on or depended upon by at least one other species in ways that are not always obvious.
- When one species disappears from an ecosystem, a strand in a food web is removed. Species Are Connected to Ecosystems Some species are clearly critical to the functioning of an ecosystem. A keystone species is a species that is critical to the functioning of the ecosystem in which it lives because it affects the survival and abundance of many other species in its community. An example is the sea otter. The loss of the sea otter populations led to an unchecked sea urchin population, which ate all the kelp leading to the loss of kelp beds along the U. Pacific Coast. Species and Population Survival The level of genetic diversity within populations is a critical factor in species survival.
CBSE Test Papers For CBSE Class 12 Biology Biodiversity And Conservation
Genetic variation increases the chances that some members of the population may survive environmental pressures or changes. Small and isolated populations are less likely to survive such pressures. Species and Population Survival When a population shrinks, its genetic diversity decreases as though it is passing through a bottleneck. Even if such a population is able to increase again, there will be inbreeding within a smaller variety of genes.- The members of the population may then become more likely to inherit genetic diseases. Medical and Industrial Uses About one quarter of the drugs prescribed in the United Sates are derived from plants, and almost all of the antibiotics are derived from chemicals found in fungi. New chemicals and industrial materials may be developed from chemicals discovered in all kinds of species.
- The scientific community continues to find new uses for biological material and genetic diversity. Agricultural Uses Most of the crops produced around the world originated from a few areas of high biodiversity. Most new crop varieties are hybrids, or crops developed by combing genetic material from other populations. History has shown that depending on too few plants for food is risky. Famines have resulted when an important crop was wiped out by disease. But some crops have been saved by crossbreeding them with wild plant relatives. Ethics, Aesthetics, and Recreation Some people believe that we should preserve biodiversity for ethical reasons. They believe that species and ecosystems have a right to exist whether or not they have any other value.
- People also value biodiversity for aesthetic or personal enjoyment such as keeping pets, camping, picking flowers, or watching wildlife. Ecotourism is a form of tourism that supports the conservation and sustainable development of ecologically unique areas. Describe several ways that species are being threatened with extinction globally. Explain which types of threats are having the largest impact on biodiversity.
- List areas of the world that have high levels of biodiversity and many threats to species. Compare the amount of biodiversity in the United States to that of the rest of the world. Earth has experienced several mass extinctions, each probably caused by a global change in climate. It takes millions of years for biodiversity to rebound after a mass extinction.
- The rate of extinctions is estimated to have increased by a multiple of 50 since , with up to 25 percent of all species on Earth becoming extinct between and The current mass extinction is different from those of the past because humans are the primary cause of the extinctions. However, small populations in limited areas can easily become extinct. Species that are especially at risk of extinction are those that migrate, those that need large or special habitats, and those that are exploited by humans. A threatened species is a species that has been identified to be likely to become endangered in the foreseeable future. In the past 2 centuries, human population growth has accelerated and so has the rate of extinctions. The numbers of worldwide species known to be threatened, endangered, or recently extinct are listed on the next slide.
- The major causes of extinction today are the destruction of habitats, the introduction of nonnative species, pollution, and the overharvesting of species. In the process, we destroy and fragment the habitats of other species. It is estimated that habitat loss causes almost 75 percent of the extinctions now occurring. In , fewer than 80 Florida panthers made up the only remaining wild cougar population east of the Mississippi River. Even familiar organisms such as cats and rats are considered to be exotic species when they are brought to regions where they never lived before. Exotic species can threaten native species that have no natural defenses against them. Thousands of rare species worldwide are harvested and sold for use as pets, houseplants, wood, food, or herbal medicine. Poaching is is the illegal harvesting of fish, game, or other species. The long term effects of chemicals may not be clear until after many years.
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