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Chapter-55 - Chapter 55 Conservation Biology and...

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Chapter 55 Conservation Biology and Restoration Ecology Lecture Outline Overview: The Biodiversity Crisis Conservation biology integrates ecology, evolutionary biology, physiology, molecular biology, genetics, and behavioral ecology to conserve biological diversity at all levels. Restoration ecology applies ecological principles in an effort to return degraded ecosystems to conditions as similar as possible to their natural, predegraded state. Scientists have described and formally named about 1.8 million species of organisms. Some biologists think that about 10 million more species currently exist. Others estimate the number to be as high as 200 million. Throughout the biosphere, human activities are altering trophic structures, energy flow, chemical cycling, and natural disturbance. The amount of human-altered land surface is approaching 50%, and we use more than half of the accessible surface fresh water. In the oceans, we have depleted fish stocks by overfishing. Some of the most productive aquatic areas, such as coral reefs and estuaries, are severely stressed. Globally, the rate of species loss may be as much as 1,000 times higher than at any time in the past 100,000 years. Concept 55.1 Human activities threaten Earth’s biodiversity Extinction is a natural phenomenon that has been occurring since life evolved on Earth. The current rate of extinction is what underlies the biodiversity crisis. Humans are threatening Earth’s biodiversity. The three levels of biodiversity are genetic diversity, species diversity, and ecosystem diversity. Biodiversity has three main components: genetic diversity, species diversity, and ecosystem diversity. Genetic diversity comprises the individual genetic variation within a population but also the genetic variation among populations that is often associated with adaptations to local conditions. If a local population becomes extinct, then the entire population of that species has lost some genetic diversity. The loss of this diversity is detrimental to the overall adaptive prospects of the species. The loss of wild populations of plants also means the loss of genetic resources that could potentially be used to improve crop qualities, such as disease resistance. Species diversity, or species richness, is the variety of species in an ecosystem or throughout the entire biosphere. Much of the discussion of the biodiversity crisis centers on species. The U.S. Endangered Species Act (ESA) defines an endangered species as one in danger of extinction throughout its range, and a threatened species as one likely to become endangered in the foreseeable future. Here are a few examples of why conservation biologists are concerned about species loss.
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The International Union for Conservation of Natural Resources (IUCN) reports that 12% of the 9,946 known bird species and 24% of the 4,763 known mammal species are threatened with extinction.
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