Final exam review summaries (Chapter 16) PDF

Preview

Summary

chapter 16 summary and take home message...

Description

TAKE-HOME MESSAGE 16.1: Biodiversity—the variety of genes, species, and ecosystems on earth—has intrinsic value as well as extrinsic value to humans. The value of biodiversity to humans is often described in terms of four categories of ecosystem services: provisioning, cultural, regulating, and habitat services. These categories help distinguish among various utilitarian values, such as the production of food and medicines, aesthetic and symbolic value, and the regulation and support of our environments. 16.2 This is how we do it: When 200,000 tons of methane disappears, how do you find it? TAKE-HOME MESSAGE 16.2: Following a massive oil leak in the Gulf of Mexico, researchers noted a rapid disappearance of methane. Finding a simultaneous drop in the oxygen saturation of the water, the researchers were able to determine that populations of bacteria already living in the area grew rapidly in response to the new food source and consumed the methane. 16.3 Biodiversity occurs at multiple levels. TAKE-HOME MESSAGE 16.3: Assessing biodiversity can be difficult because it must be considered at multiple levels, from entire ecosystems to species to genes and alleles. In practice, biodiversity is most often defined as the number of distinct species in a habitat, which has important implications for conservation biology—the field that addresses questions of how to preserve the natural resources of earth. 16.4 Where is most biodiversity? TAKE-HOME MESSAGE 16.4: Biodiversity is not evenly distributed over the earth. For nearly all groups of plants and animals, both marine and terrestrial, biodiversity is greatest near the equator and falls progressively toward the North and South Poles. Factors that influence the species richness in an area include the amount of solar energy available, the area’s evolutionary history, and the rate of environmental disturbance. Biodiversity hotspots are regions of significant biodiversity under threat of destruction. 16.5 There are multiple causes of extinction. TAKE-HOME MESSAGE 16.5: Extinctions occurs for fundamentally different reasons. Mass extinctions, which can destroy man or all of the species in an area, may reflect bad luck more than the particulars of a species’ biology, including its biochemistry, physiology, and behavior. Background extinctions, on the other hand, tend to be a consequence of one or more features of the species’ biology. Small population size, limited habitat range, and narrow habitat tolerance contribute to background extinctions. 16.6 We are in the midst of a mass extinction. TAKE-HOME MESSAGE 16.6: Most biologists believe that we are currently in the midst of a mass extinction, that it is the result of human activities, and that it poses a serious threat to the future survival of humans. 16.7 Some ecosystem disturbances are reversible, others are not. TAKE-HOME MESSAGE 16.7: An ecosystem disturbance is reversible as long as the disturbance does not include the complete extinction of any species, so they can re-establish their populations. An ecosystem disturbance that involves the complete loss of a species to extinction is irreversible because a species, once lost, can never exist again. 16.8 Human activities can damage the environment: 1. Introduced non-native species may wipe out native organisms TAKE-HOME MESSAGE 16.8: Exotic or introduced species are species intentionally or accidentally introduced in a new habitat. They are considered invasive species if they cause harm

in their new habitat. Exotic species often come to be considered invasive because, in the new habitat, they often have no natural predators to reduce their population size, and they often encounter prey that have few or no defenses. Invasive species can dominate and irreversibly alter communities and entire ecosystems. 16.9 Human activities can damage the environment: 2. Acid rain harms forests and aquatic ecosystems. TAKE-HOME MESSAGE 16.9: Burning fossil fuels releases the gases sulfur dioxide and nitrogen dioxide, and these compounds form sulfuric and nitric acids when they combine with water vapor in the atmosphere. Rain, fog, sleet, and snow that contain these acids can be more than 10 times more acidic than clean rain. Acid precipitation kills plants and aquatic animals directly, by contact with living tissues, and indirectly, through changes in soil and water chemistry. 16.10 Human activities can damage the environment: 3. The release of greenhouse gases can influence the global climate. TAKE-HOME MESSAGE 16.10: Carbon dioxide and methane are called “greenhouse gases” because they trap heat in the atmosphere. As humans burn fossil fuels and clear forests, the concentrations of greenhouse gases have been increasing and global temperatures have been rising. Ecological changes in plant and animal communities have already been observed and are likely to become more serious unless there is a global reduction in emissions of greenhouse gases. Ozone in the stratosphere prevents short-wavelength ultraviolet light (UVB) from reaching the earth’s surface, but for many decades the amount of ozone was decreasing largely due to synthetic chemicals called chlorofluorocarbons (CFCs). An increase in UVB light reaching the earth’s surface can seriously damage ecosystems and has adverse effects on health, including increasing the incidence of skin cancer in humans and other animals. A decline in the production and use of CFCs is reducing the atmospheric ozone depletion. 16.11 Human activities can damage the environment: 4. Deforestation of rain forests causes loss of species and the release of carbon. TAKE-HOME MESSAGE 16.11: Tropical rain forests are being destroyed at an alarming rate. This deforestation is devastating for two main reasons: First, tropical rain forests contain more species of plants and animals than all other terrestrial habitats combined, and half of the earth’s biodiversity hotspots are in these forests. Second, tropical rain forests remove more carbon dioxide from the atmosphere than any other terrestrial habitat and, as a result, these forests are enormously important in limiting global warming. Deforestation further influences climate change by altering land cover characteristics. Programs addressing the complex difficulties of slowing tropical deforestation are beginning to see some encouraging results. 16.12 Reversing ozone layer depletion illustrates the power of good science, effective policymaking, and international cooperation. TAKE-HOME MESSAGE 16.12: Ozone in the stratosphere prevents short-wavelength ultraviolet light (UVB) from reaching the earth’s surface, but for many decades the amount of ozone was decreasing, largely due to synthetic chemicals called chlorofluorocarbons (CFCs). An increase in UVB light reaching the earth’s surface can seriously damage ecosystems and has adverse effects on health, including increasing the incidence of skin cancer in humans and other animals. A decline in the production and use of CFCs is reducing atmospheric ozone depletion, and a full recovery of the ozone layer appears possible. 16.13 With limited conservation resources, we must prioritize which species should be preserved.

TAKE-HOME MESSAGE 16.13: Effective conservation requires the setting of goals on the elements of biodiversity (genes, species, or ecosystems) that should be conserved and priorities among those elements. The U.S. Endangered Species Act has focused much conservation effort on the preservation of species. 16.14 There are multiple effective strategies for preserving biodiversity. TAKE-HOME MESSAGE 16.14: Conservation biology has focused, in the past, on preserving individual species. Increasingly, there is a shift toward the preservation of important habitats, focusing on conserving communities and ecosystems. Several methods focusing on single species remain useful, however, particularly when preserving the selected species requires the preservation of an amount and type of habitat that simultaneously preserves many other species....