6011964
Descripción
Fichas por Chelsi Souch, actualizado hace más de 1 año
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Creado por Chelsi Souch
hace más de 8 años
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| Pregunta | Respuesta |
| Why Biodiversity Matters | • The expanding human population threatens • biodiversity and • the disappearance of natural ecosystems. • Only about a quarter of Earth’s land surfaces remain untouched by human alterations |
| • Healthy ecosystems provide resources, such as water, wood, and fish, and services such as | recycling nutrients, • preventing erosion and mudslides, • controlling agricultural pests, and • pollinating crops. |
| Coastal wetlands... | act as a buffer against hurricanes, • reduce the impact of flooding, • filter pollutants, and • furnish nesting sites and breeding areas for birds and marine turtles and nurseries for a wide variety of fish and shellfish. |
| • Biological diversity, or biodiversity, includes | • genetic diversity, • species diversity, and • ecosystem diversity. • Thus, the loss of biodiversity encompasses more than just the fate of individual species. |
| Genetic Diversity | raw material that makes microevolution and adaptation to the environment possible. • If local populations are lost, then • the number of individuals in the species declines, and • the genetic resources for that species decline. |
| Species Diversity | Ecologists believe that we are pushing species toward extinction at an alarming rate. • The present rate of species loss may be 100 times higher than at any time in the past 100,000 years. • Some researchers estimate that at the current rate of destruction, over half of all currently living plant and animal species will be gone by the end of this century |
| Two recent victims of human-caused extinctions are the | • Chinese river dolphins and • Formosan clouded leopard |
| Ecosystem Diversity | An ecosystem includes the organisms and the abiotic factors in a particular area. • Because of the network of interactions among populations of different species within an ecosystem, the loss of one species can have a negative effect on the entire ecosystem. • The disappearance of natural ecosystems results in the loss of ecosystem services, functions performed by an ecosystem that directly or indirectly benefit people, including • air and water purification, • climate regulation, and • erosion control. |
| Causes of Declining Biodiversity | Ecologists have identified four main factors responsible for the loss of biodiversity: 1. habitat destruction and fragmentation, 2. invasive species, 3. overexploitation, and 4. pollution. • The ever-expanding size and dominance of the human population are at the root of all four factors. |
| Habitat Destruction | • Biodiversity is threatened by the massive destruction and fragmentation of habitats by • agriculture, • urban development, • forestry, and • mining. • According to the IUCN, habitat destruction affects more than 85% of all birds, mammals, and amphibians that are threatened with extinction. |
| Invasive Species | • Invasive species have • competed with native species, • preyed upon native species, and • parasitized native species. |
| Overexploitation | People can overexploit wildlife by harvesting at rates that exceed the ability of populations to rebound. • Excessive commercial harvesting, poaching, and sport hunting have greatly affected populations of • tigers, • the American bison, and • Galápagos tortoises. • Overharvesting also threatens rare trees such as mahogany and rosewood that produce valuable wood. |
| Pollution | Air and water pollution is a contributing factor in declining populations of hundreds of species. • The global water cycle can transport pollutants from terrestrial to aquatic ecosystems hundreds of miles away. • Pollutants that are emitted into the atmosphere may be carried aloft for thousands of miles before falling to earth in the form of acid precipitation. |
| BIOMAGNIFICATION | |
| The Carbon Cycle | |
| The Phosphorus Cycle | Organisms require phosphorus as an ingredient of nucleic acids, phospholipids, and ATP and as a mineral component of vertebrate bones and teeth. • The phosphorus cycle does not have an atmospheric component. • Rocks are the only source of phosphorus for terrestrial ecosystems • Phosphates move from land to aquatic ecosystems much more rapidly than they are replaced. • Soil characteristics may also decrease the amount of phosphate available to plants. As a result, • phosphate is a limiting factor in many terrestrial ecosystems and • farmers and gardeners often use phosphate fertilizer, such as crushed phosphate rock or bone meal, to boost plant growth. |
| The Nitrogen Cycle | Nitrogen is • an ingredient of proteins and nucleic acids and • essential to the structure and functioning of all organisms. • The atmospheric reservoir is huge; almost 80% of the atmosphere is nitrogen gas (N2 ). • However, plants cannot use nitrogen gas. • The process of nitrogen fixation converts gaseous N2 to ammonia (NH3 ). • Ammonia then picks up another H+ to become ammonium (NH4 + ), which plants can assimilate. |
| Nitrogen has two abiotic reservoirs: | 1. the atmosphere and 2. the soil |
| • Two major sources of nitrogen are | 1. combustion of fossil fuels and 2. modern agricultural practices. • Some nitrogen escapes to the atmosphere, where it forms nitrous oxide (N2O), a gas that contributes to global warming. Human activities are disrupting the nitrogen cycle by adding more nitrogen to the biosphere each year than natural processes do. |
| Nutrient Pollution | The growth of algae and cyanobacteria in aquatic ecosystems is often limited by low nutrient levels, especially • phosphorus and • nitrogen. • Nutrient pollution occurs when human activities add excess amounts of these chemicals to aquatic ecosystems |
| Conservation and Restoration Biology | Many of the environmental problems facing us today have been caused by human enterprises. • Ecological research is the foundation for • finding solutions to these problems and • reversing the negative consequences of ecosystem alteration. |
| Conservation biology | goal-oriented science that seeks to understand and counter the loss of biodiversity |
| Restoration ecology | uses ecological principles to develop methods of returning degraded areas to their natural state. |
| Biodiversity “Hot Spots” | Conservation efforts are often focused on biodiversity hot spots, relatively small areas that have • a large number of endangered and threatened species and • an exceptional concentration of endemic species, those that are found nowhere else. • The “hottest” of Earth’s biodiversity hot spots are shown in Figure 20.37 |
| Conservation at the Ecosystem Level | Conservation biology increasingly aims at sustaining the biodiversity of entire • communities, • ecosystems, and • landscapes, regional assemblages of interacting ecosystems, such as an area with forest, adjacent fields, wetlands, streams, and streamside habitats |
| Landscape ecology | is the application of ecological principles to the study of land-use patterns. • Its goal is to make ecosystem conservation a functional part of the planning for land use. |
| Edges between ecosystems | |
| movement corridor | a narrow strip or series of small clumps of suitable habitat connecting otherwise isolated patches. can promote dispersal, • help sustain populations, and • are especially important to species that migrate between different habitats seasonally. • But a corridor can also spread disease, especially among small subpopulations in closely situated habitat patches. |
| Restoring Ecosystems | Bioremediation uses living organisms to detoxify polluted ecosystems. Some restoration projects have the broader goal of returning ecosystems to their natural state. |
| The Goal of Sustainable Development | As the world population grows and becomes more affluent, the demand increases for the provisioning services of ecosystems, such as • food, • wood, and • water. The goal of sustainable development is to meet the needs of people today without limiting the ability of future generations to meet their needs. • Sustainable development depends on • continued research, • the application of ecological knowledge, and • the connection of the life sciences with • social sciences, • economics, and • humanities. |
| Evolution Connection: Can Biophilia Save Biodiversity? | Edward O. Wilson uses the term biophilia to describe the human desire to affiliate with other life in its many forms. • Many biologists have embraced the concept of biophilia and turned their passion for nature into careers. • If biophilia is evolutionarily embedded in our genomes, then there is hope that we can become better custodians of the biosphere. |
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