Chapter 11 Outline - 1 2 3 4 Chapter 11 Outline Three types...

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Chapter 11 Outline 1. Three types of Species Extinction a. Local Extinction: occurs when a species is no longer found in an area it once inhabited but is still found elsewhere in the world. b. Ecological Species: occurs when so few members of a species are left that it can no longer play its ecological role in the biological communities where it is found. c. Biological extinction: a species is no longer found anywhere on the earth. 2. Endangered and Threatened Species: Ecological Smoke Alarms a. Endangered: so few individual survivors that the species could soon become extinct over all or most of its natural range. (Passenger pigeon) b. Threatened: is still abundant in its natural range but because of declining numbers it is likely to become endangered in the near future. c. Behavioral Characteristics: behaviors that may make a species prone to extinction. 3. Estimating Extinction Rates Is a Tough Job a. Biologists trying to catalog extinction have three problems: a.i. First, the extinction of a species typically takes such a long time that it is not easy to document. a.ii. Second, scientists have identified only about 1.4 million of the world’s 4 million to 100 million species. a.iii. Third, scientists know little about most of the species that have been identified. b. Red list: the world standard for listing the world’s threatened species b.i. Published by the International Union for the Conservation of Nature and Natural Resources. b.ii. In 2005, the Red List contained more than 16,000 species at risk of extinction. c. In 2006, the WWF researchers indentified 794 species in danger of imminent extinction. d. Species-Area Relationship: 90% loss of habitat causes the extinction of about 50% of the species living in that habitat. e. Theory of island biogeography: A model to estimate the number of current and future extinctions in patches of “islands” of shrinking habitat surrounded by degraded habitats or by encroaching human developments. 4. Effects of Human Activities of Extinction Rates a. In due time, all species become extinct. a.i. The extinction rate is about 0.0001% per year. b. Most biologists would consider the premature loss of 1 million species over 100- 200 years to be an extinction crisis or spasm. c. Most biologists consider extinction rates of 0.01%-1% to be conservative estimates for several reasons. c.i. First, both the rate of species loss and the extent of biodiversity loss are likely in increase during the next 50-100 years because of the projected growth of the world’s human population and resource use per person.
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c.ii. Second, current and projected extinction rates are much higher than the global average in parts of the world that are endangered centers of the world’s biodiversity. c.iii.
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Chapter 11 Outline - 1 2 3 4 Chapter 11 Outline Three types...

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