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31.1 The new science of conservation biology is focusing on conserving biodiversity.
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• Early humans caused many extinctions when they appeared in new areas, but rates of extinction have increased in modern times.
• Some areas are particularly rich in species diversity and particularly merit conservation attention.
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1. What areas are particularly important for conserving biodiversity?
2. Describe some of the indirect economic values of biodiversity.
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31.2 Vulnerable species are more likely to become extinct.
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• Interdependence among species in an ecosystem leads to the possibility of cascading extinctions if removal of one species has major effects throughout the food web.
• Species are particularly vulnerable when they have
localized distributions, are declining in population size, lack genetic
variability, or are harvested or hunted by humans.
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3. What factors contribute to the extinction rate on a particular piece of land?
4. How does a low genetic variability contribute to a species' greater risk of extinction?
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31.3 Causes of endangerment usually reflect human activities.
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• Habitat loss is the single most important cause of species extinction.
• As suggested by the species-area relationship, a reduced habitat will support fewer numbers of species.
• This reduction in habitat can occur in four different
ways: a habitat can be completely removed or destroyed, a habitat can
become fragmented and disjunct, a habitat can be degraded or altered,
or a habitat can become too frequently used by humans so as to disturb
the species there.
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5. How can problems resulting from lack of genetic diversity within a population be solved?
6. How can extinction of a keystone species be particularly disruptive to an ecosystem?
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31.4 Successful recovery plans will need to be multidimensional.
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• Pristine restoration of a habitat may be attempted, but removing introduced species, rehabilitating the habitat, and cleaning up the habitat may be more feasible.
• Captive propagation, sustaining genetic variability, and preserving keystone species have been effective in preserving biodiversity.
• Megareserves have been successfully designed in many
parts of the world to contain core areas of undisturbed habitat surrounded
by managed land.
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7. Why is maintaining large preserves particularly important?
8. Is captive propagation always an answer to species vulnerability?
9. Why is it important to attempt to eradicate introduced species soon after they appear?
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