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Figure 7.1 Preserving 50% of total habitat area often
leaves about 90% of the original species remaining alive
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7.2.3 Extinction Species extinction:
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The smallest population size needed to stay above the extinction vortex is often called the minimum viable population (MVP)
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7.2.4 Reasons for Decline of Biodiversit
Chapter 7
Conserving Biological Resources
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Chapter 7 Conserving Biological Resources
7.1 Value of Wild Species 7.2 Biodiversity
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7.1 Value of Wild Species
Physical Alteration of Habitats
The Population Factor
Exotic Species
Overuse
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7.2.5 Convention on Biological Diversity (1992 in Rio de Janeiro)
➢Adopt specific national biodiversity action plans and strategies ➢Establish a system of protected areas and ecosystems within the country ➢Establish policies that provide incentives to promote sustainable use of biological resources
a species has died out in a local area
Ecological extinction:
a species has become so rare that it has essentially no role or impact on its ecosystem
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between 4 million and 112 million additional species have not
yet been systematically explored .
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7.1.2 Two Kinds of Value
➢instrumental value: its existence or use benefits some other entity ➢intrinsic value: it has value for its own sake
the number of species that occur in an area
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7.2.2 The species-area curve:
The number of species is counted in a gradually enlarged area of sampling, the result is a curve. The number of species rises rapidly at first, but it slows as the area of sampling increases because the same species are encountered again and again.
7.1.1 Biological Wealth
About 1.75 million species of
plants, animals, and microbes have been examined, named, and classified, but scientists estimate that
value ➢Intrinsic value
.Байду номын сангаас
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7.2 Biodiversity
7.2.1 Concept
Biodiversity: the variety and variability among
living organisms and the ecological complexes in which they occur Species diversity:
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The value of natural species
➢Sources for agriculture, forestry, aquaculture, and animal husbandry
➢Sources for medicines, pharmaceuticals ➢Recreational, aesthetic, and scientific
pollution
Change biological environment:
2.Introduce new species
New predator
3. Overhunting
Big-game hunting
4. Secondary extinctions
Loss of food species
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Two basic causes for this extinction vortex
➢One is that small populations may have breeding problems. ➢The second cause is that small populations are much more easily wiped out by random environmental fluctuations
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Table 7.3 Four ways that humans cause population decline and species extinction
Change physical environment: Examples
1.Habitat disruption
Drain swamp, toxic