25 in addition to habitat complexity biodiversity hot

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Unformatted text preview: o habitat complexity, Biodiversity Hot Spots other major factors related to community diversity: • Available geographical area for the community Number of species (log scale) 1,000 • A biodiversity hot spot is a relatively small area with an exceptional concentration of endemic species and a large number of endangered and threatened species • Particularly resulting from habitat destruction. • Most impacted biomes: – Tropical rain forest – Chaparral Terrestrial biodiversity hot spots 100 10 Equator 1 1 10 100 103 104 105 106 107 108 109 Area (acres) Extinction is forever 1010 Figure 53.26 Hundred-heartbeat club-members • Endangered species ß In immediate danger of becoming extinct throughout its range (a) Philippine eagle (b) Chinese river dolphin • Hundred-heartbeat Club ß <100 individuals left! • Threatened species ß Likely to become endangered in the foreseeable future if current trends continue Figure 55.17 The Extinction Vortex • A diminished population is prone to positive-feedback loops that draw the population down an extinction vortex • Once population size is reduced to a critical level [the Minimum Viable Population ], it may not be able to recover! Small population Inbreeding Genetic drift Lower reproduction Higher mortality Loss of genetic variability Reduction in individual fitness and population adaptability Smaller population (c) Javan rhinoceros Heyer 11 Community Ecology Invasive Introduced Species “On a global basis...the two grea...
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