Weeks9and10 - The Status of Biodiversity Extinction is a...

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The Status of Biodiversity Extinction is a known part of the taxon cycle. Extinction track record from 400 yr of historical records: 115 spp of birds, 58 spp of mammals 100 spp of reptiles 64 amphibians (incl. 38 genera and one family) worldwide, 1800 spp of freshwater fishes have gone extinct or are in danger of extinction 40 spp or subspp of freshwater fishes in North America have gone extinct in the past decade 200 spp of Cichlid fishes have disappeared from Lake Victoria in East Africa 191 spp of molusks 600 spp of plants Taxonomic descriptions exist for 1.4 million spp, but estimates range between 5 and 50 million spp of organisms. The lack of classification of the world’s biota is referred to as the Linnean shortfall. Biodiversity hotspots -- regions where species diversity is very high Rarity leads to extinction -- thus a high priority should be placed on taxa with restricted ranges, and on areas where diversity is very high (i.e., hotspots). The problem of choice has to do with how much overlap is there in patterns of distribution among different organisms. There are also hotspot regions in the oceans coral reefs deep ocean communities (endemism ranges 50%-90%). 9 - 1
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surveys - one new phylum, 14 new families, and 50 new genera. Diversity results from (1) isolation, (2) antiquity (existing throughout the Phanerozoic), (3) adaptation to extreme habitat. The Geography of Extinctions Prehistoric record Mass extinctions at K-T boundary reveal at 60 to 80% decline in species diversity worldwide; highest amoutn in equatorial regions Plate tectonics and continental drift may have played an important role in many extinctions recorded in the fossil record It has just been the last 2 million years that humans have entered this equation. This has escalated with human population growth and the expanding technology base. The first major technological advance was the mastering of fire; agriculture, advances in hunting techniques, and methods of transportation followed. Australia North America Africa Historical record Record of extinctions have a geographic signature -- one showing the fragility of insular communities. Island extinctions resulted from a combination of factors - primarily ecological naivete of animals and introduction of exotics. Waves of extinctions for oceanic islands: aboriginals of Malaysia, 9 - 2
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Indonesia, Australia, Tasmania, Micronesians, Melanesians, Polynesians, Amerindians, Europeans. Polynesians may have caused the extinctions of half the birds on Hawaii prior to European invasion. The Maori people killed off the 11 species of moas in New Zealand. The Ecology and Geography of Invasive Species Anthropogenic introduction of exotics The most striking feature of the geographic distribution of introductions is that oceanic islands have received the most species introductions. 60% of all mammal and bird introductions
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Weeks9and10 - The Status of Biodiversity Extinction is a...

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