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12 Cards in this Set
- Front
- Back
Devonian
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-75 % of animal spp, 35% of animal families-most plants are algaes, another Pangea - evidence of meteor strike- may have been double whammy
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Permian
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290-250mya
-boundary of paleozoic and mesozoic -95% of all marine and terrestrial spp -most massive extinction -trilobites, tree groups, amphibian groups, pangea formed, may have been high vulcanism resulting in a lot of competition and lost of habitats-coastal shelves and inland deserts-90% of spp, 50% of families- |
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Triassic
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-180 mya, 65% of species, 35% of families-reptiles, marine mollusks
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Cretaceous
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65 mya
-lost 75% of spp on planet (modest # of families) -dinosaurs, ptaurosaurs (flying dinos), mollusks, foraminiforins, |
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Why are we worried about losing species
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-some species have large effect on other species-much of current extinction rate seems to be anthropogenic induced-rate of extinction seems to be higher now than over much of geologic time (historical rate over geological time is ~2spp per year)~ 10-50 million years to recover diversity lost in extinction events
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Are we at the beginning of the 6th major extinction-evidence for accelerated extinction
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Islands, many have lost bird species
-HI (50 lost during Polynesian invasion, 18 since Europeans) -Guam (brown tree snakes have extirpated all 16 endemic birds since WWII) -Polynesia (lost 2000 spp of birds in last 3000 years) Continents -New World (72-88% of large (>100lb) mammals have been lost since human colonization) human colonization in other places had a larger impact than in Africa because animals in Africa co-evolve with early humans but without them on other continents so when humans arrived animals weren’t wary -Lake Victoria ciclids -were 300 spp very diverse but small, nile perch was introduced for food in 1920-have lost 200 spp by 1990-not all are extinct but in very small hiding spots -Sentinal ridge in Andes had abundance of unknown plants -botanist in 1978 id’d 97 spp, by 1986 people and ag had moved in and 90 spp were gone ~some estimates of current extinction rate ~17,000-18,000 per year ~5-50% gone by 2020 some may be suspect but no denying large rate of extinction-not as big as other 5 yet-how it goes depends on us |
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alpha-richness
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number of species found in a small, homogenous area
~areas with high alpha-richness often have many rare species |
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beta-richness
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rate of change in species composition across habitats or among communities
~high beta-richness means that the cumulative number of species recorded rapidly increases as additional areas are censused along some environmental gradient-species may also drop out rapidly along such gradients, resulting in high rate of species turnover |
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gamma-richness
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changes across larger landscape gradients
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species richness
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number of species of organisms present in an area, habitat or evolutionary lineage
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measures of evenness or species diversity indices
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weigh species by some index of their importance, such as their abundance, productivity, or size
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indices of similarity
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measures degree of difference among species (or populations, or biotas
~also to assess the degree of genetic simiarity among evolutionary lineages, or the diversity of habitat types across landscapes or ecosystems |