Bio 101 - Lecture 6

Bio 101 - Lecture 6 - 1/21/2008 Announcements MakeMake-up...

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Unformatted text preview: 1/21/2008 Announcements MakeMake-up quizzes: 2:45 pm Wednesday, Jennings 251 Need acceptable written documentation of absence Must be made up the week following the quiz If you make an appointment with Adrea Rodriguez (head TA) for an alternate time and default without letting her know, you will receive a 0 on the quiz Speciation and Extinction Why and how do new species happen? Interactions of natural selection and gene flow Gene flow movement of alleles between populations Gene flow Stabilizing selection New N species Gene Flow Between Oak Populations X Original population Natural selection Genetic drift Mutations Disruptive selection Does allele frequency change? Evolution is the net effect between natural selection and maintaining genetic similarity Allopatric Speciation Geographic barriers lead to reproductive isolation over time Rapid volcanoes Slow plate tectonics, erosion 1 1/21/2008 Allopatric: in different places Sympatric: in the same place Sympatric population Purple-fin trout Allopatric populations a A few individuals of a mainland species reach isolated island 1. In the new habitat, populations of their descendants diverge, and speciation occurs. b Later, a few individuals of a newspecies colonize nearby island 2. Speciation follows genetic divergencein the new habitat. c Genetically different descendants of the ancestral species may colonize islands 3 and 4 or even i invade island d i l d 1. Genetic divergence and speciation may follow. Green-fin three-spot trout Speciation has occurred! X = No viable offspring Akepa (Loxops coccineus) Insects, spiders from buds twisted apart by bill; some nectar; high mountain rain forest Fig. 17.22b, p.281 Nihoa finch (Telespiza ultima) Insects, buds, seeds, flowers, seabird eggs; rocky or shrubby slopes Fig. 17.22d, p.281 2 1/21/2008 Akohekohe (Palmeria dolei ) Mostly nectar from flowering trees, some insects, pollen; high mountain rain forest Fig. 17.22l, p.281 Fig. 17.22n, p.281 Sympatric speciation: Usually associated with accidents in cell division (polyploidy) Common in plants Sometimes, abnormal cell division is useful... in the origin of wheat Let's move on to Extinction Have species frequently gone extinct over the history of life on earth? What causes these episodes of mass extinction? 3 1/21/2008 Major Extinction Events (6) 0 -1 0 0 ? 50-80% of genera lost e n d o f C re ta c e o u s Volcanic Activity Millions of Years BP Y -2 0 0 -3 0 0 -4 0 0 -5 0 0 e n d o f T ria s s ic e n d o f P e rm ia n e n d o f D e vo n ia n e n d o f O rd ivic ia n e a rly C a m b ria n -6 0 0 0 20 40 60 80 100 P e rc e n t o f G e n e ra L o s t Large meteor strikes are not uncommon Barringer, g Arizona Wolf Creek, Australia Bosumtwi, Africa (6.5 mi) What happens after a major environmental upheaval and its resultant mass extinction? Explosive Diversification A burst of macroevolution (diversification of phyla, classes, orders) followed by A period of microevolution (diversification of genera and species) 4 1/21/2008 platypus, other monotremes kangaroos, other marsupials elephants, other proboscideans manatees anteaters whales, dolphins deer, other artiodactyls horses, other perissodactyls armadillos shrews, other insectivores; bats carnivores Recovery from Extinction Events primates rodents rabbits 0 -100 ? 2-7 million yrs recovery end of Cretaceous Millions of Years BP Y -200 -300 -400 -500 end of Triassic end of Permian end of Devonian end of Ordivician CENOZOIC MESOZOIC early Cambrian -600 0 ancestral mammal Fig. 17.28, p.285 2 4 6 8 Time to Recovery (Myr) Signs of extinction We are currently going through another episode of extinction 20% of freshwater fish species endangered or extinct in the last 500 yrs 11% of the 9040 known species of birds are currently endangered 970 tree species are classified as critically endangered; 5 are down to less than 10 living individuals The Hundred Heartbeat Club Species down to <100 individuals: Philippine eagle California condor* J Javan rhinoceros hi Chinese river dolphin Spix's macaw Hawaiian crow and many others Causes of extinction: Habitat Destruction: Expansion of agriculture Urban development Mining Air, water, and soil pollution Associated with population declines 5 1/21/2008 Causes of extinction: Overexploitation Commercial harvest of economically important species (e.g., cod, tuna) Accidental death during commercial harvest (e.g., turtles, dolphins) Sport hunting (e.g., bison, passenger pigeon) Europe's Appetite for Seafood Propels Illegal Trade NYT 15 Jan 08 Europe world's largest market for fish - $22 billion/year Imports 60% of fish Increase in illegal fish - $1.6 b o pe yea c ease ega s $ 6 billion per year E.g., China is largest supplier of African fish to Europe 60% of cod from Baltic are illegal Implications: further decrease in world fish stocks Price of fish increases as lower quotas allowed by EU to protect European fish stocks Monitoring illegal trade in fish is in it's infancy few good methods A Finnish Turf Battle Pits Wolf Against Reindeer Herder NYT 21 Jan 08 A Finnish Turf Battle Pits Wolf Against Reindeer Herder NYT 21 Jan 08 Age old battle between wolf and man in Northern Finland Fight between backers of EU regulations and reindeer h d i d herders EU regulations aimed at halting the sharp drops in populations of wolves and other top predators in Europe Reindeer herders say wolves are killing too many reindeer Finland joined EU in 1995 original laws didn't mesh with EU habitat directives Large increase in wolves, bears, lynx, wolverine populations Every predator killed must be covered by permit Herders compensated for killed reindeer, but say it's not enough Annual mortality rate of wolves is 20% - 9 of 10 are killed by humans Causes of extinction: Introduced, invasive, exotic species Starlings vs bluebirds Cheatgrass in the US west Purple loosestrife in wetlands Case study in extinction: Nile Perch Introduced into Lake Victoria in east Africa Responsible for the extinction of ~200 native, smaller fish species (cichlids) ...BAD, right? 6 1/21/2008 Nile Perch became a major food source for people of east Africa and for export to, on balance, it's probably good...right? good right? Nile Perch have reduced the populations of smaller, prey fish species to the point where the Nile Perch fishery is in danger of collapsing: The danger of introduced species! What's the primary cause of the on-going extinction onepisode? People How many species will go extinct during the current extinction episode? How l H long will it take to recover? ill t k t ? When will humans become extinct? Summary Allopatric speciation (geographical isolation) Sympatric speciation (same place) Often associated with cell division errors Six episodes of mass extinction followed by rapid diversification (macroevolution phyla, classes) and formation of genera and species (microevolution) 7th extinction underway anthropogenic (human(humancaused) Habitat destruction (likely most important) Overexploitation Exotic species 7 ...
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