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Week of February 15th Notes

by: Amanda Howard

Week of February 15th Notes BIO 113

Marketplace > Wake Forest University > Biology > BIO 113 > Week of February 15th Notes
Amanda Howard
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About this Document

These notes cover the 14 events needed for the quiz and the beginning of speciation
Evolutionary and Ecological Biology
Anderson, Todd Michael and Clifford W. Zeyl
Class Notes
Bio, evolutionary, speciation, Events in the history of earth




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This 3 page Class Notes was uploaded by Amanda Howard on Sunday February 21, 2016. The Class Notes belongs to BIO 113 at Wake Forest University taught by Anderson, Todd Michael and Clifford W. Zeyl in Spring 2016. Since its upload, it has received 20 views. For similar materials see Evolutionary and Ecological Biology in Biology at Wake Forest University.


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Date Created: 02/21/16
Notes for the week of February 15th 14 Events for the quiz (know 4 well)  first known biological activity: methanogens (Archaea) o 3.8 BYA o Hypothetically occurred at Hydrothermal vents o Prior to this life would have been impossible due to a lack of oxygen o Archaea however can process elements around the vents  photosynthesis by cyanobacteria generates first oxygen  o ~3.5 BYA o Stromatolites are fossilized alternating layers of mud and cyanobacteria with the living  layer at the top o There are actually currently living cyanobacteria in a marine in Australia which is  unusually salty o Cyanobacteria produced the first oxygen allowing for the development of life  endosymbiotic origin of mitochondria o 1.2 BYA o Mitochondrion­descended from bacteria  o These organisms could survive on their own and are the early ancestors of the  mitochondria found in many organisms today  endosymbiotic origin of chloroplasts o 800 MYA o Again these organisms could survive on their own and are the ancestors of today’s  chloroplasts found in plants  origin of animals, multicellularity o 800­700 MYA o The earliest animals were found in the ocean and were generally soft bodied  Cambrian explosion o 540­505 MYA o Sudden radiation of phyla (basic body plans) in less than 10MY o origin of major animal groups­new clades evolve relatively quickly followed by slower  diversification o millions of new organisms o beginning of diversity, new lineages have different niches in the environment o earliest predators  earliest land plants o 470 MYA  first known land vertebrates (amphibians) o 350 MYA  Permian mass extinction o 250 MYA o Worst mass­extinction in history  first flowering plants o 160 MYA o After a massive drop 2n O  levels  earliest mammals o ~160MYA  end of Cretaceous mass extinction o 65 MYA o Ended the cretaceous o This is the extinction that wiped out the dinosaurs, really anything bigger than a dog was  destroyed o Possible meteor his of the coast of the Yucatan   major mammalian radiation o 60­40 MYA o Possible because the dinosaurs were wiped out at the end of the cretaceous   first grasslands o ~22 MYA o Developed to survive grazing mammals Plate Tectonics  Land masses are plates of rock floating on magma o Magma­molten rock  This is important because shifting plates change the climate o example  Huge interior regions of the continent  Selection for grasses  Whole new ecosystem: grasslands Speciation  The evolution of two species from one ancestral species  Not necessarily associated with new adaptations in either species  The problem: o if a single mutation causes genetic incompatibility with the rest of the species, that’s one  lonely does that mutation spread? o if multiple mutations are required, what prevents interbreeding between the initial  mutants and the rest of the population from spreading them throughout the population?  Explanations: o allopatric speciation: interbreeding is prevented by some physical obstacle  two groups are separated by geography for a period in which they differentiate  even if the groups come back together they are no longer compatible  the “Dobzhansky­Muller model” (a form of allopatric speciation)  after populations are separated, different mutations spread through each  new lineage   those mutations turn out to be genetically incompatible – combinations  other than the ones that evolved have low fitness  after that, if contact between the populations is restored, there is selection against individuals that choose the wrong (genetically incompatible)  mate o sympatric speciation: selection somehow favors both different traits (usually ecological,  e.g. avoiding competition) and mating preferences (individuals avoid mates with traits  different from their own)  for example: bird beaks  in the rainforest there are birds with both very large and very small beaks  this is an example of two extremes of the mutations for beak size,  however both are favored because they are specialized for a specific type of food  the reason a bird with a big beak would not have mated with a bird with a small beak is that the offspring would have been in the midsized beak  range which is not specialized for either type of food  another example: flowers  some flowers are developed to attract humming birds  red  tube shaped flower developed to fit the beak of the hummingbird  large volume of nectar  others are developed to attract bees  pink  place to land  concentrated nectar  here, pollinators are both an ecological resource for which plants  compete, and a genetic isolation mechanism  attracting different pollinators requires different combinations of floral  traits  because reproduction requires pollen from another plant, specialization  for different pollinators also prevents cross­pollination – genetic isolation o recent evidence suggests that in at least some lineages this is not as hard to explain as  evolutionary biologists have thought all along o temporal isolation  if species have allopatric speciation they are in different locations so they can  breed any time of year with no overlap  however if two species are in the same location they will often mate at different time to decrease the chances of overlap o examples of convergence: cichlids (will be continued next class) o different groups of fish in ponds have similar features in terms of mouth  adaptations in different ponds, however they are not as closely related to each  other as to very different fish in the same pond from which they descended


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