Week 6 Bio Notes
Week 6 Bio Notes Biol 180
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This 7 page Class Notes was uploaded by Nikki Hovland on Thursday November 5, 2015. The Class Notes belongs to Biol 180 at University of Washington taught by Scott Freeman in Summer 2015. Since its upload, it has received 58 views. For similar materials see Introductory Biology in Biology at University of Washington.
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Date Created: 11/05/15
INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 Week 6 Notes Lecture 20 Speciation Review homology similarities between species due to common ancestry homoplasy similarities between species not derived from common ancestry convergent evolution loss or gain of trait for different reasons that common ancestor hypothesis of homoplasy predicts genetic and developmental similarities are not necessarily related because they can arise for different reasons like environments homoplasy caused by in morphological traits convergent evolution due to selection for similar traits in similar environments multiple mutations also cause homoplasy in DNA data subspecies populations that live in distinct areas and have distinguishing features but are not distinct enough to be completely separate species they still have similarities speciation begins when gene flow between pop is reduced which causes genetic isolation genetic isolation happens frequently when populations become separated geographically allopatry different homeland when pop are separated geographically gt leads to allopatric speciation vicariance physical splitting of a habitat geographic isolation can happen via vicariance or dispersal when pop go to new habitat and colonizes it to create a new pop allopatric speciation by dispersal genetic drift creates colonizing population founder effect natural selection in new environment favors certain alleles while maybe not in old geographic area INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 population also can diverge through mutation evolution change in allele frequencies occurs in this population differently than in old population gt speciation allopatric speciation by vicariance vicariance a new physical barrier mountains river splitting etc may split the geographic area of a species can lead to species becoming sister species each others closest relative on either side of the divide populations also diverge through mutation selection and genetic drift basically pop on either side of split diverged to become separate species genetic isolation due to disrupt of gene flow this is the first requirement of gene flow sympatry together homeland when pop or species live in same area or close enough to inbreed svmpatric speciation speciation that occurs even when pop live in same area Two types of events can cause this outside events like disruptive selection for extreme phenotypes due to different ecological niches internal events like mutations in chromosomes sympatric speciation by disruptive selection niche range of resources that a species uses and conditions that it tolerates species can become reproductively isolated by adapting to different niches through disruptive selection even though they live in same area populations diverge due to selection pre zygotic reproductive isolation can occur as result of natural selection for adaptations for two different niches sympatric speciation by polyploidization polyploidy error in meiosis or mitosis leads to doubling the number of chromosomes INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 this is a form of significant mutation that can be extremely influential in speciation two types of polyploid utopolyploidy same many form when individuals have doubled chromosome number and chromosomes are all from same species usually due to nondisjunction in meiosis leading to diploid gametes instead of haploid polyploid individuals are reproductiver isolated from diploid population thus evolutionarily dependent and speciation because when diploid and polyploid organisms mate the offspring is sterile uneven number of chromosomes in gametes cant synapse right BUT if polyploid individual can selffertilize then it can reproduce correctly allopolyploidy different many form when two parents from different species mate and the offspring have two different sets of chromosomes one method two individuals that have different chromosomes numbers ie 2n6 mating with 2n4 leads to sterile offspring because the two sets of chromosome don t synapse correctly BUT error in mitosis in which doubles chromosome number leads to allopolypoid individuals each chromosome has a homolog and meiosis can continue but now 2n10 39 speciation by polyploidy is common in plants speciation by polyploidization is VERY fast sympatric and common Lecture 21 History of Life Major Innovations transitional feature trait in fossil species that is intermediate between an extinct and extant species between ancestral and derived species most powerful evidence for theories evolution by natural selection is internal consistency data from independent sources agree in supporting predictions of the theory only the fossil record provides direct evidence about what organisms lived in the past looked like where they lived and when they existed INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 most fossils form when most or all of an organism is buried in ash sad mud or any other sediment then organic remains may be preserved the weight of sediments can compress organic material into a thin carbonaceous film a cast of remains may be formed if the material decomposes after buried or a per mineralized fossil can be forms if the material dissolves slowlyhardens to stone fossilization is rare event limitations of fossil record habitat bias organisms living in area with a lot of sediments are more likely to make fossils than those in other types of habitats taxonomic and tissue bias slow decay is crucial to fossil formation so organisms with hard parts are more likely to make fossils than softer organisms temporal bias recent fossils are more common than old ones abundance bias organisms that are widespread abundant or present for longer are more likely to leave fossils than those that are rare local or ephemeral scientists can use radiometric dating based on decay rates of radioactive isotopes to determine more accurate dates to events in fossil record as years before the present than using rock formations Life s TimeLine Precambrian interval between Earth formation and appearance of animal groups divided into 3 eons Proterozoic eon newest present oxygen levels sponges algae first eukaryotic fossHs Archaean eon evidence of oxygenic photosynthesis photosynthetic cells origin of life Hadean eon oldest first oceans liquid water Earth moon and solar system formation Phanerozoic eon interval between 542 million years ago end of Precambrian and present day divided in 3 eras each divided into periods then into epochs Paleozoic era oldest appearance of most animal lineages origin and first diversification of animals land plants and fungi INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 Mesozoic era extinction of dinosaurs in terrestrial areas gymnosperms were most dominant plants and dinosaurs most dominant animals Cenozoic era newest Paleogene Neogene and Quaternary periods on land angiosperms are most dominant plants and mammals largest vertebrates Lecture 22 History of Life Radiations and Extinctions daptive radiation a single lineage produces MANY descendant species with different adaptive forms very quickly adaptive radiation criteria monophyletic group speciate rapidly diversify ecologically occupy many different niches two mechanisms to lead to adaptive radiation ecological opportunity availability of new types of resources drives wide array of radiations 39 distinctive adaptive traits for different environments species begin from different evolutionary starting points then adaptive radiation filled same niches in different areas morphological innovation evolution of key morphological trait that allowed descendants to live in new areas exploit new resources or move in different ways trigger many diversification events basically new ways to exploit resources make species diversify quickly Cambrian explosion the rapid adaptive radiation in the Cambrian period in which creatures with shells skeletons legs heads eyes muscles brains etc evolved huge increase in size and complexity of animals an also diversification of how animals made a living doushantuo ediacaran and cambrian fossils show what happened during explosion higher oxygen levels predation new niches and new genesbodies fauna collection of species INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 mass extinction rapid extinction of many lineages at least 60 of species in 1 million yrs extraordinary temporary changes in environment like volcanoes EndPermian extinction is the biggest and worst ever background extinction lower average rate of extinction when no mass extinction normal environmental changes predation disease or competition kills populations usually die out during gradual changes impact hypothesis hypothesis for extinction of dinosaurs suggesting asteroid struck Earth and killed 6080 of multicellular species killing mechanisms tsunamis ash layers fires changes in chemicals in water atmosphere craters predictions we should find craters that connect with the time period of the impact and chemical markers like iridium World Went to Hell hypothesis suggests extreme global climate change such as high 002 levels global warming and anoxic conditions in oceans killing mechanisms suffocation ocean acidity predictions look for chemical evidence in rocks and fossils Precambrian empire strikes back mass extinctions allowed for microbial populations to dominate the world for short period of time deathly to complex life because of production of hydrogen sulfide we are in completion with microbes H28 is possible killing mechanism and may be the cause of 10 mass extinctions mass extinction is most similar to evolutionary process of genetic drift Lecture 23 History of Life Rare Earth Review consequences of extinctions extreme bottleneck INTRODUCTORY BIOLOGY 180 Thursday November 5 2015 major shifts in environment adaptive radiation diversification Rare Earth hypothesis complex multicellular life and intelligence required rare astrological and geological events on the planet simple life may be common but complex life requires specific environments in order to occur argues extraterrestrial life is unlikely and rare requirements for complex life 39 right location in the right galaxy like radiation levels right planets surrounding it right orbit shape close to a circle and distance for temp stabe orbit plate tectonics large moon 39 right timeline of evolution with occurrence of right timing of all other environmental circumstances criticism current technology limits testing of required conditions for Rare Earth hypothesis accurately 39 oxygen not a requirement for multicellular life some believe Rare Earth hypothesis is explanation for why life arose on Earth here not a hypothesisprediction for other life in the universe alternate point of view Principle of Mediocrity Earth is typical rocky planet in universe and because we have so much life and the planet isn t really that special out of the whole universe its likely that the universe teems with life misconceptions do not need same Earth conditions to sustain life elsewhere lots of Earthlike planets have been found probability of all these rare events increases as we find more similar planets
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