BIOL 3350, Week 1 & 2 Notes
BIOL 3350, Week 1 & 2 Notes 12050 - BIOL 3350 - 001
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This 8 page Bundle was uploaded by Kennedy Deaver on Friday January 8, 2016. The Bundle belongs to 12050 - BIOL 3350 - 001 at Clemson University taught by Dr. Michael Sears in Fall 2016. Since its upload, it has received 95 views. For similar materials see Evolutionary Biology in Biological Sciences at Clemson University.
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Date Created: 01/08/16
Biol 3350 Chp. 1 Evolution, what is it? o Genetic changes over time between generations Why study evolution? o Underlies every discipline in biology o Drug resistance o Medical disorders – consequences of past evolution (ex: baseball rotator cup issues because ancestors on all fours) Why is evolutionary thinking important? o HIV: a case study Need evolutionary understanding to answer What is HIV? o Retrovirus o Spreads through contact with bodily fluids o Different parts of planet have different levels of infection o Different people affected in different parts of the world How does it spread? o Multiple different ways in different places o Lifecycle Proteins on outside of virus bind to CD4 on cells Fuse with membrane and then empty out genetic materials Converts RNA to DNA and integrates into host DNA Uses transcription and translation to make more of itself o Cell has to have certain receptors to get HIV Attacks T cells especially o First contract AIDS, initial spike in replication then drops off (acute phase) o Chronic phase o At some point causes immune response and then stresses out immune system/attacks new T cells AZT o Stops reverse transcriptase o Cannot turn RNA into DNA (game over for retrovirus) o Longer patient on AZT, less effective it became Virus not responding or body breaking it down Concentration to have benefit had to increase over time (AZT basically ineffective over time) Longer on therapy = resistance Why does it fail? o Reverse transcriptase makes mistakes o Change it so it doesn’t find AZT or puts in then pulls it out o Makes virus immune to drug Mutations give rise to new variations Natural selection Other therapies o Lots of ways to attack antivirus o BUT, just pick one then few months later virus comes back o Lots of mutations in AIDS population SO Multi-drug treatment (cocktail) Decrease odds that virus will have enough mutations to overcome all drugs HAART Better chance to live longer if stick to the drugs Are humans evolving as a result of HIV pandemic? o Maybe? Delta 32 – resistant to AIDS virus See least AIDS where most ppl have delta 32 Potential to have impact but too early to tell Where did HIV come from? o Every virus traced back to original ancestor (phylogeny) o Create family tree o HIV similar to SIV – trace back to original organisms Why are untreated HIV infections usually fatal? o Have to have enough copies in blood to pass it along o High replication makes it lethal but transmits well Chp. 2 – The pattern of evolution Two opposing views o Special creation Species are immutable and variation among individuals is limited All species created separately and genealogically unrelated to each other Young Earth (6000 yrs) o Evolution Diversity due to descent with modification All life forms related Old Earth Microevolutionary change – variation across generations o Ex: beak sizes in Darwin’s finches Macroevolutionary change – variation across generations leads to speciation over time Evidence to see which one is more supported Evidence of microevolution o Voluntary wheel running behavior of mice Evolve to have higher activity o Examples of selective breeding Dogs – lots of variation Cattle – humans have created variation Corn Wild mustard o Flowering time shows genetic differences o Vestigial structures Kiwi wing – evolve flightlessness Snake – limbs, has genes to grow legs still Human pelvis (coccyx) – evidence of tail in ancestors Goosebumps – remnant of thermoregulatory past when had more hair In genome… Pseudogenes – genes we have that are inactive but active in other species o Evolution in real time Stickleback – freshwater vs marine Why microevolution matters o Need policies o Pests/Invasives – develop resistance o Conservation – conserving species, need to know about genetics Evidence of Speciation o What is a species? Hard to define o Biological species concept – Ernst Mayr Species are populations or groups of populations in which individuals are interbreeding or have potential to interbreed and produce fertile offspring o Phage 6 – virus that infects pseudomonas bacteria Strain that can infect other bacteria Two strains no longer exchanging genetic info – two lines that are considered different species o Fruit flies Lived on different substrates When put together, flies tend to breed with those that eat the same thing as they do Producing reproductive isolation o Stickleback Body size differences (genetically based) depending on location Gill raker sizes depending on what they’re eating o Ring species Spread north = more complex songs Meet and cannot interbreed in one part of the ring Why speciation matters o Human disease o Zoonotics – flu jumps from animals to humans o Conservation – what different things are Evidence of Macroevolution o Fossils exist and most don’t look like things that are alive today o Can predict where in time you should find certain fossils o Things in fossil records resemble things alive today (in same area things resemble each other and not found in distant places) o Transitional forms Blenny – terrestrial fish Has intermediate forms Common ancestor Dinosaurs and birds Archaeoptreryx transitional form from dinosaur to bird Link between early dinosaurs and birds and finding intermediates Turtles Early stages of life look like evolutionary past Why macroevolution matters o Evolutionary medicine – look at past to understand disorders now Evidence of common ancestry: all life-forms are related o Homology – similarities (despite different functions) between different species – inherited from common ancestor o Homoplasy – due to convergent evolution but NOT common ancestry o Structural homology Bones Orchids Why is homology important? o Helps construct evolutionary tree (phylogeny) Use parsimony Represents descent with modification o Helps to make predictions in evolutionary systems Longer the line = older lineage/older trait Norrell and Novacek 18/19 cases highly correlated Molecular homologies o Repeats lead to misalignment in crossing over o Can end up with diseased genotypes o Nearest ancestors have same mutations and same problems but go further back and ancestors don’t share same defects o Processed pseudogenes – nonfunctional in DNA Cuts out intron and inserted at another locus after reverse transcription Accumulate mutations Older = further back in lineage More recent = found in less species o Genetic code itself is a universal molecular homology Works the same across almost all organisms Suggests common origin Why common ancestry matters o Kriston McGary Mutations lead to some phenotype The age of the earth o Geological time scale o Uniformitarianism – idea that processes we observed now occurred at same rate in past as they do now Earth must be really old o Use radiometric dating to date age of earth Radioactive isotopes break down at certain rate Use rate to age things Decomposition rates aren’t sensitive to climate, temp. Why does age of earth matter? o Earth has to be as old/older than oldest forms of life known KNOW o 5 characteristics that distinguish evolution from special creation Chp. 3 Evolution by natural selection o Mice on beaches Mismatch background then attacked more by predators Could lead to evolution by shift in allelic frequencies Artificial Selection: Domestic Animals and Plants o We are giving plant/animal high reproductive fitness o Tomatoes Wild tomato has genes that limit its growth (fw2.2) o In nature, could be selecting against variants Evolution by natural selection o KNOW 4 postulates Necessary for evolution to occur by natural selection o 1. Individuals in a population differ from one another o 2. The differences are heritable o 3. Some individuals are more successful at surviving and reproducing than others o 4. Successful individuals succeed because the variant traits they have inherited and will pass to their offspring The Logic of the Theory of Natural Selection o Five Facts 1. Populations would increase exponentially 2. Populations normally remain fairly stable 3. Resources are limited so struggle amongst members of population 4. Populations display variation 5. Variation is heritable Darwin’s theory of evolution by natural selection o Mice population (different colors) Variation is inherited More individuals are born than can be sustained by environment Some variants survive and reproduce better than others Survivors contain less dark alleles – population mean has moved to lighter colored mice Important points o Natural selection is a process that results in descent with modification, or evolution o Selection acts on individuals o Populations evolve o Evolution is a statistical phenomenon o Natural selection has no intent, unlike artificial selection Which works best in environment What is fitness? o Individuals that survive had higher fitness o Good fit in environment then survive well o Not most physically fit organisms Evolution of Flower Color in an Experimental Snapdragon Population o Exhibit Darwin’s 4 postulates o Evolved means allele frequency has changed, not necessarily genes o White flowers visited more than yellow o Has evolution occurred? Frequency of white 2% higher Small gradual change Evolution of beak shape in Galápagos finches o How do you get speciation from some founding population Common ancestor o Medium ground finch studied on Daphne Major o Is the trait (beak depth) variable? Yes, variation in population in nature o Is the variation heritable? Heritability – resemblance between parents and offspring due to genetics Small parents = small beaked offspring Large parents = large beaked offspring BMP4 gene may drive differences in beak size o Do individuals vary in success at surviving and reproducing? And is this nonrandom? Crash in population with drought After drought, average size a little larger (bigger beak = more access to food = better survival) o Did the population evolve? Offspring have increased in beak size Evolution cannot predict future No ideal phenotype Natural selection acts on individuals but its consequences occur in population o Individual itself has not changed o Evolution does not always proceed as quickly as possible to produce best adapted organism Natural selection acts on phenotypes but evolution consists of changes in allele frequencies o If beak size not heritable – offspring will be all different phenotypes o If beak size is heritable – offspring will look more like parents Selection isn’t forward looking o Does not have access to future o Evolution only uses info from past to produce future phenotype o Makes things good enough to get genes to next generation and survive Can new traits evolve? o Corn continued to evolve to more oil content Epistatic interactions can produce increases Could be accumulating mutations o Carnivorous plants Natural selection does not lead to perfection o Depending on environment, tradeoffs occur o Preferred trait could be preyed on more o Evolution often lagging behind Natural selection is nonrandom but not progressive o Changing target every year o Traits can only evolve to extent environment selects for it o Never use terms higher or lower life forms Fitness is not circular o Fit after environment set it up not fit to begin with Selection acts for good of individual, not good of species o Higher fitness – more genes represented in future generations o Male lions in new pride kills the babies (not good for species but gets rid of others’ genes) o Viruses try to make it to next generation Evolution of Evolutionary Bio o “Nothing in biology makes sense except in the light of evolution” Three serious problems with the evolutionary theory o Variation Didn’t know about genes o Inheritance Mendel’s work explained mutation rates and how variation is maintained Ways for traits to be inherited Skin color Blending inheritance Mutation could take off o Time Given rates of evolution, did not seem like earth had been around long enough for variation we have No idea how old the world was The modern synthesis o Fisher and Wright o Can change postulates to include modern knowledge
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