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week 8 409

by: Mary-elizabeth Notetaker

week 8 409 Bio 409

Mary-elizabeth Notetaker
U of L

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week 8
Evolutionary Biology
Jeffery Bara
Class Notes
Bio, bio409, evolutionarybiology, UofL
25 ?




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This 2 page Class Notes was uploaded by Mary-elizabeth Notetaker on Sunday October 16, 2016. The Class Notes belongs to Bio 409 at University of Louisville taught by Jeffery Bara in Fall 2016. Since its upload, it has received 2 views. For similar materials see Evolutionary Biology in Biology at University of Louisville.


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Date Created: 10/16/16
Week 8 Sunday, October 16, 2016 8:28 PM • Testing adaptive hypothesis ○ Adaptionist program ○ Alternative explanations ○ 3 approaches to evaluating adaptive hypotheses • Adaptive trait: ○ Heritable thru transmission of genes ○ Enhances reprod success ○ Results from selection for its current fx • Adaptionist paradigm- org is atomized into "traits" and these traits are explained as stxs optimally designed by NS for their fxs ○ Problem: orgs are integrated entities, not collections of discrete traits • Alternate explanations for creating adapatations: ○ No adaptation and no selection for the hypoth'd adaptive trait  Selection could be acting but doesn’t cause the thing that looks adaptive □ Genetic drift can fix nonadpative alleles □ Selection can take a long time to purge deleterious alleles □ Even if a better allele arises, drift can keep it from getting a foothold ○ Selection and adaptation are happening, but at a diff correlated trait  Plietrophy- one locus affects multiple traits, creating variation in them to be correlated □ Ex) genes that cause long arms also cause long legs… correlated from pleitrophy □ But… long arms could be only bc linked to long legs..long arms have no adaptive value  Antagonistic pleiotrophy- creates genetic tradeoffs- assoc btwn the 2 traits is such that genos that have the good form of trait 1 have the bad form of trait 2 □ Selection on one trait can cause evol of the less beneficial form of the other trait □ Ex) horned beetles can either mx horn size or teste size but not both  Horns more imp for fighting for mates so selected for over teste size ○ Selection w out adaptation ( no heritable variation)  Ex) NS for green flower color.. Here Green color cant be adaptation bc its caused by food coloring, not genes ○ Trait is useful but does not come about due to NS  Acclimatization(Physiological adaptation): □ Ex) more RBC in ppl at high altitude… not adaptation  Traits that are inherited by communication rather than genetics (language… tools)  Phenotypic plasticity- plastic response can actually be an adaptation □ Ex) helmet and spine of daphnia are induced in resp to cues from predators  Presence/absence of spines not adaptation… could change with time  Ability to repond to envir and make those spines when needed is an adaptation □ Ex) leaf shape (broad v narrow) is ddiff above/below the water in crowfoot plant Convergent traits are adaptive but diffs btwn pops are not ○  Ex) hooves lengthen the stride of an animal, bc bones that were part of the ancestors foot move up into the leg □ So… hooves are an adaptation for greater speed…. Arose indep in mult lineages □ Convergent evol of hooves is good evidence for adaptation □ But… diff btwn groups could be from chance or developmental particulates of groups ○ Exaptation- ft that performs fx but that was not produced by NS for its current use  Ex) protofeathers- probable that feathers arose as adaptation that provided insulation □ Created expatation for flight □ Or… elaborate feathers used in mating displays,created exaptation for flight • 3 approaches to evaluating adaptive hypoth ○ Experimental eval- good exp controls possible sources of variation among outcomes  Ex) greene et al- green thought banded winged fly that would wave wings when distrubed was trying to imitate leg wavng in jumping spider(to intimidate fly that preys on it) □ Competing hypoth:  Flies do not mimic jumping spiders(stripes are there for some other purpose, or by chance(null)  Flies mimic jumping spiders in order to deter other nonspider predators  Flies mimic jumping spiders specifically to deter the spiders themselves □ Results:  All flies were eaten in all exp gorups when exposed to other predators □ Characteristics of good exp: Bio 409 Page 1 □ Characteristics of good exp:  Include control tratments to confirm that the effect you are studying is due to the trait of interest and not the exp manipulation  Treat all exp indivs exactly the same, except for the one thing you are varying for the treatment  Randomize your exp it helps you avoid unanticipated bias  Replicate your exp… avoids misinformation from unusual indivs,allows you to det how strong your conclusions are thru statistics ○ Observational eval ○ Comparative studies  Ex) adaptive hypoth- are large testes in flying foxes an adaptation to inc in reprod success in larger social groups? a) Correlation based on species b) Could have arisen due to singel change in shared common ancestor c) Graphig the only phylogenetically indep events, we see there is much less evidence supporting the hypoth  Felsensteins cross species correlation method: □ When species diverge from common ancestor, does species that evolves larger group sizes also evolve larger testes? ○ Don’t assume every trait is adaptive and from NS Bio 409 Page 2


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