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Week 2 of Evolutionary biology

by: America Seach

Week 2 of Evolutionary biology BIOL

Marketplace > Clemson University > BIOL > Week 2 of Evolutionary biology
America Seach
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About this Document

These are the notes from the second week of lecture.
Evolutionary Biology
Class Notes
evolution, Biology, Clemson, 3350




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This 4 page Class Notes was uploaded by America Seach on Wednesday January 27, 2016. The Class Notes belongs to BIOL at Clemson University taught by Sears in Spring 2016. Since its upload, it has received 83 views.


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Date Created: 01/27/16
NOTES 1/19/16 - Homology: classically defined as curious structural similarity between species despite different structures; today defined as similarity between species that results from inheritance of traits from a common ancestor - Homoplasy: similarity in the characters found in different species due to CONVERGENT EVOLUTION, parallelism, or reversal- NO COMMON DESCENT; have no relation to something that looks similar to it (may look the same but aren’t related); doesn’t have to be animals- can be plants as well for structural homologies - Why is homology important? --- it allows us to connect a “family tree”; lets us test the idea of common ancestry; descent with modification produces nested sets of shared traits; shows when each trait emerges; can make predictions - Predictions in fossil records: Norrell and Novacek (1992) find correlation between actual order of appearance with predictions; supports idea of descent from common ancestor; only case that didn’t work was hadrosaurs - Molecular homology: based off of DNA and chromosomes; both common chimps and bonobos share with us is the paired CMT1A repeats that can induce unequal crossing over- difficult to explain under the view that humans and chimps were separately created; can use DNA to show which species are more closely related than others and if they have a common ancestor - Predictive test of Ancestry using Molecular Homologies: o Processed pseudogenes are distinguished from their mother genes because they lack introns and promoters o Theory of descent: they should form nested sets; that they do is evidence of common ancestry - if they have a shared phylogeny, then all ancestors should have the pseudogene - pseudogenes that encompass the most species are the oldest; more recent show less species that have it - Universal Molecular Homologies: the genetic code - Why common ancestry matters: it is a foundation upon which all modern biology is built (including biomedical science); allows us to look at specific genes and whether they are mutations in one organism and not in others- infer causality - The age of the earth: - Uniformitarianism: the assumption that processes identical to those at work today are responsible for events that occurred in the past; first said by James Hutton- founder of modern geology; The earth was once a supercontinent that split at a very slow rate of 2.5 centimeters per year and it would take 148 million years for the continents to be where they are - Know age of earth by radiometric dating; based off of radioactive isotope and comparing how much of the parent isotope is still active in comparison to the daughter isotopes; parent values decrease as daughter values increase; can use halflife and remaining amounts to calculate dates - The age of the earth matters because it gives us a starting point of where everything came from - Evolution by natural selection: based off of the color of mice fur and their surroundings; mismatch the background shows greater chance of being attacked; natural changes in coat color without help from outside sources other than genes - Artificial selection: domesticated animals and plants; FW2.2; increase the frequency of desirable traits; making tomatoes (plants and animals) that are larger than an unmanipulated tomato; we are changing it - Evolution by natural selection: 1. individuals within a population differ from one another- VARIATION 2. the differences are, at least in part, passed from parents to offspring- HERITABLE VARIATION 3. some individuals are more successful at surviving and reproducing than others 4. the successful individuals are not lucky; instead they succeed because of the variant of traits they have inherited and will pass on to their offspring- ISNT JUST BY CHANCE - LOGIC OF THE THEORY OF NATURAL SELECTION (Mayr): based on 5 facts 1. all species have such a great potential fertility that their population size would increase exponentially if all individuals that were born would reproduce successfully 2. except for minor and major fluctuations, normally display stability 3. natural resources are limited 4. no two individuals are the same, displaying enormous variability 5. much of this variation is heritable HAS 3 INFERENCES ALSO---- SEE POWERPOINT - natural selection has no intent while artificial selection has intentions - populations evolve - selection acts on individuals - what is fitness? An individuals ability to survive and reproduce 1/21/16 - Evolution of Flower Color in Snapdragon: seeing if a certain color affects the germination of flowers - Postulate 1- Individuals differ from one another: have different genotypes (SS, Ss, and ss); - Postulate 2- variation is inherited - Postulate 3- do individuals vary in success? Test by gender - Postulate 4- is reproduction nonrandom? Used seeds to see which one produced more - Offspring changed in 2% after one generation - Evolution of Beak Shape in Galapagos finches: all finches came from one common ancestor and they are divided into different groups based on how they feed; - Medium ground finch: studied on the island of Daphne major (very small in size); - Postulate 1: population is variable- beak sizes have different sizes and depths (it occurs naturally) - Post 2: is it heritable? Take the average of the parents and compare that to the offspring; want the slope of the line to be close to 1; large beaked parents produce large beak children; BMP4 expression may cause larger differences in beak size - Post 3: do individuals vary in success? When it rains, the seeds are smaller and therefore smaller beaked birds can survive; when there is a drought, the seeds are bigger and the smaller bird population dropped - Post 4: after the drought, the beaks became larger overall - Did the population evolve? The average beak size after the drought increased by almost 1 millimeter - Natural selection acts on phenotype while evolution causes changes to allelic frequencies; populations only evolve if the traits are heritable - New traits can evolve- after one gene is fixed, other genes start to be able to be manipulated - Guppies have different sized gonopodia based on predation- larger size slows it down so lives in lower predation areas - Natural selection is nonrandom, but it is not progressive - Traits can only evolve when their environment requires it - If you change the environment, the genes that may have evolved in the previous environment may not work or be beneficial in another - You don’t do anything to someone else, unless its benefits their own genes: new male lion comes into a pride and kills all the previous male’s babies and make his own cubs - The evolution of evolutionary biology: Darwin’s theory had three problems- 1. Variation 2. Inheritance- had no idea that mutations were possible and could be passed on from parent to offspring; he thought it was all due to blending inheritance 3. Time- didn’t have the ability to correctly date things back to when they occurred; also had no idea how old the world was - Modern synthesis (Fisher and Sewell): restating of Darwin’s 4 postulates 1. Individuals vary as a result of mutation creating new alleles, and segregation and independent assortment shuffling into new combinations 2. Individuals pass their alleles on to their offspring intact 3. In every generation, some individuals are more successful at surviving and reproducing than others 4. The individuals most successful at surviving and reproducing are those with the alleles and allelic combinations that best adapt them to their environment


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