BIOL 152 1st Edition Lecture 4Outline of Last Lecture I. Case Study 4. Malaria: Co-evolution of humans and a parasitea. Summary of Case Studyb. Ted Talk Summaryc. Wadman Article SummaryOutline of Current Lecture II. Exploring evolutionary processes a. Natural Selectioni. Darwin and Wallace1. Observations generate hypotheses2. Artificial selection as a proxy for natural selectionii. Directional, Disruptive, Stabilizingb. Mating System Influencesi. Sexual selectionsii. Non-random matingc. Immigration/Emigrationd. Population Size/Genetic DrifIII. Species and SpeciationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Biodiversityb. Maintaining continuous variationi. Gene flowCurrent LectureWhy is the Hardy-Weinburg Equilibrium so important when talking about evolution?- Evolution occurs when Hardy-Weinburg equilibrium is NOT met.Evolution and its processes- Natural Selection- proposed by Charles Darwin and Alfred Russel WallaceHow did Darwin discover it?- Personal observationso Ex: insect collecting as a kid (gained him a sense of biodiversity)o Went around the world as a naturalist on the “Beagle” to gain more knowledge of the world around him- Compared floras and faunas- Considered the concept of adaptation- Particularly fascinated with the animals of the Galapagos Islands (more specifically the marine iguana, posed the question of why they were the only iguana species that could swim, did they adapt to their environment?)Alfred Russel Wallace- Also fascinated by insects- Collected to raise moneyo Found a job sending back specimen from alien landso Wallace saved only notes when his biggest lot of specimen sank in a ship accident- Traveled to Indonesia/Malaysiao Sent ideas to Darwin Motivated Darwin to publish Coauthored a publication, presented to London societyNatural Selection- Proposed by Darwin and Wallaceo Given that: Organisms “over produce” (Thomas Malthus) Size of population is stable Resources are limitedo Individuals compete to surviveo Also… Variations happen (individuals differ) Variation is inheritedo Variants best adapted to environment produce more offspringo Such individuals are “selected” to surviveWhat is survival of the fittest?- Think “fitness” in terms of reproductionDarwin’s Proof- Demonstrated natural selection o Artificial selection Pigeons, dogs, cats, crops Strong selective pressureso LONG time periods Had a long time period to work with due to geological evidenceo Extinction Evidence from fossilsDarwin and Wallace concluded:- Natural selection is an important evolutionary process resulting in:o Adaptation o Diversificationo Origin of speciesNatural Selection and Populations- Natural selection acts on phenotypes (which are expressed due to genetics and environment interactions)o IF The phenotype variation is controlled by genetic variationo THEN Traits can be inherited Genotypic frequencies change Change over time= evolution- Three types of Natural selectiono Directional Selection- favoring one phenotype over another, shifs the mean phenotype frequencyo Disruptive Selection- selection favors extreme phenotypes, average phenotypes removedo Stabilizing Selection- selection favors average phenotypes, extreme phenotypes removedYES AND NO’S ABOUT NATURAL SELECTIONYES:- Variation exists- Can be inherited- More individuals with favorable traits survive and reproduce- Traits spread in population- Alleles increase in frequencyNO:- Not just “survival of the fittest”Mating SystemEvolution without Natural Selection- Sexual Selectiono Special caseo Discussed by Darwino Females prefer males with certain traitso May not be adaptiveo Leads to “run away” selection Those traits become more common due to the females mating with thesemales- Non-random Matingo Change caused by choice Offspring allele frequency differ because of thiso Lekking Males congregate in display areas Females visit and choose potential matesImmigration and Emigration- Migration of individuals o Fastest way to evolve- Extremely important in human historyPopulation Size- Bigger population, less likely for change to occur- Small population sizeso Chance effects can change allele frequencyo Genetic Drif- result of chance events in finite populations Random change in small populations have major effects Ex: population bottleneck- population crash leads to a small population (frequency of an allele dramatically changes) Ex: founder effect- few individuals “found” new population (migration or dispersal cause it)None of the processes are related to adaptation to the environment.Species and speciationBiodiversity- - Depends on contexto Organismal context= “number of species on Earth”o Systematic context= developing hypotheses about species’ history (origin and distribution)o Ecological context= how the environment originates/ maintains species- Synthesis=o Goes up or down in numbers of lineageso Systematics + population ecologyBIODIVERSITY OCCURS- Observing variation o Individuals differ within and among the populationo Continuous= microevolution No “gaps” or “major shifs” in featureso Discontinuous= Macroevolution Gaps or major shifs in features (can give different names to a species dueto characteristic
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