1st Edition BIOL 152 Lecture 4 Outline of Last Lecture I Case Study 4 Malaria Co evolution of humans and a parasite a Summary of Case Study b Ted Talk Summary c Wadman Article Summary Outline of Current Lecture II Exploring evolutionary processes a Natural Selection i Darwin and Wallace 1 Observations generate hypotheses 2 Artificial selection as a proxy for natural selection ii Directional Disruptive Stabilizing b Mating System Influences i Sexual selections ii Non random mating c Immigration Emigration d Population Size Genetic Drif III Species and Speciation These 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 Biodiversity b Maintaining continuous variation i Gene flow Current Lecture Why 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 Wallace How did Darwin discover it Personal observations o 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 money o Found a job sending back specimen from alien lands o Wallace saved only notes when his biggest lot of specimen sank in a ship accident Traveled to Indonesia Malaysia o Sent ideas to Darwin Motivated Darwin to publish Coauthored a publication presented to London society Natural Selection Proposed by Darwin and Wallace o Given that Organisms over produce Thomas Malthus Size of population is stable Resources are limited o Individuals compete to survive o Also Variations happen individuals differ Variation is inherited o Variants best adapted to environment produce more offspring o Such individuals are selected to survive What is survival of the fittest Think fitness in terms of reproduction Darwin s Proof Demonstrated natural selection o Artificial selection Pigeons dogs cats crops Strong selective pressures o LONG time periods Had a long time period to work with due to geological evidence o Extinction Evidence from fossils Darwin and Wallace concluded Natural selection is an important evolutionary process resulting in o Adaptation o Diversification o Origin of species Natural 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 variation o THEN Traits can be inherited Genotypic frequencies change Change over time evolution Three types of Natural selection o Directional Selection favoring one phenotype over another shifs the mean phenotype frequency o Disruptive Selection selection favors extreme phenotypes average phenotypes removed o Stabilizing Selection selection favors average phenotypes extreme phenotypes removed YES AND NO S ABOUT NATURAL SELECTION YES Variation exists Can be inherited More individuals with favorable traits survive and reproduce Traits spread in population Alleles increase in frequency NO Not just survival of the fittest Mating System Evolution without Natural Selection Sexual Selection o Special case o Discussed by Darwin o Females prefer males with certain traits o May not be adaptive o Leads to run away selection Those traits become more common due to the females mating with these males Non random Mating o Change caused by choice Offspring allele frequency differ because of this o Lekking Males congregate in display areas Females visit and choose potential mates Immigration and Emigration Migration of individuals o Fastest way to evolve Extremely important in human history Population Size Bigger population less likely for change to occur Small population sizes o Chance effects can change allele frequency o 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 speciation Biodiversity Depends on context o 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 lineages o Systematics population ecology BIODIVERSITY OCCURS Observing variation o Individuals differ within and among the population o Continuous microevolution No gaps or major shifs in features o Discontinuous Macroevolution Gaps or major shifs in features can give different names to a species due to characteristic changes
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