Unit 3 Evolution 10 12 2015 Lecture 20 Chapter 22 Why is all this heritable genetic variation important o Example Italian Wall Lizards In 1971 5 lizards from the Kopiste Island were introduced intentionally to the Mrcaru Islands habitat change The observations over the next 30 years showed that the lizards on the new island looked and behaved different Diet change o The new island lizards ate more plant material vs the lizards still in the Kopiste Island ate mainly insects o The new island lizards had bigger jaws it is harder to chew plants Appearance than insects o The new island lizards have bigger stomachs and have a modified digestive system with an entirely new structure cecal valve Are these changes because of evolution What would you need to know How would you find out A Evolution is something that happens in populations NOT individuals Evolution change in time in the properties of self replication organism As Darwin first described evolution as a descent with modification Changes the genetic nature of populations o Changes in genotype frequency changes the phenotype Can lead to changes in the mean phenotype of populations Can lead to the differentiation of populations Over the long term it can lead to the formation of new species Results in branching pattern of change over time Example Change through time o Soapberry bugs Eat on seeds have to stick their beaks through the paper shell and stick their beak all the way down to the seeds When people started planting the golden rain tree these bugs beaks changed because the fruit is different Shorter beaks From 9mm to now 7mm Bugs do not need a long beak anymore to reach the seeds Beaks match what is appropriate to their food Study questions for lecture 20 1 Define evolution a biological definition Change in time in the properties of self replicating organisms 10 16 2015 Lecture 21 unchanging species Aristotle Plato Descent with modification the idea that living species are descendants of ancestral species that were different from the present day ones also defined more narrowly as the change in the genetic composition of a population from generation to generation A The Darwinian revolution challenged traditional views of a young Earth inhabited by o Viewed species as fixed or unchanging He concluded that life forms could be arranged on a ladder scale of increasing complexity o Platonic idea we are all flawed copies of the perfect male female figure He did not think species changed no evolution Charles Lyell o Proposed the idea that the same geologic processes that are seen today are the ones that occurred in the past and at the same rate o Uniformitarianism idea that we believe that the physical processes we see today were uniform in the past o Most compelling evidence sedimentary geology and fossils Jean Babtisle Lamarck o Proposed The idea of use and disuse parts of the body that are used extensively become larger and stronger while those that are not used deteriorate The idea of inheritance of acquired characteristics stated that an organism could pass the acquired modifications to their offspring o 1st comprehensive idea of evolution Giraffes their necks evolved to a long length over time o Mostly wrong because he did not know anything about genetics Carlos Linnaeus o Can classify things by order classification He developed a two part binomial format for naming species He based his classification on the pattern of the organisms creation instead of on resemblances among species o Named a lot of things mainly plants If he was attracted or liked someone he would name a plant after them If he disliked someone then he would name a weed after them o Approximately 100 years before Mendel s ideas and studies Malathus o constant struggle of existence o A continuous struggle for resources because more offspring born Charles Darwin o Natural selection piece of evolution o Parents o Embarked from England on the Beagle where he was able to go to the Galapagos Islands collect and study birds These birds lead to his conclusion on natural selection and adaptation o Natural selection is a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits Natural selection acts on the individual while evolution affects the population Study questions for lecture 21 1 Give the more precise population genetics definition of evolution Given by Dr Brian on 10 16 Evolution is a change in allele or genotype frequencies within a population across generations leading to a change in phenotypes 2 Define natural selection Darwin and Wallace s proposed mechanism for evolution and explain how it is different from Lamarck s proposed mechanism for evolution inheritance of acquired characteristics Lamarck s hypothesis of inheritance did not take in to account the understanding of genetics He said that the change occurred on the organism level over time while Darwin proposes that change is based on a population level Lamarck also says that all organisms stated off the same with no variation while in Darwin s theory of natural selection a population must start off with variation due to a mutation Lastly Lamarck says that a change in characteristics occurred due to the need or desire that an organism possessed while Darwin says that natural selection favors the best suited individuals and those are the characteristics passed on to the offspring 3 Which famous islands did Darwin visit on his trip around the world and what kind of animal that he found there influenced his later thoughts about evolution Read section 22 2 in the book Galapagos Islands birds 10 19 2015 Lecture 22 Chapters 23 1 23 4 A Evolution and Genetics Organisms generations o Evolution change in allele or genotype frequencies within a population across o Population a group of interbreeding organisms Within a population we can keep track of the phenotype and genotype frequencies We can also find the allele frequency by dissociating the two alleles that each organism has o To see if a population evolves through time we need to keep up with these 3 frequency changes over generations o All alleles at any locus have a frequency in a population between 0 and 1 Frequency of alleles in the parent generation is equal to the frequency of expected alleles in the gametes each parents alleles 2 apiece dissociate during Meiosis An allele is fixed only when one allele is present In other words there is no variation at
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