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Evolution: descent with modification Genetic change over time in a common ancestor which makes an organism more suited for an environment Unifying principle of all biological sciences Universally accepted fact What factors can change DNA over time? DNA changes can result in organismal changes Phenotype vs genotype Evolutionary Terms Adaptive trait-any form or function that allows an organism to survive in its current environment Fitness-measure of reproduction, ability to produce viable and fertile offspring Gene pool-all the genes of a population Allele-different forms of a gene (trait) Mutation-change in the DNA; the original source of genetic variation History of Evolutionary Thought and Ideas 400 BC Plato, Aristole: Every object was an imperfect copy of an ideal form; diversity of organisms some more complex than others, species organized by degree of complexity 1400s Century Global exploration: discovery of organisms never seen before 1600s discovery of fossils; organisms that were no longer found on earth, but they were similar to some still alive History of Evolutionary Thought and Ideas 1700s Carolus Linnaeus began taxonomy of living organisms based on differences and similarities (binomial nomenclature) 1700s Leclerc (Count Buffon) documented with evidence descent with modification generation after generation, will result in variation 1700s Erasmus Darwin (Charles’ grandfather) wrote on common descent based on development, artificial selection, vestigial structures 1798 Malthus, population size correlates with famine, disease, war 1830 Lyell, “Principle’s of Geology” by studying the earth’s layers, natural catastrophes, determined that the earth was not 6000 years old, but millions History of Evolutionary Thought and Ideas 1700s careful studies of differences and similarities between organisms, Lamarck’s Inheritance of Acquired Characteristics, giraffe’s neck and the “stretching” hypothesis; genotypes are inheritednot necessarily phenotypes 1700s Cuvier founded paleontology and catastrophism after a natural disaster or extinction new species from surrounding areas repopulated area; used to explain the variation of fossils in different stratum layers History of Evolutionary Thought and Ideas 1831 Charles Darwin 5 year voyage around the world on the HMS Beagle. S America and The Galapagos islands; collected over 200K species, observed massive geological changes, stratification of earth’s layers, read Lyell’s Principles of Geology History of Evolutionary Thought and Ideas Found fossil of glyptodonts- ancestors of current day armadillo Could the armadillo come from this? A change would require millions of years; earth must be olderLyell suggested the earth was much older than 6000 years and the observed changes occurred gradually over long periods of time History of Evolutionary Thought and Ideas Darwin looked at the biogeography of organisms No rabbits in SA, but Patagonian hares, same niche…different ancestors? In Galapagos Islands (965 km from mainland) tortoises with different lengths of necks, and finches with different sizes of beaks, depending on island they were located and food source available Could the tortoises/finches on the islands come from an ancestor on the mainland? History of Evolutionary Thought and Ideas: Darwin Darwin’s Finches- Galapagos Islands Depending on the island and resources available, nectar vs. seed size, the birds beaks were different, yet they were finches History of Evolutionary Thought and Ideas: Darwin Looked at dog breeding; wolf dog Artificial Selection by humans produced different dog breeds. Could there be a natural selection process not driven by humans but by environmental factors? Variation in Populations Why is there so much species diversity? Yet, so many common traits? What Factors Produce Genetic Variability in a Population? Crossing Over-prophase I, Meiosis Independent assortment-metaphase I, Meiosis Chromosome number changesnondisjunction in Anaphase, mitosis/meiosis Chromosome structure changesdeletions, duplications, translocations, inversions Mutations-somatic vs. germ cells, silent Fertilization-1 sperm + 1 egg Darwin’s Theory of Natural Selection Through his travels to SA and Galapagos Islands, collecting and observing different species By reading the works of other scientists who presented data on geology, anatomy, competition, population size, and artificial selection Darwin published “The Origin of the Species” which contained Natural Selection as a mechanism that drives Evolution Natural selection: Obs. 1) All species have great potential fertility and population size would increase exponentially if all born reproduced successfully Obs. 2) Populations tend to remain stable in size Obs. 3) Environmental resources are limited -Inference 1: Production of more individuals than the environment can support leads to a struggle for survival; only a fraction survive Obs. 4) Individuals vary, no 2 individuals are exactly alike Obs. 5) Variation is heritable -Inference 2: Survival is not random; those individuals with beneficial inherited traits will leave more offspring Differential reproductive success -Inference 3: This differential reproduction leads to gradual change in populations; the product of natural selection is adaptation of populations to their environment selects Natural Selection drives Evolution is individual phenotype over time change in genotype frequency of population Individuals do not evolve; populations do ex. English Peppered Moth Factors That Drive Natural Selection Competition for limited resources High reproductive rates Variability and adaptability of traits Heritability of traits Natural Selection is Observable Darwin’ finches beak depth Peppered moths switch from light to dark color Marine snail thickness of shell Honey creeper beak smaller Bacteria antibiotic resistance Cancer cells/HIV drug resistance Evidence for Evolution Fossils-buried remains and mineralized impression of organisms from the past; older fossils deeper sediment layers Transitional fossils-an organism that shows features from 2 different lineages; intermediate form, common ancestor Archaeopteryx transitional form between reptiles and birds Ambulocetus terrestrial ancestor of whales The Fossil Record Only those organisms with hard parts preserved the best Have to find the fossil Some fossils not intact; erosion, water and earth movement, predators Complete records for many lineages have been found. Ex. Horse The evolution of the horse involves the gradual development of the modern horse from the fox-sized, forest-dwelling Hyracotherium. Paleozoologists have been able to piece together a more complete picture of the modern horse's evolutionary lineage than that of any other animal. Evidence for Evolution Biogeography Study of the range and distribution of organisms on earth When organisms are related, they evolved in one region and spread to other accessible regions Different organisms would be expected when geography separates land masses, islands, oceans Evidence for Evolution Comparative Morphology Study of bone structures and body organization between different organisms Looking for similar structures with similar functions between groups Stem reptile forearm has homologous structures that are found in human, bat, porpoise, penguin, chicken, pterosaur Analogous structures: bird vs. bat vs. insect wing Evidence for Evolution Comparative Embryology Study of embryos and early development patterns between different organisms Early embryos (up to 6 weeks) of humans, fish, chicken, reptile look identical. Why? Human embryos have gill slits, webbed fingers/toes, tail, fur Vestigial structures: features that are fully developed in one group of organisms but are reduced and have no function in similar groups Must have same ancient instructions (DNA); variations in later development due to mutations and transposons Evidence for Evolution Comparative Molecular Biology: all living organisms use the same hereditary molecules; these molecules were present in the first living cell and have been passed to all extant organisms Study differences/similarities of proteins. Many “housekeeping” enzymes will be the same in function, but not aa sequence between organisms Study differences/similarities of DNA sequences. The more closely related the DNA sequence between 2 organisms, the more closely related they are to each other. Humans and chimps DNA are 99% identical