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EVOLUTION Charles Darwin 1809-1882 born to a wealthy English family went to medical school, but earned a degree in theology took a job as a naturalist on the ship, H.M.S. Beagle one of the places he visited were the Galapagos Islands he observed tortoises that were so different, he could identify which island they lived on he saw two distinct different types of iguanas that have evolved so differently that they no longer belonged to the same species he saw birds that were all finches, but whose beaks were adapted to eat different food knowing the Galapagos Islands were volcanic and recently formed, the life there must have come from the mainland But why were the animals on the Galapagos so different???? "At last gleams of light have come, and I am almost convinced (quite to the contrary to the opinion I started with) that species are not immutable." after consulting with other scientists and researching, Darwin believed species evolved to fit into their habitats and called it natural selection he wrote The Origin of Species explaining his hypothesis of natural selection Darwin’s Natural Selection 4 Main Principles (1)In every population, variation exists within the inherited traits of the individuals (2) More offspring are produced than can survive (3) Individuals with beneficial traits (have adaptations) have a higher survival rate than those less adapted (4) Each species will have descended, with adaptations or modifications, from previous generations (descent with modification) In 1973, Theodosius Dobzhansky wrote an essay “Nothing in Biology Makes Sense Except in the Light of Evolution.” Evolution of biology’s unifying theme that connects together genetics, ecology, taxonomy, etc. Organisms must have a way of passing information to offspring Sexual reproduction – production of gametes through meiosis; fertilization results in an embryo with genes from each parent (results in variation) Asexual reproduction – one parent produces an offspring (offspring are genetically identical) If the genetic change increases fitness, it will eventually be found in many individuals in the population. Diversity is important for survival of a population A species is a group of organisms that share similar characteristics and can interbreed with one another to produce fertile offspring Because of a shared gene pool, a genetic change that occurs in one individual can spread through the population FACTORS THAT INFLUENCE GENETIC VARIABILITY Genetic drift – random change in a population’s gene pool due to chance Gene flow – movement of genes into or out of a population (such as migration) Non-random mating Mutations Natural selection – allows for the most favorable genotype to survive HARDY-WEINBERG PRINCIPLE When there is no change in gene frequency, the population is in genetic equilibrium This is known as the Hardy-Weinberg Principle 5 conditions are required to maintain genetic equilibrium Large population size (no genetic drift) No immigration or emigration Random mating No mutations No natural selection (all genotypes have equal chance to survive) Microevolution small changes in a population that take place quickly and can be documented; for example, antibiotic resistance in bacteria or change in peppered moths Macroevolution large-scale evolutionary changes that take place over long time periods fossils are evidence of macroevolution since there is no human documentation Horse Fossil From 55 Million Years Ago Horse Fossil From 52-45 Million Years Ago Horse Fossil from 32-25 Million Years Ago Horse Fossil From 17-11 Million Years Ago Horse Fossil From 5 Million Years Ago Evidence for Evolution Paleontology - fossil record (fossils are any evidence of life, such as bones, amber, imprints, etc.) The fossil record provides evidence of life forms along a timeline and supports evolutionary relationships by showing similarities between current and ancient species. The fossil record is not complete, because most organisms do not form fossils. Transitional fossils show links in traits between groups of organisms used to document intermediate stages in the evolution of a species Biochemistry - analysis of DNA base sequences and amino acid sequences in proteins Embryology – comparing embryos DO YOU KNOW WHAT ANIMAL THIS IS? structures - serve the same function in different species but they evolved independently rather than from the same structures in a common ancestor. An example of an analogous structure would be the wings on butterflies, bats, and birds analogous ANALOGOUS STRUCTURES homologous structures characteristics shared by related species because they have been inherited in some way from a common ancestor. For example, the bones on the front fins of a whale are homologous to the bones in a human arm and both are homologous to the bones in a chimpanzee arm. vestigial structures - have no apparent function, but resemble structures their presumed ancestors had. For example, the human appendix or the pelvic bones of a whale. SPECIATION – FORMING A NEW SPECIES New species form when organisms are isolated or separated Once isolation occurs, genetic variation and natural selection increase the differences between the populations TYPES OF ISOLATION Temporal – members of different populations don’t mate (closely related species of plants produce pollen during different times of the year) Behavioral – differences in courtship or mating behaviors Geographic – physical barriers divide a population PATTERNS OF EVOLUTION – changes that take place over long periods of time (take place gradually) Punctuated equilibrium – periods of abrupt changes after long periods of little change Gradualism Adaptive radiation (divergent evolution) – species diverge (split off) from a common ancestor Convergent evolution – organisms living in similar habitats have similar appearances and/or behaviors Coevolution – two species change in response to each other Extinction – elimination of a species Gradual extinction – occurs at a slow rate Mass extinction – very sudden extinction from a catastrophic event PHYLOGENETIC TREES Diagram that represent the phylogeny (evolutionary history) of a species It classifies organisms into major taxa (groups) based on evolutionary relationships Species are classified according to the order in which they descended from a common ancestor. Some trees show the order of divergence and don’t show relative time frames Some indicate an estimated time of divergence Tree drawn by Charles Darwin Taxonomy (classifying organisms) is constantly changing The current system includes 3 domains (Bacteria, Eubacteria, and Eukarya) and 6 kingdoms (Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia)