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Organic Evolution & Natural Selection Evolution ► development of complex life forms through mutation and selection natural selection - survival of the ►fittest (for a niche) ►luckiest ►combination Evolution ► species reproductively isolated group of living organisms ► population group of organisms consisting of all the members of a species living in an area Evolutionary Trends ► speciation & extinction ► divergence & convergence ► phyletic gradualism & punctuated equilibrium Organic evolution: observations ► sedimentary rocks deposited in layers oldest layers are on the bottom layers may be correlated with other sedimentary layers ► fossil record oldest rocks have only simple fossils younger rocks have more organisms similar to those living today (at levels from species to kingdom) fossils record includes appearances and extinctions of many species Organic evolution: observations ► geographic distribution of organisms many organisms are similar but unique they are confined to specific areas (islands, continents, water bodies) includes modern and fossil organisms distribution has changed through time Organic evolution: observations ► anatomy cell structure is similar in all living organisms embryology - embryos of mammals, birds, and reptiles are very similar homologus organs - similar organs, different functions vestigal organs - no purpose in one, purpose in another Organic evolution: observations ► genetics structure of DNA and RNA is the same in all living organisms similarity in genetic code varies between organisms (some organisms are more similar than others) Organic evolution: conclusions ► the characteristics of populations of living organisms have changed through time life has become more complex life has become more diverse this is excepted as a factual observation ► all life is related Organic evolution: observations ► What about “missing links” the “link” between two fossil species OR between a fossil species and a living species many found, yet none found each “gap” filled creates two new “gaps” Natural selection: observations ► populations of organisms display a variety of characteristics characteristics may be useful, not useful, or detrimental the variety is reflected in an organisms genes ► new genes provide variety produced by mutation, duplication, or exchange of genes passed to offspring during reproduction Natural selection: observations ► artificial selection domesticated plants and animals can be bred to favor certain characteristics populations of wild and domestic plants and animals develop characteristics that favor their survival Natural selection: observations ► the natural environment provides opportunities and stresses for living organisms a new niche or stress on an existing niche will enhance selection Natural selection: observations ► populations isolated of a species may become by geography or behavior provides new opportunities and stresses isolates the population from the larger gene pool Natural selection: conclusion ► ► ► the natural environment provides conditions (opportunities and stresses) that result in evolution through the process of natural selection organisms with favorable characteristics for their niche are more likely to thrive and reproduce while organisms with unfavorable characteristics are less likely to thrive and reproduce over time, favorable characteristics can accumulate in a population until the members of the population can no longer reproduce with the population from which they became isolated Evolutionary trends ► speciation & extinction ► divergent & convergent evolution ► phyletic gradualism & punctuated equilibrium Natural selection: speciation ►a population has a gene pool ► members of the population interbreed ► the population may become isolated from others of a species development of niches & resource partitioning migration development of physical barriers ► populations may be selected by stress by opportunity ► isolation may result in genetic divergence Natural selection: extinction ► stress on limiting factors reduce or destroy a population ► evolution into subsequent species (pseudo-extinction) Phylogeny ► relationships between organisms can be determined using genetics anatomy & physiology Fossils Phyletic Gradualism & Punctuated Equilibrium ► gradualism slow, steady change ► equilibrium & punctuation long periods with little change short bursts of rapid change How did it start? ► Chemical evolution? ► Where? deep ocean vents? tidal pools? ice surface? clay surface? Randomness ► evolution is not random ► natural selection is not random ► mutations are random ► favorable mutations survive through reproduction End point ► Evolution has no end