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EVOLUTION Some history on the theory of evolution Early theories (pre-1700’s and 1700’s) nature is seen as not changing and having originated through spontaneous generation (pre-1700’s) Comte de Buffon (1707-1788) talked about possible common ancestry of humans and apes Linnaeus was the first one to try to classify life (1735, placed us with primates) Erasmus Darwin discussed competition and sexual selection More developments in the 1700’s an understanding of the age of the Earth develops through geology inheritance of acquired traits (use and disuse) ex. Baby giraffes are born with long necks because their parents stretched their necks to reach leaves (Jean-Baptiste Lamarck, 1801) Other contributions Thomas Malthus – plants and animals produce more offspring than can survive (led to Darwin’s formulation his theory of natural selection) Georges Cuvier – studied fossils/established that extinctions occur Charles Lyell – geologist who rejected catastrophism; suggested gradual geologic changes (uniformitarianism) – similar to evolution Thomas Huxley – supported natural selection; applied evolution to humans Darwin and the Voyage of the Beagle in December, 1831’ Charles Darwin, a naturalist in his 20’s began a 5-year journey around the world on a ship called HMS Beagle Darwin’s role was to observe, record, and collect specimens of rocks, minerals, plants, and animals Darwin: PBS Darwin collected 1000’s of specimens and shipped them to England, mainly from South America and a chain of volcanic islands called Galapagos he collected them but did not realize what he was seeing until years later (ex. didn’t catalogue the finches very well, ate turtles that would later support his theories, etc.) Darwin spent the next 20 yrs analyzing his findings in light of artificial selection (ex. breeding of pigeons, breeding of dogs, etc.) Darwin’s Finches Arrival Success Competition Diversity & Opportunity Radiation How does evolution really work? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html Hawaiian honeycreeper Natural Selection defined: The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated. Darwin’s theory of evolution A theory that explains the origin of species (not life) At the genetic level, it is the theory of change in the inherited traits of a population of organisms through successive generations Or as Darwin would have put it: descent with modification from a common ancestor This modification or change through successive generations come from variation in a population Variation comes from mutations and genetic recombination (e.g. crossing over).; both can be passed on to the next generation (more on this later) Misconception: “Evolution is a theory about the origin of life.” Evolution its origin. deals with how life changed after Misconception: “Evolution is like a climb up a ladder of progress; organisms are always getting better.” “good enough” is just that – there is no “perfect” organism, your ability to survive will vary with environment Misconception: “Evolution means that life changed ‘by chance.’ ” Mutations not. are random, natural selection is Misconception: “Natural selection involves organisms ‘trying’ to adapt.” Natural selection is based on variation within a population and selection, not trying. Misconception: “Natural selection gives organisms what they ‘need.’ ” Natural selection has no intent.