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Transcript
Ch. 22 Descent with Modification 1 Enduring Understanding: Evolution is populations changing over time 2 Essential Question: How is evolution explained? http://www.lucidcafe.com/library/96feb/darwin.html 3 Who came before Darwin? Plato believed in 2 worlds: real = ideal/eternal illusionary world of imperfection Aristotle (384322 B.C.) organisms are arranged in ladder of increasing complexity species = permanent, do not evolve 4 1700's natural theology = philosophy (religion based) to discover the Creator's plan by studying nature adaptations = evidence that God made each organism for a purpose Carolus Linnaeus (17071778) founder of taxonomy binomial nomenclature relationship of organisms is a pattern of creation http://www.anbg.gov.au/biography/linnaeus.html 5 Georges Cuvier (17691832) paleontologist documented succession of fossil species in Pans Basin (Paris) older fossils on bottom of sedimentary rock, younger on top believed in catastrophism each rock boundary caused by a catastrophe (flood, drought that destroyed species) local species died, new from other areas 6 James Hutton (17261797) realized geologic formations formed by processes ex. canyons formed by rivers believed in gradualism = change occurs slowly & continuously 7 Charles Lyell (17971825) believed in uniformitarianism processes don't change over time ex. forces that build mountains and erode them, forces are same today http://www.hallencyclopedia.com/topic/Charles%20Lyell.html 8 Jean Baptiste Lamarck (17441829) studied fossils saw relationships 2 principles: a. use and disuse of body parts body parts that were used more were stronger and larger Ex. neck of giraffe got longer because it had to stretch for leaves on trees b. inheritance of acquired characteristics modifications of an organism can be passed on long neck is passed on Evolution happens because organisms have an innate drive to be more complex http://hallencyclopedia.com/topic/JeanBaptiste%20Lamarck.html 9 Who was Charles Darwin? son of a country doctor at 22 (1831) sailed aboard the HMS Beagle on a 5 year voyage companion to captain/naturalist sailed from England to Argentina, Strait of Magellan into Pacific and around world Spent 5 weeks at Galapagos Islands where he documented both visually and written flora and fauna of area 10 influenced by Lyell's work lead Darwin to believe: 1. Earth is older than 6,000 years (theologians belief) 2. slow, subtle processes over long period of time lead to substantial change 1844 wrote essay about natural selection did not publish it 1858 Alfred Wallace sent manuscript to Darwin about theory of natural selection 1859 Published "The Origin of Species" uses evolution ("descent with modification") to explain life's unity and diversity concept of natural selection did not use word "evolution" until end of book 11 12 Ernst Mayr interpretation of Darwin's work on natural selectionmade 3 inferences based on 5 observations Observation 1 For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully Observation 2 populations tend to remain stable in size, except for seasonal fluctuations Observation 3 Resources are limited Inference #1 production of more individuals than the environment can support leads to a struggle for existence among the individuals of a population, with only a fraction of their offspring surviving 13 Overproduction of offspring 14 Observation 4 Members of a population vary extensively in their characteristics, no two individuals are exactly alike Asian Lady Beetles 15 Observation 5 Much of the variation is heritable Inference #2 Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have higher fitness and are likely to leave more offspring than less fit individuals 16 Camoflague is an evolutionary adaptation 17 Inference #3 This unequal ability of individuals to survive and reproduce will lead to gradual change in a population,with favorable characteristics accumulating over generations 18 Darwin based other ideas on artificial selection selective breeding of domesticated plants and animals if change can happen in a short period of time, than can happen long term ("natural selection") * populations evolve over time, not individuals * natural selection can amplify or diminish only those traits that are passed on * a trait that is favorable in one situation, may not be favorable in another ** life evolves through "gradual accumulation of small changes" 19 Artificial selection Diverse vegetables from wild mustard 20 What evidence is there for evolution? Reznick and Endler study in Trinidad in one pool: Predator: Killifish eats small guppies Guppies: larger at sexual maturity in other pool: Predator: Pikecichlid eats large guppies Guppies: smaller at sexual maturity than in killifish pool in experimental pool: no guppies, but killifish introduced guppies from Pikecichlid pool conclusion:after 3060 generations transplanted guppies were average 14% heavier at maturity and average age also increased 21 Drug resistant HIV HIV resistance to drug 3TC 3TC interferes with reverse transcriptase 3TC molecule is similar to cytosine nucleotide, so 3TC is used instead of cytosine causes termination of elongation of DNA so blocks reproduction of HIV 3TC resistant viruses can distinguish between 3TC and cytosine 22 Homologous structures: structures in different species that are similar because of common ancestry 23 Comparative embryology early stages of development show anatomical homologies 24 Vestigial organsstructures within an organism that no longer serve a purpose ex. In humans: wisdom teeth appendix In snakes: pelvic and leg bones in some species 25 Molecular homologies similar DNA, RNA, amino acid sequences between organisms 26 tetrapod limbs amnion feathers crocodiles are more closely related to birds than lizards 27 Convergent evolution the independent evolution of similar features in different lineages. ex. sugar glider marsupial squirrel in Australia and flying squirrel in North America (eutherians uterine development) 28 ex. Ocotillo in southwestern N.A and the Alluaudia of Madagascar analogous structures structures that have a similar function but are structurally different Ex. bird and butterfly wings. 29 Biogeography geographic distribution closely related species tend to be found in same geographic region 30 Galapagos finches Islands tend to have endemic species found nowhere else in the world Darwin found that they have similar species on mainland of other nearby islands http://encarta.msn.com/media_461517965/Gal%c3%a1pagos_Finches.html 31 Fossil Record prokaryotes = oldest fossils found birds from dinosaurs whales/dolphins from terrestrial animals 32 So, what evidence do we have that evolution occurs? 33 34