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Evolution Evolutionary change is based on interactions between populations of organisms and their environments.

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Presentation on theme: "Evolution Evolutionary change is based on interactions between populations of organisms and their environments."— Presentation transcript:

1 Evolution Evolutionary change is based on interactions between populations of organisms and their environments

2 Origin of the Species 1859 Darwin Published On The Origin of Species by Means of Natural Selection. –A convincing case for evolution Evolution: the process by which populations of organisms acquire and pass on novel traits from generation to generation

3 2 points of Darwin’s book 1.Species were not created in their present forms but evolved from common ancestors. 2.Natural Selection is the mechanism for evolution

4 Western culture resisted evolutionary views of life Darwin’s view contrasted with the conventional paradigm of an 6000 year old Earth, and Universe made in 7 days –Natural theology, Creationism, or Intelligent Design are all names for this point of view Others were laying groundwork for Darwin’s view. People were talking about evolution for years before Darwin articulated a concise argument.

5 Darwin’s Predecessors Economist & Demographer Thomas Malthus’ 1798 essay on England’s population noted that humans increase faster than food supplies.

6 Darwin’s Predecessors Carolus Linnaeus –Founder of Taxonomy –Developed 2 part naming system Organized the diversity of life into groups But believed that God created all the life, he only organized it

7 Darwin’s Predecessors Georges Cuvier developed Paleontology Documented where fossils were found in successive stratum of rock layers. –Deeper the rock layer; the older the life –Also noted extinctions happened Yet opposed evolutionary theory In the view of Catastrophism the layers of fossils result because of flood or other disasters –Extreme views of catastrophism hold that God wiped out all life and recreated it several times


9 Geologist’s Charles Hutton: came up with gradualism. –Idea that erosion and continental drift slowly shape the Earth James Lyell: came up with uniformitarianism: geologic processes happen at a constant rate

10 Darwin’s conclusions from Geology If geologic change is constant and slow, the Earth must be much older than 6000 years Slow, subtle processes over long periods can cause big changes in the Earth, so why not in populations of living things? –Others were already saying this


12 Galapagos




16 Jean Baptiste Lamarck Saw lines of descent, how older fossils evolved into younger fossils –Thought their were many ladders of descent –Bacteria escalated into more complex life forms His problematic mechanism: If a giraffe stretches its neck to get more food, then its kids will have stretched necks. Or if a blacksmith works out only his right arm, his children will have larger right arms.


18 Darwin’s Field Research Born on 2/12/1809 (same as Lincoln) Darwin grows up, doesn’t really have any direction, changes majors a couple of times. –Just wants to go hunting and collect bugs –Dad’s a big time doctor and getting fed up –Sends him to medical school, Darwin drops it –Darwin goes into the clergy, his mentor recommends him to be the on-board priest on the voyage of the Beagle


20 On the voyage Darwin found the an excellent Megatherium Skull

21 Darwin also discovered a new species of dolphin which he named Delphinus Fitzroyi

22 Voyage of the Beagle Captain of the Beagle: Fitzroy, really religious, needs educated company so he recruits the young clergyman Darwin They’re the original odd couple –Fitzroy: 23y/old Creationist –Darwin: 22y/old Liberal Evolutionist Both sharing a cramped cabin filled with fossils, flora & fauna samples Darwin collects when they go ashore –Lots of fighting –Much later Fitzroy slits his own throat

23 Beagle Goes around South America & Galapagos for 5 years Darwin keeps bad records, who knows where this or that bird came from. –Takes him six years after getting back to organize it all –Sees unique adaptations of different species, notably Finches.

24 Darwin focuses of adaptation New species arise as ancestral forms from the gradual accumulation of adaptations to different environments. –Species fragment and get isolated –Over a long time isolated population change enough that they become new species So Darwin’s famous for his adventure and has the idea for Evolution, then he does something weird…

25 He puts away his manuscript He doesn’t publish for 14 years –Has 10 kids, spends 8 years writing a book on barnacles, writes letters to Lyell, and a young naturalist named Alfred Wallace Why? –Creationist criticism was rampant –Darwin had a strange unidentified illness Maybe Chaga’s Disease caused by a Benchuca bug bite in South America Maybe Pscyhosomatic Maybe daddy issues


27 1858: Wallace  Alfred Wallace sends Darwin a manuscript for his ideas on evolution. Darwin says Holy Crap! This Wallace kid is going to steal the show, I’d better get moving. Publishes Origin of the Species. It sells out and everybody goes crazy with logic Wallace is cool, goes on to be a good thinker & naturalist, but gets weird ideas about spirits and life on other planets

28 Darwin didn’t call it evolution until the sixth printing of the book. He called it “Descent with Modification” We’re all descended from some unknown ancestor –Like an tree. Species at the leaves and the ancestor at the trunk. Closer related species share branches. Forks in branches are common ancestors –Lots of dead ends: 99% of species that have ever lived are extinct


30 The Linnean hierarchy of classification fit nicely with the branching genealogy of species Kingdom>phylum>class>order>family> genus>species>sometimes race or breed Kids Playing Chicken On Freeways Get Smashed King Philip came over for good spaghetti

31 Darwin’s Sweet Logic Observation #1: All species have such great potential fertility that population size would increase exponentially if all individuals born had maximum reproductive rates Observation #2: populations are stable Observation #3: Natural resources are limited

32 Inference #1: Production of more individuals than the environment can support leads to struggles for existence, and only a fraction survive. Observation #4: Individuals of a population vary in characteristics Observation #5: Much of this variation is heritable

33 Inference #2: Survival in the struggle for existance is not random, but depends in part on the hereditary constitution of surviving individuals. Those individuals whose characteristics fit them best to the environment are likely to leave more offspring than less fit individuals Inference #3: The unequal survival and reproductive ability will lead to a gradual change in a population with favorable characteristics accumulating over generations

34 Natural selection Natural selection is the differential success in reproduction and its product is adaptation of populations of organisms to their environment. Though we didn’t know it Mendel’s work published ~ 1868 explained this but no one recognized that for ~ 30 years

35 Evidence Artificial Selection: We breed domesticated animals for certain traits. Humans modify species. Cauliflower, Cabbage, Brussels Sprouts, Broccoli, Kale, and Kohlrabi are all modified Wild Mustard




39 Unintentional Artirficial Selection We don’t always want things to adapt Drugs have evolved resistance to Antibiotics Pests have evolved resistance to pesticides Pesticide Year mark eted Year Resistance first observed DDT19431950 2,4 D19451954 Delaphon19531962 Atrazine19581968 Picloram19631988 Trifluralin19631988 Triallate19641987 Diclofop19801987 Palumbi, S.R. 2001. Humans as the World's Greatest Evolutionary Force. Science 293: 1786-1790.

40 Subtleties It takes a population to evolve, not an individual The best adaptations depend on place and time. Just because you’ve got a great mutation that lets you survive at -100 degrees it won’t do you any good if you live in Brazil

41 Evidence Biogeography: Why are animals of South American tropics more closely related to South American deserts than African tropics? Why are most marsupials in Australia? Armidillos are only in America, fossils that look like Giant Armidillos are only in America. Go America!


43 Biston moth industrial melanism - tree bark either light in color (covered with lichens) or dark in color (because of industrial soot). Light moths favored when most trees have lichens (no pollution) and dark moths favored when tree bark is dark from pollution.

44 Fossil Record Biochem, Cell bio, and molecular bio all predict that prokaryotes should be the oldest organisms, and the oldest fossils are prokaryotes –Stromatalite: Blue Green Algae that trapped sediments and makes fossils that show evidence of biological activity, 500 -4500 million years old

45 –Transitional evidence. A criticism of evolution by some. However a series of skulls exist in the strata that show the transition from reptiles to mammals. Also Archaeopteryx was found just in 1861 –Saltationists like T.H.Huxley (Darwin’s Bulldog) thought evolution happened suddenly –What good is ½ an eye? –Paley’s argument from design likened it to finding a pocket watch, so complex it must have had an intelligent creator.

46 Comparitive anatomy: the same skeletal elements make up the forelimbs of all mammals even though these appendages have different functions. Hands, paws, whale fins, bat wings, all have the same basic bones because they have a common ancestor. These bones are homologous structures Also why have vestigial organs? Some snakes have a simpilfied hip bone.

47 Homologous as opposed to analagous structures

48 Comparitive embryology Closely related organisms go through similar stages during development. All vertebrates go through a stage of development when they have gill slits. “Ontogeny recapitulates Phylogeny” The development of an individual replays the evolutionary history of the species


50 Molecular Biology Similar DNA and proteins indicate a closer relationship. –Who has the DNA most similar to yours? We’ve got cytochrome C, a respiratory protein, and so do bacteria. There is a global common genetic code

51 Is it just a theory? Depends on what you mean by theory. Theories are more than hypothesis. They account for many facts and explain a variety of phenomena. Its not Dogma. Evolution can be challenged, but you’ve got to come up for a better explanation for the evidence. You can debate gravity, but objects keep falling

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