2Life’s Natural History is a record of Successions & Extinctions myaQuaternaryTertiaryCretaceousJurassicTriassicPermianCarboniferousDevonianSilurianOrdovicianCambrianEdiacaranPrecambrian,Proterozoic,&Archarozoic1.5Plants63BirdsMammals135ReptilesSeed PlantsFloweringAmphibiansInsects180DinosaursTeleost FishLand Plants225Jawless FishMolluscsArthropodsChordatesMulticellular Animals280Green AlgaePhotosynthetic Bacteria350Anaerobic Bacteria4004305005707004500Life’s Natural History is a record of Successions & Extinctions
3LaMarck Organisms adapted to their environments by acquiring traits change in their life timeDisuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapewormPerfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying battransmit acquired characteristics to next generationLamarck noted how well-adapted organisms were to their environments, and believed that fossils could be understood as less perfect forms which had perished in the struggle for increasing perfection. He explained adaptation as a result of change caused by environmental pressures.
4Charles Darwin 1809-1882 British naturalist Proposed the idea of evolution by natural selectionCollected clear evidence to support his ideasWhat did Darwin say?What evidence supports Evolution by Natural Selection?What impact did Evolution have on biology?
5Voyage of the HMS Beagle Invited to travel around the world(22 years old!)makes many observations of naturemain mission of the Beagle was to chart South American coastlineAfter graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world.FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain.Darwin noted that the plants and animals of South America were very distinct from those of EuropeRobert Fitzroy
6Voyage of the HMS Beagle Stopped in Galapagos Islands500 miles off coast of EcuadorThe origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin.On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland.It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands
7Succession of typesArmadillos are native to the Americas, with most species found in South America.Glyptodont fossils are also unique to South America.Why should extinct armadillo-like species & living armadillos be found on the same continent?
8Mylodon (left) Giant ground sloth (extinct) Modern sloth (right)“This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.”
10Darwin found… birdsCollected many different birds on the Galapagos Islands.Thought he found very different kinds…Finch?Sparrow?Woodpecker?Warbler?
11But Darwin found… a lot of finches Darwin was amazed to find out:All 14 species of birds were finches…But there is only one species of finch on the mainland!Large Ground FinchSmall Ground FinchFinch?Sparrow?How did one species of finches become so many different species now?Warbler FinchVeg. Tree FinchWoodpecker?Warbler?
12Tree Thinking Descendant species Ancestral species Large-seed eater? Large Ground FinchSmall-seed eater?Small Ground FinchDarwin noted that the plants and animals of South America were very distinct from those of Europe.Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe.Further, South American fossils more closely resembled modern species from that continent than those from Europe.Warbler?Warbler FinchLeaf-browser?Veg. Tree Finch
13Correlation of species to food source Seed eatersFlower eatersInsect eatersRapid speciation: new species filling new niches, because they inherited successful adaptations.Adaptive radiation
14Darwin’s finches Differences in beaks associated with eating different foodssurvival & reproduction of beneficial adaptations to foods available on islandsWarbler finchCactus finchWoodpecker finchSharp-beaked finchSmall insectivoroustree finchSmall groundfinchWarblerfinchLargeinsectivoroustree finchCactuseaterTree finchesMedium ground finchGround finchesInsect eatersSeed eatersVegetariantree finchLarge ground finchBud eater
15Darwin’s finches Darwin’s conclusions small populations of original South American finches landed on islandsvariation in beaks enabled individuals to gather food successfully in the different environmentsover many generations, the populations of finches changed anatomically & behaviorallyaccumulation of advantageous traits in populationemergence of different species
16Seeing this gradation & diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species has been taken & modified for different ends.
17Darwin’s finches Differences in beaks allowed some finches to… successfully competesuccessfully feedsuccessfully reproducepass successful traits onto their offspring
18Correlation of species to food source More observations…Correlation of species to food sourceWhoa, Turtles, too!
19Many islands also show distinct local variations in tortoise morphology… …perhaps these are the first steps in the splitting of one species into several?
20Artificial selection This is not just a process of the past… It is all around us today
21Selective breedingthe raw genetic material (variation) is hidden there
22Selective breedingHidden variation can be exposed through selection!
23In historical contextOther people’s ideas paved the path for Darwin’s thinkingcompetition:struggle for survival population growth exceeds food supplyland masses change over immeasurable time
24A Reluctant Revolutionary Returned to England in 1836wrote papers describing his collections & observationslong treatise on barnaclesdraft of his theory of species formation in 1844instructed his wife to publish this essay upon his deathreluctant to publish but didn’t want ideas to die with him
25And then came the letter…. Then, in 1858, Darwin received a letter that changed everything…Alfred Russel Wallace a young naturalist working in the East Indies, had written a short paper with a new idea. He asked Darwin to evaluate his ideas and pass it along for publication.
26The time was ripe for the idea! Your words have come true with a vengeance… I never saw a more striking coincidence…so all my originality, whatever it may amount to, will be smashed.To Lyell—
27“On the Origin of Species by Means of Natural Selection” Voyage:November 24, 1859, Darwin published“On the Origin of Species by Means of Natural Selection”
28Essence of Darwin’s ideas Natural selectionvariation exists in populationsover-production of offspringmore offspring than the environment can supportcompetitionfor food, mates, nesting sites, escape predatorsdifferential survivalsuccessful traits = adaptationsdifferential reproductionadaptations become more common in population
29LaMarckian vs. Darwinian view in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspringDarwingiraffes born with longer necks survive better & leave more offspring who inherit their long necks