Chapter 22 Wednesday January 27 2016 1 55 PM Chapter 22 Descent with Modification What is Evolution Misconceptions o Species are always evolving into higher better beings o Evolution creates new forms of life by dramatic mutations o An organism can evolve during its lifetime o An organism can influence the evolution of its own structures in response to its environment o Evolution is a completely random process Evolution o the change in organisms throughout earth s history o descent with modification Charles Darwin Views of Life Before Darwin Antiquity through 1600 s Aristotle and fixed ideal species Scala naturae ladder of nature Age of Reason 1700 s 1800 s Linnaeus s nested classification system Cuvier s interpretation of fossils Hutton and gradual processes A record of change over time different layers Sedimentary rock strata reveal relative ages o Lower levels were older vs higher levels Catastrophic events caused extinctions followed by recolonization o Lyell and uniformitarianism Gradualism Slow continuous processes in the past produced big geological features Father of geology Geologic features were made by same processes both catastrophic and gradual at the same rate as today Thus earth is extremely old Lyell s Principles of Geology was read by Darwin Erasmus Darwin s natural philosophy on evolution Lamarck tied evolution to adaptation Ideas that minute forms improved over time gaining complexity Extinct species were replaced by descendants with new features adaptations that helped them survive in environment First to propose a mechanism for evolution o Features are modified by use and disuse Lamarckism wrong o These changes are passed on to offspring inheritance of acquired characteristics Charles Darwin and His Theory Darwin s Voyage o Naturalist on HMS Beagle 1831 1836 o Goal mostly to South America including Galapagos Islands o Collected plants wildlife fossils o Observed species geographic locales and adaptations o Studied local geology Saw evidence for Lyell s uniformitarianism that earth was possibly millions y o Darwin s Life Work o Marriage and family allowed time for research o Evolution theory developed Essay written in 1844 but not published In 1858 Alfred Wallace wrote a letter to Darwin with the same ideas In 1858 both works presented publicly o In 1859 Darwin s book Origin of Species o Researched and wrote until death at 73 Darwin s Theory o Part 1 All present life is related through descent with modification from a common ancestor in the past Evolution not a completely new idea Extinction is common o Part 2 Natural selection is the mechanism for evolution Obs 1 In most species there is some variation among individuals that is heritable 22 10 Lady bug variation easy to see enhancing over time Darwin saw that artificial selection breeding could enhance small heritable variations 22 9 Wild cabbage variation is more subtle but through artificial selection variation is made more obvious Obs 2 All species produce more offspring than the environment can support Many offspring will die before maturity 22 11 An abundance of fish tadpole eggs are laid however not all will survive Malthus observed this in humans Human population growth potential is exponential But growth is restrained by limited resources leading to increase competition Poorest and weakest suffered the most Inference 1 Individuals with traits that help them survive and reproduce in their environment leave more offspring than other individuals unequal reproductive success 1 18 The bug that is more likely to be eaten by birds will have no offspring the darker bugs less eaten are more likely to leave offspring Inference 2 those favorable heritable traits adaptations accumulate over vast time matching species to environment and ultimately leading to new species 1 18 Population with varied inherited traits with the elimination of individuals with certain traits There will be a reproduction of the survivors Increasing frequency of traits that enhance survival and reproductive success adaptations Different varieties in artificial selection Different species in natural selection due to different environments and nature s choice 22 12 Ancestral praying mantis natural selection leads to different adaptations in different environments NOT in Darwin s Theory o Origin of life o How variation arises o How inheritance works o Why variation still exists o Sudden changes in fossil record o Source of totally new characters Evidence in Support of Darwin s Theory Direct Observation o Ex Bugs adapt to new food source o 22 13 Soapberry bug on native balloon vine fruit Native balloon vine fruit most efficient if beak length matches the depth of fruit Nonnative raintree fruit flatter pods with less depth o Ex Antibiotic resistance in bacteria Surviving S aureus gave rise to MRSA Fossil Record o Fossil evidence of many extinct species o Fossil evidence of transition of form 22 20 Ex Whales pelvis and hind limbs in recent whale ancestor fully aquatic predominantly aquatic terrestrial Homology o similarity in form as a result of common ancestry Homologous structures structure derived from a common ancestor but may be modified for different functions 22 15 Ex Mammal forelimbs are homologous We used shared homologies to build evolutionary trees Vestigial structures remnants of ancestral homologous structures with no present adaptive function Ex Blind cave salamanders have eyes but must have descended from salamanders with eyes inferred that descended from a species that could see Developmental homologies 22 16 Ex Vertebrate embryos Molecular and cellular homologies Genetic code is universal Similarity of cells proteins DNA corresponds to degree of relatedness Ex Species with the more similar proteins DNA cellular components are more closely related to each other Convergence o unrelated species have similar adaptations analogous structures under similar environmental conditions Why Convergent evolution Ex Torpedo shape for swimming Ex Cacti thick stems and thorns in deserts Ex Tree gliding mammals Flying squirrel relative of squirrel Sugar glider relative of opossum Biogeography o distribution of species Corresponds to geographic history 25 16 Ex Isolated Australian marsupials koalas possum wombat kangaroo Ex Unique endemic species on islands are similar to nearest mainland species Just a Theory Scientific Theory o a broad well supported explanation with rich predictive value It leads to many accurate predictions Ex Theory of