11-ch15-history - Chapter 15& 16 Tracing Evolutionary...

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Unformatted text preview: Chapter 15 (& 16) Tracing Evolutionary History; Origin of Life Phylogenies Phylogenies are based on homologies in fossils & living organisms phylogeny – evolutionary history of a species or group of related species “phylo” = tribe hylo” “genesis” = origin, birth Phylogenies Phylogenies are based on homologies in fossils & living organisms (monophyletic) clade – group including ancestral species all of its descendants ancestral species & all of its descendants In class group exercise: learn to read a phylogenetic tree In class group exercise: learn to read a phylogenetic tree s s a a e e Most branches of evolution are dead ends; 99.9% of all species that ever lived are extinct! 1) How many species here share a common ancestor? 2) How many elephant species are alive today? 3) Which two are most closely related? 4) Who is the closest known extinct relative to modern elephants? 5) Who is the closest known living relative to modern elephants? 6) When did woolly mammoths & modern elephants diverge? Phylogenetic grouping is based on shared characteristics shared primitive character – character displayed in species outside a particular taxon (everybody in the tree has this in common...) shared derived character – evolutionary novelty unique to a particular clade (sharing of this character identifies these as close relatives) Ord Elliot Mushu 1) Describe (A) one shared primitive character all four dragons (above) have in common, (B) a shared derived (above) have in common (B) shared derived character common to three out of the four, (C) a shared derived character found in only two. In class group exercise: building a phylogenetic hypothesis In class group exercise: building a phylogenetic hypothesis g g c c o o y y Puff C B A 2) Complete the cladogram, and identify the characters you have used to build this hypothesis (A,B,C). Groups of related organisms have been traditionally arranged in a hierarchy taxonomy – set of characteristics used to characteristics used to assess the similarities and differences between various species, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life taxon – group binomial nomenclature – standard Latin name: “taxis” = arrangement Genus species e.g., Panthera pardus Why Why is the hierarchical system out of style? 1) grouping levels are arbitrary (and misleading) 2) new evidence has re-organized the tree consider the following traditional vertebrate tetrapod classes vertebrate tetrapod “classes” amphibia / reptilia / aves / mammalia more recent evidence places the bird more recent evidence places the bird clade deeply nested within reptiles! clade (turtles) Phylogenies Phylogenies based on morphological data can be tricky due to convergent evolution also, adaptive radiation can produce close relatives that don’t look alike Consider Consider the DNA analysis we have discussed; for example, gel electrophoresis with RFLP’s molecular systematics – comparison of nucleic acids or other molecules in different species to infer relatedness to infer relatedness corroborate with morphological data... molecular clock – evolutionary timing method clock timing method based on the observation that at least some regions of genomes evolve at constant rates calibrate against fossil record... Arranging life is a work in progress 3 current domains: bacteria, archaea, eukarya (from molecular evidence) vs. 5 kingdom system (Whittaker 1969) (based largel on feeding (based largely on feeding systems) Why not 5 kindgoms? Protists are deceptively diverse! 2 kingdom system dates as far back as Linnaeus Cosmology 101: The Big Bang Theory based on two principles: known universe, 12-14 bya • several millimeters across • very hot & very dense • massive explosion • still expanding outward evidence for the big bang: • observed distribution of galaxies • detection of microwave radiation http://www.nasa.gov a • relativity • cosmological principle Astronomy 101 • in the beginning, there was Hydrogen • all other elements formed by fusion (only one place in the universe hot enough) core of an active star! • these new atoms (elements) are trapped; (only one way to escape) star runs out of fuel & explodes! Astronomy 101 • what happens to the escaping matter? 1) new stars (much matter) 2) planets (a decent amount) 3) moons, asteroids, comets why? gravity pulls matter together • everything on Earth is made from recycled stars! Carl Sagan’s Cosmic Calendar p Jan Feb Mar Apr May Jun July Aug Sep Oct Big Bang Milky Way Nov Solar Life System December http://school.discoveryeducation.com/schooladventures/universe We are star stuff harvesting starlight. Our lives, past and future, are tied to the sun, the moon, and the stars. We are a way for the cosmos to know itself. Carl Sagan Richard Dawkins on our “queer” universe http://www.youtube.com/watch?v=1APOxsp1VFw The The fossil record chronicles life on earth fossil record (mostly in sedimentary rock) is incomplete but nonetheless useful... - relative dating by strata - calibrate with index fossils hard-bodied marine animals radiometric dating – estimate age of rocks & fossils on a scale of absolute time, based on the half-life of radioactive isotopes Geologic Geologic history in real time 13 bya ........ formation of universe (big bang) 13 bya of universe (big bang) 10 bya ........ formation of Milky Way galaxy 4.6 bya ....... formation of our solar system bya of our solar system 4.5 bya ....... earth experiences frequent collisions with debris all water is vapor (no oceans yet) 3.8 bya ....... origin of life on earth Stromatolites (bacterial mats) are the oldest fossils – dated at 3.5 billion years old Early Early earth conditions were very different (incompatible with life in its current form) • perhaps rich in Nitrogen, Carbon Dioxide rich in Nitrogen, Carbon Dioxide • very high temperatures & radioactivity • molten surface or unstable crust surface or unstable crust • no atmospheric Oxygen this came only after photosynthesis • massive water vapor content cooling & condensing to form oceans • constant volcanic eruptions nitrogen, nitrous oxide, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide How did life evolve on earth? the right chemicals the right chemicals H2O CH4 CO2 H2 NH NH 3 N2 Water Methane Carbon Dioxide Hydrogen Ammonia Nitrogen were in the right place at the right temperature at the right time: the right time: organic molecules (primitive soup) (primitive + massive energy (lightning, UV radiation?) + membranemembrane-bound protobioints = first organisms Scientists Scientists have tried to create life from scratch... product: amino acids Miller & Urey 1953 Major Major events in early evolutionary history: origin of life defining characteristics of life • • • • • • cells metabolism homeostasis reproduction heredity response to environmental stimuli the first organisms were almost certainly unicellular prokaryotic autotrophic aquatic (RNA may have been the first hereditary molecule) Major Major events in early evolutionary history: production of molecular Oxygen Cyanobacteria (photosynthetic prokaryotes) http://www.ucmp.berkeley.edu/bacteria/cyanointro.html brought about the “Oxygen revolution” “Oxygen = sufficient O2 to support aerobic life Symbiosis, Symbiosis, for better or worse symbiosis – ecological relationship between relationship between organisms of two different species that live together in direct contact host – larger participant symbiont – smaller participant parasitism – symbiotic relationship in which the symbiont (parasite) benefits at the expense of the host commensalism – symbiotic relationship benefits one participant; does not help or harm the other th mutualism – symbiotic relationship benefits both both participants sometimes leads to obligate mutualism (host & symbiont cannot survive apart) Major Major events in early evolutionary history: the first eukaryotes endosymbiosis hypothesis mitochondria & plastids were once whole (prokaryotic) organisms organisms, which lived in larger host cells li in larger host cells evidence... mitochondria & chloroplasts are the size of prokaryotic cells, contain their own (prokaryote-like) membranes, DNA, ribosomes 2.2 bya ....... first eukaryotes (fossils 1.5 byo) byo) Endosymbiosis Endosymbiosis Major Major events in evolutionary history: multicellularity happened several times independently (plants,animals, etc.) etc from colonies – aggregations of unicellular organisms (of same species) cell specialization leads to increased interdependency… 600 mya...... diverse multicellular organisms (algae, soft-bodied invertebrates) soft- Mass extinctions in the geologic record were followed by adaptive radiations Cretaceous mass extinction, 65 mya who? 50% of marine species many terrestrial plant & animal families including most dinosaurs most dinosa how? asteroid collision; resulting dust cloud blocks sunlight, drops temperatures & prevents photosynthesis, wiping out food chains evidence? Chicxulub impact crater layer of iridium (in terrestrial clay sediment) of iridium (in terrestrial clay sediment) Out with Out the old, in with the new! The fall of dinosaurs made room for new mammals. Scene Scene from Bring ‘Em Back Preserved Bring ‘Em ...
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