Transcript Slajd 1
2. The discovery of the past To study evolution means to dig in the past. The science of past organims is paleontology (greek: palaews: old, logos: science) Paleontology deal with fossils (lat. fodere = to dig) Charles Lyell Georges Cuvier Early paleontology mainly described ancient life within the Linnean framework Modern paleontology tries to reconstruct ancient life. It links therefore ecology and taxonomy. Mary Anning (1799-1847) Richard Owen (1804-1892) How do animals fossilize? Taphonomy (Greek: tafos: burial; nomos: law) Immediate burial Death Living organism Remains Mineralization Fossil Buried remains Decomposition Decay Bleaching Delayed burial Exposed remains Ginkgo biloba Stratinomy Ginkgo adiantoides Much less than 1% of all organisms fossilize Coral fish Coral fish from Jura Bioerosion A fossil forest in Dorset, England formed by fossilized bacteria around old tree stumps. A fossilized dinosaur footprint from New Mexico Fossilized Cyanobacteria (stromatolites) from South Africa A mammoth coprolith (fossilized excrements) Immediate and delayed buriages From B. Ziegler: Allgemeine Paläontologie. Thieme, 1975. What fossilizes? Hard body materials Soft body materials Substance Examples Calcite (CaCO3) Octocorallia Bryozoa Brachiopoda Polychaeta Ammonita Belemnita Echinodermata Aragonite (CaCO3) Hydrozoa Gastropoda Calciumphosphate (Ca5(OH)(PO4)3) Vertebrata Trilobita Crustacea Opal (SiO2.H2O) Radiolaria Diatomea Porifera Chitin Algae Fungi Arthropoda Cnidaria Priapulida Annelida Cellulose Plantae Tunicata Soft tissues very seldom fossilize Exceptions are Fast drying out in very arid climates Permanent frozen Preservation in amber or asphalt A feathered Dinosaur: Sinosauropteryx How complete is the fossil record? Without hard skeleton Fossils With hard skeleton Fossils Cephalochordata Unknown Vertebrata Often Tunicata Rare Echinodermata Often Chaetognatha Rare Tentaculata Often Pentastomida Unknown Arthropoda Often Tardigrada Unknown Mollusca Often Onychophora Rare Cnidaria Often Pogonophora Unknown Porifera Often Sipunculida Rare Rhizopoda Often Echiurida Unknown Nematoda Rare Hard skeleton infrequent Plathelminthes Unknown Branchiotremata Some taxa often Ctenophora Unknown Annelida Some taxa often Mesozoa Unknown Ciliata Some taxa often Sporozoa Unknown Flagellata Some taxa often Under what conditions do organisms fossilize? Moisture gradient Nutrient rich soils River sediments Anaerobic conditions (moorlands) Volcanic ashes Probability of fossilization Salinity gradient How complete is the fossil record? Metrics Benton MJ, Willis MJ, & Hitchin R. 2000. Quality of the fossil record through time. Nature 403: 534-537. 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 SCI GER RCI Divergence time inferred from cladogram Divergence time inferred from fossils SCI: Quotient of consistent to inconsistent nodes 0 5 10 15 20 25 30 PZ PZ/MZ NZ MZ/CZ CZ Older -----Younger RCI: Relative completeness index GAP: Gap excess index Alba DM, Jordi A, Moya-Sola S. 2001. Completeness of mammalian fossil record in the Iberian neogene. Palaeobiology 27: 79-83 The completeness of the fossil record PT can be calculated from the probability R that a fossil species is preserved at least in one geological layer: Neogene Iberian mammals 7 6 ln R 5 n 4 Genera y = -0.37x + 5.03 3 2 1 0 Species y = -0.88x + 6.5 0 2 4 6 PT [1 (1 R T )(e qT 1 e qT )] T 1 Species level: 77% 8 10 Actual range 12 14 Genus level: 91% Continental drift Alfred Lothar Wegener (1880-1930) The tectonic plates (from David Sanfwell, Scripps Inst. Oceanography) Evidence for plate tectonics: Fit of coastlines Distribution of mountains Continuity of fossils Continuity of geological features Isostasy: Earth acts like a fluid From Press et al.. 2004. Understanding earth, http://www.whfreeman.com/presssiever/con_index.htm?99iex Continental drift From C. R. Scotese: http://www.scotese.com/future.htm How to match phylogeny and plate tectonics Cassowary 35 62 Emu New Guinea 0.1 65 Kiwi Australia 55 69 Ostrich 82 South America 79 Rhea 100 New Zealand Moa Africa Tinamou Fossil dating Relative dating methods Relative dating uses geological strata to infer whether fossils are older or younger than a given stratum Layer 1 Younger Layer 2 Time Layer 2 Older Stratigraphy Morphological primitivism Absolute dating methods Radiometric dating Radioactive Element Potassium 40 Rubidium 87 Thorium 232 Uranium 235 Uranium 238 Carbon 14 Stable element Argon 40 Strontium 87 Lead 208 Lead 207 Lead 206 Nitrogen 14 Half time 1.25 billion yrs 48.8 billion yrs 14 billion years 704 million years 4.47 billion years 5730 years potassium feldspar (orthoclase) muscovite amphibole glauconite Volcanic rocks Sometimes in sediments 1 Decay y Most minerals which contain radioactive isotopes are in igneous rocks. The dates they give indicate the time the magma cooled. Potassium 40 is found in: 0.8 0.6 y=e-kt t = ln(y)/k Half time 0.4 0.2 Surviving atoms 0 0 3.4657 Daughter atoms 6.9314 10.3971 13.8628 17.3285 20.7942 Time [half times] Uranium may be found in: zircon urananite monazite apatite sphene Volcanic rocks Carbon 14 is used for bones How to use radiometric dating? The Rb/Sr System 87 37 Rb 87 38 Sr Nt N0elt 87 Rbt 87 Rb0elt l= 1.42 x 10-11 a-1, t1/2 = 4.8 x 1010 a b-decay Pt: Amount of daughter atoms through decay Pt N 0 N t lt lt Pt N t e N t N t (e 1) 87 87 86 Srt Srt Srt 87 Rbt (elt 1) 87 Sr0 Total Decay Original slope (elt 1) 87 86 86Sr is an isotope that is Sr0 Srt 0 87 •not radioactive ex 1 x •not radiogen 87 Srt 86 Srt 87 Rb t Srt 86 87 Rbt lt Sr0 (e 1) 86 86 Srt Srt 0 x3 x 4 ... 1 x; x 1 3! 4! 87 Srt 87 Sr0 86 87 87 87 86 Srt Rb t Sr0 Srt 0 1 Srt l t t 87 86 86 86 Rb t Srt Srt Srt 0 l 86 Srt Radiometric dating Stratigraphy Raw data Relative time scale Recognition of unique events to subdivide time Absolute time scale Geological time scale Calibrating Radiomtric geological dating of layers time Modified from Andy MacRae: Radiometric Dating and the Geological Time Scale. http://www.talkorigins.org/faqs/dating.html Fission track Fission Tracks (FT) are micrometer-sized, linear damage tracks that occur in insulating minerals and that are caused by the spontaneous fission of heavy, unstable nuclides (mostly 238U in natural minerals). Dendrochronology Dendrochronology analyses treering growth patterns. History of the earth Steno founded stratigraphy by stating that geological layers are horizontal and superposed. Deeper layers are older. Nicolas Steno (1638-1686) The Red Rock Canyon, California The geological time scale Eon Era Phanerozoic Cenozoic Mesozoic Paleozoic Proterozoic Neoproterozoic Mesoproterozoic Palaeproterozoic Archean Hadean Period Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Ediacaran (Vendian) Cryogenian Tonian Age at Base (Mya) Duration (Mya) 1.6 1.6 65 63.4 140 75 205 65 250 45 290 40 355 65 410 55 440 30 510 70 540 30 630 90 850 220 1000 150 1600 600 2500 900 3800 2950 4550 750 Today’s reading History of palaeontology: http://en.wikipedia.org/wiki/History_of_paleontology History of earth: http://wiki.cotch.net/index.php/History_of_the_Earth Radiometric dating details: http://www.tulane.edu/~sanelson/eens211/radiometric_dating.htm Geological time scale: http://en.wikipedia.org/wiki/Geologic_time_scale