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2. The discovery of the past Georges Cuvier Charles Lyell To study evolution means to dig in the past. The science of past organims is paleontology (greek:

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Presentation on theme: "2. The discovery of the past Georges Cuvier Charles Lyell To study evolution means to dig in the past. The science of past organims is paleontology (greek:"— Presentation transcript:

1 2. The discovery of the past Georges Cuvier Charles Lyell To study evolution means to dig in the past. The science of past organims is paleontology (greek: : old, : science) Paleontology deal with fossils (lat. fodere = to dig) 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 ( ) Richard Owen ( )

2 How do animals fossilize? Taphonomy (Greek: : burial; : law) Living organism Death Remains Exposed remains Buried remains Stratinomy Decomposition Decay Bleaching Delayed burial Immediate burial Ginkgo biloba Ginkgo adiantoides Much less than 1% of all organisms fossilize Coral fish Coral fish from Jura Fossil Mineralization Bioerosion

3 A fossil forest in Dorset, England formed by fossilized bacteria around old tree stumps. Fossilized Cyanobacteria (stromatolites) from South Africa A mammoth coprolith (fossilized excrements) A fossilized dinosaur footprint from New Mexico

4 From B. Ziegler: Allgemeine Paläontologie. Thieme, Immediate and delayed buriages

5 Hard body materials Soft body materials What fossilizes? SubstanceExamples Calcite (CaCO 3 )Octocorallia Bryozoa Brachiopoda Polychaeta Ammonita Belemnita Echinodermata Aragonite (CaCO 3 )Hydrozoa Gastropoda CalciumphosphateVertebrata (Ca 5 (OH)(PO 4 ) 3 )Trilobita Crustacea Opal (SiO 2.H 2 O)Radiolaria Diatomea Porifera ChitinAlgae Fungi Arthropoda Cnidaria Priapulida Annelida CellulosePlantae 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: Sinosauro- pteryx

6 Vertebrata Echinodermata Tentaculata Arthropoda Cnidaria Porifera Branchiotremata Annelida Flagellata Ciliata Cephalochordata Echiurida Tunicata Chaetognatha Plathelminthes Pentastomida Nematoda Tardigrada Onychophora Pogonophora Sipunculida Rhizopoda Ctenophora Mesozoa Sporozoa Without hard skeleton With hard skeleton Hard skeleton infrequent Fossils Unknown Rare Unknown Rare Unknown Rare Unknown Rare Unknown Often Some taxa often Often Mollusca Often How complete is the fossil record?

7 Under what conditions do organisms fossilize? Volcanic ashes Anaerobic conditions (moorlands) River sediments Moisture gradient Nutrient rich soils Probability of fossilization Salinity gradient

8 How complete is the fossil record? Neogene Iberian mammals The completeness of the fossil record P T can be calculated from the probability R that a fossil species is preserved at least in one geological layer: Species level: 77% Genus level: 91% SCI: Quotient of consistent to inconsistent nodes RCI: Relative completeness index GAP: Gap excess index Divergence time inferred from cladogram Divergence time inferred from fossils Benton MJ, Willis MJ, & Hitchin R Quality of the fossil record through time. Nature 403: Alba DM, Jordi A, Moya-Sola S Completeness of mammalian fossil record in the Iberian neogene. Palaeobiology 27: 79-83

9 Continental drift Alfred Lothar Wegener ( ) 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 Understanding earth,

10 From C. R. Scotese: Continental drift

11 How to match phylogeny and plate tectonics

12 Relative dating methods Relative dating uses geological strata to infer whether fossils are older or younger than a given stratum Layer 1 Layer 2 Time Older Younger Stratigraphy Morphological primitivism Fossil dating

13 Absolute dating methods Radiometric dating 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: potassium feldspar (orthoclase) muscovite amphibole glauconite Volcanic rocks Sometimes in sediments Uranium may be found in: zircon urananite monazite apatite sphene Volcanic rocks Carbon 14 is used for bones

14 How to use radiometric dating? The Rb/Sr System -decay = 1.42 x a -1, t 1/2 = 4.8 x a P t : Amount of daughter atoms through decay Total Original Decay 86 Sr is an isotope that is not radioactive not radiogen

15 Modified from Andy MacRae: Radiometric Dating and the Geological Time Scale. Raw data Recognition of unique events to subdivide time Radiomtric dating of layers Calibrating geological time StratigraphyRelative time scale Absolute time scale Geological time scale Radiometric dating

16 Fission track Dendrochronology 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 analyses tree- ring growth patterns.

17 History of the earth Nicolas Steno ( ) Steno founded stratigraphy by stating that geological layers are horizontal and superposed. Deeper layers are older. The Red Rock Canyon, California

18 The geological time scale EonEraPeriodAge at Base (Mya)Duration (Mya) PhanerozoicCenozoicQuaternary 1.6 Tertiary MesozoicCretaceous Jurassic Triassic PaleozoicPermian Carboniferous Devonian Silurian Ordovician Cambrian ProterozoicNeoproterozoicEdiacaran (Vendian) Cryogenian Tonian Mesoproterozoic Palaeproterozoic Archean Hadean

19 History of palaeontology: History of earth: Radiometric dating details: Geological time scale: Todays reading


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