2. The discovery of the past

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)

2. How do animals fossilize? Taphonomy (Greek: tafos: burial; nomos: law) Immediate burial Living organism Death Fossil Mineralization Remains Buried remains DecompositionDecayBleaching Delayed burial Exposed remains Stratinomy Ginkgo adiantoides Ginkgo biloba Much less than 1% of all organisms fossilize Coral fish Coral fish from Jura 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. Immediate and delayed buriages From B. Ziegler: Allgemeine Paläontologie. Thieme, 1975.

5. What fossilizes? Hard body materials Soft body materials Substance Examples Calcite (CaCO3) Octocorallia Bryozoa Brachiopoda Polychaeta Ammonita Belemnita Echinodermata Aragonite (CaCO3) Hydrozoa Gastropoda Calciumphosphate Vertebrata (Ca5(OH)(PO4)3) 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: Sinosauro-pteryx

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

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

8. How complete is the fossil record? Benton MJ, Willis MJ,  &  Hitchin R. 2000. Quality of the fossil record through time. Nature 403: 534-537. Divergence time inferred from cladogram Divergence time inferred from fossils SCI: Quotient of consistent to inconsistent nodes 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 Species level: 77% Genus level: 91%

9. 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

10. Continental drift From C. R. Scotese: http://www.scotese.com/future.htm

11. How to match phylogeny and plate tectonics

12. 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

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 • = 1.42 x 10-11 a-1,  t1/2 = 4.8 x 1010 a b-decay Pt: Amount of daughter atoms through decay Total Decay Original • 86Sr is an isotope that is • not radioactive • not radiogen

15. Radiometric dating Geological time scale Absolute time scale Stratigraphy Relative time scale Recognition of unique events to subdivide time Calibrating geological time Radiomtric dating of layers Raw data Modified from Andy MacRae: Radiometric Dating and the Geological Time Scale. http://www.talkorigins.org/faqs/dating.html

16. Dendrochronology 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 analyses tree-ring growth patterns.

17. History of the earth Steno founded stratigraphy by stating that geological layers are horizontal and superposed. Deeper layers are older. The Red Rock Canyon, California Nicolas Steno (1638-1686)

18. The geological time scale

19. 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