most important point DNA and the fossil record are the best evidence for the history of the Earth.

textbook points lecture review quiz preview links

• The history of the earth, as summarized in figure 24.4 or the figure on page 15 or in   is a collection of scientific facts.  Almost all biologists accept these facts.  Some of the details change when biologists do new experiments or find new fossils, but overall there is no controversy about the prehistorical events described in Chapters 21-24.  You can find the same set of facts and very similar tables in almost any science textbook or science museum, like the ones listed below.                             (so you don't have to memorize all these prehistorical facts). 
  • http://www.sciencemag.org/cgi/content/full/289/5485/1703/F1
  • http://www.ucmp.berkeley.edu/exhibit/geology.html (click on the chart) 
  • http://www.ucmp.berkeley.edu/alllife/threedomains.html 
  • http://tolweb.org/tree/phylogeny.html
  • http://www.sciencemag.org/feature/data/tol/ (new 2003)

     

• The evidence supporting these facts is massive, consistent, reliable, and logical to scientists. But how can you predict results about prehistorical events and how can you test hypotheses about processes of the past?  
  It's similar to testing the hypothesis that a limestone burial box is really the ossuary for James, the brother of Jesus ( http://www.nytimes.com/2002/10/21/science/21CND-JESU.html ).  
  For these types of hypotheses,  your predictions are about the results of analyzing structures and molecules, and the analytical evidence is similar to forensic evidence--  reconstructing scenarios from physical evidence.  In today's courts, eye-witness memories are often shown to be less reliable than circumstantial evidence based on scientific analysis of biological and geological samples.  

    Evidence relevant to evolution includes

  • studies of fossils and geologic layers  
  • radioactive isotope dating  
  • comparative anatomy (like the examples of homologous and vestigial structures in chapter 21) and developmental homologies (sometimes called comparative embryology)--the stages which develop these anatomical structures, as described in chapter 21.
  • genetic homologies and other types of comparative molecular biology, especially DNA analysis  
    for example, http://vector.cshl.org/dnaftb/40/concept/index.html 
  • artificial selection (chapter 1)
  • changes in diseases and other changes noted in written records (chapter 21 +)
   

MAIN POINTS FROM THE TEXTBOOK

• The evidence featured in this chapter includes
  • Fossils 
  • Phylogenies based on genetic homologies, especially duplications of genes controlling embryonic development
• Basic Fossil Info pp. 466-469:  The best way to figure out what's most important here is to practice answering "Applying Ideas" #1 at the end of the chapter.
• How to estimate fossil ages 
  • radiometric dating (Review chapter 2)
  • pp. 470-471 "molecular clocks" (how do they work?)
  • geological patterns also.)
• Famous events revealed by fossils and DNA-based phylogenetic analysis:
  • Cambrian Explosion more than half a billion years ago,  pp. 469-472. :  What happened during this explosion that would make it so important to zoologists? (summarize in 25 words or less) 
  • pp. 473.  What is gene duplication and how could it help explain the Cambrian explosion?
  • Vertebrate radiations.  The fossils of vertebrates are not discussed in textbook, but we actually have far more fossils of vertebrates than we do of Cambrian fossils.  (Explain why)
    pp. 474-477:
    • How could gene duplications help establish phylogenies?
    • What are hox transcripts and how are they photographed to make fig. 24.9?
    • What does a star phylogeny tell a scientist about adaptive radiation?  
    • Do the two "twig" lizards on fig 24.11 have homologous morphologies?  Or are their similarities analogous, examples of convergent evolution?
    • The lizards are contemporary species, like the more famous case of adaptive radiation (Darwin's finches).  Optional:  "Finch DNA Shows Darwin Was Right": http://www10.nytimes.com/library/national/science/051199sci-finches-evolution.html (click on chart to show phylogeny)
    • Do you think the fossil record also suggests patterns of adaptive radiation?  Check CD activity 24.1
    • Be ready to sketch a phylogeny.
• pp. 477-480.  Extinctions.  optional.  but you should know the difference between an extinction and an explosion.
• CHECKLIST:  tree of life, history of life, phylogenies, fossil record, fossilization, fossils, petrified fossils, Cambrian explosion, diversification, Cambrian period, homeotic loci, Hox Loci, gene expression, adaptive radiation, star phylogeny, morphological innovation, mass extinction

• LINKS
  • Fossils
  • Molecular Analysis of Evolution
  • Human Evolution
  • News stories about evolution