THE EVIDENCE FOR EVOLUTION

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INTRODUCTION

• Charles Darwin
  • The Voyage of the Beagle [1831-1835]: Galapagos
  • Galapagos Islands
  • tortoises, mockingbirds, and finches
• theory of evolution by natural selection

2.1 RELATEDNESS OF LIFE FORMS

Homology

• homologous: character state inherited from common ancestor (e.g. ostrich and robin wings; bones in in the mammal forelimb, bones in [analogous] bird, bat, & pterosaur wing)
• homology is determined by position relative to other structures; development (embryological tissue, pattern of ontogeny) & evolution
• Patterns of Evolution
  • Micro and macroevolution from Dennis O'Neil. 
  • punctuated equilibrium and phyletic gradualism
  • Don Prothero on punctuated equilibrium at 20, a paleontological perspective
• structural homologies [Fig. 2.1a-vertebrate forelimbs; 2.13-vertebrate embryos; 2.14-orchard flowers] are the products of shared developmental pathways which are a product of homologous genetic programs [Fig. 2.2] which are a product of shared ancestry

Relationships Among Species

•  Similar species tend to be clustered geographically, suggesting descent from a common ancestor, not independent creation
• e.g., Galapagos Finches.

An Introduction to Tree Thinking

Reading a Tree

• Darwin’s hypothetical tree [Figure 2.3] showing a phylogeny with tips, branches, and nodes
• species are related by descent from a common ancestor.
• modern phylogenetic trees [Fig. 2.4]. Cladograms show the relationships of taxa
• An introduction to cladistics from Dr. Rebecca Irwin of the University of Tennessee Martin

• Journey into the world of phylogenetic systematics from the UCMP

Using Phylogenies

• evolution of the swim bladder in fish [Fig. 2.5]
• parsimony indicates swim bladders evolved late in two lineages independently 

2.2  CHANGE THROUGH TIME

1. Evidence for Evolution from mj farabee Maracopa
2. Evolution from PBS
3. Evidence Supporting Biological Evolution from the National Academy of Sciences
4. Evolution: Converging Lines of Evidence 
5. Evidence for Evolution from Talk Origins

Evidence from Living Species

1. remnants of once useful structures--e.g., hindlimb in boas or whales; human appendix; Human coccyx, blind cave salamanders [fig. 2.6a], etc.  developmental appearance and loss of extra digits in birds [Fig. 2.6b]
   • Rudimentary organs Fitch--NYU
2. Pseudogenes: e.g., globin family that do not code for proteins

Direct Observation of Change Through Time

• soapberry bug beak length decreased in response to introduced food source [Fig. 2.7]

Evidence from the Fossil Record

The Fact of Extinction

• Georges Cuvier (1769-1832)--fossils  and the fact of extinction: Irish Elk [Fig. 2.8]

The Law of Succession

• relationship between fossil and extant species from same geographical area [Fig. 2.9]

Transitional Forms

• Archaeopteryx (from UCMP Berkeley)
• whale evolution [Fig. 2.10]
  • The Order Cetartiodactyla is based on molecular evidence that hippopotamuses are more closely related to whales than they are to other artiodactyls.  Early cetacean fossils from Pakistan demonstrate that whales are artiodactyls.  More from National Geographic
    • Thewissen, J. G. M., E.M. Williams, L.J. Roe, and S.T. Hussain.  2001.  Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls, Nature 413: 277-281.  Philip D. Gingerich, et al.  2001.  Origin of whales from early artiodactyls: Hands and feet of Eocene Protocetidae from Pakistan, Science, 293: 2239-2242.
  • read Hunt for a more detailed phylogeny
  • read Hooking Leviathan by its Past by S. J. Gould from Dinosaurs in a Haystack (1997).
• gain and loss of prominent characteristics over time

Environmental Change

• change of environments and species over time--e.g., the two billion years recorded in the Grand Canyon

2.3 THE AGE OF THE EARTH

•  uniformitarianism

The Geologic Time Scale [Fig. 2.11]

• relative dating
• geologic time
  1. Unraveling Geologic Time from Paul Olsen's excellent WebPages for his dinosaur class
  2. Geologic Time Scale from the UCMP
     1. Geologic Time from the USGS
  3. relative ages
     1. stratigraphy
     2. Principle of Fossil Succession:  William Smith and Georges Cuvier
     3. Index Fossils
     4. A relative dating activity from the UCMP
• evolution is a time dependent process, special creation is not

Radiometric Dating

• a basic introduction by Pamela Gore
• radioactive decay [Fig. 2.12, Box 2.2, Table 2.1] is an independent clock
• the earth is 4.6 billion years old; first life 4 billion years ago

2.4   CORRESPONDENCE AMONG DATA SETS

Geologic Change and Plate Movement

The History of Marsupial Mammals

• data from plate tectonics, radiometric dating, and the fossil record can be combined to reconstruct the history of marsupials [Fig. 2.13]

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