THE PATTERN OF EVOLUTION

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INTRODUCTION

1. Two views of the history of life:   These cartoons illustrate the contrasting claims (Figure 2.1)
   1. Special creation
      1. Immutability of species
      2. Each species is separately created
      3. Earth and life are young
   2. Descent with Modification
      1. Species change through time
      2. Species derive independently from common ancestors
      3. Earth is very old

2.1 EVIDENCE OF CHANGE THROUGH TIME

1. Introduction
   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
      1. examples
          
2. Direct observation of change
   1. Soapberry bugs (Figures 2.2, 2.3)
      1. Naturally feed on round balloon-vine fruit
      2. In 1926 flat-podded golden-rain tree fruit were introduced
      3. Beak lengths have decreased over time.
      4. Shorter-beaked soapberry bugs are found in Central Florida and longer beaked ones in the Keys.
   2. Vestigial Organs :  remnants of once useful structures
      1. The brown kiwi, a flightless bird, has tiny, useless wings. (Fig 2.4)
      2. Rudimentary hindlimb in boas or whales. The brown kiwi, a flightless bird, has tiny, useless wings. (Fig 2.4)
      3. human appendix;
      4. Humans have a rudimentary tailbone, called the coccyx [fig. 2.5a]
      5. Humans have a muscle, the arrector pili, at the base of each hair follicle. When it contracts, producing a goosebump, the hair stands up.  If we were hairy, like this chimpanzee, then contraction of our arrector pili muscles would increase the loft of our fur to keep us warm, or to make us look more intimidating. (Fig. 2.5b, c)
      6. blind cave salamanders
      7. Developmental vestigial traits Adult chickens have three digits in their wings and four in their feet. But during development, an extra digit appears for a short time in the "hand" (top) and foot (bottom). [Fig. 2.6]
      8. Rudimentary organs Fitch--NYU
          
3. Evidence from the fossil record
   1. The Fact of Extinction
      1. Georges Cuvier (1769-1832)--fossils  and the fact of extinction: Irish Elk [Fig. 2.8]
   2. The Law of Succession
      1. Fig. 2.9: Early researchers so routinely observed close relationships between fossil and extant species from the same geographical area and between fossil forms in adjacent rock strata that the pattern became known as the law of succession. Darwin noted the similarities between the contemporary pygmy armadillo (Zaedyus pichiy) (top left) and the fossil glyptodont (bottom left) of Argentina. Richard Owen confirmed a pattern first recognized by William Clift when Owen identified the extinct Australian mammal Diprotodon (lower right) as a marsupial similar to the wombats (upper right) that live in Australia today  
   3. Transitional Forms
      1. Chapter 2 Opener:  A snake with legs
         1. This 95-million-year-old fossil snake has small but fully formed hind limbs. It documents the previous existence of snakes leggier than any alive now.
      2. The dinosaur-bird transitiom
         1. Figure 2.10 A bird with a dinosaur's skeleton and a dinosaur with feathers
            1. Archaeopteryx (from UCMP Berkeley), a bird with modern feathers and a dinosaur-like skeleton.
            2. Sinosauropteryx prima, a dinosaur with bristly structures on its neck, back, flanks, and tail that many paleontologists believe are down-like feathers.
         2. Figure 2.11 More feathered dinosaurs
            1. Caudipteryx zoui, a dinosaur with elongated feathers on its arms and tail.
            2. A young dromaeosaur, probably Sinornithosaurus millenii, with simple feathers; arrows mark the most visible impressions.  The inset shows a feather from another S. millenii; the arrow marks the base of the tuft of filaments.
         3. Figure 2.12a Dinosaur feathers (a) Modern feathers, with filaments branching from a central shaft, from a dromaeosaur.  (b) Microraptor gui, a dromaeosaur with flight feathers on all four limbs—that is, a four-winged dinosaur.
      3. 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. 
           • 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.
         • Sutera Talk Origins
         • read Hooking Leviathan by its Past by S. J. Gould from Dinosaurs in a Haystack (1997).
         • Thewissen: National Geographic
         • Thewissen: Home page

2.2 EVIDENCE OF COMMON ANCESTRY

3. Homology
   1. 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)
   2. homology is determined by position relative to other structures; development (embryological tissue, pattern of ontogeny) & evolution
   3. structural and developmental homologies [Fig. 2.18-vertebrate forelimbs; 2.20-vertebrate embryos; 2.21orchard flowers] are the products of shared developmental pathways which are a product of homologous genetic programs which are a product of shared ancestry
   4. Molecular homologies
      1. Universal genetic code (Fig 2.22)
      2. Shared flaws in genetic makeup
         1. Figure 2.23 A genetic flaw that humans share with chimpanzees (a) The proximal CMT1A repeat, near the gene for PMP-22, is a duplication of the distal repeat on the other side of the gene. (b) The proximal repeat can align with the distal repeat during meiosis, resulting in unequal crossing-over. (c) The genotypes that result from the unequal crossing-over are associated with neurological disorders.
      3. Pseudogenes: e.g., globin family that do not code for proteins
      4. Figure 2.24 Processed pseudogenes used to test Darwin's hypothesis of common ancestry (a) Processed pseudogenes arise when processed messenger RNAs are reverse transcribed and inserted into the genome; biologists can estimate their age by the number of mutations they have accumulated.   (b) If Darwin's hypothesis of common ancestry is correct, then older, processed pseudogenes should occur in a broader range of species.  (c) The taxonomic distributions of these six processed pseudogenes are consistent with this prediction.
4. Relationships Among Species
   1. Similar species tend to be clustered geographically, suggesting descent from a common ancestor, not independent creation
   2. e.g., Galapagos Finches.

1. Micro and macroevolution from Dennis O'Neil.
2. Don Prothero on punctuated equilibrium at 20, a paleontological perspective

Evidence from the Fossil Record

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. 2.25]

• 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. 2.26, Box 2.3, Table 2.1] is an independent clock
• the earth is 4.6 billion years old; first life 4 billion years ago

2.4   Is there necessarily a conflict between evolutionary biology and religion?

1. Methodological naturalism
   1. As a scientist, regardless of other personal beliefs, hypotheses can only be framed in terms of natural causes
2. Ontological naturalism
   1. The natural world is all there is

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