1 / 18

BAESI

April 28, 2012 Speciation, Homology, and the Iconography of Evolution Instructor: Jonathan Hendricks Assistant Professor of Paleontology, SJSU, Dept. Geology Email: jonathan.hendricks@sjsu.edu. BAESI. What is Evolution?. Evolution: descent with modification.

elysia
Download Presentation

BAESI

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. April 28, 2012Speciation, Homology, and the Iconography of Evolution Instructor: Jonathan Hendricks Assistant Professor of Paleontology, SJSU, Dept. Geology Email: jonathan.hendricks@sjsu.edu BAESI

  2. What is Evolution? Evolution: descent with modification. The theory of evolution seeks to explain two things: Goodness of fit of organisms to the environments in which they live (adaptation). Biodiversity.

  3. Slide shows an old illustration of the Great Chain of Being, ranging from hell to rocks to plants to animals to humans to heaven. The Great Chain of Being The Great Chain of Being:Idea that all species were designed and created by God along a linear continuum of increasing complexity (simple life to humans). Each species represents a different, but eternal link. Idea dates back to Greeks, but remained influential into the 1700’s. By: DidacusValades (1579)

  4. Bonnet’s Contemplation of Nature (1764)

  5. 3,000 out of 9 million species thought to be alive today. About 0.18% of the some 1.8 million species that have been described. Illustration from David M. Hillis, Derrick Zwickl, and Robin Gutell, University of Texas. Figure showing the complete “zoomed-out” tree of life, highlighting regions occupied by humans, animals, plants, fungi, protists, and bacteria & archaea. Diversity of Life You are here Animals Plants Fungi Protists Bacteria & Archaea

  6. Speciation Evolution is a branching process because of speciation. Speciation: The origin of a new species from a preexisting species due to a prolonged break in genetic exchange between two or more populations.

  7. Allopatric Speciation Allopatric Speciation: The idea that new species arise only when a small, local population becomes isolated at the margin of the geographical range of the parent species. Within such small, isolated populations, new & favorable mutations spread quickly, leading to rapid evolutionary divergence. If enough time passes, speciation may result if the parent and daughter “populations” can no longer successfully reproduce (supposing that they come into contact).

  8. Allopatric Speciation Physical barrier forms. V V V V V V V Light Blue = population • Slide shows an illustration of how allopatric speciation works (as do two subsequent slides, which continue the animation). Yellow = 1 species

  9. Allopatric Speciation Barrier to gene flow. V V V V V V V New species

  10. Allopatric Speciation V V V V V V V The evolution of a new species DOES NOT imply the extinction of its ancestor!! Time 4 • Slide shows an illustration of how allopatric speciation works (as do two subsequent slides, which continue the animation). Time 3 Following speciation, most species don’t change very much (stasis). Time 2 Branching and most morphological change occurs during speciation Time 1

  11. Homology: similarity due to common ancestry. Analogy: similarity not due to common ancestry, but rather evolutionary convergence; similar functional solution to same problem. Example: Forelimbs of tetrapods (4-limbed vertebrates) Slide shows a figure that illustrates the forelimbs of different vertebrate examples. The limbs have different functions, but are composed of the same bones. Homology vs. Analogy Pterosaur Bat Bird By: ВолковВладиславПетрович (Wikimedia Commons) By: John Romanes (1892)

  12. German Entomologist, 1913-1976. Phylogenetic Systematics (1950, 1966). Argued that not all characters are equal. Only characters useful for phylogenetic systematics are synapomorphies (shared derived characters). Slide shows a photograph of Willi Hennig, founder of cladistics. WilliHennig, Our Hero

  13. Synapomorphy: shared derived characters. Example: In a study of vertebrate relationships, the presence of milk production and hair would be synapomorphies for mammals. Symplesiomorphy: shared primitive characters. Example: In a study of mammal relationships, milk production and hair would be symplesiomorphies (they all share the condition). Autapomorphy: derived character present in only one taxon in the analysis. Example: In a study of primate relationships, the ability to speak is an autapomorphy (only humans possess it). Important Terms

  14. Cladogram: a branching diagram that shows the degree of relationships between species. Descendants of common ancestors share synapomorphies (body parts or DNA). No inherent time dimension. A B C D E Cladograms & Common Ancestors Species Common ancestor of A, B, and C. Branching point (node) is supported by one or more synapomorphies.

  15. On a cladogram, groupings may be rotated about individual nodes without a change in meaning. A C B C A D E B D E Identical Cladograms =

  16. The goal of phylogenetic systematics is to identify and name natural, or monophyletic groups (=clades). Monophyletic group: group that includes a common ancestor and all of its descendants. A B C D E Monophyletic Groups

  17. http://www.youtube.com/watch?v=faRlFsYmkeY The Evolution of Homer

  18. 99% of all species that have ever lived are now extinct. Modern organisms are the descendants of a long (~3.5 billion years!) history of survivors. History matters! The Veneer of History

More Related