Zoology 445 Fall 2006Reading: Text 639-653 & Chapter 17Macroevolution HandoutI. Phylogeny of life.Whittaker’s five kingdom classification.Phylogenies of all life:Genes involved in the processing and storage of genetic informationGenes involved in basic metabolism.AM Jarosz 1Zol 445 JaroszThree pathways for horizontal gene transfer1. Transduction – The uptake of naked DNA from the environment. Any part of the bacterial chromosome can be exchanged.2. Conjugation – Transfer of DNA mediated by plasmids and transposons. Requires cell to cell contact but occurs between distantly related bacteria and even between bacteria and eukaryotic cells.3. Transduction – Transfer of DNA by phage.Net result: Typically, 10% or more of a bacterial genome can be traced back to a horizontal gene transfer event.Example: HMGGCoA reductase gene. Correct depiction of all life.Conclusion: The phylogeny of a particular gene represents the evolutionary history of that gene, and not that of the organism. Evolution within and between the Bacteria and Archaea are interconnected due to horizontal gene transfer.Endosymbiosis and the eukaryotic mitochndria and chloroplasts.2Zol 445 JaroszII. Evolution within the Eucarya.Earlier presentation:First determined by the suite of fossils. See text section 17.1 pages 664 – 666.III. The Cambrian ExplosionAdaptive radiation3Zol 445 JaroszThe Cambrian explosion.Fig 17.12 Shows all the major phyla of animalsImplication: All major animal phyla appeared in a time frame of 50 Million Years, which is around 4% of the total time life has existed on the earth.During that time the major innovations of animals occur.a. Radial & bilateral symmetryb. diploblasts & triploblastsc. protostomes & deuterostomesHowever, molecular clock data based on the neutral theory suggest that the branches for the origination of the phyla are much deeper than the Cambrian.4Zol 445 JaroszIV. Pattern in evolutionPunctuated equilibrium:They proposed that ALL morphological changeoccurs at speciation events (i.e. nodes on a phylogenetic tree).Traditional gradualism:Morphological change occurs independently ofspeciation.Set off two debates:1. Our view of speciation was incorrect. Allopatric speciation is a GRADUAL process and can take a long time.a. This was reconciled when population biologists realized that a “rapid” change on a phylogenetic tree represents a million or more years. A million years is plenty of time for allopatric speciation.2. Do species change morphologically only during speciation?A. Support for Punctuated EquilibriumBryozoans 5Zol 445 JaroszB. Support for GradualismC. Equivocal resultsChange without species – chronospecies introduced earlier in semester.6Zol 445 JaroszV. Is stasis due to a lack of genetic variability?Hypothesis: Species cannot change in morphology because they do not have the genetic variability to allow change.Test: Compare Horseshoe crab lineage (living fossil) with hermit crab lineage (much change morphologically) for levels of genetic variability.Growing consensus is that morphology due to “Habitat tracking.” If environment is stable and unchanging we see stasis.If habitat is changing constantly we see gradual and constant change.\Evolution Zol 445\2006\Macroevolution