Outline of Last LectureOutline of Current LectureHistory of LifeFossil RecordMisconceptions about Speciation and the Fossil RecordThe Geologic Time ScaleCambrian Period. 570-510 Mya:Permian Extinctions - 250 MyaCretaceous- Tertiary (K-T)Mass Extinctions“Evo-Devo” - Genetic Mechanisms of ChangeHox genesSystematicsPhylogenetic treesReconciles genetic and fossil dataBIO SCI 150 1st Edition Lecture 17Outline of Last Lecture 1. Speciationa. Speciesi. Distinguishing Species1. The Biological Species Concept2. The Phylogenetic Species Conceptii. How Species Form1. Allopatrica. Colonization eventsb. Vicariance eventc. Adaptive radiationd. Secondary Contact2. Sympatrica. PolyploidyOutline of Current Lecture 1. History of Lifea. Fossil Recordi. Misconceptionsii. Geological Time Periodiii. Mass Extinctionsiv. “Evo-Devo”b. Systematicsi. Phylogenetic treesii. Reconciles genetic and fossil dataHistory of LifeKey TermsFossil Record - preserved remains of organismsSystematics - the science of reconstructing phylogenyTaxonomy - ID and classificationPhylogeny - evolutionary historyHox genes - Trigger the development of antennae, wings, legsFossil Record- Fossil organisms are buried by sediments- Evolution predicts what new fossils should look like- New fossils are found every yearLimitationsA nonrandom sample of the past:- Hard-bodied animals are much more likely to fossilize than soft-bodied animals.- Recent fossils are more common (more likely to be exposed)- Aquatic species more common (sediments cover them)Older Fossils- Are found in lower strata- Nicholas Steno (1669): Law of superpositiono Provides a relative time scaleMisconceptions about Speciation and the Fossil Record-Ancestral Species do not necessarily disappear following speciation eventso Thus, simple organisms can be found in both higher (younger) and lower (older) strata, but more complex organisms are not found in deeper (earlier) strata.The Geologic Time ScaleBased on “Explosions” of new forms and ExtinctionsCambrian Period. 570-510 Mya: - Most major Phyla formed- The first animals appeared 563 million years ago and diversified tremendously in only 40 million years. - The Burgess Shale faunas- All 35 animal phyla appearedInnovations- Shells, skeletons, claws, spines- Adaptive Radiation: A single lineage produces descendants with a wide variety of adaptive forms. - Adaptive radiation can be triggered by extinction,colonization events, and morphological innovations. Permian Extinctions - 250 MyaPermian Extinctions associated with formation of Pangea (marked end of Paleozoic)- 50% of all species went extinct- 90% of marine animals went extinct- Pangea associated witho Less shorelineo Drier continental interiors- VolcanismCretaceous- Tertiary (K-T)- wiped out the dinosaurs and 60-80% of life at that time.- A second major extinction 65 MyaMass Extinctions- A large asteroid striking the surface of the earth (“impact hypothesis”) probably caused the Cretaceous-Tertiary (K-T) extinction.o Recovery from Cretaceous-Tertiary (K-T) extinction was slow.o Marine and terrestrial flora and fauna were different from whatwas present before the impact.o Mammals took the place of dinosaurs and marine reptiles.“Evo-Devo” - Genetic Mechanisms of ChangeDiversification can take place through several mechanisms:- Gene duplication (“new genes, new bodies” hypothesis)- Changes in gene expressionIs morphological diversity correlated with genetic changes?TBDHox genes Trigger the development of antennae, wings, legs- Homeotic genes (Hox genes)- homologous clusters in the same color - Hypothesis: gene duplication leads to new body forms- p.287-288 (Chapter 14)- Early groups with simple body plans have fewer hox genes- New hox genes created by duplication (similar to previous ones)- Vertebrates have several copies of the entire hox gene- Gene expression also importantSystematicsThe Fossil Record provides an outline of Evolutionary History- Systematics allows us to fill in the gapso Reconstruct Phylogeny => TreesPhylogenetic trees1. Phenetic approach: based on overall similaritya. Convergence is a problem (e.g., sugar glider and flying squirrel)2. Cladistic approach: based on sharing of derived traitsa.b. shared derived traits for dolphin & Whale: front fins, horizontal tail fin (fluke), blowholec. shared primitive traits: hair, mammary glands, three middle ear bonesReconciles genetic and fossil data- Old fossil evidence: Whales do not have an Astragalus and, thus, are not related to Artiodactylso The astragalus is a shared derived trait that identifies artiodactyls as amonophyletic group.o But genetic evidence indicates whales are related to Artiodactyls- Whales and Hippos Share four unique SINES- a shared derived traito Whales and Hippos Form a Monophyletic Groupo In 2000, a whale ancestor was found that did have an Astragalus like other