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Friday: 5.1.09 Title: Homologous Structures DO NOW: What are the three types of homologies? HOMEWORK: Finish Anatomical Tree from Part B EVIDENCE FOR EVOLUTION: What is the evidence that all species on earth are related to each other and share common ancestors? 1. Homologous Structures a) Anatomical homologies and vestigial structures b) Embryos c) Molecular/Genetic 2. Fossils 3. Geographic Distribution of Species 1. HOMOLOGOUS STRUCTURES – similar structures due to sharing a common ancestor that had those structures Three Types of Homologies: 1. Anatomical (including vestigial) 2. Embryological/ Developmental 3. Molecular/ Genetic 1a. Anatomical Homology – similar body parts or bone structures (They don’t necessarily have the same function now, but did in the common ancestor) Ex: human arm, cat leg, whale flipper, bat wing all have same bones * Don’t confuse homologous structures with analogous structures structures that have the same function but NOT the same skeletal structure This suggests these organisms did NOT descend from a common ancestor with that trait Ex: insect wing and bird wing Bird wing Insect wing bio.miami.edu Homologous structures can be vestigial - don’t have a function now, but suggest that they descended from an ancestor that did use them. Ex: human tailbone, human goose bumps, ostrich wings Ex: human tail bone, human goose bumps, animal.nationalgeographic.com www.toptenz.net 1b. Embryological/Developmental Homology Ex: fish, reptile, bird, and human emrbyos all have gill slits and a tail (but some lose these features before birth 1c.Molecular/Genetic Homology – similar DNA or amino acid sequences Complete Question 4 from All in the Family Finish Question 4 for “All in the Family” Phylogenetic Tree for All Living Things Time -------------------------------------------------------------------->present Nodes indicate most recent common ancestor of two branches Evolution Dry Lab PART B: Comparing Anatomical and Genetic Evidence Monday: 5.4.09 DO NOW: Which is more reliable, Molecular Evidence or Anatomical Evidence? Why? HOMEWORK: No Homework.. Get ready for Exhibition Night Complete Evolution Dry Lab PART B: Comparing Anatomical and Genetic Evidence Tuesday: 5.5.09 Title: Evidence for Evolution (cont.) DO NOW: We have discussed Homologous Structures, what are the other two TYPES of evidence used to suggest common ancestry among species? HOMEWORK: Type Analysis Questions for Part B by Friday… EVIDENCE FOR EVOLUTION: 1. Homologous Structures a) Anatomical homologies and vestigial structures b) Embryos c) Molecular/Genetic 2. Fossils 3. Geographic Distribution of Species 2. Fossils: - show species that are now extinct - show transitions to new body forms Example A: Tiktaalik (lived 375 million years ago) – fish with legs and (maybe) primitive lungs… earliest amphibian? Fossil evidence, continued: Example B: Archaeopteryx (lived 150 million years ago) – earliest bird… but has many dinosaur features www.ansp.org Interpreting Fossil Evidence Fossils form in layers of rock (older = lower layer) Fossils in the same layer lived at the same time Radiometric dating: determine the age of a fossil based on how much radioactive carbon it contains What lived at the same time as the fossil fish? 3. Geographic Distribution of Species Species that live on the same continents are often closely related to each other (based on DNA and embryos), even though they look more similar to species elsewhere. Example: North vs. South American rodents Example: Placental Mammals vs. Australian Marsupial Mammals Australia has been separated from other continents for a long time – its marsupials evolved independently Marsupial traits are analogous, NOT homologous, to placental mammals Recap: Analogy vs. Homology Analogous Structures – similar due to natural selection in similar environments (common ancestor did not have it, but descendents evolve it independently) Homologous Structures – similar due to shared ancestry (common ancestor had this feature, so all descendents have it) Results from divergent (branching) evolution Wednesday: 5.6.09 Title: No Title in Notes DO NOW: Actively Read PBS Evolution Library: Whale Evolution HOMEWORK (both due Fri.): 1. 2. Complete up to Task 4 on Part C Type Analysis Questions for Part B DIVERGENT (branching) EVOLUTION Evolution Dry Lab PART C: Whale Evolution Day 1 Complete Tasks 1-4 before watching the video You may also have the reading to go along with this video Friday: 5.8.09 Title: No Title Today DO NOW: Take out the Part C of Evolution Dry Lab. Check Answers… HOMEWORK: Type Analysis Questions for Part C Ambulocetus natans in action A reconstruction of an early close cousin of whales Shown here with the kind permission of artist Carl Buell. http://www.indiana.edu/~ensiweb/lessons/whale.ev.html Check the Answers… Check the Answers… Check the Answers… Modern Whales… Evolution Dry Lab PART C: Whale Evolution Day 2 PBS Evolution Library: Whale Evolution http://www.pbs.org/wgbh/evolution/library/03/4/l_034 _05.html Create your Phylogenetic Trees for Whale Evolution (Task 5) Class Discussion: Compare Timelines from Task 4 Where Did Whales Evolve From? Zooming in on Whale Evolution EVOLUTION SUMMARY Populations of living things change over time. Due to change over time, a species can evolve into one or more new species. This results in the branching view of the tree of life. All living things are related because we all evolved from a common ancestor. Phylogenetic Tree for All Living Things Time -------------------------------------------------------------------->present “There is grandeur in this view of life…” – Charles Darwin