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Pre-Tidbit Instructions Get out your clickers Get out your laptops, i-pads, i-phones, or other internet connected device – Go to www.codecarnival.comwww.codecarnival.com – Click on the first link – Don’t click any further!!
Natural Selection John Burke, Matt Elrod-Erickson, Sandra Johnson, Troy Nash, Chris Peterson, Mike Rischbieter, Dorset Trapnell 17 May 2013
Context of Unit Introductory Biology course for majors Class of 21-50 students, already divided into working groups of 4 Foundational knowledge from earlier units – Mendelian genetics – Mechanisms of heredity
Unit Learning Goals Students will understand… – the definition of natural selection – the source(s) of phenotypic variation – how natural selection drives evolution in a population
Unit Learning Outcomes Students will be able to… – define evolutionary fitness (relative v/s absolute) – predict the relative importance of fertility & viability differences to overall fitness – identify types of selective forces and how they affect fitness – explain relationship between random mutation and non-random selective processes – predict responses to changing selective pressure – compare and contrast outcomes of differing modes of selection (directional, disruptive, stabilizing)
Tidbit Learning Outcomes Students will be able to… – define evolutionary fitness (relative v/s absolute) – predict the relative importance of fertility & viability differences to overall fitness – identify types of selective forces and how they affect fitness – explain relationship between random mutation and non-random selective processes – predict responses to changing selective pressure – compare and contrast outcomes of differing modes of selection (directional, disruptive, stabilizing)
Tidbit Preparation As part of the larger unit on natural selection, students will have been assigned a news brief reading assignment on Galapagos Finches
Clicker Question According to the article, the change in beak size in Galapagos finches was driven by _____. A.competition B.predation C.gene flow D.mutualism
Clicker Question Where did the variation come from? A.Some finches mutated because they needed smaller beaks. B.Some finches had access to more seeds, so they grew larger beaks. C.Undirected chance mutation in beak size gene(s). D.Some finches hybridized with another species of bird with different sized beaks
Imagine a population of plants With mutation and no selective pressure Parent Offspring in the 8 other squares.
Biomorph Simulation Use control/command and +/- to adjust size of box Use “reset” button to reset initial population Take 2 minutes and get used to program – Clicking on one of the offspring will make it the parent of the next generation It will move to blue center box 8 new offspring will be randomly generated Now take 1 minute to simulate the effects of random mutations through at least 15 generations – Randomly select offspring with out regard to their morphology
Clicker Question In the previous demo, you saw all manner of shapes and sizes in the plant population over lots of generations when no selective pressure was applied. What does this imply about the effects of mutations on phenotypes? A. Provide a continuous source of variation B. Mutations alone do not lead to directional change C.Both A and B D.Neither A nor B
Imagine a population of plants With a selective pressure – access to sunlight Group activity – Come up with a hypothesis for a morphological change that would be advantageous in the above scenario (2 minutes) – Run the simulation, consistently selecting for the morphological trait of your choice (2 minutes) – Note: Once finished, don’t hit the reset button!!
3 possible outcomes of selecting for increased branching
In the same population of plants The environment changes… Group Activity – Propose what might happen in the environment that might alter/reverse the previous trend (2 minutes) – Continue the simulation, consistently selecting for the new morphological trait of your choice (2 minutes)
Peppered Moth Group Activity These are two phenotypes of the same species of moth, which is heavily preyed upon by birds. The white morph was much more common prior to the industrial revolution. With the rise of industry, pollution and soot started to darken tree trunks. On a notecard, answer the following: 1) Why are there different colors of moths? (1 minute) 2) Given the changes caused by the industrial revolution, predict what happened to the relative frequencies of these two color morphs. Explain your answer. (2 minutes) 3) What would happen if all the predatory birds died? Explain your answer. (3 minutes)
Acknowledgements Norris Armstrong – Facilitator Extraordinaire! Kathrin Stanger-Hall – Director Southeast RSI Groups 2 and 3 for their helpful reviews Don Raber, Provost – Presbyterian College Michelle Momany, Plant Biology Department Head – University of Georgia Lynn Boyd, Biology Chair – Middle Tennessee State University