Biology 1B Ecology Lecture 12 Page 1 Assigned readings 8th Edition pp No assigned readings 7th Edition pp 1106 1133 Microevolution and Ecology Outline of Lecture 12 A Irish deer B Freshwater mussel Lampsilis C Preadaptation D Altruistic behavior E How can altruistic behavior evolve F Sexual selection G Does evolution fashion perfect organisms A Irish deer Evolutionary changes should be adaptive but there is no guarantee that a useful structure will continue to be adaptive in changing circumstances B Freshwater mussel Lampsilis retains eggs in a pouch called a marsupium marsupium is fish shaped larvae are called glochidia and attach parsitically to the gills of a fish before being released larvae are inside the marsupium a related mussel Cyprogenea has a worm like marsupium functional change in structural continuity A STRUCTURE CAN CHANGE ITS FUNCTION WITHOUT CHANGING ITS FORM Professor Resh Spring 2011 Biology 1B Ecology Lecture 12 Page 2 Assigned readings 8th Edition pp No assigned readings 7th Edition pp 1106 1133 Microevolution and Ecology C Preadaptation Two definitions 1 The occurrence of genetic traits by spontaneous mutation prior to or irrespective of any adaptive value they may have OR 2 The appearance of any phenotypic trait morphological or behavioral prior to the origin of its present adaptive function 3 Intermediate stages may have a different function than final stage i Selection for an external marsupium to increase O2 exchange for Lamsilis glochidia ii Selection for external marsupium to look like a fish which then attracts fish and increase the change of glochidia attachment to fish gills Directional Selection natural selection that favors individuals at one end of the phenotypic range Professor Moritz has covered this topic in greater detail Professor Resh Spring 2011 Biology 1B Ecology Lecture 12 Page 3 Assigned readings 8th Edition pp No assigned readings 7th Edition pp 1106 1133 Microevolution D Altruistic behavior self sacrifice for the benefit of others a behavior that increases the fitness of the recipient but that reduces the fitness of the altruistic individual 1 Belding s ground squirrel How can a squirrel enhance its individual fitness by aiding other members of its population which are in fact its closest competitors 2 Bees E How can altruistic behavior evolve if it reduces the reproductive success of the self sacrificing individual 1 Natural selection will increase genes for altruism if individuals that benefit from the unselfish acts are themselves also carrying those genes for altruism 2 Kin selection 3 Reciprocal altruism F Sexual selection sexually dimorphic characteristics 1 Males with the most impressive of these will be most attractive to females or 2 Secondary structures may be used in direct contact with other males 3 Not all sexual dimorphism is obviously adaptive Professor Resh Spring 2011 Biology 1B Ecology Lecture 12 Page 4 Assigned readings 8th Edition pp No assigned readings 7th Edition pp 1106 1133 Microevolution G Does evolution fashion perfect organisms NO 1 Each species has a long history of descent with modification 2 Adaptations that exist today are compromises 3 Not all of what we ve talked about is adaptive 4 Natural selection favors the fit variation from what s available in the gene pool Professor Resh Spring 2011
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