Biology 1B, Ecology Lecture 12, Page 1 Professor Resh • Spring 2010*Assigned readings, 8th Edition pp. No assigned readings7th Edition pp. 1106-1133Microevolution and EcologyOutline of Lecture 12A. Irish deerB. Freshwater mussel LampsilisC. PreadaptationD. Altruistic behaviorE. How can altruistic behavior evolve?F. Sexual selectionG. Does evolution fashion perfectorganisms?A. Irish deer: Evolutionary changes shouldbe adaptive but there is no guarantee thata useful structure will continue to beadaptive in changing circumstances.B. Freshwater mussel Lampsilis• retains eggs in a pouch called amarsupium; marsupium is fish-shaped• larvae are called glochidia, and attachparsitically to the gills of a fish; beforebeing released, larvae are inside themarsupium• a related mussel, Cyprogenea, has aworm-like marsupium• functional change in structuralcontinuity; A STRUCTURE CANCHANGE ITS FUNCTION WITHOUTCHANGING ITS FORMBiology 1B, Ecology Lecture 12, Page 2 Professor Resh • Spring 2010*Assigned readings, 8th Edition pp. No assigned readings7th Edition pp. 1106-1133Microevolution and EcologyC. PreadaptationTwo definitions:1. The occurrence of genetic traits (byspontaneous mutation) prior to, orirrespective of, any adaptive valuethey may have.OR2. The appearance of any phenotypictrait (morphological or behavioral)prior to the origin of its presentadaptive function.3. Intermediate stages may have adifferent function than final stagei. Selection for an externalmarsupium to increase O2exchange for Lamsilisglochidia.ii. Selection for externalmarsupium to look like a fish,which then attracts fish andincrease the change ofglochidia attachment to fishgills.• Directional Selection: naturalselection that favors individuals atone end of the phenotypic range(Professor Moritz has covered thistopic in greater detail).Biology 1B, Ecology Lecture 12, Page 3 Professor Resh • Spring 2010*Assigned readings, 8th Edition pp. No assigned readings7th Edition pp. 1106-1133MicroevolutionD. Altruistic behavior: self-sacrifice for thebenefit of others; a behavior that increasesthe fitness of the recipient but that reducesthe fitness of the altruistic individual.1. Belding’s ground squirrel – How cana squirrel enhance its’ individualfitness by aiding other members ofits population, which are in fact itsclosest competitors?2. BeesE. How can altruistic behavior evolve if itreduces the reproductive success of theself-sacrificing individual?1. Natural selection will increase genesfor “altruism” if individuals thatbenefit from the unselfish acts arethemselves also carrying those genesfor “altruism.”2. Kin selection3. Reciprocal altruismF. Sexual selection: sexually dimorphiccharacteristics1. Males with the most impressive ofthese will be most attractive tofemales; or2. Secondary structures may be used indirect contact with other males.3. Not all sexual dimorphism isobviously adaptive.Biology 1B, Ecology Lecture 12, Page 4 Professor Resh • Spring 2010*Assigned readings, 8th Edition pp. No assigned readings7th Edition pp. 1106-1133MicroevolutionG. Does evolution fashion perfect organisms?NO.1. Each species has a long history ofdescent with modification.2. Adaptations that exist today arecompromises.3. Not all of what we’ve talked about isadaptive.4. Natural selection favors the fitvariation from what’s available in thegene
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