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NAU BIO 435C - Capstone Final Exam Review

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Capstone Final Exam ReviewThe environmental unpredictability model suggests that sexual reproduction is favored in unpredictable environments, but not in predictable environments. The multiple niche model suggests that sexual reproduction is favored when there are a large number of different niches available in the environment, but not when there are only a few. The Red Queen hypothesis suggests that sexual reproduction is favored when parasite load is high, but not when parasite load is low.1) AsexualApomixis-daughter cells identical to mother cellAutomixis-haploid gametes via meiosis, but fuse back together. However potential for crossing over means daughter cells may not be the same (could be sexual reproduction?)2) SexualJoining together of genetic material from two parents to produce an offspring with genes from both.1) AsexualNuclear DNA & mtDNA phylogenetic trees very similar 2) SexualNuclear DNA & mtDNA phylogenetic trees very different.Other Costs of Sex Finding matesCourting Increased predationMates can transmit diseases YIKES!The twofold cost of sex arises only in anisogamy (The production of 2 different kinds of gametes) Benefits of SexSex purges deleterious mutationsSex accelerates adaptive evolutionSex and the Red QueenSex and Environmental Unpredictability Direct Benefits ModelSelection favors females who choose mates that provide them with some resource…. Good Genes HypothesisFemales receive nothing other than sperm but choose males who have a visible trait/behavior that is correlated to “good genes” –i.e., resistance to parasites…..Trait/behavior has to be costly to produce so that it is an honest indicator Runaway Selection Modelor Fisherian Sexual SelectionA gene that codes for a trait in males becomes linked with a gene for a particular behavioral mating preference in females. If genetic correlation between male trait and female preference is high then it will start a positive feedback loop How can you test this vs good genes?Sensory Bias HypothesisFemales prefer trait not because of a perceived mating benefit but just because they are “wired” that way.Benefit may be outside of mate choice or just an artifact.Test is easy with a phylogeny: female preference must predate male trait.Important to remember:Intrasexual selection: when male-male (more rarely, female-female) competition leads to exclusive mating rights for the winner.Intersexual selection: when females choose mates and access to females is not controlled by adominant male.*In species where male parental investment is equal to or greater than females, the roles noted above are often reversed.Direct Fitness Measured by your reproductive successIndirect Fitness Increasing the number of your genetic kin that survive and reproduceHamilton’s RuleA model to predict whether helping one’s relatives will be favored by natural selectionDepends upon how closely related individuals are to one anotherrb>c wherer =coefficient of relatedness b =benefit the genetic relative receivesc =cost to individual expressing the traitEusocialityA social system with:1. Reproductive division of labor2. Cooperative rearing3. Overlapping generationsFamous in ants, bees, and wasps but also known in termites, beetles, aphids, thrips, shrimps, and naked mole ratsNot explained by haplodiploidy alone because not all hymenoptera are eusocial.Requires high genetic relatedness caused by monandry (same as monogamous)Sisters also thought to influence uneven sex ratio by killing off their brothersGroup SelectionHistoric use naïve; now thought to be the least probable. Its use should be absolute last resort to explain behavior such as altruistic restraint. The most accepted version: Trait-group models favor group beneficial traits even when that trait imposes costs to individuals. Examples?Within Kin/FamiliesParent-offspring conflictParents want to invest resources equallyOffspring want more for themselvesIn primates: degree of relatedness (monogamous vs polyandrous species) can predict amount of conflict Conflict within the GenomeSegregation distorters in meiosisAlleles that bias the bias meiotic segregation so that there is not even segregation---1 allele will be over represented in the gamete pool.Deleterious mutations weed out gametes with non-favored


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