REVIEW QUESTIONS FOR EXAM 3 FROM SECTION III A 1 ONWARD 1 What evidence do we have for the operation of reciprocal altruism in nature Reciprocal altruism individuals trade behaviors engaging in social cooperation or altruism preferentially with other individuals who reciprocate is a behavior whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism s fitness with the expectation that the other organism will act in a similar manner at a later time Ex Kin Selection investments contribute to fitness of relatives and Group selection investments contribute to unrelated individuals with a net benefit to the actor BECAUSEof net benefits derived from living in the group Alarm calls predator detection prairie dogs Many give alarm calls in a community when predators approach may draw attention to itself but warns the community pack 2 Describe briefly how gene families originate Gene Family a group of gene related in function and apparently in origin aligned in tandem clusters and usually repeated in the genome A gene family is produced when a single gene is copied one or more times by a gene duplication event This duplication occurs by an abnormal misaligned crossover which produces a chromosome with a deficiency and another chromosome with a gene duplication Over time this type of duplication may occur several times to produce many copies of a particular gene In addition translocations may move the duplicated genes to other chromosomes so that the members of the gene family may be dispersed among several different chromosomes Eventually each member of a gene family will accumulate mutations which may subtly alter their function Overall the evolution of gene families has resulted in gene products that are better suited to a particular tissue or stage of development This has allowed a better fine tuning of human traits 3 What is the evidence that nucleotide sequence variation within the antigen recognition site of the human MHC gene has been driven by natural selection MHC genes replacement rates exceed synonymous rates at the antigen recognition site Extraordinary levels of polymorphism 4 Distinguish Trivers principle from Bateman s principle and describe what they suggest about how sexual selection is likely to operate in males and females Robert Trivers 3 who drew attention to postzygotic parental investment such as feeding young and defense against predators Trivers predicted that the sex with the largest parental investment usually female would become a limiting resource for which members of the other sex compete When females invest more than males the ratio of reproductively available males to females the operational sex ratio OSR 4 is assumed to be male biased In these situations reproductive success would be expected to vary more amongst males than females with females competing less intensely for mates and seeking out fewer partners than males Bateman s famous experiments showed that the number of offspring fathered by a male Drosophila increased with his number of mates whereas a female fruit fly did not gain an increase in number of offspring from mating with several males Bateman concluded that because single ova are more costly to produce than are single sperm the number of offspring produced by a female fruit fly was limited mainly by her ability to produce eggs whereas the reproductive success of a male was limited by the number of females that he inseminated He also stated that in our own species the sex difference in gamete size would result in greater within sex competition amongst males than females 2 One view is prezygotic anisogamy and one is postzygotic 5 Which factors appear to limit the size of groups like packs of wild dogs or social spiders Optimal Group Size is equal to the optmal number where cost and benefits cancel Ex Wild dogs of Africa Live in packs run down their prey always moving As group size goes up it eventually has an energy decline too many dogs to share all the meat Optimal group size 10 cost and benefits cancel here 6 What do we mean when we say two genes are paralogous What do we mean when we say two genes are orthologous Orthologous and paralogous genes are different types of homologous genes Homologous genes are two or more genes that descend from a common ancestral deoxyribonucleic acid DNA sequence An example of homologous genes are a bat wing and a bear arm both retain similar features and are utilized in similar manners These traits which were passed down from their last common ancestor have adaptive pressures that may lead to variations within the gene The point or event in evolutionary history that accounts for the DNA sequence variation within the gene determines whether the homologous genes are considered ortho or para Orthologous genes are homologous genes that diverged after a speciation event The genes generally maintain a similar function to that of the ancestral gene in which they evolved from In this type of homologous gene the ancestral gene and its function is maintained through a speciation event though variations may arise within the gene after the point in which the species diverged Paralogous genes are homologous genes that occur within one species and have diverged after a duplication event Unlike orthologous genes a paralogous gene is a new gene that holds a new function These genes arise during gene duplication where one copy of the gene receives a mutation that gives rise to a new gene with a new function though the function is often related to the role of the ancestral gene The genes that produce the hemoglobin and myoglobin proteins are homologous genes that have both orthologous and paralogous relationships Both humans and dogs hold the genes for both hemoglobin and myglobin proteins so we can infer that the hemoglobin and myoglobin genes evolved before human s and dog s last common ancestor Myoglobin arose in this ancestral species as a paralogous gene to hemoglobin myoglobin arose from a mutation in the hemoglobin gene during a duplication event and carries out a new yet similar function Since divergence in human and dog hemoglobin did not occur until after speciation these genes are orthologous Human myoglobin and dog hemoglobin however are homologous genes that are neither paralogous or orthologous 7 Which among the lines of evidence from which we deduce that the continents move is the most persuasive Is any single line of evidence sufficient to falsify the notion