Eeob 3310 Exam -4 Exam With Correct Solution

Eeob 3310 Exam #4 Exam With Correct Solution




Asexual Reproduction - CORRECT ANSWER✔✔*Fission:* growth and splitting of a single organism into two identical
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organisms (coral polyps, bacteria).
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*Budding:* outgrowth from reproductive leading to generation of a new organism and separation (hydra)
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*Fragmentation:* casting off a part that can then grow into a new entity (sea star)
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Production of offspring from unfertilized gametes. JJ JJ JJ JJ JJ



*Apomixis:* mitotic replication yielding daughter cells that are genetically identical to the mother.
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-documented in 120 angiosperms (flowering plants). JJ JJ JJ JJ JJ



--would be valuable in agriculture.JJ JJ JJ JJ




*Parthenogenesis:* reproduction from an ovum without fertilization. JJ JJ JJ JJ JJ JJ



-Observed in invertebrates but rarely so in vertebrates.
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Many asexual species can undergo sexual reproduction also.
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Various cues can stimulate shift between reproductive strategies.
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Why would species maintain multiple strategies?
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Clonal reproduction can be efficient...no need for males.
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-a single female can expand (or establish) a population at the edge of a range.
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If clones are tolerant of environmental conditions, then nearly all individuals will harbor the genes necessary to survive.
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Asexual Reproduction--Advantages - CORRECT ANSWER✔✔*Avoid Recombination*
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-'disrupts and dilutes' the female's genetic contribution.
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*Avoid the 'two-fold cost of sex'* (JM Smith)
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-An asexual female's genes will, on average, be represented in twice as many of her offspring as a sexual female's gene
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--based on several assumptions including lack of parental care, 1:1 sex ratio, anisogamy (fusion of dissimilar gametes).
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*Avoid finding and securing a mate*
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-time and energy consuming...and the actual act of mating can be harmful to females.
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,Why Doesn't The Asexual Reproduction Predominate? - CORRECT ANSWER✔✔If intrinsic short-term benefits persist,
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why doesn't asexuality fix?
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(...or why does sexual/recombinative reproduction persist?)
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1) *Red Queen Hypothesis*--outpacing pathogens.
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2) Deterministic Mutation Hypothesis--efficient purging of deleterious mutations.
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3) Reduces selective interference among deleterious mutations in finite populations.
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Likely some or all of these are at work simultaneously.
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Severe long-term consequences JJ JJ



-mutation is the only way new alleles can enter the gene pool.
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--impeded adaptation JJ



--accumulation of irreversible deleterious mutations ("Muller's ratchet," coined by Joe Felsenstein 1974).
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Can lead to reduced survival.
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The Red Queen Hypothesis - CORRECT ANSWER✔✔The most important selection pressures in nature are predators,
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parasites, and pathogens.
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Organisms are in coevolutionary arms races with their biological enemies.
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-There is a premium on evolving to circumvent negative selection from enemies.
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-Yet the enemies are evolving to better exploit the target population.
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-Thus populations must evolve as fast as they can in order to stay in place.
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Genomic diversity enhances a population's ability to coevolve against their predators, parasites, and pathogens.
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There rarely are winners in these evolutionary races; these races are as old as evolutionary time.
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Types of Parthenogenesis - CORRECT ANSWER✔✔*Obligate parthenogenesis* (complete abandonment of sexual
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reproduction).
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-observed rarely; limited to some fish, bdelloid rotifers and some lizard.
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*Facultative parthenogenesis* JJ



-switching between sexual and asexual reproductive strategies.
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--*Cyclic parthenogenesis:* alternation between generations (aphids).
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--*Induced parthenogenesis:* maternally-inherited bacteria (Cardinium sp.) can induce some insects to reproduce asexua
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to ensure their perpetuation.
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Genetics Behind Parthenogenesis - CORRECT ANSWER✔✔*Haplodiploidy*
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-genders differentiated by chromosomal number.
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Males develop from unfertilized egg and females from fertilized.
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*Maintenance of ploidy can be an issue in parthenogenesis* JJ JJ JJ JJ JJ JJ JJ JJ




*Apomixis* is the formation of eggs through meiotic suppression.
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*Automixis* is the restoration of diploidy by genome or gamete duplication (mitosis) or polar body fusions.
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Automixis In The Wild - CORRECT ANSWER✔✔Evidence of critically endangered smalltooth sawfish reproducing via
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automixis.
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Capture of 190 individuals and genotype analysis of 16 alleles revealed that while most showed an average internal
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relatedness (IR) values of 0.03 (0=completely unrelated), 3.7% of individuals have 0.84-1 IR values.
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-all were female and exhibited identical heterozygosity, suggesting automixis.
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Lecture 11/14 - CORRECT ANSWER✔✔18-19/21
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Genetic Load - CORRECT ANSWER✔✔Reduction in average population fitness resulting from deleterious mutations in
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, the gene pool.
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Fitness deficit correlates with the number of mutations.
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We have actually considered this effect before when we discussed mutation-selection balance.
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-For selection against a recessive, (mean w) = 1-sq^2.
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Genotypic Variance Within A Population - CORRECT ANSWER✔✔low intrinsic value.
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However, in a variable environment, variance increases the likelihood that some genotypes within the mix can adapt.
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What makes environments vary? JJ JJ JJ



Invasion
Migration
Disease
Abiotic changes. JJ




Maintaining the ability to have genetic variation is the ultimate hedge. JJ JJ JJ JJ JJ JJ JJ JJ JJ JJ




Mutation Load - CORRECT ANSWER✔✔Some individuals undergo mutation, and move from "0 mutations" category int
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"1 mutation" category.
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This persists through 2, 3, 4, etc. mutations.
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Eventually, there are no individuals with relatively few mutations. JJ JJ JJ JJ JJ JJ JJ JJ




Lecture 11/16 - CORRECT ANSWER✔✔10/37 JJ JJ JJ JJ




Key Predictions - CORRECT ANSWER✔✔Asexual lineages oscillate.
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-Common lineages suffer from parasites and become rare, while rare lineages are resistant and become common.
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-Should be a short time lag between an increase in an asexual host lineage and an increase in parasites that can infect
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What is sex (evolutionarily speaking)? - CORRECT ANSWER✔✔Joining together of genetic material from two parents.
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Involves meiosis (including recombination) and fusion of gametes.
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As we'll see, the role of recombination is particularly important in explaining the evolution of sex.
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"Twofold Cost" of Sex - CORRECT ANSWER✔✔Females must reproduce self 2X just to keep population at baseline.
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Sex can break apart combinations of alleles that work well together.
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Asexual preproduction can preserve beneficial trait frequency. - CORRECT ANSWER✔✔Sexual reproduction with rando
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mating can recover Hardy-Weinberg proportions of traits.
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Evolution of Sexual Reproduction - CORRECT ANSWER✔✔Reduce mutation load.
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Facilitate adaptation. JJ



Increase diversity of offspring. JJ JJ JJ




Recombination and Mutation Load - CORRECT ANSWER✔✔The best chromosome in the population has two deleterio
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mutations.
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A new chromosome with only one deleterious mutation is produced by recombination.
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Recombination allows for offspring to have fewer deleterious mutations than their parents. JJ JJ JJ JJ JJ JJ JJ JJ JJ JJ JJ




Facilitating Adaptation - CORRECT ANSWER✔✔Parallel beneficial mutations get aggregated more quickly with sexual
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reproduction.
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Promote Genetic Diversity - CORRECT ANSWER✔✔Why is diversity good?
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