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59 Cards in this Set
- Front
- Back
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What acts on INDIVIDUALS, natural selection or evolution?
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Natural selection!
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Change in allele frequencies in a population over generations is called...
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Microevolution
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Natural selection, genetic drift (chance events that alter allele frequencies), and gene flow (the transfer of alleles between populations) all affect and determine...
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Microevolution
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T/F: ONLY natural selection brings about the change in populations that makes a species more suitable to its particular environment: called adaptive evolution.
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True
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Discrete characters are...
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Usually "either/or" traits, like widows peak or not.
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Quantitative characters are...
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Varying along a continuum, like skin color, and usually involve many genes and alleles
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Gene variability is measured... (average heterozygosity)
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At the whole gene level, an area on a chromosome.
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Nucleotide variability is measured...
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On the molecular level of DNA bases
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The average percent of loci on genes that are heterozygous is called the...
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Average heterozygosity
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T/F: Gene variability/average heterizygosity tends to be greatet than nucleotide variability.
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True, because an entire gene can be changed into another allele with the change of one nucleotide!
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Differences in the genetic composition of separate populations is called...
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Geographic variation
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A graded change in a character trait along a geographic axis is called...
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A cline (like how those fish in Maine more frequently have the cold allele gene allowing them to swim faster, than those fish in Georgia who rarely express that allele)
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Why are there different alleles for one locus that creates genotypic variation within a population?
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Because of mutations
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Why are more mutations able to be passed on to future generations in plants and fungi than in animals?
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Because plants can create gametes from many different cell lines, where as animals can only pass on mutations that occur in the somatic (sex) cells and usually such mutations cause death.
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Why are point mutations in eukaryotes generally harmless?
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Because most eukaryotic DNA doesn't code for proteins so mutations there are often harmless.
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T/F: Although it is rare, a mutant allele may actually make an animal better suited to its environment, enhancing reproductive success.
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True
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T/F: The translocation of part of one chromosome to a different chromosome could link DNa segments in a way that results in a positive effect.
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True
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T/F: Gene duplications that do not have severe effects can persist over generations, allowing mutations to accumulate. The result is an expanded genome with new loci that may take on new functions.
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True
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What is an example of a mutation that has become beneficial?
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The recent mammalian ancestor had only one gene for smelling, and now humans have 1,000 olfactory genes and mice have 1,300. More recently, mutations have cause humans to lose about 60% of their olfactory genes while mice have only lost 20%, showing how much more important the ability to smell is to them than to us.
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Although mutations occur very, very rarely in both prokaryotes and eukaryotes, why are they more prevalent in prokaryotes?
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Because their rate of reproduction is so quick; sometimes 5 minutes versus human reproduction rates of 25 years.
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Why does HIV mutate so quickly?
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Because it has a generation span of about 2 days and because it has an RNA genome which doesn't have the proofreading mechanisms of DNA poly.
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A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring is called a...
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Population
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All the alleles for all the loci in all individuals of the population is called the...
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Gene pool
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When there is only one allele for a loci in a population, what is it said to be?
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"FIxed," meaning all individuals of that population are homozygous. (If there are 2 or more alleles, then individuals may be either homo or heterozygous.)
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When studying a locus with two alleles, what is the convention when using letters to represent that allele's frequency?
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"p" for one allele and "q" for another.
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What is one way you can figure out if a population is evolving at one locus?
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You can determine the data the population would have if it were NOT evolving at that locus, and then compare it with real data at that population.
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What can be used to describe a population that is not evolving?
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The Hardy-Weinberg principle
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Animals that are not evolving will have frequencies of alleles and genotypes that remain constant from generation to generation. What are they thus said to be in?
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Hardy-Weinberg equilibrium
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The equation for Hardy-Weinberg equilibrium state that at a locus with two alleles, the 3 genotypes will appear in the following proportions:...
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p^2 + 2pq + q^2 =1
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T/F: For genes with two alleles, all the 3 possible genotype frequencies will equal 1 or 100%, but only those in Hardy-Weinberg equilibrium will demonstrate genotype frequencies exactly like the equation predicts.
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True
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When at least one of the 5 Hardy-Weinberg conditions are not met, genotype and allele frequencies in a population actually can change. What are these 5 conditions?
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No mutations, random mating (NOT inbreeding), no natural selection (bc this will change allele frequency), extremely large population size, and no gene flow.
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The three mechanisms that alter allele frequencies directly and cause most evolutionary change are...
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Natural selection, genetic drift, and gene flow.
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Evolution that results in a better match between organisms and their environment is called...
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Adaptive evolution
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How is genetic drift like a coin flip?
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You would probably get about 500 heads and 500 tails if you flipped a coin 1,000 times, but if you only flipped it ten times and got 7 heads and 3 tails, it wouldn't be odd.
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Chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in populations, is called...
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Genetic drift
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What are two good examples of genetic drift in the wildflower population?
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If a moose stepped on all the white flowers and only red ones reproduced, or if a small # of flower offspring was produced, and only red ones were created (which is why a large population is one of the equilibrium requirements).
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What is it called when a few individuals become isolated from a larger population and thus come to have a differing gene pool, creating a new population?
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The founder effect
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When purely chance events alter allele frequencies it is called...
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Genetic drift
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What is the bottleneck affect and how does it change allele frequency?
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It is when a bad event such as a fire decimates most of a population to where only a few survive. Thus, in the new population some genes may be over or under represented and the population's overall allele frequency can be changed forever.
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T/F: Genetic drift is significant in small populations, it can cause allele frequency to change at random, it can lead to a loss of genetic variation, and it can cause harmful alleles to become fixed.
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True
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The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes is called...
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Gene flow
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What is an example of gene flow altering allele frequency with the wild flower population?
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If a nearby mostly-white flowered population has its pollen brought over by some new bees, then the original wildflower population will have different gene frequency.
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T/F: Gene flow of bent, copper-tolerant grass to places where copper-tolerance is unnecessary prevents the regular grass population from fully adapting to its environment, and vice versa.
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True
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The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals is called...
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Relative fitness
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What are the 3 types of natural selection that can alter the frequency distribution of heritable traits?
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Directional, disruptive, and stabilizing selection.
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What type of selection occurs when conditions favor invididuals exhibiting one extreme of a phenotypic range, thereby shifting the frequency curve for the phenotypic character in one direction or the other?
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Directional selection
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What type of selection occurs when conditions favor individuals at both extremes of a phenotypics range over individuals with intermediate phenotypes, such as favoring either finches who can eat soft seeds or really hard ones?
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Disruptive selection
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What type of selection acts against both extreme phenotypes and favors intermediate variants?
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Stabilizing selection
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T/F: Natural selection is the only evolutionary mechanism that consistently leads to adaptive evolution.
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True
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The form of natural selection in which individuals with certain inheritd characteristics are more likely than other individuals to obtain mates is called...
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Sexual selection
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Marked differences between the two sexes of a species in secondary sexual characteristics is called...
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Sexual dimorphism
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What is intrasexual selection?
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Usually direct competition between males competing for a female.
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In what type of selection are females "choosy" in selecting their mates?
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Intersexual selection
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When natural selection maintains two or more forms in a population, it is called...
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Balancing selection
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I individuals who are heterozygous st a particular locus have greater fitness than do both kinds of homozygotes, then they exhibit...
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Heterozygote advantage
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What is an example of Heterozygote advantage?
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People who are hetero for sickle cell in Africa are still protected against the most deadly symptoms of malaria, but they don't have full blown sickle cell, and they also aren't totally susceptible to malaria.
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In what does the fitness of a phenotype decline if it becomes too common in the population?
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In frequency dependent selection, such as the right and left mouthed fish from the lake in Africa
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Mutations in no coding DNA sequences that have no positive or negative effects on selection are called...
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Neutral variations
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T/F: Because selection can act only on existing variations, it is limited by historical constraints, adaptations always have some sort of compromise, and because chance/natural selection/environment all interact, natural selection cannot fashion perfect organisms.
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True
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