Populations, Not The Individual Evolves Case Study
Population Genetics
2 Explain the statement “Populations, not the individual, evolves.”
~The statement "It is the population that evolves, not the individual," means that a single organism cannot evolve by itself. Natural selection is survival of the fittest, so the adaptations are relative to each other.
3 Explain how Mendel’s particulate hypothesis of inheritance provided much needed support for Darwin’s theory of evolution by natural selection.
~Mendel's hypothesis of inheritance supported Darwin's theory of natural selection because Mendel's theory accounts for the more subtle variations within a population that are central to natural selection.
4 Distinguish between discrete and quantitative traits. Explain how Mendel’s laws …show more content…
of inheritance apply to quantitative traits.
5 Explain what is meant by “the modern synthesis.”
~The modern synthesis -> A comprehensive theory of evolution emphasizing natural selection, gradualism, and populations as the fundamental units of evolutionary change, also referred to a Neo-Darwinism
6 Define the terms population, species, and gene pool.
~Population -> A group of individuals of one species that live in a particular geographic area. Species -> A group whose members possess similar anatomical characteristics and have the ability to interbreed. Gene pools -> the total aggregate of genes in a population at any one time.
7 Explain why meiosis and random fertilization alone will not alter the frequency of alleles or genotypes in a population.
~Meiosis and random fertilization alone do not alter the gene pol because the genes do not actually change. The genes keep going back into the gene pool.
8 List the five conditions for a population to remain in Hardy-Weinberg equilibrium.
~Condition 1 -> Very large population size. In a population of finite size, especially if that size is small, genetic drift can cause genotype frequencies to change over time. Condition 2 -> No migration. Gene flow due to the movement of individuals or gametes can increase the frequency of any genotype that is in high frequency among the immigrants. Condition 3 -> No net mutations. By changing one allele into another, mutations alter the gene pool. Condition 4 -> Random mating. If individuals pick mates with certain genotypes, then the random mating required for Hardy-Weinberg equilibrium does not occur. Condition 5 -> No natural selection. Differential survival and reproductive success of genotypes will alter their frequencies and may cause a detectable deviation from frequencies predicted by the Hardy-Weinberg equation.
9 Write the Hardy-Weinberg equation.
Use the equation to calculate allele frequencies when the frequency of homozygous recessive individuals in a population is 25%.
~p^2+2pq+q^2=1; p+q=1; p=1-q; q=1-p ALLELE FREQUENCIES --> p^2 => .5 2pq =>.5 q^2 => .5
Mutation and Sexual Recombination
10 Explain why the majority of point mutations are harmless.
~The majority of point mutations are harmless because there are several arrangements that can code for one amino acid. For example, UCU and UCC both code for serine, so a point mutation changing the U into a C would be completely harmless.
11 Explain why mutation has little quantitative effect on allele frequencies in a large population.
~Mutations have little quantitative effect on allele frequencies in large populations because genetic drift also factors into allele frequencies. Mutations are the driving force behind natural selection, and due to genetic drift, mutations are not the only thing that factor into changing allele frequencies.
12 Describe the significance of transposons in the generation of genetic variability.
~if the gene mutation via transposons isn't harmful then it will be passed on through generations. This increases the number of genes that are passed on, playing a huge role in
evolution.
12. Explain how sexual recombination generates genetic variability.
~Sexual recombination means that half of one parent's genes are combined with half of the other parent's genes in the offspring, which results in gene combination that did not previously exist. Sexual recombination and mutations would increase the amount of variation within a group. With sexual recombination, you constantly generate new variations in the population. If it weren't for this, all offspring would be identical to their parents and the only way for diversity to develop would be through mutations.
Natural Selection, Genetic Drift, and Gene Flow
13. Explain the following statement: “Only natural selection leads to the adaptation of organisms to their environment.”
~Genetic flow and genetic drift occur totally randomly. However, natural selection will allow the genomes that are a good adaptation to the environment pass on to the next generation and cause the genomes that aren't good adaptations die out.
14. Explain the role of population size in genetic drift.
~Genetic drift is the process of change in the genetic composition of a population due to chance or random events rather than by natural selection, resulting in changes in allele frequencies over time. If a population is small, there is is less variation between the organisms. If a catastrophe occurs, the population will not be able to recover as quickly because the alleles will not be as diverse.
15. Distinguish between the bottleneck effect and the founder effect.
~Bottleneck effect (catastrophe)-> Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population. Founder Effect -> Genetic drift attributable to colonization by a limited number of individuals from a parent population.
16. Describe how gene flow can act to reduce genetic differences between adjacent populations.
~Gene flow can act to reduce genetic differences in adjacent populations because gene flow increases the movement of genes from different populations of species. The more interbreeding between two populations, the more similar their genes.
Genetic Variation, the Substrate for Natural Selection
17. Explain how quantitative and discrete characters contribute to variation within a population.
18. Distinguish between average heterozygosity and nucleotide variability. Explain why average heterozygosity tends to be greater than nucleotide variability.
~Directional selection -> Natural selection that favors individuals at one end of the phenotypic range. Disruptive selection -> Natural selection that favors individuals at either extreme end of the phenotypic range. Stabilizing selection -> Natural selection that favors intermediate variants by acting against intermediate phenotypes.
19. Define a cline
~a graded change in a character along a geographic axis.
20. Define relative fitness.
~Relative fitness - the contribution of an individual makes to the gene pool of the next generation relative to the contribution of other individuals. a. Explain why relative fitness is zero for a healthy, long-lived, sterile organism. b. Explain why relative fitness could be high for a short-lived organism.
21. Distinguish among directional, disruptive, and stabilizing selection. Give an example of each mode of selection.
~Directional - occurs when conditions favor induviduals exhibiting one extreme of a phenotypic range, therby shifting a populations frequency curve for the phenotypic character in one direction or the other. Common when a pop environment changes or when members migrate to a new habitat. Disruptive – occurs when conditions favor individual at both extremes of a phenotypic range over individuals with intermediate phenotypes. Example - pop of black-bellied seed crack finches in Cameroon whose members have two distinct beak sizes. Small billed for soft seeds and large birds for hard seeds to crack them. Birds with intermediate sized bills were insufficient for the soft seeds and the hard seeds, have low relative fitness. Stabilizing - acts against both extreme phenotypes and favors intermediate variants. This reduces variation and tends to maintain the status quo for a particular phenotypic character. Example- babies average weight is around 6 pounds, large ands miller babies have a higher motility rate then the middle ones.
22. Explain how diploid can protect a rare recessive allele from elimination by natural selection.
~Diploid maintains genetic variation in the form of hidden recessive alleles because the cell has two sets of the recessive allele.
23. Describe how heterozygote advantage and frequency-dependent selection promote balanced polymorphism.
~Heterozygote advantage occurs when heterozygotes have a higher fitness than do both homozygotes. In frequency-dependent selection, the fitness of a phenotype declines it becomes too common in the population.
24. Define neutral variations. Explain why natural selection does not act on these alleles.
~Neutral variations are differences in DNA sequence that do not confer a selective advantage or disadvantage. Natural selection doesn't act on these alleles because the tendency for directional and stabilizing selection reduce variation is countered by mechanisms that preserve or restore it.
25. Distinguish between intersexual selection and intersexual selection.
~Intersexual selection -> a direct competition among individuals of one sex (usually the males in vertebrates) competes for mates of the opposite sex. Intersexual selection -> Individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex, (also called mate choice)
26. Explain how female preferences for showy male traits may benefit the female.
~More extravagant individuals mean that their offspring will also have more extravagant features.
27. Describe the disadvantages of sexual reproduction.
~Sexual Reproduction can be much slower than asexual reproduction. This is because it relies on other things. For animals, they need to find a mate to breed with and plants need to be pollinated (they rely on the presence of wind or animals for this)
28. Explain how the genetic variation promoted by sex may be advantageous to individuals on a generational time scale.
29. List four reasons why natural selection cannot produce perfect organisms.
1. Selection can only act on existing variations
2. Evolution is limited by historical constraints
3. Adaptations are often compromises
4. Chance, natural selection, and the environment interact
Major factors that alter allele frequencies
1. Genetic drift
2. Gene flow
3. Natural selection
Struggle for existence- competing for limited resources food shelter mate water
Struggle for the fittest – best fit for the environment at the time speed camouflage
Relative fitness-Ability to gives leave genes for offspring
Three modes of selection
Directional->->or->
2 Explain the statement “Populations, not the individual, evolves.”
~The statement "It is the population that evolves, not the individual," means that a single organism cannot evolve by itself. Natural selection is survival of the fittest, so the adaptations are relative to each other.
3 Explain how Mendel’s particulate hypothesis of inheritance provided much needed support for Darwin’s theory of evolution by natural selection.
~Mendel's hypothesis of inheritance supported Darwin's theory of natural selection because Mendel's theory accounts for the more subtle variations within a population that are central to natural selection.
4 Distinguish between discrete and quantitative traits. Explain how Mendel’s laws …show more content…
of inheritance apply to quantitative traits.
5 Explain what is meant by “the modern synthesis.”
~The modern synthesis -> A comprehensive theory of evolution emphasizing natural selection, gradualism, and populations as the fundamental units of evolutionary change, also referred to a Neo-Darwinism
6 Define the terms population, species, and gene pool.
~Population -> A group of individuals of one species that live in a particular geographic area. Species -> A group whose members possess similar anatomical characteristics and have the ability to interbreed. Gene pools -> the total aggregate of genes in a population at any one time.
7 Explain why meiosis and random fertilization alone will not alter the frequency of alleles or genotypes in a population.
~Meiosis and random fertilization alone do not alter the gene pol because the genes do not actually change. The genes keep going back into the gene pool.
8 List the five conditions for a population to remain in Hardy-Weinberg equilibrium.
~Condition 1 -> Very large population size. In a population of finite size, especially if that size is small, genetic drift can cause genotype frequencies to change over time. Condition 2 -> No migration. Gene flow due to the movement of individuals or gametes can increase the frequency of any genotype that is in high frequency among the immigrants. Condition 3 -> No net mutations. By changing one allele into another, mutations alter the gene pool. Condition 4 -> Random mating. If individuals pick mates with certain genotypes, then the random mating required for Hardy-Weinberg equilibrium does not occur. Condition 5 -> No natural selection. Differential survival and reproductive success of genotypes will alter their frequencies and may cause a detectable deviation from frequencies predicted by the Hardy-Weinberg equation.
9 Write the Hardy-Weinberg equation.
Use the equation to calculate allele frequencies when the frequency of homozygous recessive individuals in a population is 25%.
~p^2+2pq+q^2=1; p+q=1; p=1-q; q=1-p ALLELE FREQUENCIES --> p^2 => .5 2pq =>.5 q^2 => .5
Mutation and Sexual Recombination
10 Explain why the majority of point mutations are harmless.
~The majority of point mutations are harmless because there are several arrangements that can code for one amino acid. For example, UCU and UCC both code for serine, so a point mutation changing the U into a C would be completely harmless.
11 Explain why mutation has little quantitative effect on allele frequencies in a large population.
~Mutations have little quantitative effect on allele frequencies in large populations because genetic drift also factors into allele frequencies. Mutations are the driving force behind natural selection, and due to genetic drift, mutations are not the only thing that factor into changing allele frequencies.
12 Describe the significance of transposons in the generation of genetic variability.
~if the gene mutation via transposons isn't harmful then it will be passed on through generations. This increases the number of genes that are passed on, playing a huge role in
evolution.
12. Explain how sexual recombination generates genetic variability.
~Sexual recombination means that half of one parent's genes are combined with half of the other parent's genes in the offspring, which results in gene combination that did not previously exist. Sexual recombination and mutations would increase the amount of variation within a group. With sexual recombination, you constantly generate new variations in the population. If it weren't for this, all offspring would be identical to their parents and the only way for diversity to develop would be through mutations.
Natural Selection, Genetic Drift, and Gene Flow
13. Explain the following statement: “Only natural selection leads to the adaptation of organisms to their environment.”
~Genetic flow and genetic drift occur totally randomly. However, natural selection will allow the genomes that are a good adaptation to the environment pass on to the next generation and cause the genomes that aren't good adaptations die out.
14. Explain the role of population size in genetic drift.
~Genetic drift is the process of change in the genetic composition of a population due to chance or random events rather than by natural selection, resulting in changes in allele frequencies over time. If a population is small, there is is less variation between the organisms. If a catastrophe occurs, the population will not be able to recover as quickly because the alleles will not be as diverse.
15. Distinguish between the bottleneck effect and the founder effect.
~Bottleneck effect (catastrophe)-> Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population. Founder Effect -> Genetic drift attributable to colonization by a limited number of individuals from a parent population.
16. Describe how gene flow can act to reduce genetic differences between adjacent populations.
~Gene flow can act to reduce genetic differences in adjacent populations because gene flow increases the movement of genes from different populations of species. The more interbreeding between two populations, the more similar their genes.
Genetic Variation, the Substrate for Natural Selection
17. Explain how quantitative and discrete characters contribute to variation within a population.
18. Distinguish between average heterozygosity and nucleotide variability. Explain why average heterozygosity tends to be greater than nucleotide variability.
~Directional selection -> Natural selection that favors individuals at one end of the phenotypic range. Disruptive selection -> Natural selection that favors individuals at either extreme end of the phenotypic range. Stabilizing selection -> Natural selection that favors intermediate variants by acting against intermediate phenotypes.
19. Define a cline
~a graded change in a character along a geographic axis.
20. Define relative fitness.
~Relative fitness - the contribution of an individual makes to the gene pool of the next generation relative to the contribution of other individuals. a. Explain why relative fitness is zero for a healthy, long-lived, sterile organism. b. Explain why relative fitness could be high for a short-lived organism.
21. Distinguish among directional, disruptive, and stabilizing selection. Give an example of each mode of selection.
~Directional - occurs when conditions favor induviduals exhibiting one extreme of a phenotypic range, therby shifting a populations frequency curve for the phenotypic character in one direction or the other. Common when a pop environment changes or when members migrate to a new habitat. Disruptive – occurs when conditions favor individual at both extremes of a phenotypic range over individuals with intermediate phenotypes. Example - pop of black-bellied seed crack finches in Cameroon whose members have two distinct beak sizes. Small billed for soft seeds and large birds for hard seeds to crack them. Birds with intermediate sized bills were insufficient for the soft seeds and the hard seeds, have low relative fitness. Stabilizing - acts against both extreme phenotypes and favors intermediate variants. This reduces variation and tends to maintain the status quo for a particular phenotypic character. Example- babies average weight is around 6 pounds, large ands miller babies have a higher motility rate then the middle ones.
22. Explain how diploid can protect a rare recessive allele from elimination by natural selection.
~Diploid maintains genetic variation in the form of hidden recessive alleles because the cell has two sets of the recessive allele.
23. Describe how heterozygote advantage and frequency-dependent selection promote balanced polymorphism.
~Heterozygote advantage occurs when heterozygotes have a higher fitness than do both homozygotes. In frequency-dependent selection, the fitness of a phenotype declines it becomes too common in the population.
24. Define neutral variations. Explain why natural selection does not act on these alleles.
~Neutral variations are differences in DNA sequence that do not confer a selective advantage or disadvantage. Natural selection doesn't act on these alleles because the tendency for directional and stabilizing selection reduce variation is countered by mechanisms that preserve or restore it.
25. Distinguish between intersexual selection and intersexual selection.
~Intersexual selection -> a direct competition among individuals of one sex (usually the males in vertebrates) competes for mates of the opposite sex. Intersexual selection -> Individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex, (also called mate choice)
26. Explain how female preferences for showy male traits may benefit the female.
~More extravagant individuals mean that their offspring will also have more extravagant features.
27. Describe the disadvantages of sexual reproduction.
~Sexual Reproduction can be much slower than asexual reproduction. This is because it relies on other things. For animals, they need to find a mate to breed with and plants need to be pollinated (they rely on the presence of wind or animals for this)
28. Explain how the genetic variation promoted by sex may be advantageous to individuals on a generational time scale.
29. List four reasons why natural selection cannot produce perfect organisms.
1. Selection can only act on existing variations
2. Evolution is limited by historical constraints
3. Adaptations are often compromises
4. Chance, natural selection, and the environment interact
Major factors that alter allele frequencies
1. Genetic drift
2. Gene flow
3. Natural selection
Struggle for existence- competing for limited resources food shelter mate water
Struggle for the fittest – best fit for the environment at the time speed camouflage
Relative fitness-Ability to gives leave genes for offspring
Three modes of selection
Directional->->or->