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| Mendelian inheritance refuted the idea of |
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Definition
| blending inheritance because white and red forms could be recovered from crosses among pink flowers |
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brought Darwin's ideas on natural selection together with genetics
-first half of twentieth century
-provided description of how the frequencies of genes in population change due to various forces
-dealt with both qualitative and quantitative traits |
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-discrete traits
-classified on an either-or basis
-variation due to one or two loci
-ex. eye color, blood type, flower color in Mendel's peas(white,pink,red) |
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vary along a continuum within a population
-variation due to the combined effects of many genes
-ex. height or weight of individuals, bill size in birds, seed weight |
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Definition
change in gene frequencies in populations through time
-natural selection acts on genes or individuals, but populations evolve |
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ultimate source of variation
-changes in the sequence of DNA
-causes new alleles and sometimes new genes to arise
-may be harmful(chromosomal), neutral, or beneficial |
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change in one base in a gene
-can have significant impact on phenotype |
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| Base-pair substitutions and Base-pair insertions or deletions |
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Definition
duplicate chromosome segments
-with two copies of a gene, one copy can diverge to a new function while the organism retains a functioning copy of the original gene
-important to long-term evolution of genomes and organisms |
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| Mutation rates among animals and plants are |
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Definition
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Definition
| brings new combinations of chromosomes together |
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Definition
| brings new combinations of mutations onto the same chromosome |
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| joining of gametes to make a new zygote |
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Term
| In sexually reproducing populations |
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Definition
| sex is far more important than mutation in producing the genetic difference that make adaption possible |
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Definition
study of how populations change genetically over time
-provides foundation for studying evolution
-reconciled Darwin's and Mendel's ideas |
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Definition
| total aggregate of genes in a population at any one time |
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evolution
-in an infinitely large population where gametes contribute to next generation randomly, allele frequencies will NOT change |
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describes population that is not evolving
-states that frequencies of alleles and genotypes in a populations gene pool remain constant from generation to generation provided that no other forces are at work
-p^2 + 2pq +q^2 = 1
-p^2 and q^2 are frequencies of the alternative homozygous genotypes
-2pq represents the frequency of heterozygotes |
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Term
| Conditions for Hardy Weinberg |
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Definition
-large population size
-Random mating
-no gene flow
-no mutations
-no natural selection |
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Term
| Hardy Weinberg Equilibrium |
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Definition
-describes a population in which random mating occurs
-population where allele frequencies do not change
-describes relationship between allele and genotype frequencies if the population mates at random |
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Term
| Things that alter a population's gene frequencies |
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Definition
| natural selection, genetic drift, and gene flow |
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Definition
differential success in reproduction
-increases the frequencies of certain genotypes, fitting organisms to their environment over generations |
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Definition
describes how allele frequencies can fluctuate unpredictably from one generation to the next
-reduces genetic variation
-the smaller a sample, the greater the chance of deviation from a predicted result |
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Definition
results from the movement of fertile individuals or gametes
-causes population to gain or lose alleles and reduces differences between populations over time |
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Definition
sudden change in the environment may drastically reduce the size of a population
-gene pool no longer reflective of original population's gene pool |
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occurs when a few individuals become isolated from a larger population
-can affect allele frequencies |
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| form of non-random mating in which similar phenotypes tend to mate with one another |
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graded change in a trait along a geographic axis
-examples of geographic variation occur as a cline |
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| differences between gene pools of separate populations or subgroups |
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| directional, disruptive, and stabilizing |
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| favors those at one end of the phenotypic range |
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| favors those at both extremes of the phenotypic range |
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| favors intermediate variants and acts against extreme phenotypes |
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Term
| frequency dependent selection |
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Definition
| when heterozygotes have higher fitness than homozygotes, the relative fitness of each allele depends on its frequency in the population |
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Definition
| occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population |
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Term
| Maintenance of Genetic Variation paradox |
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Definition
| -natural selection cannot produce evolutionary change without genetic variation even though both stabilizing and directional selection tend to reduce variation |
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Definition
| supply populations with new genetic variation |
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| Spatial and Temporal variation tend to maintain variation by |
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Definition
| favoring different alleles at different times and places |
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Definition
| maintains genetic variation in the form of hidden recessive alleles |
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| heterozygote advantage and frequency dependent selection are forms of |
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Definition
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Definition
some individuals who are heterozygous at a particular locus have greater fitness than homozygotes
-ex. sickle-cell allele which causes mutations in hemoglobin but also confers malaria resistance |
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Definition
| genetic variation that appears to confer no selective advantage or disadvantage |
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| Selection tends to remove |
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Definition
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| Things that maintain genetic variation |
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Definition
-mutation
-diploidy
-neutrality
-gene flow
-spatially or temporally varying selective pressures
-frequency dependent selection |
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