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54 Cards in this Set
- Front
- Back
Evolution |
Change in genetic composition of populations over time. Individuals do not evolve, populations do |
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Evolutionary Theory |
-Understanding and application of the processes of evolutionary change to biological problems -Allows us to make predictions about biological world |
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Darwins explanatory theory for evolution |
-Species change over time
-Share a common ancestor (descent w/modification) -Natural Selection |
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Natural Selection Acts on what? |
Mechanism that produces change. -Acts on mutation and results in adaptation |
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Mutations |
-Origin of genetic variation -Change in nucleotide sequences -Randomly |
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Alleles |
Different forms of a gene |
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Gene pool |
Sum of all copies of all alleles at all loci in a population |
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Allele frequency |
Proportion of each allele in the gene pool |
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Genotype Frequency |
Proportion of each genotype among individuals in the population |
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Adaptation |
-Favored trait that evolves through natural selection -Produces trait |
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Gene flow |
-Migration of individuals or movement of gametes between populations which can change allele frequencies -Migration |
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Genetic Drift |
-Random changes in allele frequencies from one generation to the next -Mostly in small populations -Accidents, only lucky genes -Does not promote adaptation |
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Mechanisms of Evolution |
Mutations, gene flow, genetic drift, and natural selection |
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Population Bottleneck |
-Environmental result in survival of only a few individuals due to environmental issues, hunting -Result in genetic drift -Loose much of genetic variation -Bad for endangered species and small populations |
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Founder Effect |
Genetic drift changes allele frequencies when a few individuals colonize a new area |
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Sexual Selection |
-Individuals mate with particular opposite sex rather than random -Trade-off between attracting mates and predators EX: Long tails in birds |
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Genetic Structure |
Frequency of different alleles and genotypes in a population |
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Hardy-Weinberg Equilibrium |
Model where allele frequencies dont change across generations; genotype can be predicted from allele frequencies -Random mating and infinite population size -No mutations, no gene flow, selection of genotyoes |
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Qualitative Trait |
Influences by alleles at one locus, black versus white |
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Quantitative Traits |
Influenced by alleles at more than one locus, continuous variation, body size |
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Stabilizing Selection |
Favor average individuals, reduces variation but no change in mean, also purifying selection -Gets narrower towards middle |
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Directional selection |
Favors one direction from mean -Moves to one side |
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Disruptive selection |
Favors in both directions, increased variation -M shaped graph |
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Purifying slection |
Selection vs. any deleterious mutations to usual gene sequence |
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Nucleotide substitution |
Change in one nucleotide in a DNA sequence |
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Synonymous Substitution |
Silent, doesn't change encoded amino acid |
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Nonsynonymous substitution |
Missense, deleterious but be neutral or advantageous |
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Pseudogenes |
Copies of genes that are no longer functional |
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Insertions, deletions, rearrangements of DNA sequences |
Types of mutations, larger effect than point mutations, can change reading frame of protein coding sequences |
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Neutral Theory |
@ molecular level, majority of variants are neutral, accumulate through genetic drift rather than positive selection |
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Sexual Reproduction |
Results in new gene combinations and produces genetic variety
Facilitates rape of damaged DNA |
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Asexual Reproduction |
Deleterious mutations accumulate, Mullers ratchet |
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Lateral Gene Transfer |
Individual genes, organelles or genome fragments move horizontally from lineage to another. -DNA picked up from environment, or transferred in a viral genome -Increases genetic variation -Uncommon in eukaryotes |
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Gene duplication |
Genomes gain new functions |
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Gene duplication fates |
-Both may retain original function -Diverge in diff. tissues or at different times in development -One copy may accumulate deleterious mutations and become functionless pseudogene -One copy original function, other changes |
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In Vitro Evolution |
New molecules are produces in the lab to perform novel functions |
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Species |
Organisms that mate with one another |
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Speciation |
Divergence of biological lineages and emergence of reproductive isolation b/w lineages |
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Cryptic Speciaes |
Two or more species that are morphologically indistinguishable but don't interbreed |
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Reproductive isolation |
two groups of organisms can no longer exchange genes |
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Allopatric Speciation |
Separated by physical or geographic barrier such as sea levels rising, continents drifting, climates change -Sister species, species that are e/others closest relatives but live opposite sides |
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Sympatric speciation |
Speciation w/o physical isolation |
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Disruptive speciation |
Indiv. w/ certain genotypes prefer distinct microhabitats where mating takes place |
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Polyploidy |
Duplication of sets of chromosomes within individuals -Common in plants because many can self-fertilize |
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Autopolyploidy |
Chromosome duplication in single species |
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Allopolyploidy |
combining chromosomes of two different species |
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Prezygotic isolation mechanisms |
prevent hybridization |
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Postzygotic isolation mechanisms |
Reduce fitness of hybrids, reinforcement of prezygotic mechanisms -Low hybrid zygote/adult viability -Hybrid infertility |
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Mechanical Isolation |
Differences in sizes and shapes of reproductive organs |
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Temporal isolation |
Species breed at different times of year or day |
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Behavioral isolation |
Individuals fail to recognize mating behaviors of other species |
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Habitat isolation |
Two close species evolve preferences for living or mating in diff. habitats |
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Gametic isolation |
sperm and eggs of diff species will not fuse |
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Hybrid zones |
when reproductive isolation is incomplete, narrow b/c of pressure against hybrids |