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38 Cards in this Set
- Front
- Back
Locus
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Physical location of a gene on a chromosome
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Allele
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Version of a specific Gene. Different forms of a specific gene
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Hardy-Weinberg Equation
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Measures allele changes.
P^2 + 1/2(pq) If the population is not evolving.. p^2 + 1/2(2pq) |
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Hardy-Weinberg Equation assumptions
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No Natural Selection
No Genetic Drift No Gene Flow No Mutation Random Mating |
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Directional Selection
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Alleles change in one direction. Favors one extreme of a trait. Reduces genetic diversity
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Stabilizing Selection
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Alleles associated with the average trait values are favored. No change in average. It reduces trait variability and genetic variability. Example, optimal birth weight
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Disruptive Selection
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Alleles associated with both extremes of a trait are favored. Increases genetic diversity. Can often result in 2 separate species
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Sexual Selection
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Sexual Selection acts more strongly on males. Sexual Dimorphism is when males and females look differently
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Female Choice
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Females respond to some aspect of the male phenotype.
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Male-Male Competiton
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Males compete with each other for females
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Balancing polymorphism
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Maintains less fit alleles in a population. Two types-Heterozygote Advantage, and Negative Frequency Dependent Selection
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Heterozygous Advantage
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Heterozygous, Aa, has a higher fitness. Even though A is dominant over a. Aa is more fit to fight malaria.
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Negative Frequency Selection
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Rare individuals have higher fitness. Example, scale eating fish and non-rewarding orchids
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Genetic Drift
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Changes in genetic frequency from generation to generation as a result of random chance. It's random with respect to fitness. Most pronounced in small populations. Over time it can lead to lost of fixed alleles.
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Founder Effect
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When a small set of individuals starts a new population. May not reflect the allele frequencies of the sources population. One of the causes of genetic drift
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Genetic Bottleneck
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Results from a drastic and random reduction in a population size. One of the causes of genetic drift
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Gene Flow
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Movement of alleles from one population to another. Immigration and poppagules(seed spreading). Gene flow homogenizes the population.
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Mutation
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Production of a new allele. Increases genetic diversity. Most mutations lower fitness. Natural selection acts upon the phenotype of the mutation.Once new alleles arise, meiosis and sexual reproduction combine different alleles in new ways to increase genetic variation. This is why we are unique.
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Inbreeding
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Increases homozygosity in genotypes. Alters genotype frequencies.
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Neutral Evolution
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Much of genetic variation is neutral. Neutral mutations don't affect phenotype.
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Speciation
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Formation of new species. Genetic isolation and divergence. Species are distinguished by common characteristics.
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Species arise as a consequence of?
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Lack of gene flow with other populations, genetic divergence, functionally different characteristics
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Biological Species
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Reproductively isolated, members of a species cannot interbred and produce a viable offspring. Advantages: Strong foundation with darwin. Disadvantage: Cannot apply to fossils or asexual orgs. Cannot apply to geologically isolated populations.
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Morphological Species
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Based on differences in morphology. Advantages: Widely applicable to fossils and asexual orgs. Disadvantages: Subjective criteria, intraspecies morphology is often greater than interspecies variation
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Phylogenetic Species
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Based on ancestral analysis (phylogeny). Smallest identifiable group assigned species status. Advantages: Strong foundation with darwin and is widely applicable. Disadvantages: There are few thorough enough phylogenies.
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Ecological Species
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Based on environmental context. Each species occupies a unique niche. Adavantages: avoids problems with morphologically similar species and aseuxal orgs. Disadvantages: It's difficult to characterize niches in sufficient details.
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Reproductive Isolation in respect to hybrid formation
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Prezygotic and postzygotic isolation prevents a zygote from forming or a viable zygote to produce offspring.
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Prezygotic Isolation
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Causes: Disruptions of temportal (timing) spatial (location) and behavioral. Or a gamete cannot physically form in the womb.
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Post Zygotic Isolation
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Causes: Hybrid's ability to survive is questionable or is sterile.
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Anagenesis
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One species gradually transforms into another species (no branching) Gradual Natural Selection
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Cladogenesis
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One species gives rise to two or more species (branching). Disruptive selection
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Allopatrick Speciation (Other Country)
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Occurs between geographically isolated populations. Gene flow stops and genetic divergence occurs by natural selection, genetic drift, and mutation
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Vicariance
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The separation of a group of organisms by a geographic barrier, resulting in differentiation of the original group into a new one.
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Sympatrick (Same Country)
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Speciation without geographic isolation. Natural selection overwhelms gene flow. Can occur with spatial, temporal, and behavioral isolation.
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Polyploidy
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More than 2 homologous chromosomes. Mutations can create an extra chromosome copy.
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Autoploidy
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Mutation doubles chromosome number, and the resulting individual can be infertile or can only self fertilize. mostly plants
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Alloploidy
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Two different species mate. Mutation in the zygote doubles the chromosome number and can produce offspring. Horizontal evolution
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Gene |
A gene is the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins. |