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Biology 101

by: Lindsey Wilcox
Lindsey Wilcox

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Principles of Biology: Cells
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This 3 page Class Notes was uploaded by Lindsey Wilcox on Friday July 22, 2016. The Class Notes belongs to BIO 201 at University of North Carolina - Wilmington taught by Dickens in Summer 2016. Since its upload, it has received 7 views. For similar materials see Principles of Biology: Cells in Biology at University of North Carolina - Wilmington.


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Date Created: 07/22/16
AP Biology Brochure: Ch: 21 Main Topics: 1. Genetic variation makes evolution possible  Microevolution: Evolution change in populations, the smallest scale of evolution; a change in allele frequencies in a population over generations. Darwin’s The Origin of Species, was then evidence needed to prove natural selection was main cause to life on earth evolving over time. Not long after Darwin published The Origin of Species, Gregor Mendel wrote a paper on the inheritance in pea plants. In this paper he had wrote the frame work of heritance, genes, and the genetic differences on which evolution would be later on be based off of. Individuals within a species vary in their species characteristics, like human’s height or voice.  Genetic variation: Differences among individuals in the in the composition of their genes or other DNA sequences. Some heritable phenotypic differences occur on an “either-or” basis, like flowers that are either white or pink. This is all due to a single gene locus that makes the alleles different causing the distinct phenotype contrast. Evolution is due to genetic variation as we have read above, but what is genetic variation due to? Genetic variation one of three things, these being, when mutation, gene duplication, or other processes produce new alleles and new genes. 2. The Hardy-Weinberg equation can be used to test whether a population is evolving Even if a genetic variation is present, this does not always guarantee the population will evolve. Population: Is a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. Gene pool: all copies of every type of allele at every locus in all members of the population. These populations that have genetic variations but is not evolving can be described by the Hardy-Weinberg principle. This principle states that the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work. Example: In a wildflower population, the gene pool remains constant from one generation to the next. Mendelian processes alone do not alter frequencies of alleles or genotypes. ADD PICTURE OF DAGRAM 3. Natural selection, genetic drift, and gene flow can alter allele frequencies in a population These are the five conditions required for a population to be in the Hardy-Weinberg equilibrium, and f any of these are slightly deviated it may cause evolution. Natural selection is a concept based on differential success in survival and reproduction: Individuals in a population exhibits variations in their heritable traits, and those with traits that are better equipped for their environment and tend to produce more offspring than those with traits that are not as well suited. Chance events can also cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations, this is the process of genetic drift. Allele frequencies can also be change by gene flow, or the transfer of alleles into or out f a population due to movement f fertile individuals or their gametes. 4. Natural selection is the only mechanism that consistently causes adaptive evolution Natural selection consistently increases the frequencies of alleles that provide reproductive advantages which therefore leads to adaptive evolution. Relative fitness is related to natural selection as it is the contribution an individual makes to the gene pool of the net generation relative to the contributions of other individuals. Directional Selection: Occurs when conditions favor individuals at one extreme of a phenotype range, thereby shifting a population’s frequency curve for the phenotypic character in one direction or the other. Disruptive Selection: Occurs when condition s favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes. Stabilizing Selection: Act against both extreme phenotypes and favors intermediate variants. Natural selection cannot form perfect organisms because it can only act on existing variations, it is limited by historical constraints, often its’ adaptations are often compromised, and lastly, because it interacts with chance and the environment.


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