Chapt 23 notes bio - Chapter 23 Notes Microevolution change in allele frequencies over several generations Three causes 1)natural selection

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Chapter 23 Notes Microevolution- change in allele frequencies over several generations. Three causes: 1)natural selection 2)random chance 3)gene flow (transfer of alleles between populations -Mutation and sexual reproduction produce the genetic variation that makes evolution possible Phenotypes are the product of an inherited genotype and many environmental influences Only the genetic part of variation can have evolutionary consequences Average heterozygosity- the percent on average of a populations loci that have 2 different alleles for the same locus Nucleotide variability causes genetic variability Geographic variation- differences in the genetic compositions of separate populations Cline- type of geographic variation. A graded change in a character along a geographic axis Mutation- the ultimate source of new alleles. A change in the nucleotide sequence of an organism’s DNA Only mutations in cell lines that produce gametes can be passed on to offspring Point mutation- a change in one base of a gene, can significantly alter phenotype Three mechanisms in sexual reproduction provide genetic variability: 1)crossing over 2)independent assortment of chromosomes
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This note was uploaded on 01/25/2011 for the course BIO 1100 taught by Professor Chang during the Spring '10 term at Georgia Institute of Technology.

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Chapt 23 notes bio - Chapter 23 Notes Microevolution change in allele frequencies over several generations Three causes 1)natural selection

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