Chapter 23

Chapter 23 - Chapter 23 The Evolution of Populations I The smallest unit of Evolution a One common misconception about evolution is that individual

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Chapter 23 - The Evolution of Populations I. The smallest unit of Evolution a. One common misconception about evolution is that individual organisms evolve during their lifetime b. Evolutionary processes (e.g. natural selection) acts on individuals, but populations evolve II. Concept 23.1: Mutation & sexual recombination produce the genetic variation that makes evolution possible a. If every organism is identical, then there’s nothing to select because all genes will be same and will be passed down. Instead all genes sequences and frequencies are different so everyone is different. b. Mutations occur in order to get new alleles c. Sexual reproduction helps to maintain variability III. Variation within a population a. Discrete characters: i. Classified on an either-or basis ii. E.g. flower color in pea plants iii. Either purple or white, nothing in between b. Quantitative characters: vary along a continuum within a population i. Height and weight ii. There’s more than just either/or, there are many different values IV.Mutation a. Mutations changes in nucleotide sequence of DNA i. Source of new alleles and genes b. Point mutation: i. Change in one nucleotide base in a gene 1. An A at one point in the gene and then it becomes a G all of a sudden c. Chromosomal mutations i. Delete, disrupt, or rearrange many loci on a chromosome
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1. Deletion or insertions of chromosomes in the sequence 2. They can be rearranged and moved around on the same chromosome or even a segment can be moved from one chromosome to another chromosome d. Gene duplications i. Duplication of whole segments of a chromosome 1. Sometimes they will copy themselves or even copy and insert themselves elsewhere 2. Can also increase the number of genes within the genome e. Mutation rate averages 1 in every 100,000 genes per generation i. Fairly rare occurrence V. Sexual Recombination a. In sexually reproducing organisms, sexual recombination produces
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This note was uploaded on 02/26/2009 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Chapter 23 - Chapter 23 The Evolution of Populations I The smallest unit of Evolution a One common misconception about evolution is that individual

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