Biology Chapter 23 Outline

Biology Chapter 23 Outline - Chapter23Outline: BarbaraHonig...

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Chapter 23 Outline: The Evolution of Populations Barbara Honig Microevolution  – a change in allele frequencies in a population over generations. Concept 23.1 – Mutation and sexual reproduction produce the genetic variation that makes  evolution possible. Genetic Variation  within a population may be discrete or quantitative. a. Discrete characters  – can be classified on an either-or basis; many are determined by  a single gene locus with different alleles that produce distinct phenotypes – i.e. white or  purple flowers. b. Quantitative characters  – traits that vary along a continuum within a population;  usually results from the influence of two or more genes on a single phenotypic  character. Geographic Variation  – differences in genetic composition of separate populations living in different  geographic locations. Mutation  – the ultimate source of new alleles – is a change in the nucleotide sequence of an  organism’s DNA. Sexual Reproduction  – most of the genetic variation in a population results from the unique  combination of alleles that each individual receives. a. Three mechanisms contribute to the shuffling of alleles. i. Crossing over ii. Independent assortment of chromosomes iii. Fertilization Concept 23.2 – The Hardy-Weinberg equation can be used to test whether a population is  evolving. Population  – a group of individuals of the same species that live in the same area and interbreed,  producing fertile offspring. We can describe a population’s makeup by describing its  gene pool Hardy-Weinberg Principle  can be used to determine if a population is evolving or not.
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a. Hardy-Weinberg used to determine what the genetic makeup for a particular locus  would be for a population if it was NOT evolving. b. We can than compare these numbers with the actual numbers of the real population i. If there is NO difference in the numbers = NO evolution taking place. ii. If there is a difference in the numbers = evolution is taking place c. Hardy-Weinberg Equilibrium  – population’s gene pool remains constant from  generation to generation – provided Mendelian segregation and recombination of  alleles are the only factors at work.  d.
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