Chapter 23 Notes - Chapter 23 Evolution of Populations...

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Chapter 23 Evolution of Populations 1. Genetic variations in populations provide the "raw material" on which natural selection can act 2. Although selection acts on individuals, it is the population that evolves. Population Genetics 1. Population genetics is the study of how populations change genetically over time o Focuses on populations as the units of evolution 2. Microevolution - is change in the genetic makeup of a population from generation to generation o It is the smallest "unit" of evolution Inheritance… In Darwin's Time 1. Darwin lacked a satisfactory explanation for how heritable variation appears in a population and how this variation is transmitted to offspring 2. The widely accepted view at the time was "blending inheritance" 3. However, Darwin and others recognized this would actually eliminate variation! Gregor Mendel (Austria 1822-1884) 1. A little known Augustian monk, developed a theory of inheritance based on his experimental work with pea plants 2. Mendel proposed a particulate model of inheritance a few years after Origin of Species was published 3. Darwin never read it, and it's implications was not understood by those that did read it. 4. Mendel's law of segregation o Figure 14.5 The Modern Synthesis 1. The re-discovery of Mendel's work by several researchers in the early 20th century led to the rise of the Modern Synthesis 2. The Modern Synthesis was a more comprehensive theory of evolution that reconciled Mendel's theory of inheritance and Darwin's Natural Selection into an integrated whole. Gene Pools and Allele Frequencies 1. Population - Is a localized group of individuals that are capable of interbreeding and producing fertile offspring. o Figure 23.3 2. Gene pool - the total aggregate of genes in a population at any one time. o Consists of ALL alleles at ALL gene loci in ALL individuals of the population 3. Alleles - The variants of a particular gene that produce distinguishable phenotypic effects 4. If only one allele exists at a particular gene locus then that allele is said to be fixed in the population 5. Phenotype - the physical, physiological, and behavioral traits of an organism, which are determined primarily by its genetic makeup.
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