Ch 13 Outline PDF

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Chapter 13 - How Populations Evolve

Evolution: genetic change in a population or species over generations A. The Diversity of Life a. Naming and Classifying the Diversity of Life The Linnaean system is used to name and classify species Taxonomy: the branch of biology concerned with identifying, naming, . and classifying species Each species is given a two-part Latinized name consisting of a genus, a group of closely related species Hierarchical Classification: Species, genus, family, order, class, phylum, kingdom, domain b. Explaining the Diversity of Life Aristotle thought that species were fixed and did not change over time Fossils: imprints or remains of organisms that lived in the past Lamarck claimed that evolution was the best explanation for the differences found in fossils and current life B. Charles Darwin and The Origin of Species a. Darwin’s Journey Darwin sailed on the HMS Beagle around the South American coast observed plants and animals He found that organisms from the same geographic area had more in common than organisms from a similar environment

I.

somewhere else Natural Selection: individuals with certain inherited traits are more likely to survive and reproduce than are individuals with other traits b. Darwin’s Theory of Evolution: the idea that living species are descendants of ancestral species that were different from present-day ones C. Evidence of Evolution a. Evidence from Fossils Fossils show differences between past and present organisms b. Evidence from Homologies Homology: similarity resulting from common ancestry Homologous structures: features that often have different functions but are structurally similar because of common ancestry Vestigial structures: remnants of features that served important functions in an organism’s ancestors c. Evolutionary Trees: branching diagrams that reflect a hypothesis about evolutionary relationships between groups of organisms D. Natural Selection as the Mechanism for Evolution a. Natural Selection in Action the products of natural selection, adaptations that suit organisms to their environment, can be found anywhere some insects are resistant to pesticides b. Key Points about Natural Selection Natural selection affects individual organisms -

Individuals do not evolve A population evolves over time as adaptive traits become common E. The Evolution of Populations a. Sources of Genetic Variation Mutation: a change in the nucleotide sequence of DNA Sexual reproduction: individuals inherit a unique combination of alleles b. Populations as the Units of Evolution Population: a group of individuals of the same species that live in the same area and interbreed Evolution can be measured by observing certain heritable traits in a population over generations Gene pool: consists of all copies of every type of allele at every locus in all members of a population c. Population Genetics and Health Science The Hardy-Weinberg equation is used to calculate the percentage of a human population that carries the allele for certain inherited diseases d. Microevolution as Change in a Gene Pool A nonevolving population is in genetic equilibrium, or Hardy-Weinberg equilibrium Microevolution: a change in a population’s gene pool over a succession of generations F. Mechanisms That Alter Allele Frequencies in a Population

a. Genetic Drift: a change in the gene pool of a population due to chance The bottleneck effect: genetic drift resulting from a drastic reduction in population size The founder effect: the type of genetic drift resulting from the establishment of a small, new population whose gene pool that of the parent population

differs from

b. Gene Flow: genetic exchange with another population c. A Closer Look at Natural Selection Relative fitness: the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals Directional selection: shifts the overall makeup of a population by selecting in favor of one extreme phenotype Disruptive selection: natural selection that favors extreme over intermediate phenotypes Stabilizing selection: favors intermediate phenotypes Sexual selection: a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates Sexual dimorphism: distinction in appearance based on secondary sexual characteristics...