Chapter 2 Evolutionary Mechanisms

Chapter 2 Evolutionary Mechanisms - Chapter 2 Evolutionary...

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Chapter 2 – Evolutionary Mechanisms Levels of Selection and Change - The modern synthetic theory of evolution (changes in species’ traits are the results of altered gene frequencies) focuses on genetic change produced by natural selection within a population of plants and animals. - A population is defined as a group in which any two individuals have the potential of mating with each other - Ernst Mayr (1982) described the emergence of modern synthesis as a shift to “population thinking” - Mutationists are partially right in believing that individuals contribute to evolutionary change; but individuals do not evolve, only populations do. Individuals make their contributions by surviving, or not, reproducing, or not, and getting their genes into the next generation, or not . As individuals succeed and fail, the population gradually changes. Microevolution: Genes, genotypes, and Gene Pools - Microevolution is evolution below the species level (evolution that affects populations) - Macroevolution is evolution that involves the origin or extinction of species or higher taxonomic groups - Living creatures are characterized by its genotype, its entire set of genes (functional units of chromosomes in cell nuclei, controlling the coding and inheritance of traits; some genes are also in mitochondria) - Genes are structured into chromosomes in the nuclei of cells, but also in mitochondria , or bodies in the cytoplasm of cells that function in the metabolism of fat and proteins - Genes provide a blueprint for the construction, operation, and maintenance of individual organisms; humans have structural, regulatory, and other genes that control different traits and functions of the individual - The resulting phenotype depends on complex interactions between the organism’s genes and the environment. The gene-and-environment relationship can be summarized by: Genotype + Environment = Phenotype - When all the genes within a population/species are summed up, a gene pool is created; a shift in gene frequencies over time would support microevolution Phenotypes and Collective Phenotypes - A collective phenotype , or the set of phenotypic averages and norms that characterize a population or species, can show that population-level evolution has taken place Genes, DNA, and RNA - Each living species has a characteristic number of chromosomes ( diploid, or 2n ) occurring in all somatic cells (excluding gametes , which contain a haploid, or n number of chromosomes). The diploid number of chromosomes for humans is 46
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- Somatic cells primarily contain pairs of homologous chromosomes , or pairs that resemble each other in shape, size, and gene sequence; an exception are the pair of sex chromosomes , or X and Y, which distinguish males from females - The suggestion that chromosomes contain the cell’s hereditary material was suggested by Walter Sutton and Theodor Boveri in 1902 - Chromosomes consist of long strands of DNA (deoxyribonucleic acid), discovered by Friedrich Miescher in 1869, and whose composition and structure were worked out by
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This note was uploaded on 04/07/2008 for the course ANTH 145 taught by Professor Gatewood during the Fall '07 term at Lehigh University .

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Chapter 2 Evolutionary Mechanisms - Chapter 2 Evolutionary...

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