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Evolution and Diversity: Sometimes, differences between organisms of the same kind provide advantages for surviving and reproducing in different environments. These selective differences may lead to dramatic changes in characteristics of organisms in a population over extremely long periods of time. KEY IDEA: The diversity and changing of life forms over many generations is the result of natural selection, in which organisms with advantageous traits survive, reproduce, and pass those traits to offspring. I. New traits may result from new combinations of existing genes or from mutations of genes in reproductive cells within a population. a. 4 principles of natural selection: b. In order for natural selection to occur, some organisms must have traits that are more advantageous than others. c. Variation may result from: i. Genetic recombination during meiosis 1) Way homologous chromosomes line up (independent assortment) 2) Crossing over ii. Contributions of each parent to offspring during sexual reproduction iii. Mutations d. Differential reproductive success e. POPULATIONS, not individuals, evolve i. Gene pools ii. Change in genetic make-up of a population changes over time f. Natural selection: i. Peppered moths & Industrial Revolution ii. Other examples iii. Adaptations g. Evolution is NEVER based on NEED i. Individuals that do not possess favorable traits may die off ii. Populations/Species may go extinct II. Molecular evidence (e.g. DNA, protein structures, etc.) substantiates the anatomical evidence for evolution and provides additional detail about the sequence in which various lines of descent branched. a. Various types of evidence support evolution (think “What did T. rex taste like?” i. Fossil record ii. Anatomy 1) Homologous structures 2) Vestigial structures iii. Geographic patterns 1) Uniqueness of Australia iv. Molecular Evidence 1) Common bases in DNA 2) Common gene sequences in related organisms 3) Similarities in amino acid sequences of proteins b. Technology can be used to determine evolutionary relationships among species i. Gel electrophoresis/DNA Fingerprinting ii. DNA sequencing iii. Protein sequencing III. The principles of evolution (including natural selection and common descent) provide a scientific explanation for the history of life on Earth as evidenced in the fossil record and in the similarities that exist within the diversity of existing organisms. a. Changes in species do not follow set pattern or timeline i. Gradualism vs. Punctuated equilibrium ii. Adaptive radiation b. All species on Earth today descended from common ancestor i. Life 1st appears in fossil record 3.5 bya ii. Fossil record provides evidence for ancient life forms 1) Fossil record incomplete iii. Prokaryotes eukaryotes (endosymbiosis) iv. Unicellular Colonial Multicelluar organisms c. Phylogentic Trees/Cladograms IV. Evolution occurs as a result of the following factors: (1) ability of a species to reproduce; (2) genetic variability of offspring due to mutation and recombination of genes; (3) finite supply of resources required for life; (4) natural selection, due to environmental pressure, of those organisms better able to survive and leave offspring a. Evolutionary process is influenced by: i. Environmental pressures ii. Genetic drift/chance events iii. Mutation iv. Competition for resources b. Implications of environmental changes: i. Volcanic eruptions ii. Global climate change iii. Pollution