ISB 202 1nd Edition Lecture 10Outline of Last Lecture I. EvolutionOutline of Current Lecture - Evolution Continued…II. Natural SelectionIII. Selection PressuresIV. EvolutionCurrent LectureNatural Selection• Natural Selection is the major mechanism driving the process of evolution.o Those best fit to exist under the current conditions survive and produce more offspring• Results from no human intervention, control, or direction• Results in changes in the inherited characteristics of a population• Increases a species’ fitness in the environment over time• Two current theories of how evolution occurs1. Gradualism 2. Punctuated equilibrium• Modern Synthesis: A comprehensive, unified explanation of evolution based on combining previous theories, especially of Mendelian genetics, with Darwin’s theory of evolution by naturalselection • The process whereby individuals suited to a particular environment pass on more of their genes to the next generation is called natural selection.• Where do the differences in the genes within individuals come from?o Mutation: changes in DNA sequence that occur by chance (random mistakes in DNA replication, exposure to radiation, etc.)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Selection Pressures• It is the environment that gives certain mutations an advantage under those particular conditions and causes other variants to be disadvantaged. The environment exerts selection pressures.• No variation is inherently good or bad. As environments change, the trait being selected for will change. A trait that was once selected against can be selected for if the environment changes.Gene Pool• The complete set of all of the genes in the individuals of a given population or species• Function of Genes:o Codes for an organisms traits.– Physical– Behavioral– PhysiologicalSource of new Genetic Material• Mutations • Most are lethal• Introduce new genes into a population if successfulEvolution• Change in allele frequency over time• The change in a population’s genetic makeup (gene pool) through successive generations.Evidence for Evolution• Geological formations• Isotope / Carbon Dating and other types of dating• Fossils - Provide a record of earlier plants and animals , understanding of where and when they lived, an idea of their lifestyleso Fossils of organisms of different geologic ages trace lines of evolution that gave rise to those organisms• Living things have been evolving on Earth for millions of years…• Evidenceo Geographic distribution of living specieso Homologous body structures: body part with the same basic structure and embryonic origin as that of another organism, though not necessarily sharing the same function o Similarities in early development (embryology)• Convergent Evolution: Independent evolution of similar adaptations in unrelated species living insimilar
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