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Key Concepts: Ch. 5

Key Concepts: Ch. 5. Origins of life. Evolutionary processes . Ecological niches. Species formation. Species extinction. Origins of Life. Chemical evolution: of organic molecules 4.6 bya. Biological evolution: of life, 3.7 bya. Fig. 5-2 p. 96; Refer to Fig. 5-4 p. 98.

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Key Concepts: Ch. 5

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  1. Key Concepts: Ch. 5 • Origins of life • Evolutionary processes • Ecological niches • Species formation • Species extinction

  2. Origins of Life • Chemical evolution: of organic molecules 4.6 bya • Biological evolution: of life, 3.7 bya. Fig. 5-2 p. 96; Refer to Fig. 5-4 p. 98

  3. Evolution and Adaptation • Macroevolution: long-term genetic changes through which new species form and others are adapted. • Microevolution:small genetic changes in the gene pool of a population of a species. • Gene pool: total genes of all the individuals in a population

  4. Mutation: random changes in the structure or number of DNA molecules • 2 methods: 1. Exposure to external agents 2. Random mistakes in the genetic code Evolution and Adaptation • Natural selection: process in which some members of a population have genetic variability that increases their chance of survival and production of offspring. • Evolution by natural selection requires three things:1. Variability, 2. Heritable, 3. Differential reproduction

  5. Natural Selection • Differential reproduction: Enables individuals with beneficial traits to leave more offspring than others of the population • Adaptive trait: A heritable trait that enables organism to better survive and reproduce under a given set of conditions Fig. 5-5 p. 101 Ex. Kettlewell Peppered Moth

  6. Directional Selection

  7. Stabilizing Selection

  8. Diversifying Selection

  9. Evolution and Adaptation • Gene flow: immigration and emigration of genes into and out of a population • Genetic drift: Chance events can cause the frequencies of alleles in a small population to drift randomly from generation to generation. Another mechanism of evolution

  10. Coevolution • Interactions between species can result in microevolution in each of their populations. • When populations of two different species interact over a long time, changes in one population can lead to changes in the gene pool of the other population

  11. Ecological Niches and Adaptation • Ecological niche:The species way of life or functional role in the ecosystem • Habitat: physical location of where it lives • Fundamental niche: Full potential range of physical, chemical, and biological conditions and resources it could theoretically use if there were no direct competition from other species. • Realized niche: to survive and avoid competition for the same resources a species occupies only part of its fundamental niche

  12. Ecological Niches and Adaptation Fig. 5-7 p. 104

  13. Broad and Narrow Niches • Generalist species: species with a broad niche • Specialist species: species with a very narrow niche Refer to Spotlight p. 105

  14. Speciation: Macroevolution that leads to the development of new species. Long term changes. Speciation, Extinction, and Biodiversity • Geographic isolation: isolation due to geographic changes that isolate populations of the same species. If maintained the gene pools of the populations alter by natural selection and lead to the development of new species. • Reproductive isolation: Isolation due to differences is reproductive ability, timing, production of fertile offspring that lead to new species.

  15. Fig. 5-8 p. 105 Geographic and Reproductive Isolation

  16. Alternate Macroevolution Forms • Gradualism (Darwin): A series of many microevolutions that lead to an isolation of populations and eventual speciation • Punctuated Equilibrium (Stephen J. Gould): Evolution in which species evolve and maintain for a long period of time with short punctuated bursts of evolution.

  17. Extinction • When environmental conditions change living organisms have 3 ways to react: 1. Evolve (better adaptations) 2. Move 3. Cease to exist (extinction)

  18. Background extinction: low level of localized extinctions due to local environmental changes Extinction • Mass extinction: significant rise in extinction beyond the background rate. It is catastrophic, widespread and global event in which large groups of species are wiped out. • Mass Depletion: higher than normal but not high enough to classify as mass extinctions • Adaptive radiation: Divergent evolution that comes about when there is a large amount of openniches, often the result of mass extinctions

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