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Evolutionary Biology: The Theory and Mechanisms of Evolution

Explore the theory of evolution, from the origin of species to macroevolution. Learn about genetic drift, gene flow, and natural selection as mechanisms of evolution. Dive into Darwin's principles and the process of speciation.

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Evolutionary Biology: The Theory and Mechanisms of Evolution

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  1. Bio 7: General Biology IIEvolutionary, Organismal, & Ecological Biology Dr. Diane Livio liviodl@lamission.eduCANVAS: ilearn.instructure.com CMS 229 (in the 221 suite) M 4:00-6:00pm W 12:30-2:30pm T/Th 10:30-11:30am

  2. About this course • Majors course – rigorous and challenging, designed to be rewarding • Student responsibilities • Review the syllabus • Check CANVAS regularly

  3. Expectations & Goals • What is expected of you? • What do you expect of me? Or your class mates?Of the course? • First module on CANVAS has help! • “Learn How You Learn” www.vark-learn.com

  4. Evolutionary Processes "Nothing in biology makes sense except in the light of evolution" - Theodosius Dobzhansky

  5. Scientific Theory • Def: a proposed explanation for a very general class of phenomena, supported by a large body of evidence • Possesses both pattern and process components

  6. Theory of Evolution • On the Origin of Species (1859) • All life evolved gradually from one primitive species [lived 3.5 bya] • Split off into many diverse species over time • Mainly by natural selection

  7. Pattern of Evolution • Descent with modification • Inherited characteristics in a population of a species change over time • Sometimes population changes over time to form a new species • Newer species descend from older species

  8. Macroevolution • Pattern of evolution over large scales • Larger than the species level • Over geologic time scale How old is the Earth? How old is life?

  9. Earth’s Early History • Estimates of Age of Earth/Solar System -- Current estimate: 4.54 by • Oceans formed by 3.8 bya • No O2, much solar radiation

  10. Life – 3.6 to 3.8 bya Oldest fossils: 3.5 by Most history of “higher” organisms in most recent 500 million years…

  11. Macro- vs Micro-

  12. Process of Evolution Microevolution: the change in allele frequencies in a population over time Population: a group of individuals of one species living in a particular place

  13. DNA • Genetic info – heritable • Genes: code for proteins to make and maintain organisms • Allele: form of a gene

  14. GENOME CHROMOSOMES NUCLEOTIDES GENOTYPE vs PHENOTYPE

  15. Process of Evolution Microevolution: the change in allele frequencies in a population over time Mechanisms of Evolution: Mutation Genetic Drift Gene Flow Natural Selection

  16. Mutation in DNA • Def: change to the nucleotide bases (adds variation to the population)

  17. Mutation = Source of DNA Variation DNA Replication = Potential MISTAKES

  18. Genetic Drift • Def: any change in allele frequencies in a population that is due to chance • Random with respect to fitness

  19. More pronounced in small populations • Drifting allele frequency could lead to loss of allele or fixation (100% frequency) Fig. 23.4

  20. Genetic Drift - how it occurs: • Genetic bottleneck – sudden reduction in # of alleles in a population

  21. Conservation biologists manage “gene pool” of species with small population sizes to prevent loss of alleles through drift.

  22. Genetic Drift - how it occurs: • Founder’s effect – change occurs when a new population is established • Small subset does not represent allele frequencies of source population

  23. Gene Flow • Def: change in allele frequency due to migration between populations

  24. Gene Flow: movement of alleles from one population to another • Tends to make one or both populations look more like the other

  25. Charles Darwin: The Origin of Species (1859) • Identified natural selection as the major mechanism of adaptive evolution • Much focus on survival aspect of reproduction  “survival of the fittest”

  26. Adaptive Evolution Adaptation = a heritable trait that increases an individual’s ability to produce offspring (its fitness) in a particular environment relative to individuals lacking the trait

  27. Natural Selection • Process by which heritable variation leads to differential success in survival and reproduction • Differential reproductive success can result from differences in survival, fecundity, and mating success.

  28. Artificial selection – deliberate manipulation by humans

  29. Summary • Natural selection adapts a population to its environment. • Selection operates on individuals. Evolution occurs in populations and species. • Other mechanisms of evolution: mutation, drift, gene flow.

  30. Speciation • Species: “an evolutionarily independent population or group of populations” • Reproductive compatibility • Similar physical appearance • Shared, unique genetic history • Allopatric vs sympatric speciation • Physically separated populations vs “living together”

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