© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e1 Biological Evolution A change in the genetic characteristics of a population over time If any allele frequency in a population changes w/ time, the population is evolving Most people think of evolution as Darwin’s speciation, but this is not correct

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e2 Only populations can evolve; individuals cannot  (on molecular level, genes can evolve) Small scale change = microevolution Large scale change = macroevolution Macroevolution can lead to speciation, but it does not have to  macroevolution that has occurred in dogs Biological Evolution

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e3 Evolution occurs through two major genetic forces:  Natural Selection (includes artificial seltn)  Genetic Drift What are the other two forces that can change allele frequencies in a population?  Mutations  Gene flow  Do not generally cause evolution, mutation is too rare & gene flow tends to equalize the gene frequencies Mechanisms of Evolution

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e4 Natural Selection Occurs because: Organisms with favorable traits have a better chance at survival The longer an organism lives, the more offspring it may produce More of the next generation will have the favorable trait than the previous generation

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e5 Genetic Drift Differences in reproduction or survival between organisms due to random chance Environmental disturbances can cause genetic drift:  Hurricanes or Volcanic eruptions  Clearing land for development or Over-hunting Can be from random events  seeds from white flowers are blown to gravel, some seeds from red flowers blown to good soil.

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e6 Genetic Drift

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e7 Result of Evolution Evolution results in 3 major themes in biology: 1. Adaptation of populations 2. Diversity of life 3. Shared inherited characteristics between organisms

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e8 Adaptations & Diversity Adaptation –a characteristic that improves the survival of an organism  The result of natural selection Diversity is the result of speciation

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e9 Impact of Evolutionary Thought Understanding evolution has impacted technology:  Development and use of pesticides  Antibiotics and the development of drug resistance Doonesbury cartoon? Doonesbury cartoon

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e10 Readings on Evolution I have assigned the readings, but I have only lightly covered this topic Want to spend more time on Life on Earth

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e11 Shared Inherited Characteristics Characteristics arise due to a common ancestry:  Homologous structures  Vestigial structures

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e12 Shared Non-Inherited Characteristics Convergent evolution in similar adaptations These are considered analogous structures  Thorns on roses and cactus  Wings in birds and insects

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e13 Evidence for Evolution Fossils

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e14 Evidence for Evolution Organisms contain evidence of their evolutionary history:  Vestigial structures  Embryological development

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e15 Evidence for Evolution Continental drift The lungfish existed before the break up of the super continent, Pangaea Living representatives of the lungfish are all over the world

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e16 Evidence for Evolution Direct observations of genetic change in populations Artificial selection:  Farming crops  Domesticated animals

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e17 Evolution in Action Medium ground finch in the Galapagos Changes in beak and body size correlate with rainfall over time

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e18 Of the following situations that pertain to evolution, which one is false? A. Organisms inherit traits from their parents. B. Organisms can adapt to prepare their offspring for future events. C. Evolution can happen by chance. Concept Quiz

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e19 Concept Quiz Evolution is the change that occurs in __________ over time. A. a population B. an organism C. the environment

© 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e20 Concept Quiz Of the following, which term or phrase best describes the process of natural selection? A. Genetic drift B. Differential reproductive success C. Speciation