BIO3400 1nd Edition Lecture 4 Outline of Last Lecture I 5 Elements of the Theory of Evolution II Phylogenetic Trees III Evidence for Evolution IV Vestigial Organs V Biogeography VI Transitional Forms Outline of Current Lecture I Homology II Evolution Fact vs Theory III Natural Selection IV Fitness and Adaptation V Modes of Selection Current Lecture Evidence for Evolution Continued Evidence of Speciation Prediction There will be examples of speciation one species splitting into two Ring species Ensatina salamander Homology Prediction related species will show structural similarities irrespective of different functions Homology similarity due to the inheritance of traits from a common ancestor o Limbs one bone 2 bones bunch of little bones fingers o Dolphin and shark o Developmental similarities embryo o Molecular similarities The genetic code is shared among all organisms The same triplets specify the same amino acids start and stop codons 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 98 8 of DNA is the same between humans and chimps The genes involved in more basic functions are shared with more distantly related organism Cell cycle genes are homologous between humans and baker s yeast DNA repair genes are homologous between humans and E coli In humans shared flaws suggest common ancestry flanking repeats misalignment during meiosis unequal crossing over pathology Predictions about evolution can be falsified Hypothesis theory must be falsifiable Examples o Fossils in the wrong place o Lack of change in fossil record o Adaptations in one species that are only good for a second species o Adaptations that are good for the species but not the individual o Adaptations that could not evolve in a stepwise process of increasing fitness o Lack of genetic variation in populations o Complete disagreement for phylogenies based on morphology and phylogenies based on DNA Evolution Fact and Theory Fact o Organisms have descended with modifications from common ancestors o All available evidence supports the fact of evolution Theory o How why life evolves o The mechanisms by which evolution occurs Natural Selection Requirements There is variation for a trait among individuals Some of that variation is heritable There is differential reproductive success among individuals There is a consistent relationship between the trait and reproductive success RESULT The genetic composition of the population changes from one generation to the next Selection acts on individuals but populations evolve Fitness and Adaptation Fitness the ability of an individual to survive and reproduce o Fitness is relative compared to other members of the population Adaptation a trait that increases an individual s fitness relative to individuals without the trait Artificial Selection Domesticated Foxes 1959 Dimitri Belyaev Target trait tameness Natural Selection Gallflies Focal trait gall size Modes of Selection Stabilizing Selection Selection that eliminates the extremes of a distribution and favors the center Gall flies Human birth weight o Very small babies and very large babies have higher mortality Modes of Selection Directional Selection Selection that favors individuals at one end of the phenotypic range Domesticated foxes Antibiotic resistance in bacteria o More resistant bacteria survive and reproduce Modes of Selection Disruptive Selection Selection that favors the extremes and eliminates the middle of a frequency distribution of trait values Spadefoot toad tadpoles