Evidence for Darwin’s Ideas about EvolutionII. Common DescentIII. Multiplication of SpeciesIV. GradualismV. Natural SelectionTuberculosis Resistance to AntibioticsSexual Selection:BIO SCI 100 1st Edition Lecture 2Outline of Last Lecture I. Scientific MethodII. Theories are tested & modifiedIII. The history of evolutionary thoughtIV. Evidence for Darwin’s ideas about evolutionOutline of Current Lecture o Evidence for Darwin’s Ideas about EvolutionI. Perpetual ChangeII. Common DescentIII. Multiplication of SpeciesIV. GradualismV. Natural SelectionCurrent LectureI. Perpetual ChangeFossil Record:- Fossils show evolutionary trends in the changes in morphological traits.- Evolution of the horse: changes in:o body size, foot & hoof structure, and teeth.- Evidence of the order in which groups of organisms evolved: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.o Know that fish evolved before reptiles, which evolved before birds, which evolved before mammals.- The existence of species in fossil record:o Can provide evidence for the evolutionary steps from one group of animals to another.o Examples: o Archyopteryx a transitional form between dinosaurs and birds.o Ichthyostega a transitional form between Fish and Amphibians.Geologic Time Scale: - 2 Major extinctions:- Permian, loss of 90% marine invertebrate species- Cretaceous, end of the dinosaurs- 3 Major radiations (diversifications):- Cambrian; origin many invertebrate groups and earliest vertebrates- Triassic; first dinosaurs and mammals- Tertiary; mammal diversification II. Common Descent- Homology: similar traits (even if they are functionally different) appear in different organisms; because they were acquired from a common ancestor.o Vertebrate limb function varies, but similar structure.III. Multiplication of Species- Species :a group of interbreeding individuals, of common ancestry that:o 1. arereproductively isolated from other groupso 2. producefertile offspring- Multiplication of species occurs due to the process of:o Speciation: a new species evolves from a common ancestor, often in response to environmental changesExample: Darwin's Finches- Large differences in beak size and shape from small changes in these traits accumulatinggradually over time as individuals became adapted to their local environment =>new species.IV. Gradualism- In the fossil record a complete record of gradual change is rare.- Artificial selection produces minor variations; different breeds of dogs- Alternative view:- Punctuated Equilibrium:o Changes occur in “spurts” during short periods of time between long periods of evolutionary “stasis”.V. Natural Selection- Industrial melanism of peppered moths:- Response of insects to insecticides, doses that kill the majority of a population may laterbecome ineffective as resistant individuals survive and reproduce.Natural selection for antibiotic resistance in the Mycobacterium tuberculosis (TB)- In 1800s, TB killed thousands of people annually- 1900's improved sanitation, nutrition &antibiotics, almost eliminated TB infection in western world.- Over time, the few bacteria that had the trait necessary for resistance to antibiotics were favored by natural selection.- Today, TB once again kills about 2 million people every yearTuberculosis Resistance to Antibioticso Initial population of TB cells included regular TB cells &variants resistant to antibiotics.o TB cells after antibiotics included only a few resistant cellso TB cells resistant to antibiotics reproduced.1. Variation in the resistance trait existed in the population2. Variation was heritable and passed on to offspring.3. Natural SelectionCells with resistance gene survived &reproduced.Inheritance of Traits:- Inheritance of traits that improve survival &reproduction is an important aspect of Darwinian evolutiono Darwin did not know the mechanism of inheritance.o At the time, the theory of equal “blending inheritance” was popular: distinct traits inherited from parents.Examples:o White and red flower parents =>Pink offspringo Tall and short parent =>medium height offspringo This did not support the conditions necessary for Natural Selection to occur.o Why? Because it creates “averages” of trait variation, thus reducing the variationNeo-Darwinism:- Gregor Mendel: Austrian Monk, 1860's- Genetic material did not blend- Offspring carry both distinct traits from parents, but only one trait is expressed- Neo-Darwinism: Synthesis of Evolution by Natural Selection with Mendelian Genetics.3 Modes of Natural Selection:- Directional Selection :decreases diversity by favoring one extreme trait in the population. - Example: Birds with long beaks are better at foraging, surviving & reproducing.- Stabilizing Selection:Favors the average and reduces trait variation. Example: humans born at average weights have higher survival.- Disruptive Selection : selection favors both extremes ; and increases the amount of trait variation. Example: Individuals with either long or short beaks have higher survival rates and reproductionSexual Selection:- Males have ornamental traits to attract females for mating.- These traits develop through sexual selection male-male competition or female mate choice- The most elaborate males are most attractive and produce the most