BIOL 1050 Lecture 21 Outline of Last LectureI. GeneticsII. Sex genes Outline of Current LectureI. EvolutionII. Evolution of populationsIII. Theory of evolution IV. Evidence of evolution Current LectureI. Evolutiona. Two meanings to biologists: a process and a theoryi. Process: a change over many generations in the relative frequency of allelesthat occur in a population 1. Population: a group of individuals of the same species living in the same area at the same time2. Individual organisms do NOT evolve a. Populations are the smallest biological unit that can evolveII. Evolution of populationsa. Evolution is a change in the allele frequencies of a population over time. For example, a change in the proportion of pigment alleles in the population of tigers means that evolution has occurredb. Direct observation of a processi. Examples1. Antibiotic resistance in bacteria2. Pesticide resistance in insects3. Drug-resistance in HIVii. Experiment1. Can fruit flies evolve so that they can resist starvation longer?a. Initial setupi. Start with a cage that contains a large number of fruitflies (5,000) and remove the foodb. Testing starvation resistanceThese 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.i. Wait until 80% of the flies starve to death, and then return the food to the cage. Record the average starvation-resistance timec. Start a new generationi. After the surviving flies eat a bit, collect the eggs those flies laid and transfer them to a new caged. Resultsi. 1st generation avg. starvation resistance 20 hrsii. 2nd generation avg. starvation resistance 23 hrsiii. 60th generation avg. starvation resistance 160 hrsIII. Theory of Evolutiona. All species are descendants of a single common ancestor, and all species are the result of millions of years of changeb. Charles Darwini. Observed many species while traveling the world1. The finch in the Galapagos islands ii. The origin of species (book) 1. Provided evidence of evolution2. Proposed a mechanism for evolution, called natural selection3. Alsoa. Waited 19 years to publishb. Survival of the fittest: being able to reproduce successfullyc. World before and after Darwini. Before1. Organisms were all put on earth by a creator at the same time2. Organisms are fixeda. No additions no subtractions3. Earth is about 6,000 years old4. Earth is mostly unchangingii. After1. Organisms change over time2. Some organisms have gone extinct3. Earth is more than 6,000 years old4. The geology of earth is not constant, but always changingd. Agents of evolutionary changei. Mutation1. An alteration of the base-pair sequence in the DNA of an individuals gamete producing cells that changes an alleles frequencyii. Genetic drift1. A random change in allele frequencies, unrelated to any alleles influence on reproductive successiii. Migration1. A change in allele frequencies caused by individuals mkoving into or out of a populationiv. Natural selection1. A change in allele frequencies that occurs when individuals with oneversion of a heritable trait have greater reproductive success than individuals with a different version of the trait2. Natural selection in naturea. Variation for a traiti. Running speed in rabbits can vary from one individual to the nextb. Heritabilityi. The trait of running speed is passed on from parents to their offspringc. Differential reproductive successi. In a population, rabbits with slower running speeds are eaten by the fox and their traits are not passed on to the next generation IV. Evidence of evolutiona. Evidencei. Fossil record1. Fossils are the preserved remnants or impressions left by organisms that lived in the past2. Fossil record: oldest fossils are bacteria (3.5 billion yrs old), younger fossils are animalsii. Biogeographyiii. Homologiesb. Why hasn’t evolution lead to the production of perfect organisms?i. Environments change quicklyii. Variation is needed as the raw material of selection (mutation is key)c. Homologies: sharing similar physical characteristics with other organismsd. Paleontologist: someone who studies fossilsi. Have discovered many transitional forms that link past and presentii. Example1. Evolutionary history of horsesa. The evolutionary history of horses is among the most well preserved in the fossil record. Because of this record we know that since first appearing around 55 million years ago, there have been many branches to the horse’s evolutionary