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. Lecture 5 Outline of Last Lecture I. Adaptive evolution a. Darwin’s Four Postulates of Evolution b. Natural Selection: Evidence that the Four Postulates are Accurate c. The Grants’ Medium Ground Finch Experiment: Witnessing evolution Outline of Current Lecture II. Artificial Selection a. Evidence for natural selection b. Yoo’s Artificial Selection Experiment c. Genetic Drift Different from Natural Selection III. Natural Selection is observed in the Wild a. Losos’s Lizards IV. Rapid Evolution Can Effect Human Wealth and Welfare a. Antibiotic resistance b. Pesticide resistance Current Lecture Artificial selection • Artificial selection Convinced Darwin that natural selection was the mechanism of adaptive evolution. I is the process of selecting who is allowed to breed for a specific benefit our population • Evidence for Natural selection: Artificially selecting desired traits o Ex: small plant tomato ancestor ! larger plants were selected over time! modern day tomato plant • Almost all of our crops today resulted from artificial selection o Ex 1): Teosinte plant! intermediates! Modern corn o Ex 2): Animals! dog breeds—that’s how all these different dog species came about " Ancestral wolves! only selecting some wolves with different and desired traits and allowing them to breed! yielded characteristics desirable to humans o Darwin was interested in domesticated pigeon, namely the Rock Pigeon o From the original pigeon, we have derived a variety of different pigeon breeds • Yoo’s artificial selection experiment o Yoo had several populations of fruit flies o Yoo removed a random sample of 250 flies and from that sample he removed 50 from that had the most bristles! he is artificially selecting for bristle number BIO 280 1st Editiono He Did this continuously 86 times o Graphing multiple populations shows that bristle number continued to increase after 86 generations! In other words bristle number evolved. • But after the 90th generation, the bristles started to go down. o Best explanation was that after the artificial selection force for bristle size was gone, there was a natural selection force that was against bristle number because bristles are costly!best inference! if there was no evolutionary cost then the bristle number would not have gone back down. • Genetic drift. Different from natural selection-! random mutations that are introduced into the population gene pool. o In Yoo’s experiment The best evidence against genetic drift being the cause for reduction of bristles is that all population’s bristle size went down after the 90th generation. Since genetic drift is random, we would expect to see some bristle numbers go up as well. It would be most likely a selective force involved. Genetic drift is not an agent of natural selection Natural selection can be observed in the wild o Experimental test (Losos et al) o Losos wanted to know if anole (lizard) morphology evolves in response to a changed environment? o He began by measuring Anolis sagrie on Staniel Cay(Island with large trees and shrubs)! measured aspects of their morphology o He next found some islands that didn’t have lizards. So he took a dozen lizards and released them on 14 lizard free islands with no trees and only small shrubs " He defended against invasive species argument by explaining the islands were so close together that lizards would end up there anyway o He tried to make sure he mixed sexes to establish a good breeding population o Losos came back 15 years and found all lizards thriving o Since he used 14 different islands, he was utilizing the experimental property of Replication! important ! to prove any results were not from random chance o He compared to the parent generation on Staniel Cay: o All the lizards on the new islands had: " Shorter legs " More slender legs o On Staniel Cay, the legs didn’t change o He hypothesized that on the new islands with now trees and small shubs, having skinnier and shorter legs allowed the lizards to be more agile in escaping prey. But on Staniel Cay, having thicker longer legs in the trees was advantageous for escaping pray Rapid adaptive evolution can affect human health and welfare• Antibiotic resistance o If we have a population of bacteria with a few mutant strains that have antibiotic resistance o When antibiotic is used to treat these bacteria, all the nonresistant bacteria eventually die, leaving only the resistant strain to reproduce o Eventually the entire population is resistant and the particular antibiotic no longer works at that point. o Ex " MRSA (HA, CA)!(hospital acquired and community required) " MDR-TB! multi drug resistant tuberculosis " XDR-TB! resistant to all drugs known available to resistance " Klebsiella, Echerichia, Clostidium, Enterococcus, Pseudomonas " Steptococcus pneumoniae " Neisseria gonorrhoeae " Ect. o All common and non-common pathogens are evolving resistance to treatments o This phenomenon is caused a lot by physicians prescribing medications that aren’t necessarily needed " Ex: if you have a viral infection, sometimes antibiotics are prescribed because it might help the patient feel better, or might get patient off the back of the doctor. o A lot of cows, chickens, pigs are treated with antibiotics as a preventative measure! all their waste has antibiotics, and all food as antibiotics as result. More a resistant bacteria in our food/ in the environment ect. o Antibacterial soap is another example of introducing antibiotics into the environment o Very rarely new antibiotics are produced • Pesticide resistance o Similar concept to the antibiotic resistance o Pesticides are used to control “pest” population o But pesticides are also causing pesticide resistance to develop in insects. o BT! crops! transgenic plants with pesticide genes that naturally produce pesticide! pests die, but resistance to BT has gone up in pests populations as BT crop populations increase o Way around this is the Refuge farms: o Refuge farm without BT corn slows the evolutionary resistance! this is because resistance has an evolutionary cost! not good for survival in refuge " Farmers are hoping that there is gene flow from the nonresistant individuals to the