Lecture 5 - ANTHROPOLOGY 1 Professor Terrence Deacon...

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ANTHROPOLOGY 1 Professor Terrence Deacon 01/31/12 Lecture 05 ASUC Lecture Notes Online is the only authorized note-taking service at UC Berkeley. Do not share, copy, or illegally distribute (electronically or otherwise) these notes. Our student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. D O N O T C O P Y Sharing or copying these notes is illegal and could end note taking for this course. ANNOUNCEMENTS Free tutoring is offered through the Student Learning Center for this class. Study groups will be hosted every week on Tuesdays and Wednesdays from 2:00 3:30 p.m. at the Caesar Chavez Center, Room 201b. Contact Colleen Young for more information at [email protected] . The midterm date has been changed because of my schedule. It will be advanced by a week, on Thursday, March 15 th , instead of the Thursday before spring break. If you are disadvantaged by this change, please contact me immediately so we can make some accommodation for you. I will post the revised syllabus, but be prepared because the test is coming a lot quicker than you thought. LECTURE I want to wrap up the basics of evolution today. Evolutionary processes are much more complex than we ever thought before; as we move through the course, I will progressively tweak this concept, and make it more sophisticated as we go on. It is important to recognize that there are many ways that evolution takes place. Sometimes it’s that genes have changed, but sometimes it’s something else. The first thing I want to talk about is when there is no natural selection at all, but a change occurs anyway because of chance . We previously talked about the cosmic accident that killed the dinosaurs, but there is also another type of simple accident: the basic act of passing your genes along. The most familiar example is that of a sperm passing on one half of the father’s chromosomes to an egg , which does the same with the mother’s chromosomes, resulting in a zygote . There is a chance process that segregates these chromosomes. Which of the 23 chromosomes will be passed on in a sperm or an egg? There is a 50/50 chance in each generation that particular genes will be passed on. Because this is a chance process, there is the possibility that some of your genes are not going to be passed on. Smaller populations will be more affected by this and will tend toward gene simplification; populations where reproduction rates are low will be more affected by random gene loss effects, because there are higher chances that some genes will get left out of reproduction. So, gene relationships change over time, simply because some genes get lost in the shuffle. This is called genetic drift . Drift effects might be equal to or even more significant than natural selection.
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