a201-11f-04-EvolutionConceptsAndRates - Introduction to...

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Introduction to Biological Anthropology: Notes 4 Kinds of variation, cumulative change, local optima, and rates of evolution Copyright Bruce Owen 2011 - Announcements - The first set of self-study questions is posted, both blank and with answers - The in-class evolution quiz is next class: Thursday, Sept. 8 - so review the readings, notes, and slides up through today’s material - 5% of total course points; short written answers - suggestion: work on the self-study problems posted on the class website. - answers are also posted; naturally, I don’t expect you to use the exact words I do, except when they are necessary technical terms - the self-study questions are similar to the format of the quiz, midterm, and final exam - On Thursday, all you will need is something to write with. - You will get a printed quiz that looks a bit like the self-study problems. - No scantron or blue book is needed. - Natural selection and the evolution it can cause do not necessarily “improve” individuals or the population - evolution is just the accumulation of whatever features the most reproductively successful parents have had - natural selection can favor traits that are harmful to the group as a whole - natural selection can even drive the whole group to extinction - Let’s consider a variation on Boyd and Silk’s hypothetical example of high-fecundity vs. low-fecundity females - (fecundity is the ability to produce offspring) - Imagine a small population of bugs - food supply is limited to enough to support 100 adult bugs - in order to keep the slides simple, I will divide all the numbers by ten - and show only the females - if each female produces two offspring, and 50% of them die, the population remains constant - but what if ten of the females produce four offspring each? - the next generation starts off a bit larger - but there is still food only for the same number to survive, so more of the offspring die - mortality rises from 50% to 58% - this change is clearly harmful for individuals, who are now more likely to die before adulthood - nevertheless, the high-fecundity females produced more offspring, so more of their offspring survive into the next generation - the next generation then has even more high-fecundity females - so even more offspring are created in the next generation - the food supply is still the same - so even more of the offspring die off - mortality rises to 64%. ..
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Intro to Biological Anthro F 2011 / Owen: Variation, cumulative change, local optima, rates of evolution p. 2 - This is harmful not only to individuals, but also to the population - all those additional infants will eat some food before they die - wasting it, and leaving less for the rest - eventually, with the additional food consumption of all those doomed infants, the food will be enough for only fewer than 100 to survive to adulthood - the population of adults begins to decline - higher fecundity is clearly harmful for the population, too - if food is scarce, it might be better for the group to produce fewer offspring
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a201-11f-04-EvolutionConceptsAndRates - Introduction to...

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