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Unformatted text preview: E8 EXA M 1 STUDY GU I D E CHAPTER 1 Mystery in the Map population genetics: study of genetic composition of populations of living organisms to see how they have changed over time natural selection: small changes that are advantageous in some way give an organism a greater chance of surviving and reproduction the perpetual rat race that is life shuffling: parents chromosomes literally exchange genetic information along their lengths, breaking and reconnecting their paired strands to produce a completely new version of chromosome to pass on to you. Pritchard and his colleagues had developed a new statistical method to find regions of the chromosomes that seemed to have too little shuffling. selection. All of them had happened in the past 10,000 years. (suggests a strong selection pressure during this time)---- apes homo (2.3 million years) Homo habili Homo erectus Hominids (500,000 years) Homo sapiens (195,000 years) (FOUND IN ETHIOPIA) Population bottleneck: a population crash that happened Between 80,000 to 50,000 years ago left about 2,000 humans left. (A population bottleneck (or genetic bottleneck ) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing.) (Population bottlenecks increase genetic drift, as the rate of drift is inversely proportional to the population size. The reduction in a population's dispersal leads, over time, to increased genetic homogeneity. If severe, population bottlenecks can also markedly increase inbreeding due to the reduced pool of possible mates.) Inflection point 60,000 years ago Dawn of agriculture 10,000 years ago. massive acceleration from about 1 million to almost 7 billion today (gradually leveling off and might even decrease near the end of the century)- gained control of food supplyhow much food and how many people could live in a particular area. modifying the environment but it has also modified humans. some chromosomes have been targets of selection guess the function and then guess the force doing the selecting- skin pigmentation humans evolved originally in Africa with dark skin. It was only as we moved out of the tropics and into higher latitudes, with their lower levels of ultraviolet light, that we had to lose some of our dark pigmentation in order to allow the deeper layers of our skin to synthesize enough vitamin D- Lactase It seems that in these Middle Eastern populations, and in their descendants who brought goats and cattle to Europe, milk was an advantageous addition to the diet. Over time, a mutation that caused the lactase gene to remain active after childhood increased in frequency in milk- drinking populations. selection and diseases (positively selected but associated with negative outcome)- diabetes: roots in the transition from a hunter-gatherer lifestyle to the food- rich environment of agricultural populations, where the genes that had...
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- Winter '08