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Lecture_03_Nat_Select_%26_humans0-1 - Lecture 3 Evoluation...

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8/29/2006 Lecture 3 – Evoluation and Human Variation 4 KEY ELEMENTS OF THE THEORY OF NATURAL SELECTION 1) HEREDITY : Living things have the capacity to pass many of their characteristics on to offspring through heredity 2) VARIATION : There is variation in populations in individuals ability to survive and reproduce - We now know the ultimate source of this variation is mutation in the genetic code 3) COMPETITION : Resources necessary for survival and reproduction are finite: populations tend to grow up to and surpass this finite resource base 4) NATURAL SELECTION : variants in the population better equipped to survive, compete, and reproduce will pass on their characteristics to the next generation at a higher rate than less successful variants, eventually replacing them * The result is diversification of life forms , with different species adapting to their particular environments through evolutionary change New life forms arise through the evolutionary process * One of the most common causes of evolutionary change is environmental change - New environments can favor new or variations that affect survival and reproduction - The underlying cause of environmental change is usually climatic change * Populations undergo evolutionary change if there are changes in the environment through time - The example of the peppered moths in England - Primates first evolved in tropical rainforest environments ~ The Earth’s environment became cooler and dryer, rainforests were reduced, new large bodied terrestrial (ground living) primates appeared * Evolutionary change can also occur when populations move into or colonize new environments outside their original range - Populations may move because of competition in their original range The key process driving natural selection is differential reproductive success * FITNESS = ability of an organism to leave offspring. - Components of fitness: factors that affect differential reproductive success ~ Differences in ability to survive to produce offspring ~ Differences in efficiency at energy gathering and processing ~ Differences in attracting mates - Especially for males ~ Differences attracting the best mates ~ Differences in producing lots of offspring (quantity)
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8/29/2006 ~ Differences in producing viable offspring (quality) * Must be judged vs. other individuals in the population. Natural selection will affect ANY heritable characteristics (traits) that affect these components of fitness * Morphological traits * Behavioral traits * One catch = some important traits may not be NOT heritable Requirements to survive and reproduce : 1) get food (energy) 2) avoid environmental hazards 3) avoid parasites and disease 4) avoid becoming food for other organisms 5) find mates 6) help solve these problems for their offspring (parental care) Genotype - phenotype distinction * Genotype : genetic makeup, two sets of chromosomes one from each parent - circa 30,000 genes in our genome (set of genes) - the actual genetic makeup of an organism, which is passed on (inherited) by the offspring -
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Lecture_03_Nat_Select_%26_humans0-1 - Lecture 3 Evoluation...

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