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Lecture 3

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Lecture 3 - The fundamental theorem of natural selection -The increase in fitness in a population according to Fisher, is that the number of offspring contributed to the next generation depends on the fitness of an individual -The amount of fitness in a population is dependent on the relative variation of traits within a population -In Darwin’s observation, finches had diverged from one root or specie, diverging into several, specialized species -From the taxonomical record, this had helped him observe his theory -These animals had evolved into behavior which were not typical of the original specie -Darwin did observe the giant tortoise, which had differed morphologically depending on the island -The differences in survival rates is the reason why populations alter and evolve in characteristics -Individuals and populations -Populations refers to a group of individuals which are able to exchange genes -The population size is a moving target, it can change depending on geographic factors, and the subdivisions have decreased over time in the modern world -Nonetheless we do talk about the “characteristics of a population” -Evolution, which is the pattern or outcome of natural selection, say from the coloration of beetles, is measured at the population level -The variations in dogs and cats demonstrates the differences in specialization -Dogs are able to differ tremendously in forms, and had greater variation within the wolf population to begin with -Cats however, are quite limited due to their initial limits in variation -Mutation -The quality of mutation is measured on its effect on fitness, and it is always usually a relative measure -Most mutations are quite lethal and deleterious, which is why women tend to have a miscarriage rate of about 25% -Neutral and nearly neutral selection has a limited effect on fitness -A codon is a sequence of three DNA letters, and a particular protein can be encoded by different sequences of amino acids -A mutation which changes a letter, but codes to create a proper working protein, is an example of a mutation which has no effect -This is a form of neutral selection, which has no changes or effects on individuals -Cumulatively, this may have a mutation which will have an impact on the individual over several generations -Sexual selection -In the process of meiosis, two chromosomes replicate themselves and then separate from each other -Random Fertilization -The random fertilization refers to which egg and which sperm cell fertilizes which -Even after that, an exchange of genetic material occurs -Variation has two components -One is the genotype which encodes for “tallness” or “intelligence” -The other is the environment of an individual -The phenotype is a consequence of this, resulting from genotype and environment encoding for the phenotype -Genes who have two alleles or more, produces a trait or character which is “categorical in nature”, a discontinuous variation or distribution -Another example of genetic polymorphism, is the distribution
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