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Evolution

Evolution. Focus on Microevolution: Change in allele frequencies over a few generations. How common an allele is in a population. Population. Gene Pool = all of the alleles of a all of the genes within a population

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Evolution

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  1. Evolution Focus on Microevolution: Change in allele frequencies over a few generations How common an allele is in a population

  2. Population Gene Pool = all of the alleles of a all of the genes within a population • New alleles can be introduced into the population. These might originate by mutation (changes in DNA sequence due to: • Replication errors • Exposure to some DNA-damaging agent • Spontaneous changes • New alleles might also be introduced by individuals moving into the population or by individuals leaving the population for one reason or another (death?)

  3. Fitness Success at passing on alleles to offspring

  4. Natural Selection Some variant alleles are identical with respect to ‘fitness’. Some variant alleles confer disadvantages under certain circumstances. Some variant alleles confer advantages under certain circumstances. • Those alleles that confer a disadvantage will result in an individual being less ‘fit’ • Those alleles that confer an advantage will result in an individual being more ‘fit’

  5. Cellular Example of Natural Selection • Antibiotic resistant bacteria

  6. Natural Selection • The resistant bacterium is ‘selected’ for • Under these conditions (presence of antibiotics), the allele for resistance confers an advantage • The allele arose due to alterations in the bacteria’s DNA

  7. Macroevolution • If natural selection can happen at the cellular level, it can happen at the organismal level. • Individuals who are better suited under certain circumstances will reproduce more, so the alleles that they carry will be passed on more frequently than those of individuals who are less ‘fit’. • Eventually over time, the variation of alleles that the more fit individuals carry/pass on will become more abundant within the population (conversely, the variation of alleles of the less-fit individuals will become less frequent in the population).

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