Population Genetics

• Genetic drift


  Change in allele frequencies in a population that happens over generations because of random chance with which get passed down that has a ripple effect where one gains dominance and others get rarer. Most common in small populations where less chances means more likelihood of the average deviating from the stat average
• Fixation


  When an allele reaches 100% frequency in a population
• Genetic drift


  Type of evolution in small populations that selects for specific genes regardless of whether or not they're harmful or beneficial
• Bottleneck effect


  Extreme example of genetic drift where a large chunk of a population dies off and the random assortment of survivors might have allele frequencies not representative of the original population
• Founder effect


  Extreme example of genetic drift when a small group of individuals breaks off from a population and starts its own colony, with a less representative or skewed set of alleles determining which ones get expressed more over time
• Fitness


  Measure of reproductive success (how many offspring an organism leaves for the next generation par rappt to the population)
• Microevolution


  Increasing the frequency of helpful alleles from one generation to the next
• Stabilizing selection


  When more intermediate phenotypes are best for survival, so species evolve over time to have narrower phenotypic curves with less extreme versions (so more medium green beetles instead of neon or black ones)
• Directional selection


  When one extreme phenotype is more fit than all the other ones, so the species evolves a more slanted curve towards one side, so like dark beetles surviving more than their lighter counterparts
• Disruptive selection


  When both extreme phenotypes are more fit than the middle one, so species evolve to have a curve that dips in the middle and peaks once at each extreme, like light or dark beetles surviving more than greige ones