The roles of genes and environmental in evolution

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  • The roles of genes and environmental in evolution
    • Selection pressures
      • an environmental factor that confers greater chances of survival to reproductive age on some members of the population
      • directional selection
        • when an organism has an allele that would provide them with a selective advantage. They are more likely to survive and therefore the individuals with these alleles will increase.
        • Directional selection leads to evolutionary change and is an evolutionary force of natural selection.
    • Evolutionary force
      • Any factor that brings about changes in gene frequencies or chromosome frequencies in a population and is thus capable of causing evolutionary change.
        • Directional selection leads to evolutionary change and is an evolutionary force of natural selection.
    • isolating mechanisms
      • a large population maybe split into sub-groups be various isolating mechanisms
      • geographical (ecological) barriers such as a rive or mountain range
        • a large population maybe split into sub-groups be various isolating mechanisms
      • seasonal (temporal) barriers such as climate change throughout a year
        • reproductive mechanisms- members may no longer be able to physically mate, if their genitals are incompatible or their breeding systems may vary.
        • genetic drift
          • Also known as allelic drift. The change in allele frequency in a population, as some alleles pass onto the next generation, and some are lost. This causes some phenotypic traits to become rarer or more common.
            • some extreme cases of genetic drift, can cause to the elimination of an allele from the population.
            • it reduces the ability of a population to survive in a new environment, because of a reduction in genetic variation.
            • it could lead to the extinction of a species, or the invention of a new species

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