CAUSES OF EVOLITION - WEEK 1 GENE FLOW

Causes of Evolution

Overview of Evolution

  • Definition: Evolution involves a change in allele frequency over time.

  • Main Causes: Four primary mechanisms drive evolutionary change: mutation, natural selection, genetic drift, and gene flow.

Mutation

  • Definition: Mutation is defined as any change in the structure or amount of genetic material that can be passed on to offspring.

  • Example: A mutation occurs in an allele that causes a green color in an organism.

    • Impact: The green allele is successfully passed on to the next generation, thus increasing variation within the population.

Natural Selection

  • Definition: Natural selection is the process where some alleles produce traits or phenotypes that confer an advantage over others, enhancing survival and reproduction.

  • Example: In a scenario where predators prefer blue-colored individuals:

    • Outcome: Fewer blue individuals survive and reproduce compared to red individuals; thus, more red individuals survive and pass on their genes to the next generation.

Gene Flow

  • Definition: Gene flow is the transfer of alleles or genetic material between populations, which alters the frequency of alleles within the receiving population.

  • Example: If several red individuals immigrate from a neighboring population:

    • Consequence: The influx of red individuals increases the frequency of red alleles transmitted to subsequent generations.

Genetic Drift

  • Definition: Genetic drift refers to the random fluctuations in allele frequencies, particularly in small populations, which can occur over time.

  • Causes: Drastic changes, such as population size reduction due to natural disasters, can lead to genetic drift by randomly altering allele frequencies in the surviving population.

  • Founder Effect: This is a specific type of genetic drift that occurs when a small segment of a larger population relocates:

    • Effect: This relocation changes the allele frequencies randomly in the new population.

Population Genetics and Allele Frequencies

  • Study Method: Scientists can study population genetics by comparing allele frequencies across different generations within the same population.

  • Equilibrium: If allele frequencies remain constant, the population is in equilibrium, indicating that evolution is not occurring.

  • Evolution Indicators: Conversely, if allele frequencies change between generations, this indicates that the population is evolving.