• Gene Allele Frequencies: In a population, the frequency of alleles for a specific gene or locus can be determined. These allele frequencies are expected to remain constant and unchanged over successive generations.

• Genetic Equilibrium: The Hardy-Weinberg principle, expressed through algebraic equations, states that allele frequencies within a population are stable and constant over time. This condition is referred to as genetic equilibrium, where the gene pool (the total genes and their alleles in the population) remains constant.

• Allelic Frequencies: In a diploid organism, the frequency of two alleles (e.g., A and a) can be represented as p and q, respectively. The frequency of individuals with two copies of allele A (AA) is denoted as p². Similarly, the frequency of individuals with two copies of allele a (aa) is q², and those with one copy of each allele (Aa) is 2pq.

• Binomial Expansion: The equation p² + 2pq + q² = 1 represents the genotypic frequencies. This equation is a binomial expansion of (p + q)². When the measured frequencies differ from the expected values, this difference indicates the extent of evolutionary change.

• Disturbing Genetic Equilibrium: Any deviation from the Hardy-Weinberg equilibrium, such as changes in allele frequencies within a population, is considered a sign of evolution occurring.

• Factors Affecting Equilibrium: Five factors can affect the Hardy-Weinberg equilibrium: gene migration (gene flow), genetic drift, mutation, genetic recombination, and natural selection.

• Gene Migration (Gene Flow): When a section of the population migrates to a new location, gene frequencies can change in both the original and new populations. New genes and alleles are introduced to the new population while being lost from the old population.

• Founder Effect: If the change in allele frequency is significant in the new population (e.g., due to genetic drift), it may lead to the formation of a different species. The original population that underwent genetic drift becomes the “founders.”

• Mutation: Pre-existing advantageous mutations, when selected, can result in the emergence of new phenotypes over a few generations. This process can ultimately lead to speciation.

• Natural Selection: Natural selection is a process where heritable variations that enhance survival and reproduction become more prevalent. This process can lead to the appearance of different populations within a species.

• Three Outcomes of Natural Selection: Natural selection can result in three possible outcomes:

  1. Stabilization: More individuals acquire a character value close to the mean.
  2. Directional Change: More individuals acquire a character value different from the mean.
  3. Disruption: More individuals acquire character values at both extremes of the distribution curve.

The Hardy-Weinberg principle is a fundamental concept in population genetics and helps explain how genetic variation can persist or change within populations over time.