Microevolution Explained: The Basics of Allele Frequency

Welcome to our exploration of microevolution!Microevolution refers to the changes in allele frequencies within a population over time.Let's observe these changes in a butterfly population. The wing color represents different alleles in the population.Over successive generations, we can see how the frequency of different color alleles changes.We can track these changes using a graph. The lines show how the frequencies of different alleles change over generations.Unlike macroevolution, which involves the formation of new species, microevolution focuses on small-scale changes within a population.These small-scale changes can occur relatively quickly, sometimes within just a few generations.To understand allele frequency, let's look at a population of flowers with two color variants: red and white.Each flower has two alleles for color. In our population, we have twenty red alleles and twelve white alleles.To calculate allele frequency, we count the number of copies of each allele and divide by the total number of alleles in the population.For the red allele, we have twenty copies out of thirty-two total alleles, giving us a frequency of zero point six two five.The white allele has twelve copies out of thirty-two, resulting in a frequency of zero point three seven five.Notice that allele frequencies always add up to one, as they represent all possible versions of the gene in the population.Natural selection occurs when organisms with favorable traits are more likely to survive and reproduce.Over time, beneficial traits become more common in the population.Genetic drift is the change in allele frequencies due to random chance, especially in small populations.A population bottleneck can dramatically change allele frequencies by random chance alone.Gene flow occurs when individuals migrate between populations, bringing their genes with them.This migration leads to a mixing of genetic material between populations.Mutations are random changes in DNA sequences that create new genetic variants.These changes can create new alleles in the population.The Hardy-Weinberg principle helps us understand how allele frequencies behave in a population.This equation shows us the relationship between allele frequencies and genotype frequencies in a population.Let's visualize a population where the frequency of the dominant allele A is 0.7 and the recessive allele a is 0.3.For Hardy-Weinberg equilibrium to apply, several conditions must be met.When these conditions are met, we can predict genotype frequencies using our equation. Let's calculate them for our example population.In this case, forty-nine percent of the population will be homozygous dominant, forty-two percent heterozygous, and nine percent homozygous recessive.Let's examine three real-world examples of microevolution, starting with antibiotic resistance in bacteria.Initially, only a small portion of bacteria are resistant to antibiotics.When exposed to antibiotics, non-resistant bacteria die off, while resistant bacteria survive and reproduce.Next, let's look at how insects develop resistance to pesticides over generations.With each generation, the proportion of resistant insects increases as non-resistant insects are eliminated by pesticides.Finally, let's examine Darwin's finches and how their beak shapes adapted to different food sources.Finches with different beak sizes are better adapted to eating different types of seeds. Small beaks are better for small seeds, while large beaks are necessary for large seeds.Over generations, populations of finches evolved beak sizes that matched their primary food source, demonstrating natural selection in action.