Here's how it works:
* Survival of the Fittest: Organisms with traits that make them better adapted to their environment are more likely to survive, find mates, and reproduce.
* Passing on Genes: Organisms pass on their genes to their offspring.
* Allele Frequency: The frequency of an allele in a population is the number of times that allele appears in the gene pool, compared to the total number of alleles.
Since organisms with the unfavorable trait are less likely to survive and reproduce, they pass on their genes (and the unfavorable allele) less often. This means the frequency of the unfavorable allele will decrease over generations, while the frequency of the favorable allele will increase.
Example:
Let's say there's a species of bird where a certain allele causes birds to have bright blue feathers. If these blue feathers make the birds more visible to predators, making them more likely to be eaten, the blue allele will become less common in the population over time. Birds with less conspicuous feathers will survive better, reproduce more, and pass on their genes to their offspring.
Important Note:
* Selective Pressure: The strength of natural selection (the "pressure" to remove the unfavorable allele) depends on how detrimental the trait is. If the trait has a very negative impact on survival and reproduction, the allele will be eliminated much faster.
* Other Factors: While natural selection is a powerful force, it's not the only factor affecting allele frequency. Other factors like genetic drift and gene flow can also play a role.
