In this exploration, you will investigate a simulated model of natural selection of an organism in different environments. The simulation represents the effect of predation on natural selection. The predator finds certain phenotypes of the prey more easily in those environments where they do not blend in. This adaptation by the organism to various environments leads to potential genetic changes within the gene pool that can lead to genetic separation from those organisms in different environments. By placing pressure on specific phenotypes, a change in the frequency of the alleles that produce these phenotypes will occur. Natural selection can significantly alter the genetic equilibrium of a population's gene pool over time. One aspect of evolution can be described as the change in allelic frequencies of a gene pool over time. These changes can lead to the evolution of a new species.
You will assume that the organisms' survival depends upon a single gene with two alleles, A and a, that show incomplete dominance. These alleles combine to form three genotypes: AA, Aa, and aa. All three genotypes are phenotypically expressed as varying traits of the organism. Individuals carrying the genotype AA display "yellow/brown" chitin. Individuals heterozygous for the allele A and a he mostly "green" chitin. Individuals of the homozygous genotype aa, he "grey" chitin.
Each variation of a trait may increase or decrease the organism's survival in an environment. Note that not all phenotypic traits are visible. For instance, a plant may be drought resistant and this trait would only be detectable in a dry environment.
Procedure
1. Select the Initial Allelic Frequencies of A and a and an Environment. The number of organisms of each genotype will be displayed on the screen.
2. Click the Generation 1 button to show the allelic frequency and number of individuals with each genotype before natural selection occurs.
3. Click the Natural Selection button to show the change in allelic frequency and the number of individuals with each genotype after natural selection occurs. Observe the changes in both sets of data.
4. Repeat steps 2 and 3 for Generations 2 through 5.
5. Collect and record data on allelic frequency changes due to natural selection in the population over five generations.
6. Use the Reset Button to collect data with different initial allele frequencies or different environments.
7. Answer the Journal Questions.