In depth explation what factors can affect the components of fitness?

How would you respond to someone who said that models are useless in studying population genetics because they represent oversimplifications of the real world?

List the mechanisms that may cause allele and genotype frequencies to significantly change from one generation to the next.

In this version of the simulation (500 population size; 500 carrying capacity), all fish are equally likely (though not 100% likely) to survive and reproduce. There are no mutations, nor are there any entering or leaving the population. When they reproduce, they choose a mate from the pool at random and produce ten offspring by chance with the probability of the offspring’s genotypes determined by the punnett square. What caused the allele frequencies to change and vary in the trials? (ex attached).