Ahypothetical population of a trout lives in a lake in california. the fish in this population have two color phenotypes, brown and white. both phenotypes are relatively equal in the population. in this species, scale color is controlled by different alleles for the same gene. the population in the lake is isolated from other populations of trout as there are no rivers or streams connecting the lake to other bodies of water. one winter, a rockslide on a cliff bordering the lake kills half of the fish living in the lake. by random chance, the majority of the fish killed in the rockslide have the white phenotype. several years later, a scientist studying the population of trout in the lake observes that there are no more white fish present in the lake. what is most likely responsible for the change in phenotypic frequency of trout in the lake?