Genotypes and Phenotypes

     Selection will act on the phenotype of an organism; however, the genotype is what is affecting the phenotype of the organism and the genotype is what will be passed onto offspring. To say that selection is acting on the phenotype does not mean that the genotype is ignored- rather, the genotype is what causes the phenotype which will end up interacting with the environment.

    If the genotype in a population of rabbits determines that the organism will either have red or green fur, the fur color is what is interacting with the environment and will determine whether or not the organism will survive. In this fur color example, if the environment that the rabbits live in is a grassy field, the green fur individuals are more likely to survive and reproduce than the red fur individuals because it can better camouflage with its environment. A wolf, for example, is more likely to spot the red rabbits than the green ones so the red rabbits might not be able to survive to reproduce. 

    In terms of selection, the green fur has a selective advantage over the red fur and will act on fur color- the phenotype! Although the genotype is what is determining fur color, the phenotype is what is observable and what will determine rate of survival and reproduction.