Phenotype j the out appearance j importanc ein the process of evolution. Evolution in population depends on phenotypic traits being passed down from generation to generation. J howver, is genotype the basic that cause the change. The genotype is the complete genetic constitution of an organism. When the phenotype is change in a population, it may results from the interaction between genotype and the environment. Alternation of the phenotyoe in individual is called acclimation. Note that its not a adapation, adaptation is the term used for population not for individual! Phenotypic plasticity is the concept used by biologists to describe the degree to which a given genotype can alter its phenotypoc expression in order to acclimate to irs surroundings. Reaction norm: the relationship between the environment and the trait in question. 1st, insufficient genetic variation exists for the evolution of plasticity to occur.