What are some phenotypes that do not vary in a population of organisms? what are some phenotypes that might vary between different populations? do phenotypes have a genetic basis? does inviroment influence phenotype?

Part 1.Phenotype is the physical expression of a gene or the trait/characteristics in result of a gene or genotype.There are some phenotypes that don't vary in organism like the body plan, every one has same body plan like 2 hands, 2 legs, 1 nose, 2 eyes etc.The common structural and reproductive feature in species are examples of phenotypes that don't change in organisms.Part 2.Phenotypes that have many genotypic patterns like eye color, hair color, skin color etc have multiple alleles.Due to variation in alleles and a lot of number of alleles in one gene causes some phenotypic changes in different populations.Part 3.

According to the definition of phenotype, it is physical expression of a genotypes. Hence it is obvious that phenotype has genetic bases.

Instead different genotypes are the causes of different phenotypes in a population.Eye color is a phenotype which is the expression of eye color gene.Part 4.

Yes, environment influences the phenotype.

The best example of it is the identical twins.Identical twins have same genotype. But if we lives in Africa and other in America, their skin tone will differ due to environmental effect. High temperature of Africa leads to dark tone brother than America inhabitant brother.