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?

1. Phenotypes that decide the decide the development plan of the body do not vary in a population of organisms. Example, the segmentation of the body (number of hands, legs, ears, eyes, etc.).

2. Phenotypes that vary in a population are the eye color, hair color, hair growth, body size, body build, cold tolerance, skin color, etc.

3. Most of the phenotypes have a genetic basis, example, the colorblindness trait that is X linked inherited. But some phenotypes vary epigenetically, e.g., differences in body features of twins.

4. Yes, environment influences the phenotypes. Twins have a genetically identical DNA yet they have minute differences in their skin color, eye color, body build, etc. Such differences arise when the environment differently affects the gene  regulation within the body of the twins.

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

Yes, environment influences the phenotype.

chromosomes carry the genetic information for organisms. also, chromatin is the thread like dna which is located in the nucleus of an organism.