Question

What type of trait shows continuous variation, where there is a large range of phenotypes in a population (for example height or skin color)

Answer 1

Polygenic traits show continuous variation where there is a large range of phenotypes in  a population.

Explanation:

Polygenic traits are influenced by multiple of genes and thus cannot be explained by simple Mendelian inheritance. Height, skin color, eye color etc are some of the polygenic traits that show continuous variation. The level to which a gene is expressed determines the phenotype of an individual.

Polygenic traits can also be influenced by the environmental conditions.  That is why undernourishment in childhood stunts the growth of people. Melanin is the pigment that determines the skin color. Increased exposure to sunlight causes an increase in melanin production which darkens the skin.  

This is also an example of the influence of environment on polygenic traits. Polygenic traits show continuous variation which means that the phenotype results from the combination of the multiple genes.