Final answer:
A polygenic trait is a characteristic controlled by more than one gene, causing a wide variation in the population. Examples include height and skin color. Such traits are measureable, showing the impact of genetic diversity.
Step-by-step explanation:
A polygenic trait is a trait controlled by many (poly) genes. Unlike traits influenced by a single gene, polygenic traits are the result of the contribution from multiple genes, each which may have two or more alleles. This complexity in genetic contribution can result in a wide variation within the trait amongst a population.
Examples of polygenic traits include human characteristics like height, skin color, weight, as well as hair and eye color. For instance, height is a polygenic trait controlled by at least three genes with six alleles. When an individual carries dominant alleles for all the genes associated with height, they are likely to be very tall. Similarly, skin color, which also shows a wide range of variation, is a polygenic trait.
Most human traits, therefore, are not Mendelian but rather polygenic, where multiple genes play a role in determining a single characteristic. These traits often show a measureable range and can be influenced by environmental factors, underlining the importance of genetic diversity within a population for its survival.