Final answer:
Polygenic traits are controlled by multiple genes, contributing to the variability of measurable characteristics such as height, weight, and eye color. These traits demonstrate continuous variation and can be affected by environmental factors.
Step-by-step explanation:
Genes that are involved in determining continuously varying or multiple-factor traits are known as polygenic traits. These traits, unlike single-gene (Mendelian) traits, are influenced by multiple genes, each potentially with multiple alleles. Polygenic characteristics can typically be measured and exhibit a broad range of variation. Examples of polygenic traits include height, skin color, eye color, and weight. Environmental factors can also play a role in the expression of these traits, contributing to their variability among individuals. Furthermore, characteristics that show this kind of continuous variation are often seen as a blend of the parents' traits.
The survival of a species is closely linked to genetic diversity. When traits are influenced by multiple genes, it allows for a greater variation, which is essential for the adaptability and survival of a species. A diminished gene pool can make a species more susceptible to extinction. Mendel's early work with pea plants suggested that individual traits were controlled by single genes, but we now understand that many traits, such as eye color, which involves at least eight genes, are polygenic.