Final answer:
Qualitative traits are influenced by one or a few genes and have a clear inheritance pattern, while quantitative traits are controlled by many genes (polygenic), showing continuous variation and being more influenced by the environment. Most human traits are polygenic, complicating the nature vs. nurture debate.
Step-by-step explanation:
Qualitative traits are typically controlled by a single gene or a few genes. These traits often show a clear-cut, either/or pattern of inheritance, such as flower color in Mendel's pea plants. In contrast, quantitative traits are polygenic, meaning they are controlled by multiple genes and often show a continuous range of variation, like height or skin color. The inheritance pattern of quantitative traits does not follow the simple Mendelian rules.
The role of environment is generally more influential in quantitative traits than in qualitative ones. While the environment can affect both types of traits, quantitative traits are often heavily influenced by environmental conditions and interactions between genes and the environment, leading to a wide range of phenotypes even among individuals with similar genotypes.
Most human characteristics are not controlled by a single gene. For example, traits like skin color and weight are polygenic traits, implying they are influenced by multiple genetic factors and are also affected by environmental factors. This complexity gives rise to the nature vs. nurture debate, particularly in areas such as intelligence, psychology, and behavior, which are affected by myriad genetic and environmental factors.