Final answer:
Environmental factors influence non heritable variation by affecting the expression of phenotypes without altering the genetic code. Sun exposure and temperature-dependent sex determination are examples of environmental impact on phenotypic traits that are not genetically passed down.
Step-by-step explanation:
How Environmental Influence Affects Non Heritable Variation
Environmental factors play a significant role in the expression of the genotype and contribute to non heritable variation within a population. An environmental influence can lead to variations in phenotype that are not passed down genetically, thereby affecting population dynamics. For example, phenotypic characteristics like skin color can change due to sun exposure, which is an environmental factor. The expression of such traits can differ even among individuals with similar genetics. In some species, critical characteristics like gender can be determined by the environment, as seen in certain reptiles that exhibit temperature-dependent sex determination (TSD).
While environmental variance is critical, it is also important to understand that only heritable variations, those encoded in an organism's DNA, can be acted upon by natural selection. Non heritable traits, such as those acquired through environmental influence, do not alter the genetic code and thus are not passed on to the next generation. Nonetheless, these environmentally induced traits can significantly shape the interactions and lifestyle of individuals within a population.
Moreover, genetic environmental correlation is a bidirectional relationship where genes influence the environment, and the environment influences gene expression. This dynamic can play a pivotal role in an individual realizing their genetic potential within a given environment, further contributing to population variation that is non heritable in nature.