Final answer:
Individual differences largely arise from variations in the genetic makeup of organisms, influenced by inherited genes and their expression. Environmental factors, such as nutrition and sunlight exposure, can also affect these genetic expressions and lead to phenotypic differences.
Step-by-step explanation:
Many of the differences among individuals result from differences in genetic makeup of organisms. This is because the specific traits an organism exhibits are predominantly determined by the combination of inherited genes, along with their expression and interaction with the environment. Indeed, genetic differences can account for a wide array of phenotypic diversity, a fact underscored by how identical twins can develop distinctly due to differential gene expression in different environments. Yet, it's also essential to acknowledge that other factors like environmental influences and in some cases, even cultural backgrounds or socioeconomic status, can impact phenotypic variation through effects on gene expression or by dictating the availability of resources like nutrition.
For instance, height can be influenced by genetic predispositions, but nutritional factors during growth periods can also have a significant impact. Additionally, factors such as exposure to sunlight can cause variations in skin pigmentation, an observable trait not exclusively determined by one's genetic code. Therefore, while genes are crucial in determining characteristics, their expression and the phenotype that results are modulated by various environmental conditions.