Final answer:
The correct answer is true: a single genotype's expression as a phenotype can be influenced by environmental factors such as sunlight and nutrition, which can modify observable traits despite the organism's genetic makeup.
Step-by-step explanation:
The phenotype expressed by a single genotype can indeed be affected by environmental conditions, so the answer to the student's question is true. For instance, environmental factors such as sunlight, temperature, and food availability can significantly influence traits like height, skin color, and weight, despite the individual's genetic predispositions. A famous example of this is how the height of a plant can vary depending on the availability of sunlight, water, and nutrients, even though its genotype remains the same.
Moreover, Mendel's hybridization experiments illustrate the concept of phenotype and genotype. While the genotype is the genetic makeup of an organism, the phenotype is the observable manifestation of these genes, which can be influenced by both genetic inheritance and environmental factors.