Which of the following refers to the physical appearance of an organism?

The term that refers to the physical appearance of an organism is phenotype. Phenotype encompasses all observable characteristics, such as height, color, and shape, which result from the interaction of the organism's genetic makeup (genotype) with the environment. For instance, a plant might have a genotype that codes for tall growth, but environmental factors like soil quality and sunlight can influence whether it expresses that trait or not. This distinction is crucial in understanding how traits are manifested in living organisms.

Genotype, on the other hand, refers specifically to the genetic constitution or the alleles present in an organism. Alleles are different forms of a gene that can determine specific traits but do not describe the outward appearance themselves. Chromosomes carry the genes that contribute to both genotype and phenotype, but they represent the structure containing genetic information rather than the visible traits. Thus, phenotype is the correct term for an organism's observable characteristics.