Which term describes the observable characteristics of an individual?

The term that describes the observable characteristics of an individual is phenotype. Phenotype includes all the physical traits and qualities of an organism, such as height, eye color, and hair type. These traits result from the interaction between the organism's genotype (the genetic makeup) and its environment.

While genotype refers to the specific genetic constitution of an individual, it is the phenotype that provides a visible expression of those genes in the form of traits. Chromosomes are structures within cells that contain genetic information but do not encompass the expression of those traits. Alleles are variations of a gene that contribute to the genotype but do not themselves represent the observable characteristics. Therefore, phenotype is the most accurate term for describing the physical traits of an organism.