The physical appearance of an individual organism is called its phenotype.

Here's a breakdown:

* Phenotype: The observable characteristics of an organism, including its physical appearance, behavior, and biochemical properties. It's the result of the interaction between the organism's genotype and its environment.

* Genotype: The genetic makeup of an organism, represented by the specific alleles (versions of genes) it carries.

For example, the phenotype of a flower might be "red," while its genotype might be "RR" (meaning it carries two copies of the allele for red color).