Final answer:
The term for the observable characteristics of an organism is phenotype, which is distinct from genotype, the genetic make-up. Phenotypic variation is important for adaptation in a population.
Step-by-step explanation:
The term that refers to the observable physical or biochemical characteristics of an organism is phenotype. The phenotype includes characteristics such as hair color, skin color, height, and body build, and these traits can be observed directly or measured. On the other hand, genotype refers to the actual genetic makeup of the organism which consists of the DNA sequence. Phenotype is the expression of this genotype, coupled with the influence of environmental factors. An organism's traits are indeed determined by the specific combination of inherited genes, and phenotypic variation within a population plays a crucial role in adaptation through natural selection.