Final answer:
The signalment comprises the patient's species, breed, age, sex, and spayed/neutered status in veterinary medicine. The correct answer to the question on observable traits expressed by an organism is phenotype, which includes all visible characteristics.
Step-by-step explanation:
The patient's species, breed, age, sex, and spayed/neutered status comprise the signalment. In veterinary medicine, the signalment is a standard element of the patient evaluation and provides essential information for the diagnosis and treatment plan. Now, regarding the provided multiple-choice question:
The observable traits expressed by an organism are described as its phenotype. The phenotype includes all the visible and measurable characteristics, such as morphology, development, biochemical properties, physiology, and behavior, which result from the interaction of the organism's genotype (genetic makeup) with the environment. Other options like genotype, alleles, and zygote hold different meanings in genetics. The genotype refers to the genetic constitution of an individual organism, alleles are variants of a gene, and a zygote is a fertilized egg cell.