What characterizes an organism's phenotype?

• A. The genetic makeup of the organism
• B. The observable traits of the organism
• C. The number of chromosomes present
• D. The environment's effect on the organism

Answer: (B)

The phenotype of an organism is characterized by the observable traits that result from the interaction of its genotype (genetic makeup) with the environment. These traits can include physical appearances, such as height, color, and shape, as well as behaviors and biochemical properties. The phenotype is the actual expression of the genetic potential, influenced not only by genetics but also by environmental factors. This means that while the genotype provides the blueprint, the phenotype is what is visible and measurable in the organism. Understanding phenotype is crucial in fields such as genetics, ecology, and evolutionary biology, as it helps in studies related to natural selection and the adaptation of species.