Final answer:
Traits determined by counting, such as the number of eggs laid by hens, are known as meristic traits. These traits can be counted in whole numbers and are different from continuous or threshold traits.
Step-by-step explanation:
Traits in which the phenotype is determined by counting, such as the number of eggs laid by a hen, are called meristic traits. These traits are quantifiable as they can be expressed in whole numbers, and they are typically analyzed in a binary or non-continuous manner, which differs from continuous traits that show a range of variation (like height or weight) and from threshold traits which are either present or absent once a certain threshold is crossed.
The observable traits expressed by an organism are described as its phenotype. The phenotype includes all the observable characteristics of an organism, such as color and structural morphology, which are controlled by the alleles for a given trait. For example, in his experiments, Mendel noticed that certain traits, like violet-colored flowers in pea plants, were dominant traits, while others, like white-colored flowers, were recessive traits.