Final answer:
The breeder's equation is a measure of the amount of additive genetic variation contributing to a trait multiplied by the strength of selection for a particular trait value. (option 3)
Step-by-step explanation:
The breeder's equation, formulated as R = h²S, where R is the response to selection, h² is the narrow-sense heritability, and S is the selection differential, represents the evolutionary response to selection. This equation quantifies how much a population's mean trait value will change in response to artificial or natural selection. The term h² reflects the proportion of phenotypic variation due to additive genetic factors, and S represents the difference between the selected individuals and the population mean. Therefore, the breeder's equation captures the interplay between genetic variation and the intensity of selection, providing insights into the potential for trait evolution.
The breeder's equation encapsulates the relationship between additive genetic variation and selection strength, offering a valuable tool for understanding and predicting evolutionary changes in traits within a population.