If a characteristic which is influenced by genes and passed from parents to offspring is called a heritable trait, for example, fur color is a heritable trait for rats. An adaptation is a heritable trait that increases fitness. This table describes the characteristics of a population of rats living on gray sand.

color of fur white gray black
Av. run speed 4 cm/s 6 cm/s 12 cm/s
Av. # of offspring 4 16 10
Av. age at death 3 months 6 months 3 months

a. Which fur color is an adaptation for these mice? What evidence supports your conclusion?

b. Explain what the data is showing an what conclusions can you draw from it?

c. Predict what the population would be like for each rat if the sand turned black.