Final answer:
An environmental factor like light, temperature, or diet can affect a critter's trait. For example, the amount of sunlight an organism receives can determine its skin color.
Step-by-step explanation:
An environmental factor like light, temperature, or diet can affect a critter's trait. For example, the amount of sunlight an organism receives can determine its skin color. Temperature-dependent sex determination is another example, where the temperature at which reptile eggs are incubated determines the sex of the offspring. Changes in environmental conditions can also shift the direction of natural selection, favoring certain traits over others.