Final answer:
Mutations can be classified based on their phenotypic effects, including negative, positive, and neutral effects on fitness.
Step-by-step explanation:
Mutations can be classified based on their phenotypic effects. One way mutations are classified is based on their fitness effects. A mutation can have a negative effect on fitness, which means it reduces the likelihood of survival or the number of offspring. Alternatively, a mutation can have a positive effect on fitness, improving the organism's chances of survival and reproduction. Finally, some mutations have neutral effects on fitness, meaning they do not impact the organism's survival or reproductive success.