Answer:
The term fitness refers to the measure of reproductive success that an organism displayed; It has to do with the number of offspring that an organisms leave in the next generation compared to other organisms in the group. Populations usually evolve by natural selection. In natural selection, organisms with Inheritable traits, which help them to survive and reproduce tend to leave more children than the other organisms. Overtime, the feature that help the organisms to survive will become more common in the population and make the animals more suited to their habitats.