Arizona State University (ASU) BIO 345 Evolution Exam 2 Practice

In evolutionary biology, fitness specifically refers to an organism's ability to survive and reproduce within a particular environment. This concept emphasizes that it's not just about surviving; rather, the key aspect of fitness is the reproductive success of an organism, which means having offspring that themselves can survive and reproduce. The more successful an organism is at passing its genes to the next generation, the higher its fitness.

This understanding of fitness allows researchers to explain how certain traits become more common in a population over generations—those traits that confer higher fitness will tend to be passed on more frequently. Therefore, while other factors such as strength or adaptation may play roles in an organism's survival, it is ultimately the relationship between survival, reproduction, and the specific environment that determines evolutionary fitness. This focus on reproductive success distinguishes the correct answer from other potential interpretations of fitness.