What does 'fitness' refer to in a biological context?

'Fitness' in a biological context refers to how well an organism can survive and reproduce in its environment. This concept is central to the theory of natural selection, which proposes that individuals that are better adapted to their environment are more likely to survive and pass on their genes to the next generation. Thus, fitness is not merely about physical attributes such as speed or strength, but rather encompasses an organism's overall ability to thrive and produce viable offspring that can also survive in their environment.

This broader understanding of fitness includes various factors such as the ability to find food, evade predators, cope with environmental stresses, and successfully mate. As a result, an organism with high reproductive success contributes more to the gene pool of the next generation, highlighting that fitness is ultimately measured by reproductive success rather than just physical prowess or other attributes.