In the context of natural selection, what does the term 'fitness' refer to?

In the context of natural selection, the term 'fitness' specifically refers to reproductive success, meaning the ability of an individual to produce offspring that can survive to reproduce. This concept emphasizes the idea that it is not merely about surviving longer than others, but rather about contributing genes to future generations. Organisms that are better adapted to their environment are more likely to survive and reproduce, thus passing on their advantageous traits.

Reproductive success can be influenced by various factors such as mating behaviors, availability of resources, and competition with other organisms. In summary, when biologists discuss fitness in natural selection, they are primarily concerned with how effectively an organism can transmit its genetic material to the next generation, which is ultimately the measure of evolutionary success.