What characterizes evolutionary fitness in terms of survival?

Evolutionary fitness is primarily characterized by the production of viable offspring. This concept highlights that an organism's success is measured by its ability to pass on its genes to the next generation. It's not solely about survival; it's about reproductive success. An organism that can survive but fails to reproduce does not contribute to the genetic pool of the next generation, thus diminishing its evolutionary fitness.

While physical strength and aggression may give some individuals advantages in certain situations, they do not directly correlate with an organism's overall evolutionary fitness. Similarly, the ability to consume food and resources is important for survival but doesn't necessarily lead to the successful reproduction of offspring. Adaptation to environmental changes is relevant, as those that can adjust to their surroundings are likely to survive longer, but ultimately, if they do not produce viable offspring, they will not enhance their evolutionary fitness. Therefore, the production of viable offspring is the key characteristic that defines evolutionary fitness.