Which species-related concept describes organisms that maintain a constant mortality rate throughout their life span?

The concept that describes organisms maintaining a constant mortality rate throughout their life span is best captured by the term "constant loss species." These species exhibit a mortality pattern where individuals are equally likely to die at any age, rather than having high mortality rates in juvenile stages or older ages.

This mortality pattern is typically observed in certain species with characteristics that lead to a stable environment where individuals have a steady chance of surviving or dying regardless of their age. This contrasts with other species-related concepts—opportunistic species generally have high mortality early in life with potential for rapid reproduction, while equilibrium species tend to have lower mortality rates in their juvenile stages but can exhibit increased mortality as they age. The concept of "survival of the fittest" refers to natural selection rather than specific mortality rates. Therefore, "constant loss species" accurately reflects the mortality characteristic in question.