Which phrase is most commonly associated with the concept of natural selection?

The phrase "Survival of the fittest" is most commonly associated with the concept of natural selection because it encapsulates the idea that individuals or organisms best adapted to their environment are more likely to survive and reproduce. This phrase, originally coined by the philosopher Herbert Spencer, became widely adopted in the context of Darwinian evolution, where "fittest" refers not just to physical attributes but to the overall adaptability and reproductive success of an organism in a given environment.

In natural selection, it's the traits that enhance survival and reproductive success that get passed on to future generations. Traits that are beneficial in a specific environment tend to proliferate, while those that are not advantageous may diminish. Therefore, this phrase succinctly conveys the core principle of natural selection and the dynamics of evolutionary change.