What does the fitness of a mutation describe?

The fitness of a mutation refers specifically to its value to an organism's survival and reproductive success in a given environment. When mutations occur, they can lead to new traits that may enhance an organism’s ability to find food, escape predators, reproduce, or adapt to changing conditions. If a mutation increases an organism's fitness, it is more likely to be passed on to future generations because those individuals are more successful at surviving and reproducing.

In the context of evolution, fitness is not about the random occurrence of mutations, the effect on genetic diversity, or the potential for further mutations. Instead, it is about how advantageous a particular mutation is concerning an organism’s ability to thrive in its environment. A mutation that significantly enhances survival and reproductive capabilities will elevate the overall fitness of an organism, leading to its greater prevalence in the gene pool over time.