Final answer:
A lethal mutation results in the death of an organism, preventing it from reproducing and passing on its genes. Beneficial mutations improve an organism's fitness, while neutral mutations, such as silent mutations, have no effect on fitness.
Step-by-step explanation:
A mutation that results in the death of an organism is known as a lethal mutation. These mutations can dramatically affect a gene and the resulting phenotype, leading to reduced fitness, or a lower likelihood of survival, thus preventing the organism from reproducing and passing on its genes. Beneficial mutations, in contrast, increase an organism's fitness by improving survival or reproductive chances, while neutral mutations have no effect on the organism's fitness. An example of a neutral mutation is a silent mutation, which does not change the amino acids in the proteins they encode and, therefore, has no impact on the organism's function or survival.