Final answer:
Muller's Ratchet refers to the accumulation of deleterious mutations in asexual populations. Each "click" represents the fixation of a new mutation. This can lead to the gradual deterioration of the population's fitness.
Step-by-step explanation:
As Muller's Ratchet "clicks", it refers to a mechanism that leads to the accumulation of deleterious mutations in asexual populations. This phenomenon occurs when a population lacks the ability to recombine genetic material, as seen in many asexual organisms. Each "click" represents the fixation of a new mutation in the population. Over time, Muller's Ratchet can lead to the gradual deterioration of the population's fitness.