Final answer:
C. Loring Brace's theory of the "Probable Mutation Effect" involves the roles of mutations and genetic drift in evolutionary processes. Advantageous mutations may improve organismal fitness, aligning with Darwin's theory of natural selection. The theory explains variability in traits' adaptiveness based on environmental context.
Step-by-step explanation:
In line with C. Loring Brace's theory of the "Probable Mutation Effect," the concept revolves around the occurrence of mutations and how they can have varying impacts on a population's genetic makeup. Brace's theory suggests that, although many mutations can be deleterious, there are occasional mutations that provide a beneficial advantage to the organism within its environment. For instance, in population A, the introduction of allele B via mutation and the increase of allele A due to genetic drift highlight these concepts. Similarly, in population B, natural selection seems to favor allele A over allele B, indicating that advantageous mutations can lead to increased fitness and survival within specific environmental contexts. This theory aligns with Charles Darwin's theory of evolution by natural selection, in which organisms that are well-adapted to their environment tend to survive and reproduce, while those less adapted may perish.
The theory is further supported by real-world examples, such as the mutation allowing resistance to malaria in certain populations, which is highly adaptive in regions where malaria is prevalent. Contrarily, in environments where malaria is rare, such as the United States, the same mutation might result in health complications. The randomness of these mutations and their subsequent fixation or loss in a population by genetic drift exemplifies the unpredictable nature of evolutionary processes.