Final answer:
Without specific data, we cannot definitively say which population is experiencing a negative population change. However, genetic drift, gene flow, natural selection, mutation, and non-representative samples could contribute to a population not following an overall trend. Understanding why population changes occur involves considering both genetic and environmental factors as well as population dynamics.
Step-by-step explanation:
Based on the context provided, the question relates to changes in population sizes and factors affecting them, analyzed through data on birth rates and death rates. To determine which population is experiencing a negative change in population size, one would compare the birth and death rates; if the death rate exceeds the birth rate, the population is likely shrinking. In this case, without the specific data, we cannot identify which option (a, b, c, or d) is correct. Reasons for a population not following the overall trend could include genetic drift, gene flow, natural selection, mutation, sampling bias or non-representative samples, and unique environmental pressures. For instance, options 'C' and 'D' mention circumstances like genetic drift and natural selection, which can significantly influence allele frequencies and hence population dynamics, independent of birth and death rates.
To assess the alignment with the overall trend, we would need data from the table mentioned. If the question is referring to the options given in the last part, which mentions allele frequency changes due to factors like gene flow, genetic drift, and mutation, this would be a matter of determining deviations from Hardy-Weinberg equilibrium, which requires a closed population with no mutations, random mating, large population size, no gene flow, and no selection. A population not in Hardy-Weinberg equilibrium may be due to any of these factors being violated.