Final answer:
Genetic variation in natural populations is influenced by factors such as natural selection, gene flow, random mating, and genetic drift, demonstrating that it is neither constant and infinite nor limited and static, but rather dynamic and subject to evolutionary forces.
Step-by-step explanation:
The two early views of how much genetic variation exists in natural populations mentioned in the question are likely referring to the ideas that existed before modern concepts of population genetics were well-understood. Option A) 'Constant and infinite' suggests that genetic variation is both unchanging and limitless. Option B) 'Limited and static' implies that genetic variation is restricted and unchanging. However, neither of these captures the current understanding of genetic variation perfectly.
The diversity of alleles and genotypes within a population is certainly not static; it is affected by various factors such as natural selection, gene flow, random mating, and genetic drift. An example of population variation can be seen in Mendel's pea plants, which exhibited homozygous dominant, heterozygous, and homozygous recessive genotypes for different traits, demonstrating the concept of genotype and phenotype variation within a population.
The Hardy-Weinberg principle provides a framework to assess whether a population is in equilibrium or evolving. In reality, however, natural populations are subject to constant change in their genetic makeup due to the forces of evolution, like mutation and natural selection, making options C) 'Dynamic and infinite' and D) 'Constant and static' somewhat misleading descriptions of natural genetic variation.