Final answer:
The increase in antler points on the island's deer population is a result of directional natural selection, where individuals with larger antlers had an evolutionary advantage contributing to the prevalence of this trait over generations.
Step-by-step explanation:
The development whereby deer introduced to an island gradually evolved to have more points on their antlers can be attributed to the process known as directional natural selection. In this scenario, it's likely that having more points on the antlers provided an evolutionary advantage, potentially due to factors like sexual selection, where females might prefer males with larger antlers, or because larger antlers could be used more effectively in male-male competitions for mates. Over several generations, the trait for more antler points would become more prevalent in the population, resulting in most males having 20-point antlers as an adaptation to their environment.
The initial population of deer on the island would have had genetic variations in antler size, which included males with 11 to 13 antler points. Assuming better survival and reproductive success for the individuals with larger antlers, their genes would have spread through the deer population at a greater rate. This evolutionary process highlights the impact of selective pressures on a population, causing a shift in the frequency of particular traits such as antler size over generations.
The concept of the Hardy-Weinberg principle can be applicable in this context as a measure of genetic equilibrium, but the observed evolution of antler size reflects a deviation from this principle due to selective pressures. Thus, the final answer to the student's question lies in understanding how natural selection influences the distribution of traits within a population.