Final answer:
The scenario described is an example of speciation due to habitat isolation, where grasshopper populations in Oklahoma that can no longer interbreed with distant populations have likely become separate species. This process is facilitated by natural selection, mutations, and genetic drift leading to genetic divergence.
Step-by-step explanation:
The scenario described is an example of speciation occurring through a process known as habitat isolation. This happens when populations of the same species are geographically separated, leading to reproductive isolation. Eventually, through the processes of natural selection, mutation, and genetic drift, these populations may become so genetically distinct that they can no longer interbreed, resulting in the formation of new species. In the case of grasshoppers in Oklahoma, the nearby populations that look different but can still breed represent a possible early stage in this process. Those from further away that cannot interbreed represent populations where speciation has likely occurred.
Geographic variation can lead to changes over time, with the environment playing a significant role in shaping the organisms. Two separate yet similar species, the cricket Gryllus pennsylvanicus and Gryllus firmus, demonstrate this well, as they prefer different types of soil and live in close proximity but are genetically isolated. This demonstrates that even nearby habitats can produce significant enough differences to lead to speciation. Additionally, the concept of a cline is observed where variations in populations of a species occur gradually across an ecological gradient.