Final answer:
A sudden major climatic change is most likely to result in a rapid increase in extinction rates, as species struggle with immediate shifts in their environments and climate.
Step-by-step explanation:
A sudden major climatic change would most likely initially result in a rapid increase in extinction rates. This is because the rate of environmental change can exceed the ability of many species to adapt or migrate to more suitable habitats. When forced to cope with factors such as temperature shifts, altered precipitation patterns, and changing ecosystems, species that cannot keep pace may face substantial extinction.
Rapid changes in climate can lead to habitat loss, shifts in food resource availability, and disruptions in predation and competitive interactions among species. Coral reefs and polar environments are among the most vulnerable to rapid climatic shifts, exemplified by coral bleaching events and the loss of sea ice essential for polar bear hunting. Over time, some species may develop new characteristics to cope, but this is a longer-term process of evolution, not a direct immediate response to a sudden change.