Final answer:
The ultimate cause of the kangaroo rat's escape jump in response to a rattlesnake is a genetic predisposition, which is an innate behavior selected for over generations to improve survival.
Step-by-step explanation:
The ultimate cause of a kangaroo rat instinctively reacting to the sound of a rattlesnake by executing an escape jump is D) Genetic predisposition. This behavior is an innate behavior, which means it is a hard-wired response that the animal performs instinctively without prior learning. Over generations, traits that enhance an individual's ability to survive and escape from predators—such as the quick escape jump in response to a rattlesnake's warning sounds—are naturally selected. This is because individuals possessing these traits are more likely to survive and subsequently pass these advantageous traits on to their offspring, hence becoming more common in the population over time. The fight or flight response is a good example of such instinctive behavior driven by genetic predisposition and shaped through natural selection.