Final answer:
A reflex is an involuntary response to a specific stimulus that occurs without conscious thought. Fixed action patterns and the fight-or-flight response are other examples of innate responses to stimuli.
Step-by-step explanation:
A reflex is an involuntary, stereotypical reaction to a specific stimulus. Reflex actions are automatic responses that occur without conscious thought, protecting the body from harm and helping it to maintain homeostasis. For instance, when a person touches a hot surface, the sensory nerves in the skin send a signal to the spinal cord, which then sends back a signal to the muscles in the hand to contract and pull away—without the signal needing to go to the brain first. This is an example of a simple reflex arc.
Another type of innate behavior is the fixed action pattern, which is a sequence of actions triggered by a specific stimulus that will carry on to completion even if the original trigger is removed. One example is the aggressive behavior of the three-spined stickleback fish during the breeding season when it responds to any object with a red underside as if it were a rival.
The fight-or-flight response is a more complex set of actions involving both the nervous and endocrine systems. It is triggered when an organism perceives a threat, resulting in physiological changes that prepare the body to either face the danger or escape from it.