Final answer:
Writhing is a behavior exhibited by animals in response to pain or distress. It involves twisting and contorting movements of the body. The stimulus for this behavior can vary and it involves the nervous system and muscles.
Step-by-step explanation:
This behavior is known as writhing and it is usually a response to pain or distress in animals. It is characterized by twisting and contorting movements of the body. The stimulus or trigger for this behavior can vary and may include factors such as injury, illness, or exposure to harmful substances. When an animal experiences pain or distress, it activates the sensory pathways and motor systems in the body, leading to the writhing movements. The structures and functions involved in this behavior include the nervous system, which processes and transmits pain signals, and the muscles, which contract and generate movement.