Answer:
physiologist
Explanation:
A physiologist is a person or a professional who studies and does experiments to see the function and behavior of plants and animals under normal circumstances as well as abnormal circumstances. They also study and learn the impact of the human life on the species and how the specimens they interact with each other.
In the context, an experimenter conducting an experiment to see the affect of heart beat rate when the temperature changes is known as a physiologist.
