Daphnia, commonly known as water fleas, have a much faster heart rate compared to humans. The heart rate of a Daphnia can vary depending on environmental conditions, oxygen levels, and other factors, but it can range from about 100 to 300 beats per minute or even higher. In contrast, the average resting heart rate for a human is typically between 60 to 100 beats per minute.
This significant difference is due to the size and metabolic rates of the organisms: Daphnia are small and have high metabolic demands, while humans are larger and have a slower metabolism. Additionally, Daphnia's heart can be observed beating under a microscope, making it a popular subject for studying physiological responses in real-time.