What is the effect of caffeine and temperature on the heart rate of a Daphnia?
Caffeine is a bitter, white crystalline xanthine alkaloid and a stimulant drug. Plants produce caffeine as an insecticide. Cocoa, coffee and tea have all been used for hundreds of years to produce high caffeine drinks. Caffeine can also be used to enhance flavours in a wide range of soft drinks such as Coca Cola and as a stimulant in energy drinks such as Red Bull. For us humans the caffeine acts as a stimulant drug which increases the stimulatory neurotransmitters released in our body. Caffeine can be used medically to reduce physical fatigue and to restore alertness when drowsiness occurs. It produces increased wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination. The amount of caffeine needed to produce effects varies from person to person, depending on body size and degree of tolerance. A high intake of caffeine has been connected with causing restlessness, insomnia and anxiety. This results in a rise in blood pressure and stress leading to heart and circulation problems.
Daphnia is a genus of small, planktonic crustaceans, 1–5 millimetres (0.04–0.20 in) in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembles the movements of fleas. Daphnia live in various aquatic environments ranging from acidic swamps to fresh water lakes, ponds, streams and rivers. The heart is at the top of the back, just behind the head, and the average heart rate is approximately 180 bpm under normal conditions. Daphnia, like many animals, are prone to alcohol intoxication, and make excellent subjects for studying the effects of the depressant on the nervous system due to the translucent exoskeleton and the visibly altered heart rate. They are tolerant of being observed live under a cover slip...