Daphnia

            The Effect of Raising and Lowering Temperature and .
             Epinephrine on the Heart Rate of Daphnia.
            
             The Daphnia is a crustacean, also knows as the water flea', widespread in lakes and ponds. The average size of a single Daphnia is three millimeters. They are directly linked to other crustaceans like crabs, shrimps, and lobsters (BioMedia, 2003). .
             Even though this animal is minuscule they are needed for the survival of other aquatic life. Daphnia produce little algae cells that change sun energy into food. When other animals, like trout, consume them this energy is passed on (BioMedia, 2003).
             Daphnia are also ectothermic, or cold-blooded. They do not draw heat from their own metabolism, which is called homeothermic. Instead they must get it from an outside source. They regulate their body temperature by soaking up heat from the environment around it (Campbell et al, 2003).
             In this experiment there are many reasons why the Daphnia is used. One reason is that they are very responsive to the variations in water. Daphnia are also very cheap to raise outside of their natural environment. Another reason that Daphnia make a great organism for the testing is that they grow and mature in a matter of days, therefore a culture is easy to grow. The Daphnia is also transparent. This is very helpful because when looking at them through a microscope you can see the heart, legs, and antenna moving, so you do not have to kill the animal for observation (Authentic Inquiry, 2003).
             In humans, homeothermic animals, epinephrine, also known as adrenaline, is produced in the adrenal glands. In stressful situations, it is released from these glands, which causes a rise in heart rate, in turn allowing more blood to pump through the body. It also causes an increase in blood pressure because it contracts blood vessels. Breathing is also easier because epinephrine decreases airway resistance. Another effect on the body is that it raises blood glucose to supply needed energy (Campbell et al, 2003).