Daphnia Experiment

After effectively conducting the experiment, the results acquired clearly shows the impacts of the variables applied and materials used to create a stimulus on the daphnia which can be seen with changes in its movement behavior and heart rate. With a certain level of knowledge in biology, some of the results and responses obtained were as expected, corresponding to the changes inflicted on the daphnias.

When the daphnia was placed into water, controlled with a thermometer at different temperatures such as 5°C, 20°C, and 50°C, its heart rate increased at a high temperature and decreased to normal at 20°C and 5°C. According to Clare (2002), even though the daphnia has a wide tolerance to different temperatures, its optimum temperature of survivability

According to Clare (2002), pH between values of 6.5 and 9.5 is acceptable by daphnias, with the optimum being somewhere around 7.2 to 8.5.

When ethanol was tested on the daphnia, observations show slow movements and decreased heart rate by the daphnia. Explanation for this is because alcohol is known as a depressant for the nervous system by acting as a non-selective neurodepressant which also affects humans heart rate in the same way (Handy, 2009).

When daphnia was placed in salt solution, it showed fast, increased movements and increased heart rate until gradually stopped completely after a while of exposure to salt solution. This is because salt solution is a hypertonic solution which creates a gradient of solute concentration when daphnia is immersed in the solution and draws water molecules out of the cells of the organism resulting in shriveling of the cells of the daphnia, also called crenation, which finally leads to the death of the daphnia (Carter-Edwards et al,

This is due to caffeine, which is present in coffee, mimics the effects of the neurotransmitter adrenaline and noradrenaline in the heart. It can affect the main pumping chambers (ventricles) which leads to an increased rate of contraction and relaxation of each beat. This means the heart beats faster and an increased volume of blood pumped into the circulation per unit time (Handy, 2009).

When yeast solution is added, the movement of the daphnia increased with a normal, steady-paced heart rate. This is because yeast is a form of food for daphnias which results in faster movements of the daphnia trying to capture and engulf the yeast particles in its limbs inside its carapace.

Even though most of the results produced match almost accurately with the expected responses from the daphnia based on scientific theories, there were some flaws and abnormalities in this experiment which may be due factors such as the initial health condition of the daphnia which causes the daphnia to be extra susceptible and weak towards extreme changes in surroundings. Apart from that, size of the daphnia also makes a difference in the result of the experiments. For instance, larger sized daphnias may have its effect “kick-in” slower than smaller sized daphnias due to difference in volume and surface areas of the organism exposed to the variables, which can impact the consistency of the