What is the independent variable in the Daphnia heart rate experiment?
The control is the heart rate of Daphnia prior to exposure to caffeinated solutions. The dependent variable is the heart rate measured before and after exposure. The independent variables are the seven caffeinated solutions that are tested on the Daphnia magna.
What is the control variable in the Daphnia experiment?
In the case of our Daphnia, an example of a controlled variable would be the temperature of the water in which the Daphnia are tested. This variable needs to be controlled because Daphnia hearts beat faster in warm water than they do in cold water.
What factors affect Daphnia heart rate?
Daphnia is poikilothermic, which means that its body temperature and therefore the temperature of the environment directly affects its metabolic rate. The change in metabolic rate is reflected in the rate at which the heart beats (cardiac frequency).
What is the independent variable of your experiments with Daphnia magna in Lab 2?
The independent variable is that which will be varied during the experiment; it is the cause.
How does size of Daphnia affect heart rate?
Baylor (1942) found that Daphnia exposed to ““1024”” nicotine exhibited a 17%% decrease in heart rate. If he meant 1024 M, and not 1024 v//v (0.01%%), then our results contradict his: we found that heart rate increased at that concentration.
Why are Daphnia used in heart rate experiments?
Because Daphnia are transparent, it is possible to conduct bioassays using endpoints other than death. For example, through a microscope you can measure their heart rate or observe whether they have been eating. (Both of these signs are used to measure stress).
What is a Daphnia heart rate?
Results. Seventy-two Daphnia were used in the initial experiments. The average initial heart rate was 354 beats minute——1 (range: 91——521 beats minute——1). The large variation in heart rate between animals cannot be attributed to variation in their size.
What is Daphnia heart rate?
How does temperature affect Daphnia heart rate?
Based on the results, we found that the heartbeat was temperature-dependent in water fleas. This result was consistent with previous findings showing that daphnids become more active and increase their rate of breathing and heartbeat when temperature increased up to 6 °C [37].
How does Daphnia increase heart rate?
Dopamine, like caffeine, increases the heart rate of Daphnia in a dose-dependent manner. Dopamine’s effects on Daphnia’s heart has not been reported previously.
Does Daphnia heart rate increase with temperature?
How does alcohol affect the heart rate of Daphnia?
In the control group, no alcohol was added to the water. Results show that exposure of Daphnia to alcohol affects its heart rate. As the concentration of alcohol increases, the heart rate decreases. This observation is true for all the alcoholic beverages used in the experiment.
Do Daphnia have a heart?
Daphnia also has a heart that is contracting at a high speed – 230-290 beats per minute, resulting in blood pressure of 2-4 atmospheres. Daphnia breathes with the entire cover of the body, but primarily with the help of respiratory appendages on the extremities.
How does temperature affect metabolic rate in Daphnia?
As you increased the temperature of the water, the metabolism of the Daphnia increased as well, because chemical reactions occur faster at higher temperatures. This means that the heart rate will speed up in order to provide oxygen to the cells as the metabolism increases.