Because of its transparency we can observe the effects of substances on its body without surgical procedures. We can observe the heart rate of daphnia magna to be dorsal to the backbone just behind the head. (Helms 1998) the average daphnia magna has a heart rate of 180 beats per minute under normal conditions. We will observe the effects of water, alcohol and caffeine on the ectothermic animal. Alcohol is a depressant; this means the body systems will slow down when alcohol is introduced.
The heart rate will get consistently lower if too much alcohol is added. Caffeine is a stimulant; this means that it will cause the nervous system to work faster, also it will cause the blood vessels to constrict. (LaFave 2003) These effects will work together to increase an animal’s heart rate under normal circumstances the heart rate will increase as more caffeine is added. Questions Does changing the daphnia magma’s environment change its heart rate? How will alcohol affect daphnia’s heart rate? How will caffeine affect daphnia’s heart rate? Hypothesis
Daphnia magna are sensitive creatures and therefore they will respond to slight changes in their environment. Since alcohol is a depressant and can lower human heart rate it should also lower daphnia’s heart rate. Since caffeine is a stimulant it can cause the nervous system in humans to work faster it should also raise the heart rate of daphnia. Predictions If the environment affects daphnia heart rate as it does in humans the exposing it to different environment’s should affect its heart rate. If daphnia is exposed to alcohol at varying concentrations, then daphnia heart rate should fall.
If daphnia is exposed to caffeine at varying concentrations then daphnia heart rate should rise. Materials and methods For monitoring the effect of environmental, medium on the heart rate of daphnia magna the specimen was placed on a clean deep well slide with a small drop of water and placed under a microscope. The heart rate observed after 15 seconds and recorded. A corner of a Kim wipe was used to wipe off excess water and repeat the experiment. The daphnia is then placed in a beaker labeled recovery. Use a second daphnia to repeat the experiment.
With a third daphnia place it on a deep clean well slide, add small drop of water (0% alcohol) and view the daphnia under a microscope and then record the heart beats within 15 seconds on the table. Remove the drop of water around the daphnia using a Kim wipe and add 1 equal drop of 1% alcohol, let daphnia sit in alcohol for 60 seconds. Record the heart beat within 15 seconds. Repeat the step with increasing concentration of 2%-5% alcohol observe the heart beats of the daphnia at each concentration and record. Place this daphnia in a beaker labeled recovery and use a second daphnia to repeat step 7-10.
Obtain a fresh daphnia and remove the water around the daphnia using the corner of a Kim wipe, add an equal drop of 0% caffeine. Record the number of heart beats within 15 seconds on a table. Add an equal drop of 1% caffeine let sit in caffeine for 60 seconds. Record the heart beat within 15 seconds. Repeat the step with increasing concentration of 2%-5% caffeine observe the heart beats of the daphnia at each concentration and record. Place this daphnia in a beaker labeled recovery and use a second daphnia to repeat step 7-10.