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Ectothermic animals are animals whose body temperature is affected by their surroundings. This means that if the environment is cold the animal will be cold. If the environment is warm the animal will be warm. This is because the animal doesn’t have the capability of regulating its body systems to keep a constant body temperature. When an ectothermic animal is cold, its heart rate will lower. When the animal is warmer, the heart rate will raise – as long as the temperature isn’t sufficiently high to harm the animal. (Campbell, 2005)
Alcohol is a depressant. This means that body systems will slow down when alcohol is introduced. In particular, the heart rate will get consistently lower. If too much alcohol is added, it will result in the death of the animal. The alcohol acts by inhibiting the nervous system. (LaFave, 2003) After an intoxicating exposure to alcohol, an organisms system will be impaired for an extended period of time.
Caffeine is a stimulant. It will work by causing 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 animals heart rate. Under normal circumstances, the heart rate will increase as more caffeine is added. At some point the high concentration of caffeine will cause the heart to stop functioning.
The effect of one outside substance can impair the effects of other substances. In this experiment we will intoxicate an organism. As a result, the nervous system will have difficulty responding when we introduce a stimulant. The caffeine will have no effect on the organism, because it will be insufficient to overcome the effects of the alcohol exposure. Background
Daphnia magna is a freshwater ectothermic crustacean commonly referred to as a water flea. Its body is transparent. Because of its transparency we can observe the effects of substances on its body without surgical procedures. We can observe the heart of the Daphnia to be dorsal to the backbone, just behind the head. (Helms, 1998) The average Daphnia has a heart rate of about 180 beats per minute under normal conditions. We will observe the effects of temperature fluctuations, alcohol, and caffeine on this ectothermic animal.
The hypothesis is that lowering the temperature of the surroundings of the ectothermic Daphnia magna will cause its heart rate to lower, and raising the temperature will increase heart rate.
The hypothesis is that the heart rate of Daphnia magna will decrease as higher concentrations of alcohol solution are introduced to the system.
The hypothesis is that the heart rate of Daphnia magna will increase as higher concentrations of caffeine solution are introduced to the system.
Materials and Methods
For the sake of time, the experiment was split into two parts and each part was performed by a different team. One team worked on the effects of temperature changes on heart rate. The other team worked on the effects of Alcohol and Caffeine on the heart rate.
Both teams obtained a plastic pipette and cut off the tip at the first graduation from the bottom to allow Daphnia magna to fit into the pipette. The teams each obtained a depression slide and smeared a small amount of petroleum jelly on one of the wells. Any excess petroleum jelly was wiped off so that there was only one layer on the well. Then each team used their pipette to draw a Daphnia magna from the jar and placed it on the petroleum jelly covered well. A Kimwipe was used to draw off excess fluid from the slide. Then one drop of solution was placed on the Daphnia magna to prevent it from drying out. Each slide was placed on a dissection microscope and the heart was located using the Helms manual and help from the lab...