The daphnia lab report

Hypothesis: If the concentration of caffeine increases then the daphnia’s heart rate will also increase.

Controls:

Positive- Even a little amount of caffeine will always increase the heart rate of a daphnia.

Negative- the daphnia is always going to give an unknown result.

Materials:

Pipette

Beaker

Test tubes

Test tube rack

Energy Drink (a drink containing Caffeine)

Distilled water

Stop watch

Depression Slides

Microscope

Daphnia Magna

Petri dish

Procedure:  

1. Before beginning, it was assured that the area was clean, goggles were worn at all times and all lab safety rules were followed.
2. All materials were gathered.
3. Six different caffeine containing solutions were prepared.  In a test tube 7.8 mL of caffeine (the energy drink) was added and 17.2 mL of distilled water was added to prepare the first solution. In second test tube 5.2 mL of caffeine and 19.8 mL of distilled water was added.
4. Step 3 was repeated for the other 4 solutions with the ratios of: (in third tube )3.5 mL of caffeine to 21.5 mL of distilled water,( in fourth tube) 2.3 mL of caffeine to  22.7 mL of distilled water ,( in fifth tube) 1.7 mL of caffeine to  23.3 mL of distilled water and( in sixth tube) 1.5 mL of caffeine to 23.5 mL of distilled water.
5. Using a pipette, a daphnia was obtained and placed in a Petri dish. Then using a different pipette small amount (approx. 10 mL) of the first caffeinated solution was obtained then, this solution was poured into the Petri dish that contained the daphnia in it.
6. Using another pipette, the daphnia was picked up and transferred to the depression slide.
7. Then, slide was placed under a microscope and focused the daphnia using on 40x magnification so that the heart rate could be seen beating.
8. After getting a clear focus on the daphnia’s heart beating, the numbers of heart beats were counted in a period of 15 seconds using the stopwatch.  To get the number of beats per minute the heart beats were multiplied by 4.
9. Step 5-8 were repeated for the other five solutions  using a new daphnia every time and from each caffeine concentration, heart rate (bpm) was measured .

Data:

Graph 1.0: Heart rate of Daphnia versus Concentration of Caffeine Solution

Calculations:

Determining the amount of caffeine to water ratio:

473 mL of Monster energy drink contains 150 mg  .

                    𝑪= 𝒎𝒈/𝑳

1.    

         

2.    

         

3.     

         

4.     

         

5.     

         

6.     

         

Discussion:

The results shown in the graph conclude that heart rate does increase when the concentration of caffeine increase in the daphnia’s and that caffeine does act like a stimulant.

  As the concentration of caffeine increases, heart rate of Daphnia increases for caffeine concentration from 44.5 mg/L to 66.6 mg/L because caffeine is a stimulant which raises the heart rate of animals. Likewise, assuming that human’s heart will also increase. However there is a decrease in the heart rate for the second and fourth daphnia, this is anomaly and probably occurred because the daphnia had a low temperature or that caffeine didn’t affect daphnia because it wasn’t in the solution for long enough. Another reason for this anomaly is that class members were using daphnia from the “recovering centre” (the caffeinated daphnia were placed in a new breaker with a cleaner environment so they can overcome the caffeine and be ready to be used again.), maybe the daphnia chosen was still recovering when put in another concentration, which resulted in a low heart rate from the other data. The daphnia probably became tolerant to the caffeine and needed a higher dosage so it’s heart rate can go up. The daphnia could have been hurt or damaged when moved from one container to another resulting in lower heart rates as it was dying off.

     Generally, the trend line matches the hypothesis, the trend line increases as concentration does.

 

The ingredients present in “Monster” energy drink are glucose, sucrose, carbonated water, natural flavors, sodium citrate, ascorbic acid, l-carnitine, panax ginseng root extract , sodium chloride, niacinamide, riboflavin, guarana seed extract, inositol, glucuronalactone, pyridoxine hydrochloride, cyanobalamin, taurine and of course Caffeine.

Guarana- a small red fruit’s black seeds are known as Brazilian coco beans that act like a stimulant. It is recommended that people with heart diseases shouldn’t use this stimulant (Alternative Medicine). This will stimulate the daphnia’s CNS and its heart rate will increase.

Inositol- this is known to be a b-vitamin co-factor and is found in the eye lens and the human heart and is believed to lower stress. So probably when the daphnia was under immense pressure of put into a high concentrated environment the inostiol calmed it down and lowered its “stress” levels.

Glucuronalactone- is known to increase the feeling of well being and supplies energy similarly to glucose (Alford. C). It is unsure to know what daphnia feel, but may be their rapid movement increased even more due to this ingredient.

The herbal content in the Monster energy drink includes taurine and panax ginseng root extract.

Ginseng- also stimulates the central nervous system and once again people with heart diseases should not use ginseng because it has the opposite reaction compared to caffeine, ginseng decreases the heart rate and forces heart beats.

Taurine-  this is another stimulant that increases heart rate by 10 bpm .Taurine and caffeine make a deadly combination for the internal body especially the heart,  these stimulant would have made the daphnia’s hart beat faster than usual as it would in humans.

The sugar and caffeine provide a boost of energy but effect of sugar isn’t long lasting, after this occurrence the body’s (in humans) blood sugar levels drop causing fatigue.

Humans can’t be compared to daphnia due to there anatomy differences and more specifically their difference in the central nervous system. It should also be assumed that daphnia are small and the caffeine concentration that increased the daphnia heart rate to max will not increase the heart rate of the human. Another important fact is that, daphnia have a neurogenic heart meaning it doesn’t contract but instead conducts impulses versus human hearts; they are myogenic meaning they contract (Welcome to Georgia State University). This adds parallel to the results.

The DE/ICCA article on caffeine describes these effects in humans: "Low doses (up to 2 mg/L in blood) stimulate the central nervous system, while high blood concentrations (10–30 mg/L) produce restlessness, excitement, tremor, tinnitus, headache, and insomnia." (DE/ICCA, 2002). This shows that even low dosage of caffeine work and they probably worked the daphnia in this lab too, but their high blood concentration caused the daphnia to be stressed and slow.

The Wikipedia article in the Bibliography tells us that the median lethal dose (LD50, when administered at this dose, the drug is expected to be lethal to half of the recipients) of caffeine in rats is 192 mg/kg of body mass, and is thought to be between 150–200 mg/kg for humans (Wikipedia, 2006). The median lethal dose is given in mg/kg of body mass. Since blood volume is proportional to body mass, this is a rough way of normalizing the dose to blood volume. Finally, notice that the article also says, "While relatively safe for humans, caffeine is considerably more toxic to some other animals such as dogs, horses and parrots due to a much poorer ability to metabolize this compound. Caffeine has a much more significant effect on spiders, for example, than most other drugs do." (Wikipedia, 2006)  humans are categorized separately versus the terrestrial animals and aquatic animals. Due to their internal processes that work differently from one another. The quote above shows that different organisms have a different lethal amount of dose of caffeine that they can take and survive. Comparing this to the results from this lab it is concluded that daphnia’s can only take 182 mg/L of caffeine and survive while humans can take 200 mg/kg (note: the units) which shows that daphnia can’t be compared to humans in caffeine consumption. This fact and the lab results prove that the median lethal does is different for each organism depending on their size and blood volume.

There are a number of possible scientific errors in this experiment. Firstly, the method of measuring the heart rate of the daphnia. As the graph shows that the amount of beats per minute of daphnia are very fast and somewhat impossible for some group members to count. Using ice cubes to keep the daphnia’s in a cool environment isn’t accurate  because as the ice cubes melt over time, the daphnia’s environment is warmer resulting in a higher initial heart rate then usual. The heat radiated from the microscope could also affect the daphnia’s heart rate or make it inaccurate because not only is daphnia deprived from water and put into a new environment with caffeine but it is also being burned which might of raised the stress level of the daphnia, resulting it’s heart  to beat faster. Also, the age, size and sex of the daphnia determines its metabolic rate and when this is not considered it can change the heart rate of the daphnia (varying from daphnia to daphnia). Meaning different age groups of daphnia would probably react differently to the increase in caffeine concentration.

Conclusion:

In conclusion, as the caffeine increased, the daphnia’s heart rates also increased and the hypothesis was correct.  Further experiments can be conducted; using a stronger microscope which will increase the accuracy when counting the heart rate of the daphnia. In addition, all Daphnia should be the same size so they are affected with precision and results will be more accurate.  To specify more specific trends in affecting the daphnia’s heart rate, repeating the experiment for more than six concentrations can increase the validity.  Through the lab’s results it is believed that there  is a relationship between the daphnia’s and humans heart rate therefore if  an increase in the daphnia’s heart rate is due to high caffeine concentration , then humans also have a high heart rate after consumption of  caffeine. This is dangerous as mentioned before because this makes human prone to numerous diseases in the body that correlate with caffeine. First of all, increase in heart rate means that blood is being  pumped in the human body at a higher rate which increases the chance of damaged or erupted veins and arteries which  further will increases the human’s chance of getting atherosclerosis. It is also suggested that caffeine increases the cortisol levels in the human body. Cortisol, known as a stress hormone, if this hormone is too high it can lead to weight gain,  diabetes, heart diseases and very rare but possibly Cushing syndrome’s (Caffeine, Stress and Your Health - Is Caffeine Your Friend or Your Foe?). Moderate amounts of caffeine do, good for the body as it provides a positive awakening for anything, but too much caffeine can possibly lead to hypertension.  As a result, maintaining lifestyle and reducing risks of cardiovascular disease must first lead to the avoidance of caffeinated goods. Ultimately, it will be beneficial to one’s life as it will decrease the high heart rates and therefore decreasing the possible threats of caffeine intake mentioned above. Furthermore, this experiment can be used, replacing caffeine with nicotine, alcohol or other drugs or even temperature and then determining their effects on the daphnia.

Work Cited

• Alford C, Cox H, Wescott R. The effects of red bull energy drink on human performance and mood. Amino Acids. 2001;21(2):139-50.
• "Caffeine." KidsHealth - the Web's most visited site about children's health. Web. 09 Dec. 2009. <http://kidshealth.org/teen/food_fitness/nutrition/caffeine.html>.
• "Caffeine, Stress and Your Health - Is Caffeine Your Friend or Your Foe?" Stress Management - Stress Information and Resources from About.com. Web. 09 Dec. 2009. <http://stress.about.com/od/stresshealth/a/caffeine.htm>.
• Clare, John. "Daphnia." Caudata.org. Web. 09 Dec. 2009. <http://www.caudata.org/daphnia/>.
• "Differenc.htm." Welcome to Georgia State University. Web. 09 Dec. 2009. <http://www2.gsu.edu/~bioasx/differenc.htm>.
• "Energy Drink Dangers Ingredients Drinks Reviews Comparisons." BrianX Free Magazine | Lifestyle & Entertainment Mag. Web. 09 Dec. 2009. <http://brianx.com/nightlife/energy-drinks.html>.
• "Guarana - What is Guarana?" Alternative Medicine - Everything You Need to Know About Alternative Medicine. Web. 09 Dec. 2009. <http://altmedicine.about.com/od/completeazindex/a/guarana.htm>.

• Hasan, Heather., Drug abuse and society: Caffeine and Nicotine- A dependent society. NY: The Rosen Publishing Corporation, 2009.