AP Environmental Science Worm Lab ReportIntroductionCaffeine, while not normally considered lethal, is fatal in large doses. Its effects in varying doses were tested on Kingworms in this experiment. In toxicology, the median lethal dose is abbreviated as LD50 (lethal concentration 50%), in other words the amount of a substance required to kill 50% of the members in a tested sample. The purpose of this experiment was to determine the LD50 dosage of caffeine on Kingworms.HypothesisIf 3 doses of caffeine (0.021 g, 0.048 g, 0.096 g) are given to 3 separate petri dishes of worms and no dose to one control dish, then the percentage of live worms will decrease and the LD 50

dosage can be determined with a linear regression model.Materials· 8 petri dishes· 27 Kingworms· powdered caffeine· balance· scooping tool· tweezers· paper· beakers· distilled water· filter paperProcedure1. Scoop 7 worms into each petri dish and 6 worms into control (*not enough worms to allocate 7 worms to control group)2. Assign arbitrary caffeine dosage values to 3 petri dishes: 0.021 g, 0.048 g, 0.096 g. Control group receives no caffeine.3. Use 4 petri dishes to and dissolve each dosage of caffeine into 2 mL of distilled water4. Pour water onto filter paper side of other petri dishes5. Wait 2 days6. Record percentage of dead worms7. Calculate linear regression model between grams of caffeine and percentage of alive worms8. Use best fit model to determine LD50 dosage (aka grams needed to kill 50% of worms)Data Collection/Analysis

( x variable) Grams of Caffeine Per Petri Dish

0g 0.021g 0.048g 0.096g

(y variable) Percentage of Alive Worms After 2 Days

67%(4 alive/6)

85.71%(6 alive/7)

42.86%(3 alive/7)

14.29%(1 alive/7)

Model of Best Fit Equation: y = -664.9585334x + 79.8945395 *r2 value = 0.7952578902

Proposed LD50 Dosage: 0.0449569981 grams or 44.9569981 mg

ConclusionThe least percentage of alive worms was at the greatest caffeine dosage. The graph shows that there is a general decreasing percentage of alive worms as grams of caffeine increase, matching the hypothesis. The calculated line of best fit is relatively accurate, with the r2 value explaining 79.5% of the variability of the data. Thus the proposed LD50 dosage (44.9569981 mg) can also be considered as relatively accurate. Errors of this experiment might be sources of human error such as inaccurate measurements of caffeine. The control group is an outlier and might have been fixed by allocating the same number of worms in comparison to the other groups.