LD 50 Lab
Hypothesis: More than half of the radish plants will not be able to tolerate any concentration past 12.5% because this is the suspected lethal dose. The independent variable is the concentration of salt water in the mixture. The dependent variable is the number of seeds germinated. The controlled variables include the time allotted, the number of seeds in each petri dish, the light level, and the total amount of mixture in each petri dish. The control group is the petri dish with no salt concentration while the experimental groups have varying degrees of salt concentration.
Problem: What is the LD 50 (lethal dose) of salt concentration for radish seeds?
Materials:
-6 petri dishes
-60 seeds
-12 napkins
-Water
-Graduated cylinder
-Concentrated Salt Water solution
Procedure:
1. Use the graduated cylinders and test tubes to prepare the various concentrations as shown below.
Problem: What is the LD 50 (lethal dose) of salt concentration for radish seeds?
Materials:
-6 petri dishes
-60 seeds
-12 napkins
-Water
-Graduated cylinder
-Concentrated Salt Water solution
Procedure:
1. Use the graduated cylinders and test tubes to prepare the various concentrations as shown below.
2. Label all six petri dishes with the dish number and the percent concentration of the chemical.
3. Put two napkins together and cut them so they fit into a petri dish (repeat for each).
4. Carefully pour the chemical solutions and water onto the napkins, making sure to match the numbers and concentration percentages of the dishes.
5. Count out ten seeds for each dish. Carefully place the seeds on the moist napkins in the petri dishes.
6. Place the seed dishes in a stack, lying flat with the seeds up.
7. Let sit for six days. Count how many seeds germinated in each and record the lengths of the radicles.
Observations and Data
3. Put two napkins together and cut them so they fit into a petri dish (repeat for each).
4. Carefully pour the chemical solutions and water onto the napkins, making sure to match the numbers and concentration percentages of the dishes.
5. Count out ten seeds for each dish. Carefully place the seeds on the moist napkins in the petri dishes.
6. Place the seed dishes in a stack, lying flat with the seeds up.
7. Let sit for six days. Count how many seeds germinated in each and record the lengths of the radicles.
Observations and Data
Analysis and Conclusions:
Lab Questions:
1. What appears to be the LD 50 for salt for radish seeds? Support your answer with data.
The LD 50 for salt for radish seeds appears to be 50% of the total solution they receive. This is supported by the fact that less than half (in fact, all of them) did not germinate in solutions with 50% or more salt solution concentration.
2. Is your radicle data supported by your germination data? Support your answer with data.
The radicle data is supported by the germination data. Mean radicle length decreased as salt concentration increased and totally cut off at 50% salt solution concentration.
General Conclusions/Analysis:
Surprisingly, the actual LD 50 for salt for radish seeds was higher than the hypothesis predicted. Apparently, the salt solution does not hurt them as much as expected (although it did negatively effect the mean radicle lengths). To find a more accurate LD 50, the experiment could be repeated with many more petri dishes with more various percentages of salt solution. This experiment demonstrates the need for certain conditions for life. If a population lives an area with a condition that is their LD 50, the population probably will not be there for long. The experiment also shows the hardiness of some organisms in a population and how some are able to resist conditions that others can not.
Lab Questions:
1. What appears to be the LD 50 for salt for radish seeds? Support your answer with data.
The LD 50 for salt for radish seeds appears to be 50% of the total solution they receive. This is supported by the fact that less than half (in fact, all of them) did not germinate in solutions with 50% or more salt solution concentration.
2. Is your radicle data supported by your germination data? Support your answer with data.
The radicle data is supported by the germination data. Mean radicle length decreased as salt concentration increased and totally cut off at 50% salt solution concentration.
General Conclusions/Analysis:
Surprisingly, the actual LD 50 for salt for radish seeds was higher than the hypothesis predicted. Apparently, the salt solution does not hurt them as much as expected (although it did negatively effect the mean radicle lengths). To find a more accurate LD 50, the experiment could be repeated with many more petri dishes with more various percentages of salt solution. This experiment demonstrates the need for certain conditions for life. If a population lives an area with a condition that is their LD 50, the population probably will not be there for long. The experiment also shows the hardiness of some organisms in a population and how some are able to resist conditions that others can not.