Pesticides have helped improve the standard of living for millions of people around the world however their use has been linked to numerous ecological problems such as damaging the nervous systems of non-target organisms including humans. The purpose of this experiment is to determine the effects various environmental factors can have on the nervous systems of earthworms.
Pesticides have helped improve the standard of living for millions of people around the world however their use has been linked to numerous ecological problems such as damaging the nervous systems of non-target organisms including humans. The nightcrawler earthworm is a species of Annelid that is distributed across North America. Earthworms are prized by farmers for the benefits they bring to soil. The purpose of this experiment is to determine the effects various environmental factors (boric acid, an alkaline buffer solution, and glyphosate) used by farmers to regulate harvest yields can have on the nervous systems of earthworms.
In order to record the effects the factors would have upon the nervous systems’ of the earthworms, the speed that the action potentials travelled at was analyzed after being exposed to the experimental factors. The action potentials were recorded through the use of an electrode recording setup. The earthworms were exposed to a .1 mole solution of boric acid, an alkaline buffer solution from a buffer tablet, and a 1.5% solution of glyphosate in order to simulate concentrations that may be present in the environment.
Through a series of five trials for each experimental factor, the earthworms exposed to the control solution exhibited the fastest conduction velocity at 8.41 m/s, the earthworms exposed to the boric acid solution exhibited a conduction velocity of 8.142 m/s, the earthworms exposed to the buffer solution exhibited a conduction velocity of 6.538 m/s and the earthworms exposed to the glyphosate solution exhibited the slowest conduction velocity at 6.5 m/s.
Pesticides have been used in agriculture since approximately 2000 B.C. Originally pesticides were made from toxic chemicals such as arsenic, lead, mercury however since the Green Revolution in the 1960’s, synthetic organic compounds have become widespread. Although pesticides bring multiple benefits to humanity such as increasing harvest yields, protecting biodiversity, and decreasing prices for consumers, there are certain disadvantages to utilizing pesticides. Synthetic pesticides have been linked to nervous system damage, damage to body tissue, contaminated drinking water, eutrophication, etc.
Lumbricus terrestris or nightcrawlers belong to the phylum Annelida. They are characterized by their numerous segments that resemble “small rings”. Earthworms are a vital part of healthy soils and are prized by farmers as they burrow underground, aerating the soil; they also plant matter in soil and produce worm castings, a nutrient rich organic substance that consists of bacteria, enzymes, and remnants of plant matter. Earthworms are a model organism used in neuroscience experiments as their nervous system is similar to the human nervous system.
The nervous system of an earthworm consists of two main parts. The first part is the cerebral ganglion which functions as the brain of the earthworm. The second part is the central nerve cord containing the medial and lateral fibers that runs along the center of the earthworm.
Neuron: the fundamental building block of the nervous system. Neurons transmit electrical impulses throughout the body.
Action Potential: An action potential occurs when a neuron sends an electrical impulse. These action potentials can be seen as spikes on computer software.
Conduction Velocity: the measure of how fast neuron can transmit information. It is derived by dividing the distance between two recording electrodes by the time taken for the electrical impulse to travel between the electrodes. The unit is m/s.
Faraday Cage: a metal cage used to block out electromagnetic interferences. It causes the electrical charges in the cage’s conductive material to be distributed in such a way that they do not affect the interior. A Faraday cage was used during experimentation in order block out background electrical interferences.
Boric Acid: a widespread insecticide. It comes in a powder form and is known to cause adverse effects to the nervous system of organisms.
Buffer Solution: pH buffers are used by farmers to set the pH of surrounding land to the proper amount for the species they are growing. The pH buffer tablet I used exposed the earthworms to a pH of approximately 9.
Glyphosate: one of the most widely used herbicides in the United States. It is used to regulate plant growth and ripen fruit. It is known to bring adverse effects to the nervous system of organisms.
There were a few factors that influenced me into choosing this project. The first and foremost reason why I chose this project is because I would like to become a neurosurgeon when I grow up and this project explores the field of neuroscience. The second reason why I chose this project is that it draws from my experience from Science Olympiad competition where I earned a first place at the national tournament. My event consisted of learning the field of ecology, which contributed that aspect to this experiment.
What is the effect of various environmental factors (boric acid, an alkaline buffer solution, and glyphosate) on the conduction velocity of earthworms?
If earthworms are exposed to various environmental factors (boric acid, an alkaline buffer solution, and glyphosate), then the earthworms exposed to the control factor will have the largest conduction velocity. This is due to the fact that the boric acid, buffer solution, and glyphosate adversely effect the nervous systems of earthworms.
Independent Variables
• Boric Acid
• Buffer Solution
• Glyphosate
• Control
Dependent Variable
• Nerve conduction velocity (meters per second)
Controlled Variables
• Temperature of laboratory
• Time exposed to environmental factors
• Stretching of earthworms
The experimental control in this experiment are the worms exposed to none of the environmental factors. This is due to the fact that the worms subjected to the control will serve as baseline measurements for further environmental factors.
Boric Acid
Alkaline Buffer Solution
Glyphosate Solution
Data Analysis
The earthworms exposed to the control had the highest conduction velocity at an average of 8.41 m/s. The first earthworm exposed to the control had a conduction velocity of 7.5 m/s. The second earthworm exposed to the control had a conduction velocity of 6.84 m/s. The third earthworm exposed to the control had a conduction velocity of 8.57 m/s. The fourth earthworm exposed to the control had a conduction velocity of 10 m/s. The fifth earthworm exposed to the control had a conduction velocity of 9.14 m/s.
The earthworms exposed to the boric acid had the second highest conduction velocity at an average of 8.142 m/s. The first earthworm exposed to the boric acid had a conduction velocity of 8.57 m/s. The second earthworm exposed to the boric acid had a conduction velocity of 8.57 m/s. The third earthworm exposed to the boric acid had a conduction velocity of 8.57 m/s. The fourth earthworm exposed to the boric acid had a conduction velocity of 7.5 m/s. The fifth earthworm exposed to the boric acid had a conduction velocity of 7.5 m/s.
The earthworms exposed to the buffer solution had the third highest conduction velocity at an average of 6.538 m/s. The first earthworm exposed to the buffer solution had a conduction velocity of 4.55 m/s. The second earthworm exposed to the buffer solution had a conduction velocity of 6.82 m/s. The third earthworm exposed to the buffer solution had a conduction velocity of 7.16 m/s. The fourth earthworm exposed to the buffer solution had a conduction velocity of 7.5 m/s. The fifth earthworm exposed to the buffer solution had a conduction velocity of 9.14 m/s.
The earthworms exposed to the glyphosate had the poorest conduction velocity at an average of 6.5 m/s. The first earthworm exposed to the boric acid had a conduction velocity of 5.89 m/s. The second earthworm exposed to the boric acid had a conduction velocity of 5.89 m/s. The third earthworm exposed to the boric acid had a conduction velocity of 7.33 m/ s. The fourth earthworm exposed to the boric acid had a conduction velocity of 6 m/s. The fifth earthworm exposed to the boric acid had a conduction velocity of 6.66 m/s.
There was one outlier that occurred in the data. The first earthworm exposed to the buffer solution had a conduction velocity of 4.55 m/s approximately 2 m/s less than the average conduction velocity in that trial.
Based on the results from this experiment, the researcher’s hypothesis was supported. The earthworms exposed to the control group had the highest conduction velocity of all trials at an average of 8.41 m/s.
This supports the researcher’s scientific reasoning that the other environmental factors have been observed to enact adverse effects upon the nervous system of organisms and therefore would result in a lower conduction velocity.
One experimental error that may have occurred during the course of the experiment is both the experimental and alcohol solutions may have become exposed to carbon dioxide in the air while being used. This may have resulted in a slight increase or decrease in the results. This error may have been prevented if the solutions were kept tightly closed throughout the experiment. Another experimental error that may have occurred throughout the course of the experiment is human error in recording the time between action potentials. This may have resulted in a slight increase or decrease in the results and may have been prevented through the use of a computer program to accurately measure the time period. A third experimental error that may have occurred throughout the course of the experiment is human error in placing the electrodes. This error may have resulted in a slight increase or decrease in the results and may have been prevented through the use of a digital caliper.
There are multiple benefits to society that this experiment could bring. One benefit to society is this experiment could aid farmers in analyzing the effects pesticides would have on organisms on their land. The results from this experiment can also be used to understand the effects these environmental factors may potentially have on the human nervous system. A recommendation for further research could be testing the effects of different concentrations of these pesticides on earthworms.
You must log in to like an article
Pesticides have helped improve the standard of living for millions of people around the world however their use has been linked to numerous ecological problems such as damaging the nervous systems of non-target organisms including humans. The purpose of this experiment is to determine the effects various environmental factors can have on the nervous systems of earthworms.