C.Coulombe Extended Essay The purpose of this essay is to explore to what extent exposure to the environment can affect the rate of body decomposition.
In this experiment, postmortem in Turkey carcasses will be used as a comparison to the decomposition of a human body. The same processes will be used for determining the decomposition rate of the Turkey carcass as they would in that of the human body. These turkeys were obtained ethically during their hunting season by licensed hunters to maintain population.
Background: Decomposition can begin at 4 minutes postmortem and continue up to over a month. In the first few days after death, the organs begin to decompose. The order in which organs decompose is as follows: the brain, the liver, the lungs, the GI tract, the spleen, the urogenital system, followed by skin, muscle, tendons, and finally the bones. Rigor mortis can be present within the first few hours postmortem. It is a result of the stiffening of the muscles as they can no longer function properly after death. Over time the body will begin to lose the ability to create some heat and will eventually become the temperature of the environment it is in. This process is known as algor mortis. The appearance of insects is also an important factor in decomposition.
The most common being the Calliphorid, more commonly known as the blowfly. Thee blowfly is the first to appear of the insects that are often found at the site of decomposition. Blow flies are responsible for the presence of maggots. Blowflies themselves do not eat the carcass they are only present to lay their eggs on the carcass as a source of food for when their eggs hatch. Maggots can eat a majority of a corpse in a very short amount of time.
The amount and activity of maggots can be used to contribute to the rate of decomposition of a carcass. In this experiment, the arrival of maggot presence will be compared between the experimental group and the trail to investigate a correlation between the two. Few studies have been completed on the effect of a carcass being swaddled in a material such as cotton or a protective covering, such as plastic.. The Kelly et al study reviewed the effect of clothing on decomposition rate and biomass decay.
It concluded that clothing has a significant impact on the environment in which maggots are able to thrive. No major studies have been conducted on the effect of large materials swaddling a carcass. This study will attempt to explore a deeper level of the effects of the environment on the natural decomposition of a carcass, and if the effects could significantly impact a criminal investigation or the importance of the biological evidence of a case. Relevancy: I chose this topic to compare how decomposition plays a role in Criminal Justice.
In crime scene investigation, finding a missing person can involve searching for a body. In most cases, a body is often found hidden by being buried or covered. The time at which finding a body is important because the rate at which it has decomposed can affect how likely it is to identify and investigate the crime and the body. Discovering more about how lack of exposure to the environment affects the rate of body decomposition can aid in the development of more accurate pools of measurement on body composition, as well as enabling a more accurate and faster investigation within the criminal justice department. This study also carries interest in my future career field as a forensic pathologist.
I would like to explore the intricacies of the topic of decomposition as it plays a vital role in the work of the pathology field. Every case that is under investigation is pressured by the natural decomposition of the body. Taking too long to find a victim of homicide would risk losing valuable biological evidence within the investigation. This topic is one that I have known is crucial to the forensic process, and I would like to take on the challenge of gaining hands on experience in this practice to better my understanding of my future career.
Hypothesis: Lack of exposure to the environment in the form of a carcass covered by plastic does not have a significant difference in the decomposition rate in turkeys uncovered and exposed to the environment. (Matuszewski et al 2014) DESIGN/VARIABLES: Independent Variable: Lack of exposure to the environment As other studies have been completed to examine the effects of clothing on carcasses. This experiment focuses on the more extreme lack of exposure in the form of an unsealed trash bag. This plastic will provide protection form the environment while still allowing air and biological influences to access the carcass. Dependant Variable: Rate of decomposition, measured in biomass (lbs).
As the carcasses decompose under two conditions, the biomass will be measured consistently. This will give an accurate means of measuring the rate of decomposition and will provide reliable data to compare despite the difference in original mass of the turkeys. Controls: Control Why is it controlled? How is it controlled? Size of carcass The sizes of the carcasses will determine the baseline rate of decomposition. Simmons et al (2010) showed larger carassas decompose slower than smaller ones. This would cause the data to be inaccurate in measuring the rates of each of the birds.
All of the carcasses obtained were around the same relative maturity level and killed around the same time. The bird’s’ breast meat was extracted, and the remaining carcasses all will be within 1 lb of each other at the time of harvesting. Location of decomposition The location of the carcasses will include the control of many other variables. This is allow for the same and equal amount of exposure to the environment.
Each turkey will decompose differently if the area chosen is not consistent. The exposure to direct elements, such as out in Each of the carcasses will be placed in the same wooded area during the entirety the experiment. the open as opposed to inside a wooded clearing can expose the bird to drastically different environmental conditions, leading to inconsistent results. Shade As stated in the location control, exposure to direct sunlight can cause the carcass to dry out and decompose much faster than if it were in a shaded area. The location chosen is a shady wooded area in which all birds will be placed for the experiment. State of Bird (feathered or unfeathered) If one bird is covered in feathers while the other is not, this could affect how much exposure each carcass receives. Thus adding a confounding variable. Both of the turkeys used in this experiment will be left unfeathered.
Access to the ground As stated in the location control, the environment must have access to the carcass. Each carcass is placed in the metal cage on the ground of a wooded area. This allows for The bird must be in contact with the ground so that it can be accessible to possible insects that will aid in its decomposition. even an ample access to the ground and the environment in which it is in.
Tools used to measure mass Tools will each measure differently and each will have a different percent errors and minute differences in readings. It is important to keep the tools the same to keep the data collected precise. The same tools will be use on each of the birds throughout the entirety of the experiment. Type of Bird The bird must be the same as the composition and time of decomposition will vary between species. All of the birds collected for the experiment were Turkeys hunted in the same area. Type of enclosure The enclosure must have access to the ground.
If one enclosure lacked this element, insects and decomposers Both carcasses will be placed in a metal cages on the ground. This will allow for each carcass to had ample would not have ample access to the carcass. This could cause and an uneven decomposition rate for each of the carcasses. access to the environment and the amount of exposure will be equal. Control Group: The control group of this experiment is the turkey exposed to the environment and not covered by any cloth.
It was chosen as a comparison of the effects of plastic covering on the decomposition rate, measured in loss of biomass, to determine if the difference in time of decomposition is affected by covering the exposure to the environment and elements. Materials and Methods: Materials: – 2 Turkey carcasses obtained shortly after death (within 3 days) – Note: The carcasses must be obtained from an ethical source. The carcasses used in this experiment were killed by hunters during season and the breast meat was removed. The rest of the carcass was donated as use for this experiment as it would have otherwise been disposed of. – A metal or wire enclosure – A barometer – 1 large black garbage bag – Scale to measure biomass – (Optional) camera for photo/video of animal interference – Hygrometer or device used to measure humidity – Thermometer – Ample space to conduct experiment Procedure: 1) Clear or locate a space secluded and private to conduct the experiment. 2) Build or purchase an enclosure to protect the carcass from animal interference.
a) Note: The enclosure must allow for the carcass to maintain exposure to the environment. 3) One carcass should be covered/placed inside the black garbage bag or other plastic covering.. 4) Every day at the same intervals of time, biomass, physical description, rainfall, and humidity must be measured. 5) From Day 1 to Day 30 (or when carcass has decomposed) Bone decomposition can be measured further if necessary. Data Analysis: Qualitative Data: Blowflies were present within the first 2 days of decomposition. The first day the physical observation was recorded was day 2, but it is likely the flies first began appearing only a few hours after the carcass was placed at the site.
The blowfly larvae, maggots, were present after day 5. This recorded value refers only to when the maggots were seen on the outside of the carcass. This was after the maggots had been inside the carcass for many days.
During this time, the carcass bloated and fluctuated in size during the first week of observation. A noticeable smell was observed after day 4 and the carcass of the covered specimen began to leak blood from the bag. Maggots were present at around the same time as the uncovered carcass, but less maggots were seen on the outside of the carcass. The feathers began to fall off each of the birds after day 13. This is a graph of the raw data collection of the mass of the turkey that was left uncovered and exposed to the environment. It follows a general trend of steady decline, slowing down during the last few days of the data collection. Descriptive stats were taken on this data.
The mean of the set was 8.78 with a standard deviation of 1.91.
This data also shows a similar trend on the graph. It also begins to level out toward the end of the data collection. This supports the idea that the two conditions do not provide a significant difference, but it is also important to know that the graph does not provide an inferential statistic to determine this. Descriptive stats were run on this data set and the mean of the data was 10.58 and a standard deviation of 1.58. Comparing these statistics, there is a clear similarity in the rate of decomposition. The mean mass of the uncovered turkey is higher as the initial mass of the turkey is larger than that of the uncovered carcass.
The standard deviation of the uncovered carcas is larger than that of the covered carcass, showing that when measurements were taken on the same day, there was a slighter greater difference in the decline of the mass of the uncovered carcass. This is a compilation of the two data sets on the same graph to see the matching trends more clearly. This graph can clearly show the difference in starting weights of the covered specimen was larger than that of the uncovered specimen. The significance of the difference in decomposition rates will be examined further using an inferential statistic. This graph shows the values of mass lost between each of the days of the data collection. Series 1 represents the uncovered turkey, and series 2 shows the covered turkey. A 2-tailed t-test at the .05 alpha level was done to show if the difference between the two means of decomposition rate were significant.
The test revealed t= -.0875, p = .427. This supports the statement of no difference, the null hypothesis, meaning that the inferential statistic does not support that there is a significant difference between the decomposition rates of a carcass exposed or unexposed to the environment in the form of a plastic covering. Conclusion: Throughout the experiment, there was a clear trend in the physical, qualitative data as well as the quantitative data being collected between the two conditions. Despite the difference in size and exposure of the turkeys, both carcasses shared a similar environment in which they decomposed. This nearness of the two carcasses could lead to an increase rate of exposure to blowflies of the covered carcass as the control conditioned experiment began three days prior to the covered turkey.
This distorted time frame created an issue of continuous and precise qualitative data on the carcasses as they were on separate times of decomposition. The measurements of biomass began on separate days, but the first 3 measurements of the uncovered carcass were unable to be compared to that of the covered carcass as it arrived separately. The presence of the blowfly larvae and the general trend in the rates of decomposition provided no significant evidence of difference between the two. Though the amount of blowfly larvae present on the covered carcass appeared to be less than that of the uncovered condition, the amount did not greatly impact the turkey’s overall decomposition rate and thus showed an even decomposition between the two. Both of the carcasses were located in a shaded, wooded area. The location receiving minimum sunlight during the day, as well as the abundance of moisture could have impacted the decomposition of the uncovered turkey. Despite the experiments limitations, the rates of decomposition between a turkey carcass fully exposed to the environment and one with a lack of exposure in the form of plastic covering show no significant difference.
This investigation proved to have many uncontrolled variables and struggles that lead to a challenging way of conclusion. Throughout this experiment in the time that I collected data, I began to realize the immense pressure I had placed on myself. The state of the carcasses as well as the odor and data collection had began to morph my opinion of the experiment as a whole. As the investigation drew to a close it was clear that my preceding motivation had exhausted itself. My interest that had previously marveled at the idea of studying the deceased has now become a learning experience that I had not anticipated. This experiment lead me to the conclusion of not desiring to pursue a career within the medical field. The processes completed during the setup of the enclosures of the carcasses as well as the elevation of the decomposition of the turkeys brought to my attention my being uncomfortable with the situation as a whole.
I had been surprised by my own disgust for this experiment. Forensics previously had no effect on my visceral reactions to blood or decomposition, but the hands-on experience has lead me to think deeply about my choice in future paths. This investigation, while confirming my hypothesis, has lead me to reach a greater understanding of myself than what I had achieved prior to the start of this study. Works Cited: Simmons T, Adlam RA, Moffatt C (2010) Debugging decomposition data—comparative taphonomic studies and the influence of insects and carcass size on decomposition rate. J Forensic Sci 55:8–13 Palanivel, P., Susilawati, K., Ahmed, O.
H., & Majid, N. M. (2013). Compost and crude humic substances produced from selected wastes and their effects on Zea mays L. nutrient uptake and growth. The Scientific World Journal, 2013. Kelly, J.
A., Van Der Linde, T. C. and Anderson, G. S. (2009), The Influence of Clothing and Wrapping on Carcass Decomposition and Arthropod Succession During the Warmer Seasons in Central South Africa*. Journal of Forensic Sciences, 54: 1105–1112. doi:10.
01113.x Perez, A. E., Haskell, N. H., & Wells, J. D. (2014).
Evaluating the utility of hexapod species for calculating a confidence interval about a succession based postmortem interval estimate. Forensic science international, 241, 91-95. Appendix 1: Raw Data Date Day Mass of covered (lbs) Mass of uncovered(lbs) Humidity Rainfall (Inches) 4/18/2017 1 13.2 11.86 80% 0.13 4/19/2017 2 12.
98 11.84 57% 0.13 4/20/2017 3 12.76 11.2 49% 0.13 4/21/2017 4 12.31 11.
05 88% 0.13 4/22/2017 5 12. 02 10.53 94% 0.13 4/23/2017 6 11.79 10.31 96% 0.14 4/24/2017 7 11.4 9.84 73% 0.14 4/25/2017 8 11.05 9.49 57% 0.14 4/26/2017 9 10.84 9.11 80% 0.14 4/27/2017 10 10.5 8.59 57% 0.14 4/28/2017 11 10.12 8.02 67% 0.14 4/29/2017 12 9.84 7.63 51% 0.15 4/30/2017 13 9.66 7.56 60% 0.15 5/3/2017 16 9.41 7.34 45% 0.15 5/6/2017 19 9.02 6.88 42% 0.16 5/9/2017 22 8.88 6.7 59% 0.17 5/12/2017 25 8.75 6.53 46% 0.18 5/15/2017 28 8.39 6.25 88% 0.17 5/18/2017 31 8.12 6.08 45% 0.17 Average 10.58105263 8.779473684 59% 0.18 Standard Deviation 1.622230614 1.960545484 Ttest 3.08520