Table of contents(page number/list of graphs and tables)
Introduction
Background Information
Research Question
Methodology
Hypothesis
Variables
Apparatus
Methods
Measuring the quantity of bacteria in each soil sample
Measuring the amount of water in soil
Measuring the amount of carbon compound in soil
Precautions/Accuracy
Data Analysis
Results
Measuring the quantity of bacteria in each soil sample
Measuring the amount of water in soil
Measuring the amount of carbon compound in soil
Qualitative Data
Discussion of Data
Conclusion
Conclusion
Evaluation
References
Introduction
Background Information
Soil is the thin layer of loose material that covers the ground. Most of soil is weathered rock fragments and rotting organic matter. Tiny gaps or pores in the soil are filled with air, water, bacteria, algae and fungi, these modify the soil’s chemistry and speed up the decay of organic matter, making it a better environment for larger plants and burrowing animals. Water is continuously moving through most soils. This movement of water may create horizons in the soil as it washes minerals and organic matter downwards.
Bacteria in soil break down organic matter and help to provide plants with nutrients. Bacteria are the prokaryotes and are the most widespread, as they are found practically everywhere on Earth. In the soil, they live in water films around soil particles. There are no complex internal structures in bacteria, but they do metabolize as other organisms do.
Based on how bacteria obtain energy, they can be classified as either autotrophs or heterotrophs. Autotrophs use carbon dioxide in the air and their major source is carbon. Heterotrophs obtain carbon compounds by consuming organic matter produced from other organisms; bacteria are mostly heterotrophs. Bacteria do respire, so they need oxygen. Respiration is the metabolic process, whereby an organism takes oxygen and glucose to cells and remove waste products such as carbon dioxide and water, producing energy in the process. The energy formed is used to make larger molecules from smaller molecules, and takes place in cell’s cytoplasm. Some bacteria undergo anaerobic respiration which occurs in the absence of oxygen. These bacteria obtain their energy by fermenting sugar and produce lactic acid which is useful to us. Between 100 million and 1 billion bacteria are contained in a teaspoon of productive soil. Their growth and populations are affected by the soil type, moisture, pH and temperature. Bacteria requires water to dissolve the food and to facilitate bacterial growth. Places with high moisture therefore favor bacteria growth. They reproduce rapidly under favourable conditions via binary fission. Bacteria numbers in soil are estimated by measuring the growth of colonies on special nutrients.
There are various types of bacteria in soil which are nitrogen fixing bacteria, nitrifying bacteria, denitrifying bacteria and actinomycetes. They are helpful for plants. As there are many helpful bacteria in the soil, the soil will be fertile and productive therefore the plants will grow well. These bacteria provide crops that we consume so it’s necessary for human. There are carbon compounds in soil. They are both organic and inorganic. Organic carbon is vital for the soil health. The organic matter includes 1) living organisms such as arthropods, fungi, and bacteria, 2) recently dead and imperfectly decomposed organisms, 3) more decayed materials, and 4) humus, decomposed organic matter that is dark brown or black in colour. Humus is a complex mixture of building blocks of life. The average percentage of organic matter is high when the soil type is peats and is low when the soil is sandy. The function of soil organic carbon is as food for soil microbes and earthworms.
The method that was used in the experiment is substrate-induced respiration(SIR). This method is suitable for measuring the biomass of microbes such as fungus and bacteria so is commonly used by scientists to examine the effectiveness of bacteria and conditions of agricultural ecosystems . It works by measuring the soil respiration after feeding the microbes by adding substrates such as glutamic acid, mannitol, glucose which was used in this experiment, and amino acids. The more respiration there is, the bigger the population presents in the sample. Therefore, this method can be used to compare the microbial populations in various soil samples. This method is also adapted to measure samples of relatively small sizes The rate of respiration is measured with the PASCO carbon dioxide sensor. This sensor measures the concentration of carbon dioxide gas in enclosed system. It involves sensor, bottle, stopper and extension cable. The data logging will be used for recording the result. Data logging system involves a data logger which records data from a input and records the date on computer and saved by special software. It can capture and display data immediately as it happens. The amount of bacteria can be predicted by the quantity of produced carbon dioxide gas.
Research Question
What is the effect of the location of soil samples affect the rate of respiration of bacteria in the soil?
Methodology
Hypothesis
I hypothesize that the garden soil will produce the highest amount of carbon dioxide gas, while the playground soil will produce the lowest amount. This is because garden soil is designed for plant cultivation, and will include many nutrients that help sustain bacterial growth. Moreover, garden soil is classified as peat, which contains the highest amount of organic matter compared to the other soil samples in my experiment. In contrast, the playground soil is the driest out of all the soil samples, creating unfavorable conditions for bacterial growth because water is needed to dissolve food.
Variables
Table 1: Variables
Independent variable Type of soil
Soil samples were collected from 5 different places:
Park
Garden
Playground
Beach
Nearby water fountain
Dependent variable Amount of carbon dioxide produced by using PASCO carbon dioxide sensor
Table 2: Controlled variable
Controlled variable How to control? Possible effect on the result
Mass of glucose used 1.00g of glucose is used for each trial Different glucose mass can affect the growth of bacteria thus affect produced amount of carbon dioxide as well
Volume of distilled water used 5.00mL of distilled water is used for each trial The volume of water in soil affect the decomposition rate of organic material. Decomposition can also determine the amount of produced carbon dioxide.
Measured time All experiments are processed for 5 minutes. If the measured time of one experiment is longer than others, the bacteria in the soil of the experiment get more time to produce carbon dioxide. Therefore, the result of the experiment cannot be compared with other results.
Temperature at which the amount of produced carbon dioxide were measured Experiments were proceeded in the same room and same day at room temperature which is 23°C.
Temperature affects the bacterial activity. As the temperature is higher, the bacterial activity increases as well.
Amount of time that crucibles are left in the oven All crucibles were heated in the oven for 24 hours. The function of heat is dehydrating soil samples. Therefore, the amount of time affects the degree of dehydration.
The mass of soil 20.00g of soil samples have been used for each trial. The different mass of soil contain different amount of bacteria.
Apparatus Using the same equipment to avoid calibration errors Write sth
Apparatus
Soil samples from 5 different places
Park
Little bit humid, Relatively big particles, forest
Garden
Moderate, Relatively big particles, peat
Playground
Little bit humid, Relatively small particles, sand
Beach
Dry, Relatively small particles, sand
Nearby water fountain
Humid, Relatively small particles, soil from grassland, dark clay
Electronic balance with uncertainty of 0g
25g of Glucose
PASCO Carbon dioxide sensor with uncertainty of 100ppm
Stopper
Cable
Bottle
Spatulas
125mL of Distilled water
50mL Beaker with uncertainty of 1mL
A Syringe with uncertainty of 0.5mL
Tripod
Clay triangle
Bunsen burner
Matches
5 crucibles
Crucible tweezer
Oven
Wooden plate
Stop watch
Methods
Steps for measuring the quantity of bacteria in each soil sample:
Collect soil from five different locations
(park, garden, playground, beach and nearby water fountain)
Connect the carbon dioxide sensor to the laptop with the appropriate cable
Open the corresponding app that shows the carbon dioxide levels
Using an electronic balance, measure out 20.00g of park soil and 1.00g of glucose
Put the 20.00g of soil in the flask
Put 1.00g of glucose in a beaker
Using a syringe, measure out 5.00mL of distilled water
Add 5mL of distilled water in the beaker containing the glucose
Mix the glucose until it is fully dissolved in the distilled water
Pour the glucose solution in the bottle which contains the park soil sample
Block the bottle with a stopper that is connected to the carbon dioxide sensor
Start recording the level of carbon dioxide as soon as the bottle is blocked off.
Record the amount of carbon dioxide for 5 minutes
Save the result
Repeat steps 4 to 13 for 5 times
Repeat all the above steps for the remaining 4 types of soil
Steps for measuring the amount of water in the soil
Using an electronic scale, measure out 4g of each soil type
Measure and record the mass of each of your 5 crucibles
Place the measured soil sample into each crucible separately
Place the crucibles containing soil into the oven and start heating
After 24 hours in the oven, measure and record the mass of each crucible with soil
Steps for measuring the amount of carbon compound in the soil
Note: The same crucibles containing the dehydrated soil samples from part B need to be kept and used for part C
Set up a tripod and clay triangle over the Bunsen burner
Using a match, light the Bunsen burner
Place one crucible on the tripod and heat for 5 minutes, ensuring that the lid is opened periodically during the heating process
Measure and record the mass of the crucible after heating
Repeat these steps to the remaining crucibles
Precautions
– Wear safety glasses and safety gloves when the crucible is heated in the oven and by the Bunsen burner to prevent burns
– Use crucible tweezers when the lid has to be opened and when removing it from the flame
– Ensure that the crucible has been cooled down before measuring and recording the relevant data
Accuracy
Use distilled water when making the glucose solution to avoid potential contaminants, thereby eliminating a source of random error
Repeat the experiment for each soil for 5 times to minimize random error
Analysis
Results
Measuring how many bacteria in each soil
Data
Table 3: Carbon dioxide production
Place where soil was collected Trial Amount of carbon dioxide produced (ppm) (Highest value-starting value) Average of carbon dioxide produced (ppm)
Park 1 322 309.2
2 384
3 380
4 210
5 250
Garden 1 150 238.4
2 52
3 207
4 366
5 417
Playground 1 27 110.2
2 216
3 221
4 6
5 81
Beach 1 60 158.6
2 190
3 169
4 190
5 184
Water fountain 1 1676 1219.8
2 1711
3 1047
4 850
5 815
Standard Deviation=√((∑(x-x ̅)^2)/(n-1))
Table 4: Standard deviation
Place where soil selected 1st trial 2nd trial 3rd trial 4th trial 5th trial Average of produced carbon dioxide (ppm) Standard deviation
√((∑(x-x ̅)^2)/(n-1))
Park 322 384 380 210 250 309.2 √(((12.8)^2+(74.8)^2+(70.8)^2+(-99.2)^2+(-59.2)^2)/(5-1))=77.65
Garden 150 52 207 366 417 238.4 √(((-88.4)^2+(-186.4)^2+(-31.4)^2+(127.6)^2+(178.6)^2)/(5-1))=151.43
Playground 27 216 221 6 81 110.2 √(((-83.2)^2+(105.8)^2+(110.8)^2+(-104.2)^2+(-29.2)^2)/(5-1))=102.59
Beach 60 190 169 190 184 158.6 √(((-98.6)^2+(31.4)^2+(10.4)^2+(31.4)^2+(25.4)^2)/(5-1))
=55.78
Water fountain 1676 1711 1047 850 815 1219.8 √(((456.2)^2+(491.2)^2+(-172.8)^2+(-369.8)^2+(-404.8)^2)/(5-1))=441.55
Graph 1: Amount of produced carbon dioxide in different soil samples
Image 1 :Crucibles containing dehydrated soil after heating on Bunsen burner
T-test
t=((¯(x_1 )-¯(x_2 ))-(μ_1-μ_2))/√(〖s_1〗^2/n_1 +〖s_2〗^2/n_2 )
Table 5: T-test
Fountain & Playground Fountain & Park
Null hypothesis Soil samples from nearby water fountain and playground data sets have no significant differences. Soil samples from near from fountain and park data sets have no significant differences.
T-Values 0.004010901 0.009109476
Result Null hypothesis is rejected when the t-values are less than 0.5. Since both t-values are less than 0.05, the date for water fountain is statistically different to all other data sets collected.
Reason
Measuring the amount of water in soil
Data
Table 6: Water content
Place of soil collected Mass of crucible (g) Mass of crucible with soil before heating in oven (g) Mass of crucible with soil after heating in oven (g) Mass of water contained in soil (g)
Park 17.37 21.37 19.56 1.81
Garden 21.64 25.64 23.97 1.7
Playground 20.72 24.72 24.24 0.48
Beach 18.59 22.59 22.21 0.38
Water fountain 18.24 22.24 19.60 2.64
Graph 2: Carbon dioxide concentration against water mass in each soil sample
Measuring the amount of organic compound in soil
Data
Table 7: Carbon Compound
Place of soil collected Mass of crucible with soil before burning by Bunsen burner (g) Mass of crucible with soil after burning by Bunsen burner (g) Mass of organic
compound (g)
Park 19.56 18.94 0.62
Garden 23.97 23.74 0.23
Playground 24.24 24.22 0.62
Beach 22.21 22.17 0.64
Water fountain 19.60 19.24 0.36
Graph 3: Carbon dioxide concentration against carbon mass in each sample
Qualitative data
Soil sample nearby water fountain was the most humid soil samples and park soil was a bit humid than garden soil. The garden soil was moderate and the beach sand was dried. The most dried soil sample was playground soil. The garden soil involves other items for example, twists and leaves and the beach sand involves tiny shell fragments. The color of soil samples collected from park, garden and nearby water fountain was dark brown and the soil sample from beach was dark yellow. Playground soil’s color was darker than the beach soil.
Discussion of data
trend, and scientific theory the standard deviation is and why it was significantly high) (reason of trends) (
In experiment A, the soil sample collected nearby water fountain produced the highest amount of carbon dioxide. The order of the results from high to low is: water fountain > park > garden > beach > playground. The standard deviation of each soil sample is quite large. Soil sample from water fountain shows the highest standard deviation of 441.55 and the beach soil has the low standard deviation of 55.78 in the graph 1. Playground soil has standard deviation of 102.59 which is similar to the average amount of carbon dioxide gas produced which is 110.2. This means the result of playground soil is not reliable.
Experiment B was measuring the water content in the soil sample. The soil sample with the most moisture was again, collected from the nearby water fountain, as the soil environment is exposed to the largest amount of water. The soil sample with the least moisture is beach soil. The playground and beach contained similar amounts of water. Soil samples taken form park and garden also contained similar amounts of water which were higher than those of the playground and beach samples. There is a positive correlation between the amount of produced carbon dioxide and water contained in each soil sample. Soil samples which were drier produced less carbon dioxide gas than humid soil. which implies that dry soil samples were not good environments for bacteria to live. This is related to theory that bacterial growth is faster in humid environment because water is needed for growth.
In experiment C, the graph and table show the levels of carbon compound in each soil sample. The garden soil has the lowest amount of the carbon compound which is 0.23g and the beach soil has the highest amount of carbon compound at 0.64g. Park soil and beach soil have 0.62 g of carbon compound, showing minimal difference with the beach soil. Graph 3 doesn’t show any relationship between produced carbon dioxide gas and organic matter. As stated in my introduction, organic matter can help increase the number of bacteria. Despite the beach sample containing the most organic matter, it did not showcase the highest level of carbon dioxide production. Instead, the soil near the water fountain with second lowest organic matter showed the highest amount of carbon dioxide gas. However, the garden soil that includes the lowest organic matter did produce the lowest carbon dioxide gas, which is in agreement with my hypothesis.
According to scientific literature, both graphs are meant to show positive relationships but this was only apparent in my experiment B. Therefore, based on my results, I can conclude that the number of bacteria in the soil is dependent on water content to a larger extent than the amount of organic matter.
Evaluation
무슨 에러인지 시스테믹,랜덤
Since soil has different amount of organic compound even though it is from same place, the result can be varied. (어디에 넣지)
The range of soil samples varied enough to examine how different features of each samples affected the population of bacteria.
There were several sources of error during these experiments. To properly execute this experiment, I had to remove all other items within the soil such as stones, twists and leaves. However, due to this being a manual process, there were inevitably small pieces that would not have been removed. It could have affected the result of the experiments.
When the soil samples were heated within the soil, there was a systematic error that some crucibles were blackened, suggesting incomplete combustion of carbon compounds, causing the amount of carbon compound collected from some of the soil samples to be lower than anticipated.
When introducing the glucose solution to the soil samples, it is humanly impossible to stopper off the bottles immediately after, perhaps contributing towards some lost carbon dioxide. The varying amounts of time regarding the delayed closure of the bottles across the different trial is a source of random error and could be one of the reasons that my standard deviation were so high.
However, there are some other variables that could not be controlled but might have affected the results
According to a journal written by Michael H. Beare, substrate-induced respiration method is ‘optimized for sample size 0.5-2.0g, glucose concentration 80mg per gram and total solution volume of 5ml . I did use 5ml solution but the rest of the conditions used in my experiment were different from those this method works the best at. For example, the sample size I used was 20g which was way higher than the ideal sample size. The glucose concentration I used was 20mg per gram which was smaller than the ideal concentration. This might have resulted in the inaccuracy of data.
The result from experiment C doesn’t follow the theory. I deduce the reason of it is since each of soil samples doesn’t have big difference in the amount of organic matter and because of this, it doesn’t seem the organic matter affects the experiment a lot. –needs reason
If I were to repeat this experiment again, I want conduct my experiment with more controlled soil samples. Instead of collecting soil from five different places, I would collect one set of soil, divide it into 5 parts, and then manually adjust the moisture of each soil “group”. This gives me a better baseline and helps eliminate the problem of different soil sites containing different impurities and foreign objects.
What you need to add: scientific explanation of why water content improves bacterial growth and respiration. (before conclusion)+ 소일의 박테리아마다 적정 템퍼레이쳐가 다르다/물 양이 베이스라인 셋팅, 올가닉 매터랑 템퍼레이ㅊ려가 인크리즈. 올가닉 매터의 영향 거의 안 보인다 / 적정 템퍼레이쳐 스탠다드 디비에이션이랑 연결
Conclusion
As discussed above, the soil sample that showcased the highest rates of bacterial respiration was water fountain soil, and the lowest value was soil samples from playground. I hypothesized that the garden soil would produce the highest amount of carbon dioxide gas and the beach soil would produce the lowest amount of carbon dioxide gas. Therefore, my experimental results did not reflect this. The garden soil that I collected didn’t contain much organic matter, contrary to what I expected. Differ from research, the beach sand has the highest amount of organic matter in it. The soil from near the water fountain contained the highest water content and this soil sample was shown to produce the highest amount of the carbon dioxide gas. This finding proves that the water content of the soil does affect bacterial respiration, as with increasing water content, this is likely to favor increased bacterial growth. The soil sample with the least amount of water content and carbon compound did prove to produce the least amount of carbon dioxide, again reinforcing the relationship between water content and bacterial activity. Overall, my experimental findings suggest that the amount of water has a positive effect on the growth of bacteria, but failed to suggest any pattern between the amount of organic matter and the rate of bacterial respiration.
References
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Snedden, R. (2008). The world of the cell. Chicago, Ill.: Heinemann Library, p.28.
White, R. (1995). Introduction to the principles and practice of soil science. Oxford: Blackwell, p.32.
Snedden, R. (2008). The world of the cell. Chicago, Ill.: Heinemann Library, p.34.
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Snedden, R. (2008). The world of the cell. Chicago, Ill.: Heinemann Library, p.35.
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White, R. (1995). Introduction to the principles and practice of soil science. Oxford: Blackwell, p.32.
Zimmer, G. (n.d.). The biological farmer. p.56,57,59.
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