Collaborators:
Joshua Arteta
Introduction and Problem:
Biodiversity is a key component of a healthy ecosystem; it refers to the variety of organisms in that ecosystem. According to the background information, there are two components to biodiversity: species richness, a measure of the number of species living in that ecosystem, and species evenness, a measure of the relative abundance of different species making up the richness of a particular area. Using this information, scientists are able to calculate the Simpson's Diversity Index, a quantitative measure of biodiversity, of an ecosystem.
Healthy ecosystems tend to have high levels of biodiversity since they provide a plethora of natural resources for their inhabitants, prevent environmental stress caused by human-induced and natural events, and allow natural selection and evolution to occur over successive generations. According to the International Union for Conservation of Nature, 18,788 species out of 52,017 so far assessed are threatened with extinction due to human-related activities: deforestation, introductions of invasive species, and pollution. If this continues, it could lead to a loss of biodiversity in ecosystems all over the world. Through this lab, the problem, "What is the level of biodiversity of leaf litter collected from the outdoor trail at Heritage High School and Mr. Gunsher's woods?", will be addressed. |
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Pre-Lab:
1. Why would we want to rate the amount of biodiversity in a location?
Scientists might want to rate the amount of biodiversity in an ecosystem because biodiversity is a key component of a healthy ecosystem: ecosystems with high levels of biodiversity provide a wide range of natural resources for use by humans and other organisms, prevent environmental stress caused by human-related activities and natural events, and allow natural selection and evolution to occur over successive generations. Scientists might study ecosystems in order to determine potential causes and solutions to low levels of biodiversity, which could negatively impact the health of the ecosystems.
2. Examine the charts below and calculate the diversity indices for the three samples.
Scientists might want to rate the amount of biodiversity in an ecosystem because biodiversity is a key component of a healthy ecosystem: ecosystems with high levels of biodiversity provide a wide range of natural resources for use by humans and other organisms, prevent environmental stress caused by human-related activities and natural events, and allow natural selection and evolution to occur over successive generations. Scientists might study ecosystems in order to determine potential causes and solutions to low levels of biodiversity, which could negatively impact the health of the ecosystems.
2. Examine the charts below and calculate the diversity indices for the three samples.
Hypothesis:
If samples of leaf litter and soil are collected from the outdoor trail at Heritage High School, and samples of leaf litter are also collected from Mr. Gunsher's woods, then the samples of leaf litter will have higher levels of biodiversity than the sample of soil.
Parts of the Experiment:
- The independent variable is the location from which the samples are collected.
- The dependent variable is the level of biodiversity of the samples.
- The controlled variables are the materials, the season in which the samples were collected, and the amount of time each sample was placed under the light source.
- The control group consists of the samples of soil.
- The experimental group consists of the samples of leaf litter collected from both the outdoor trail at Heritage High School and Mr. Gunsher's woods.
Materials:
- samples of leaf litter
- samples of soil
- compound microscopes
- alcohol
- beakers
- Berlese funnels
- lamps
- invertebrate identification pages
Method:
1. Using large plastic bags, collect multiple samples of leaf litter and soil from a wooded area.
2. Place the samples of leaf litter into four Berlese funnels and place the samples of soil into two Berlese funnels.
3. Place a light source above each funnel and a beaker of alcohol beneath the funnel.
4. After a week, collect the beakers of alcohol and using a microscope, examine the organisms contained inside.
5. Using the invertebrate identification pages, identify the organisms and record the number of each species.
6. Using the formulas provided in the background information, calculate the diversity indices of each population of organisms from each location.
2. Place the samples of leaf litter into four Berlese funnels and place the samples of soil into two Berlese funnels.
3. Place a light source above each funnel and a beaker of alcohol beneath the funnel.
4. After a week, collect the beakers of alcohol and using a microscope, examine the organisms contained inside.
5. Using the invertebrate identification pages, identify the organisms and record the number of each species.
6. Using the formulas provided in the background information, calculate the diversity indices of each population of organisms from each location.
Data:
Observations
Relevant Information of Samples of Leaf Litter and Soil from Heritage High School Trail:
Location: Wake Forest, North Carolina
Type of Community: Wooded Community
Date: Tuesday, September 16, 2014
Weather Description: Sunny, clear skies
Air Temperature: N/A
Soil Temperature: N/A
Relative Humidity: N/A
Time: 9:20-9:45 AM
Type of Community: Wooded Community
Date: Tuesday, September 16, 2014
Weather Description: Sunny, clear skies
Air Temperature: N/A
Soil Temperature: N/A
Relative Humidity: N/A
Time: 9:20-9:45 AM
Relevant Information of Sample of Leaf Litter from Mr. Gunsher's Woods
Location: N/A
Type of Community: Suburban Community
Date: September, 2014
Weather Description: N/A
Air Temperature: N/A
Soil Temperature: N/A
Relative Humidity: N/A
Time: N/A
Type of Community: Suburban Community
Date: September, 2014
Weather Description: N/A
Air Temperature: N/A
Soil Temperature: N/A
Relative Humidity: N/A
Time: N/A
Data Tables
Heritage High School Trail: Leaf LitterTotal Number of Organisms: 94
Simpson's Index = 0.17 Simpson's Index of Diversity = 0.83 Simpson's Reciprocal Index = 5.9 |
Mr. Gunsher's Woods: Leaf LitterTotal Number of Organisms: 147
Simpson's Index = 0.27 Simpson's Index of Diversity = 0.73 Simpson's Reciprocal Index = 3.7 |
Heritage High School Trail:
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Pictures
Data Analysis:
After organizing the data into three tables, it was made clear that both the sample of leaf litter collected from the outdoor trail at Heritage High School (picture 1) and Mr. Gunsher's woods had high levels of species richness but low levels of species evenness. Both samples contained many organisms of different species, however, the relative abundance of each species compared to one another differ greatly. For example, the sample of leaf litter collected from the trail contained 52 mites and 1 roach, and the sample collected from Mr. Gunsher's woods contained 53 springtails and 1 pseudoscorpion. On the other hand, the sample of soil collected from the trail (control) had a lower level of species richness, but a comparatively higher level of species evenness: the sample only contained two different species (springtail and mite), but the relative abundance of each species compared to one another only differed by 2.
After the diversity indices of each sample had been calculated, it was made clear that the sample of leaf litter collected from the outdoor trail had the highest level of biodiversity. The Simpson's Index of the sample of leaf litter from the trail was 0.17, its Simpson's Index of Diversity was 0.83, and its Simpson's Reciprocal Index was 5.9. The Simpson's Index of the sample of leaf litter from Mr. Gunsher's woods was 0.27, its Simpson's Index of Diversity of the sample was 0.73, and its Simpson's Reciprocal Index was 3.7. The Simpson's Index of the sample of soil from the outdoor trail was 0.5, its Simpson's Index of Diversity of the sample was 0.5, and its Simpson's Reciprocal Index was 2.0. The Simpson's Index of the sample of leaf litter from the trail was approximately 0.33 less than that of the control sample; its Simpson's Index of Diversity was approximately 0.33 greater than that of the control sample; its Simpson's Reciprocal Index was approximately 3.9 higher than that of the control sample. These quantitative data indicate that the sample of leaf litter collected from the outdoor trail had the higher level of biodiversity when compared to the control sample.
Overall, the samples of leaf litter seemed to have higher levels of biodiversity than the sample of soil, and springtails and mites were the most commonly identified species in the samples.
After the diversity indices of each sample had been calculated, it was made clear that the sample of leaf litter collected from the outdoor trail had the highest level of biodiversity. The Simpson's Index of the sample of leaf litter from the trail was 0.17, its Simpson's Index of Diversity was 0.83, and its Simpson's Reciprocal Index was 5.9. The Simpson's Index of the sample of leaf litter from Mr. Gunsher's woods was 0.27, its Simpson's Index of Diversity of the sample was 0.73, and its Simpson's Reciprocal Index was 3.7. The Simpson's Index of the sample of soil from the outdoor trail was 0.5, its Simpson's Index of Diversity of the sample was 0.5, and its Simpson's Reciprocal Index was 2.0. The Simpson's Index of the sample of leaf litter from the trail was approximately 0.33 less than that of the control sample; its Simpson's Index of Diversity was approximately 0.33 greater than that of the control sample; its Simpson's Reciprocal Index was approximately 3.9 higher than that of the control sample. These quantitative data indicate that the sample of leaf litter collected from the outdoor trail had the higher level of biodiversity when compared to the control sample.
Overall, the samples of leaf litter seemed to have higher levels of biodiversity than the sample of soil, and springtails and mites were the most commonly identified species in the samples.
Conclusions:
Conclusion Questions
1. What are two reasons the organisms move away from the light down the funnel? What does this indicate about the organisms?
One reason that the organisms move away from the light down the funnel is that the light simulates light of the sun. The species of detrivores have developed a behavioral adaptation that allows them to hide from predators during the day by crawling under the leaf litter; therefore when exposed to the artificial light, they crawled down the leaf litter. Another reason for this is that the light simulates the heat of the sun, which is uncomfortable, and deadly with prolonged exposure. The species of detrivores have developed a behavioral adaptation that allows them to remain cool during the day by crawling under the leaf litter; therefore when exposed to the artificial light, they crawled down the leaf litter.
2. Summarize whether you think the biodiversity of this litter is high or low density. If low, try to give some reasons why this might be.
According to the data, both samples of leaf litter had higher levels of biodiversity than the sample of soil did: The Simpson's Index of the sample of leaf litter from the trail is approximately 0.33 less than that of the sample of soil; in addition, the sample of leaf litter from Mr. Gunsher's woods is approximately 0.23 less than that of the sample of the soil. The data also indicate that both samples of leaf litter have relatively high levels of biodiversity: The Simpson's Index of both samples (0.167 and 0.27) are close to 0; the Simpson's Index of Diversity of both samples (0.83 and 0.73) are close to 1.00; and the Simpson's Reciprocal Index of both samples are high. However, the indices of the sample collected from the outdoor trail indicate a higher level of biodiversity.
The niches of the species identified in the samples may explain why the biodiversity of the leaf litter was higher than that of the soil. Many of the organisms that were identified in the samples were detrivores, organisms that consume dead organic matter, such as leaf litter. These organisms occupy a niche: living in leaf litter, and consuming it and other decomposing organic matter, so that it can be broken down, decomposed, and returned to the environment. Therefore, the levels of biodiversity of the samples of leaf litter were significantly higher than that of the sample of soil because the leaf litter contains more organic waste that can be consumed by detrivores.
3. Why would an environmental scientist need to make more than one measurement if he were calculating the biodiversity? How would you take samples of a large forest?
If an environmental scientist were calculating the biodiversity of an area, he would need to make more than one measurement in order to ensure accurate and reliable results. There are many confounding variables that may skew the data by affecting the number of organisms that are caught in the samples: time of day, season, weather, humidity, and temperature. For example, samples of leaf litter taken during the winter would contain less organisms than samples taken during the summer; this is because during the winter, many organisms head below the frostline or migrate south. If samples of leaf litter were to be taken from a large forest, it would be beneficial to take multiple samples from various areas in order to ensure accurate and reliable results. There are many organisms that inhabit a large forest; therefore, a limited number of samples from the same area would not yield accurate estimates of the biodiversity of the forest.
One reason that the organisms move away from the light down the funnel is that the light simulates light of the sun. The species of detrivores have developed a behavioral adaptation that allows them to hide from predators during the day by crawling under the leaf litter; therefore when exposed to the artificial light, they crawled down the leaf litter. Another reason for this is that the light simulates the heat of the sun, which is uncomfortable, and deadly with prolonged exposure. The species of detrivores have developed a behavioral adaptation that allows them to remain cool during the day by crawling under the leaf litter; therefore when exposed to the artificial light, they crawled down the leaf litter.
2. Summarize whether you think the biodiversity of this litter is high or low density. If low, try to give some reasons why this might be.
According to the data, both samples of leaf litter had higher levels of biodiversity than the sample of soil did: The Simpson's Index of the sample of leaf litter from the trail is approximately 0.33 less than that of the sample of soil; in addition, the sample of leaf litter from Mr. Gunsher's woods is approximately 0.23 less than that of the sample of the soil. The data also indicate that both samples of leaf litter have relatively high levels of biodiversity: The Simpson's Index of both samples (0.167 and 0.27) are close to 0; the Simpson's Index of Diversity of both samples (0.83 and 0.73) are close to 1.00; and the Simpson's Reciprocal Index of both samples are high. However, the indices of the sample collected from the outdoor trail indicate a higher level of biodiversity.
The niches of the species identified in the samples may explain why the biodiversity of the leaf litter was higher than that of the soil. Many of the organisms that were identified in the samples were detrivores, organisms that consume dead organic matter, such as leaf litter. These organisms occupy a niche: living in leaf litter, and consuming it and other decomposing organic matter, so that it can be broken down, decomposed, and returned to the environment. Therefore, the levels of biodiversity of the samples of leaf litter were significantly higher than that of the sample of soil because the leaf litter contains more organic waste that can be consumed by detrivores.
3. Why would an environmental scientist need to make more than one measurement if he were calculating the biodiversity? How would you take samples of a large forest?
If an environmental scientist were calculating the biodiversity of an area, he would need to make more than one measurement in order to ensure accurate and reliable results. There are many confounding variables that may skew the data by affecting the number of organisms that are caught in the samples: time of day, season, weather, humidity, and temperature. For example, samples of leaf litter taken during the winter would contain less organisms than samples taken during the summer; this is because during the winter, many organisms head below the frostline or migrate south. If samples of leaf litter were to be taken from a large forest, it would be beneficial to take multiple samples from various areas in order to ensure accurate and reliable results. There are many organisms that inhabit a large forest; therefore, a limited number of samples from the same area would not yield accurate estimates of the biodiversity of the forest.
Conclusion
The results of this experiment supported the hypothesis that if samples of leaf litter and soil are collected from the outdoor trail at Heritage High School, and samples of leaf litter are also collected from Mr. Gunsher's woods, then the samples of leaf litter will have higher levels of biodiversity than the sample of soil. After the diversity indices of each sample had been calculated, the data showed that the samples of leaf litter had significantly higher levels of biodiversity than the sample of soil (control): The Simpson's Index of the sample of leaf litter from the trail is approximately 0.33 less than that of the sample of soil, while the sample of leaf litter from Mr. Gunsher's woods is approximately 0.23 less than that of the sample of the soil.
The reason for the high levels of biodiversity in the samples of leaf litter, as compared to the samples of soil, lies in the composition of leaf litter: "leaves, twigs, and pieces of bark that have fallen to the ground" (Lin, Kevin). According to Lin, leaf litter not only serves as great nesting material and hiding spots for organisms, but many detrivores, organisms that consume dead organic matter, occupy an important niche: living in leaf litter, and consuming it so that it can be broken down, decomposed, and returned to the environment. Detrivores play an important role in maintaining the health of an ecosystem: The decomposition of leaf litter releases nutrients back into the soil, making it fertile and allowing it to be absorbed by plants for growth.
According to Lin, organisms that can be found in leaf litter include worms, snails, spiders, and microscopic decomposers like fungi and bacteria. However, human-related activities, such as deforestation, introductions of invasive species, and pollution, have led to a loss of biodiversity in many different ecosystems, especially rain forests and coral reefs (International Union for Conservation of Nature). If this continues, it could lead to a loss of biodiversity in ecosystems all over the world, ultimately leading to the destruction of these ecosystems.
The reason for the high levels of biodiversity in the samples of leaf litter, as compared to the samples of soil, lies in the composition of leaf litter: "leaves, twigs, and pieces of bark that have fallen to the ground" (Lin, Kevin). According to Lin, leaf litter not only serves as great nesting material and hiding spots for organisms, but many detrivores, organisms that consume dead organic matter, occupy an important niche: living in leaf litter, and consuming it so that it can be broken down, decomposed, and returned to the environment. Detrivores play an important role in maintaining the health of an ecosystem: The decomposition of leaf litter releases nutrients back into the soil, making it fertile and allowing it to be absorbed by plants for growth.
According to Lin, organisms that can be found in leaf litter include worms, snails, spiders, and microscopic decomposers like fungi and bacteria. However, human-related activities, such as deforestation, introductions of invasive species, and pollution, have led to a loss of biodiversity in many different ecosystems, especially rain forests and coral reefs (International Union for Conservation of Nature). If this continues, it could lead to a loss of biodiversity in ecosystems all over the world, ultimately leading to the destruction of these ecosystems.
Citations:
Lin, Kevin. "Seasonal Science: What Lurks in the Leaf Litter?" Scientific American Global RSS. N.p., 18 Oct. 2012. Web. 28 Sept. 2014. <http://www.scientificamerican.com/article/bring-science-home-leaf-litter-biodiversity/>.
"Why Is Biodiversity in Crisis?" International Union for Conservation of Nature, 14 Oct. 2010. Web. 23 Sept. 2014. <https://www.iucn.org/iyb/about/biodiversity_crisis/>.
"Why Is Biodiversity in Crisis?" International Union for Conservation of Nature, 14 Oct. 2010. Web. 23 Sept. 2014. <https://www.iucn.org/iyb/about/biodiversity_crisis/>.