Ap Biology Ecology Lab

Kui Tang AP Biology Period 2

Biodiversity and Ecosystems I. Introduction The objective of this lab is to comparatively study biodiversity in both diverse (prairie) and sparse (lawn) sites and examine how biodiversity impacts physical and biological factors of the environment. Several factors, both biotic and abiotic, including temperature, populations of animals, and populations of plants were considered and measured in both sites. All organisms were counted both for the number of individuals and the number of species. Additionally, the biodiversity index was calculated for both sites. Furthermore, organism counts were aggregated with data from other groups and similar analyses were performed. We hypothesize that species richness and total number of organisms will be markedly higher in the prairie, as will temperature. In each site, a 1m by 1m by 2m plot was marked. Site A, the diverse site, was located deep within the West High prairie, adjacent to the back parking lot. Site B, the sparse site, was located in the front lawn of West High. Abiotic measures of temperature were obtained with the LabPro/DataMate system and a temperature probe, with reading taken in 20cm intervals from ground height (0cm) to 200cm, beginning from 200cm proceeding downwards. Species richness and relative abundances of plants were determined by counting the number of patches of different species of plants within the one square meter plot on both sites. Animals (mostly insects) were collected by passing a sweep net over the marked area several times. In addition, at heights within the sample area were swept; thus airborne organisms were captured as well. In the prairie, the sweep net was used similarly; care was taken to ensure as many surfaces of each plant was swept as possible. After collection, the net was emptied into a ziplock bag. Sample bags were brought back into the lab and placed in the freezer overnight to dessicate and preserve organisms. Over the next few days, organisms were separated from plant material, grouped by species, identified, and counted. Biodiversity is valuable both intrinsically and for its potential to aid human civilization in a sustainable, energy-efficient way. Biodiversity is essential for pharmaceuticals; a quarter of American prescriptions are derived from exotic plant species (Campbell). By losing biodiversity, we are irretrievably losing opportunities to improve the condition of the human race. Furthermore, biodiversity provides many ecosystem services, including purifying air and water, nutrient cycling, pollination, detoxification, moderating weather extremes, and generating fertile soils among a plethora of other functions. Without these services, humans would not be able to live on earth. Without adequate biodiversity, these services would grind to a halt. The study of biodiversity is increasingly important in the day and age of massive human control over ecosystems. Small changes in an ecosystem can cause a cascade of other events to happen, ultimately resulting in a major transformation of the ecosystem (Miller)—more often than not for the worse.

AP Biology: Biodiversity and Ecosystems

Kui Tang

II. Experimental Materials ●

TI Graphing Calculator with DataMate (for data collection)

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LabPro interface (for data collection)

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Temperature probe

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Two metersticks

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Sweep net

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Two large plastic ziplock bags (to store samples)

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Tweezers

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Brushes

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Hand lens

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Petri dishes (to sort and organize insect samples)

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Freezer

Methods Perform the steps on a site on the lawn and in the prairie. These directions are slightly modified from the laboratory manual’s direction either (1) the manual explicitly called for student innovation; (2) the instructor explicitly overrode certain directives, or (3) the students carrying out the lab felt that the specified directions were too vague and consequently elaborated.

Temperature 1. Mark a one-square-meter area with a meterstick. 2. Set up temperature probe on calculator interface. Plug probe into CH1; connect LabPro interface to calculator. Start DataMate program on calculator. 3. Hold two meter sticks vertically, next to each other such that they form a 2 meter pole. 4. Place the temperature probe at the 200cm mark (100cm on the top stick) and wait for temperature reading to stabilize. Record the stabilized temperature, then lower the probe 20cm. Repeat until 0cm is reached.

Plant Patches A patch for out purposes is defined as a group of the same species on plant existing in more or less a circular or linear distribution. Patches considered separate if (1) a patch is entirely surround by 2

AP Biology: Biodiversity and Ecosystems

Kui Tang

another species of plants or (2) if two regularly is connected to another only by a thin corridor of the same species. The following are simplified examples of two distinct patches; each form was observed.

Drawing 3: Two circular patches connected by a small Drawing 1: Two circular patches corridor Count both the total number of plant patches and the number of different species of plants within the boundaries marked in theDrawing 2: Two linear patches connected at a temperature measurement stage. corner.

Sampling Organisms As it is impractical/impossible to count either the number or species of different organisms, a sweep net is used to collect organisms and store for future study.

Drawing 4: A sweep net. 1. Using the site initially marked during temperature measurement, measure two meter upwards, similar to when temperature readings were taken. 2. Sweep the net as throughly as possible in all three dimensions in a systematic manner, such 3

AP Biology: Biodiversity and Ecosystems

Kui Tang

as in concentric circles from the outside capitulating into the middle. Make sure surfaces of each plant get swept, both top and undersides. Also make sure the soil surface is scraped by the sweep net. Continue moving the sweep net during sampling. 3. When sampling is done, immediately grasp the net shut to prevent organisms from escaping. Then, hold an empty Ziplock bag over the net opening and invert the net such that the contents fall into the bag. Be careful not to lose any specimen. 4. After collecting samples from both sites, return to the lab, label bags, and place them in freezer overnight.

Sorting Organisms Two team members work on the lawn sample while the other two work on prairie sample. 1. After organisms have been frozen overnight, dump the contents of bags onto white pieces of paper to ease sorting. 2. Separate all plant material from organisms. 3. Slowly and carefully, with the aid of tweezers, hand lens, brushes, and other tools, separate the collection of insects into groups of different species. 1. First group organisms by color and size, placing them into appropriate petri dishes. 2. Then examine grouped organisms closer with hand lens and stereo microscope. Put each species in its own petri dish, and try to identify the species. 4. Record the total number of organisms and number of different species.

III. Data and Calculations Sample Calculations The biodiversity index, using Simpson’s Reciprocal Index (Offwell), is given as: N  N −1  n n−1 Eqn. 1: Simpson's Reciprocal Index −1

D =

Where N is the total number of organisms, and n is the number of organisms of a particular species. n(n – 1) is calculated for each species.

Prairie Biodiversity Index The prairie ecosystems had N = 78 total organisms. Counts of individual organisms are listed in 4

AP Biology: Biodiversity and Ecosystems

Kui Tang

data table below.

7877 =11.33 21205 4 2 1213 24 3212 17 65 421 Eqn. 2: Prairie Biodiversity Index −1

D =

Thus, Simpson’s Reciprocal Index for the prairie site is 11.33.

Temperature Height (cm) 200 Prairie (°C) 26.3 Lawn (°C) 29.2

180 26.3 29

160 26.8 29

140 28.4 28.9

120 29.4 28.7

100 30.2 28.8

80 30.1 28.8

60 32.6 26.8

40 32.6 25.7

20 32.3 24.9

0 Avg. 24 29 23.1 27.54

40 32.6 25.7

20 32.3 24.9

0 Avg. 24 29 23.1 27.54

Table 1: Temperature data for lawn and prairie from 200cm to 0cm Height (cm) 200 Prairie (°C) 26.3 Lawn (°C) 29.2

180 26.3 29

160 26.8 29

140 28.4 28.9

120 29.4 28.7

100 30.2 28.8

80 30.1 28.8

60 32.6 26.8

Temperature vs. Height

Table 33 2: Temperature of Prairie and Lawn 32

Temperature (°C)

31 30 29 Prairie (°C) Lawn (°C)

28 27 26 25 24 23 0

25

50

75

100

125

150

175

200

Height (cm) Chart 1: Temperature in Prairie and Lawn 5

AP Biology: Biodiversity and Ecosystems

Kui Tang

Individual Biodiversity Count Prairie #Animal Species #Animals #Plants #Patches

Lawn 34 78 12 23

8 45 4 19

Table 3: Individual biodiversity counts for lawn and prairie

Aggregate Biodiversity Count Team #Animals A #Animals B #Plants A #Plants B #Patches A #Patches B 1 78 4 19 2 85 34 10 6 3 113 37 12 6 20 11 4 34 73 10 9 5 9 3 13 6 22 11 6 37 26 11 2 7 11 5 4 19 8 15 5 9 8 4 10 17 8 Avg 40.7 21.67 11.5 5 12.6 13.2

Table 4: Class biodiversity counts. ‘A’ denotes prairie and ‘B’ denotes lawn. Note: Blatantly incorrect data from the class lists were committed to avoid unnecessarily skewing results. For example, some entries for plant counts were listed as percents. As percents are unusable in this context and it is impossible to recover the original integral values from these percents, these entries were omitted. Some fields were left blank on the class lists. One definite outlier with a lawn animal count of 500; it was off from all of the other counts by an order of a magnitude and would weight so strongly in arithmetic means that it would skew data to incorrect conclusions. The blanks in the data represent these omissions, both by individuals who omitted data posting it and myself for removing unusable data.

IV. Results and Discussion Comparative Biodiversity As the data clearly indicates, the prairie site contains significantly more species than the lawn, with 6

AP Biology: Biodiversity and Ecosystems

Kui Tang

the class average around twice as many species in the prairie and in our data, 3-4 times as many. A count of different species of plants and their respective populations is most relevant to studying biodiversity because biodiversity concerns itself with not how many organisms are present in the ecosystem, but the ecosystem’s species richness and relative abundances (Campbell), which are measured by counting the different species of plants and the population of each species respectively. Furthermore, only measuring both these values can one compute a biodiversity index. Contrary to the dramatic difference in the number of species, the total number of organisms between the two sites did not differ appreciably; the class data for patches differed only by 0.6 and our data differed only by 4. Moreover, the average number of plant species is significantly less than (half) the number of plant patches in the lawn, but the number of species is close to the number of patches in the prairie, reflecting that the prairie has higher relative abundances of its species; hence is more diverse. The prairie offers more biodiversity because the biotic and abiotic factors are more heterogeneous; thus provide more niches and allowing for more species to flourish (Watkins). The total number of plants do not significantly differ because they are limited by root area, sunlight, and nutrients, none of which differ appreciably between the two sites. Both sunlight and area available for roots are fixed; while prairies may be naturally more fertile, the lawn is artificially fertilized, bringing the two to parity.’ Overall, our data indicates the average lawn temperature is 1.5°C cooler than the prairie temperature. This occurs because plant material conducts heat better than air and there is more plant material in the prairie. Additionally, heat of respiration is lost from both plants and animals residing on plants at a greater rate more above the surface the the prairie because the prairie grasses are tall enough to support insects at higher elevations. This relation because especially apparent when towards in the 25mm-75mm range, where the majority of plant material was. The temperature graph indicates that as the warmest location. In fact, there is a massive bulge at this range compared to lawn temperature; the highest delta is at 20cm where the temperatures differed by 8°C. As most organisms (insects) are ectoderms, a warmer micro-climate is preferable to a cooler micro-climate because the extra heat enables the organism to metabolize, thereby grow and reproduce, faster. This lab demonstrates that the variety of organisms, hence biodiversity, can have significant changes on abiotic factors of the ecosystem. These conclusions support our hypothesis of species richness being dramatically higher in the prairie, as well as temperature. The large temperature delta at 20cm was surprising, but may have included the effect of a secondary variable because measurements were taken on different days. Our hypothesis of there being more organisms in the prairie was disproven, as aggregate data indicates the number of species in to ecosystems is roughly the same.

Caveats and Sources of Error The value of this laboratory activity is largely qualitative and comparative; thus precise quantitative results are not especially important. Even though the recorded data for organism counts would be considered unreliable, because each group committed similar inconsistencies in both sites, the delta between lawns and prairies is still accurate; therefore the lab retains its value. Indeed, with so many groups each adopting slightly different procedures (a consequence of vague specification in 7

AP Biology: Biodiversity and Ecosystems

Kui Tang

the lab manual and its encouragement of student innovation in several steps, especially when counting plant patches), obtaining accurate absolute quantitative values using this set-up is exceedingly difficult, if not impossible. Below are some problem we encountered, as well as those we observed other teams struggling with, as well as different techniques that may solve some of these issues. The temperature probe can be regarded as an accurate device, however, because temperature was measured on two separate days, an extra variable was introduced. Moreover, whether the probe was facing direct sunlight or in the shade when there was a choice between light and shade (deeper in the prairie virtually all surface was shaded, so it would not apply in this instance) significantly affected the temperature. A solution is to simultaneously measure temperatures at both sites, perhaps dispatching two out of the four members to each location as well as ensuring that readings are taken in sunlight when possible. The concept of “patches” is inherently subjective; in fact, the lab manual even asks the student to define patch. We attempted to define patch to clearly delineate patches from non-patches in order to minimize the need for human judgment calls; nevertheless, there were still many vague cases. Furthermore, we do not know of how other groups defined “patches,” so our count of patches may be fundamentally incompatible with their counts. For example, if a group defined a patch as strictly delimited by another species of plants, then their counts for the same site would be lower because we count two large sites joined by a small corridor of plants as two patches whereas the alternative definition would label the sample in Drawing 3 to be one patch as the narrow corridor is not considered strict separation. An alternative technique, employed by Waktins and Wilson in their field studies, consists of subdividing a 0.25m x 0.25m plot into 160mm2 quadrats. Because each quadrat is so small, it could be considered simply if it contained a certain species and plotted on graph paper, with the added benefit of giving both a micro-geographical and numerical values. This provide a more consistent, objective way to measure number of plant species, though it would take more work to mark the quadrats.

Causes and Effects of Prairie Destruction Before Europeans settled North America, approximately 570,000km2 of tall grass prairie, extending from Nebraska and Kansas to Pennsylvania. These ecosystems supported a wide array of different organisms, rivaling the biodiversity of the African Savannah (Howe). In the Midwest, agriculture has converted almost all existing prairie into agriculture land (Howe). Elsewhere, only 10% of the original prairie survives in fragmented patches (Kaiser). Currently, although the need to conserve prairies is quite urgent, air and nitrogen pollution have severely limited the biodiversity of prairies by selectively aiding a few dominant C4 photosynthesizing plants at the expense of C3 organisms, resulting in a loss of biodiversity. However, there is significant preliminary evidence to indicate that bison grazing may in fact increase biodiversity by checking the growth of dominant plants, thereby allowing other plants a chance to compete. As no dominant plant ever significantly overpowers any other plants, grazed sections of prairies are expected by ecologists to become more natural and diverse than non-grazed areas (Howe). Further8

AP Biology: Biodiversity and Ecosystems

Kui Tang

more, some ecologists criticize current management procedures as too focused on short-term corrections. They argue that the tall grass prairie is inherently dynamic; the current scenery has evolved through many different incarnations. Therefore, treatments such as burning should be varied and not attempt to morph the prairie into certain preconceptions of what prairie ought to be; it should be allowed to continue to evolve and develop on its own. Despite the abuse the prairie has suffered over the past three hundred years, it still stands far more durable and resilient than the lawn due to its biodiversity. If disease or other factor destroys the dominant species or another species, the community can still function and other organisms may be affected little, if at all, because another species may soon replace the niche left by the locally extinct population or an existing population may divergently evolve to fill the leftover niche due to high biodiversity. Moreover, local extinction of any species will have a minimized effect to the extent that organisms depend on organisms other than the locally extinct population.

Causes and Effects of Lawn Cultivation Lawns developed as a novelty item in the eighteenth century, but spread along with urbanism as the masses could afford it. Most lawns are high-energy, high-maintenance, and high pollution entities. Annually, lawn mowing contributes to five percent of annual emissions and lawn clippings compose 21% of the municipal waste stream. Ecologically, lawns present a homogeneous monoculture—only four to five species are cultivated in the Northern United States and only one in the South (Joyce). This landscaping destroys vast amounts of valuable habitat, endangering countless species of fauna, according to Tufts, chief naturalist at the National Wildlife Federation (Joyce). The resulting artificial creation, being composed on mainly one species, is very sensitive to change; therefore, humans must spend considerable effort to prevent change from happening, resulting in excessive energy use and chemical pollution. Without human intervention, most lawns cannot exist in their current state very long because human manipulation has made the lawns very unstable. For example, regular mowing of the school’s expansive front lawn consumes not only time, energy, and money that could be used to further education, but also results in massive noise pollution that distracts study whenever it occurs. Contrariwise, the prairie is for the most part left to its own devices; occasional management procedures and prescribed burning occur, but it is largely due to the isolated, fragmented nature of the backyard location of the prairie itself than for intrinsic reasons. Even so, these actions do not the ecological penalty anywhere near the degree maintaining a lawn does.

V. References Campbell, Neil A. and Jane B. Reese. Biology. 6th ed. San Francisco: Benjamin Cummings, 2002. Howe, Henry F. “Managing Species Diversity in Tallgrass Prairie: Assumptions and Implications.” Conservation Biology Sept. 1994: 691-704. JSTOR. University of Iowa Libraries, Iowa City. 11 Sept. 2007 . 9

AP Biology: Biodiversity and Ecosystems

Kui Tang

Joyce, Stephanie. “Why the Grass Isn’t Always Greener.” Environmental Health Perspectives Aug. 1998: A378-85. JSTOR. University of Iowa Libraries, Iowa City. 11 Sept. 2007 . Kaiser, Joycelyn. “Bison Prime Prairie Biodiversity.” Science 1 May 1998: 677. MAS Ultra – School Edition. EBSCO. West High Library, Iowa City. 11 Sept. 2007 . Miller, Brian, Gerardo Ceballos, and Richard Reading. “The Prairie Dog and Biotic Diversity.” Conservation Biology Sept. 1994: 677-81. JSTOR. University of Iowa Libraries, Iowa City. 11 Sept. 2007 . “Simpson’s Diversity Index.” Offwell Woodland & Wildlife Trust. .

2005.

12 Sept. 2007

Watkins, Anni J. and J. Bastow Wilsom. “Fine-Scale Community Structure of Lawns.” The Journal of Ecology Mar. 1992: 15-24. JSTOR. University of Iowa Libraries, Iowa City. 11 Sept. 27..

VI. Conclusion We compared species richness and relative abundance of prairie and lawn ecosystems in order to examine how biodiversity impacts physical and biological factors of the environment. Temperature, plants, and animals were measured for both number of species and number of total organisms. Plants were counted based on the patch model and animals were collected with a sweep net, frozen, and sorted and identified in the lab. Biodiversity indices were calculated. The data showed clearly that the prairie had more species and was on balance warmer than the lawn. However, the total number of organisms did not change significantly. It follows that the prairie would better be able to adapt to change because locally extinct populations can be quickly replaced. Moreover, local extinction of any species will have a minimized effect to the extent that organisms depend on organisms other than the locally extinct population. whereas in a lawn, if the grass is destroyed by disease, there is no hope for recovery. The experimental procedures had several flaws that made them unrealistic for obtaining accurate absolute values, but were sufficient for our needs of ascertaining comparative conclusions. However, they can could definitely be mitigated with different procedures, for example, measuring quadrats instead of counting patches. However, many trends can be observed through analysis of this data. For example, the warmer micro-climate in prairies sustains ectoderm life better than the comparatively cooler micro-climate of lawns; hence biodiversity can lead to more biodiversity. Review of literature also reveals interesting insights. For example, counterintuitively, bison grazing can actually improve biodiversity by checking dominant species.

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