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Education
Measuring Biodiversity
 

Measuring Biodiversity

Procedure

  1. Quadrats and Transects
    • In this activity, you will be using quadrats along transect lines to take biodiversity measurements of the plant species in three distinct habitats near your classroom. Begin by splitting into groups. Four works best.
    • Select one person in your group to be the data recorder. The other three will be the data collectors.
    • Next, take one quadrat, or hula hoop, per group and place it on one side of one transect, or rope, next to a knot to allow identification of the plant species encircled by your quadrat. HYPOTHESES: For this experiment, the alternative hypothesis is that the alpha diversity will be smaller than gamma, meaning that there will be differences in the species that are present in each different habitat. The null hypothesis for this activity is that the alpha and gamma will be equal, meaning that there will be no species diversity difference between the communities sampled.
    • Each data collector must survey and identify the different plant species or any morphologically distinct varieties within your group's quadrat, giving the name of each plant type that you identify to the data recorder. It may seem like there are only a couple of species present at first, but look closer. It may take several minutes to find them all.
    • In addition to recording the species name, the data recorder must also write a short description in the table, so that each species can be identified again in subsequent quadrats. Click Here to download Table 1
    • Once all of the species within a quadrat have been identified, pick up your hoop and move on to the next knot along the same transect.
    • Continue surveying and moving to the next knot until you have completed the entire rope transect.
    • Once you have completed the rope, move to a transect in a different habitat, and begin identifying the different species within each quadrat along the new transect, until each group has identified plants along three lengths of rope, one in each habitat, for a total of 15 quadrats surveyed.
    • When all of the species data have been collected, carry the transects and quadrats back to the classroom.
  2. Species-Accumulation Curves and Richness/Evenness
    • In the next activity, you will be calculating and comparing the species richness and evenness in two distinct populations, represented here by two opaque bags containing beads of various colors. For this exercise, start by taking one paper bag of beads per group.
    • Have one person reach into the bag and randomly pull out three beads without looking.
    • Write down the bead colors, as well as the total number of colors pulled from the bag in the table. Click Here to download Table 2HYPOTHESES: In this activity, the alternative hypothesis states that species evenness in the two communities will be different, while the richness will be the same. The null hypothesis might be that species richness and evenness will be the same in both communities.
    • Place the beads back in the bag after their colors are recorded.
    • Then, shake the bag and have the next person in the group draw another set of three beads.
    • Record the colors and numbers of beads that they pulled in the table.
    • Record the colors in the second row and the cumulative number of colors drawn in the last column.
    • Continue to take turns drawing three beads from the bag until 20 samples have been drawn.
    • Next, switch bags with a group with a bag from the other community, and repeat the exercise of drawing 20 samples, recording the color data in the appropriate community column of the table.
    • When all of the data have been recorded, return the beads to the bag and return the bags to your instructor.
  3. Results
    • To calculate the alpha diversity of the transect and quadrat data collected by your group, use the data your data recorder entered for each species and enter it into your diversity table. Click Here to download Table 3
    • Then, fill out the alpha diversity for each habitat into the appropriate column in the table.
    • Use the species data from your quadrat and transect table and enter the beta diversity data into the appropriate data cells within the diversity table. NOTE: The beta diversity is the number of species that are unique between two habitats. In this video, there are three species in common between the two sites, but a total of six unique species, giving a beta diversity of six between site A and B.
    • To calculate the gamma diversity for your activity, use the data from your quadrat and transect table and enter the gamma diversity data into the appropriate data cell. NOTE: The gamma diversity is the number of species in all of the habitats within a single study. It is not the sum of all of the alpha diversities, because species that are common between habitats should be counted only once.
    • To construct species accumulation curves for both of the bead sampling communities, use your bead color selection data to plot the species by sampling effort. That is the number of total colors by sample in the graph for each bead bag community.
    • Then, estimate the asymptote of the plotted data by appearance. Predict the number of species you would expect to find in each community. Note any differences in appearance between the two curves. If it was easier to estimate the number of species in one of the communities, make a hypothesis to explain this observation.
    • To construct rank abundance curves for both of the bead sampling communities, use the color bead data to fill in the table for both community A and community B, listing the colors that were identified during the sampling in the color column, and adding the total number of beads of each color that was sampled in the abundance column. Click Here to download Table 4
    • Now, assign a rank to each color in the rank column, designating the color of the highest abundance the highest rank, rank one, and the color with the lowest abundance the lowest rank, rank 10. If there are multiple colors with the same number, just assign them consecutive ranks.
    • Plot individual rank abundance curves for the number of individuals by species ranked for the most to least common in both community A and community B. Compare the steepness of the two rank curves. Compare the richness and evenness between the two communities. Identify the community that you consider more biodiverse.

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