The diversity of species present in an ecosystem can be used as one gauge of the health of an ecosystem. Species richness is a measure of the number of different species present in an ecosystem, while species evenness measures the relative abundance of the various populations present in an ecosystem. In an ecological survey designed to measure species diversity, a wildlife biologist might determine the number of individuals of each species present in an area, then calculate a "diversity index" for the area. Comparison of the diversity index with that of other areas provides insights into the species diversity and the health of the ecosystem. In this activity your "ecosystem" will be the school parking lot or a natural area on a field trip, and the "species" will be the different car models and colors for the parking lot or real species for a field trip. As a class, we will be comparing the species diversity of the student and staff parking lots or of different plots taken on the field trip. The diversity index we will use is the Shannon Diversity Index. After determining the number of each species (or car), in each plot (or parking lot), the Shannon Diversity Index will be calculated separately for the different plots (or student lot and the staff lot). A rich ecosystem with high species diversity has a large value for the Shannon Diversity Index (H'), while an ecosystem with little diversity has a low H'.
pi = H' = – (equation 1) (equation 2)
ni = number of individuals of species "i"
N = total number of individuals of all species pi = relative abundance of species "i" (see equation 1)
S = total number of species
H' = The Shannon Diversity Index (see equation 2)
Materials
|2 parking lots full of cars or a natural habitat |
Procedure
1. Prepare a data table. There must be enough space for 20 “species”.
2. Visit a natural area and mark off a plot area (or the school’s parking lot)