Species Diversity Activity Using Simpson’s Index
Modified from Brian Kaestner and Penny Smeltzer
The purpose of this activity is to enable you to practice comparing and evaluating the biodiversity of different plant or
animal communities using a common statistical analysis tool. “Simpson's Diversity Index is a measure of diversity. In
ecology, it is often used to quantify the biodiversity of a habitat. It takes into account the number of species present, as
well as the abundance of each species.” (from Offwell Woodland and Wildlife Trust)
Driving Question: Which area around the Westwood campus is more biodiverse – forest or grassland?
Introduction
(from Ecology and Field Biology by Smith)
“Simpson’s index of diversity considers the number of species, the total number of individuals, and the proportion of the
total found in each species. If the index is used to compare diversity among communities, the sample sizes must be
equal. If complete census data are used, the areas sampled must be of equal size.
D = N(N-1) /  ni (ni – 1)
D = diversity index
N = total number different species found (if you just find fire ants and grass, you have a N=2)
ni (ni – 1) = number of each organism of a species found (if you found 3 fire ants your ni (ni – 1) = 3(3-1) = 6
 = sum of all of the total organisms of each species (add up the ni (ni – 1) for each species)
Hypothesis
Our four sampling locations are the “forest” in front of the school, the “forest” in back of the school, the “grassland” in the
back left portable area, and the “grassland” near the far right portables. Provide a written hypothesis regarding the
comparative biodiversity of the selected communities at the study site. You should indicate which community you think is
the (1) most and (2) least diverse, and provide a reason for your selection.
Materials, Measurement, and Procedure
-study site or sites
-calculator
-Quadrat grids -- quadrat grids are used to delineate a specific study area – they are a 10 inch by 10 inch square markers
If you are going to use Simpson’s Index to compare the diversity of different communities or ecosystems, you will need to
collect data from at least two different plant or animal communities. Remember, in order for Simpson’s Index to be used
for comparative purposes, the following must be true: -sample sizes must be equal. The species themselves don’t actually
need to be identified - species identification is not necessary to calculate species diversity. The higher the number on the
Simpson’s index, the more biodiverse an area is. Most values for around Westwood with be under 1 – this is normal!
Westwood High School Study Areas: 1) “Forest” in front of school
2) “Forest” in portables area
3) “Grasslands” near far left portables 4) “Grasslands” near far right portables
Sample Procedure for Quadrat Technique
1) Each group will sample the community using the small plastic quadrats.
2) Collect data from 3 random samples – throw the quadrat in your study area with your eyes closed.
3) For each quadrat sample:
a) Identify each species present in the quadrat – general identification ex: “Fuzzy spider” is OK.
b) Count the number of individuals of each species. (Be thorough)
4) Record your data on the data chart provided.
5) When you have sampled 3 quadrats, calculate your D, and post in the class data spreadsheet.
Prelab Questions:
1) What is species richness?
2) Which part of the equation (numerator or denominator) accounts for species richness?
3) What is species evenness?
4) Which part of the equation (numerator or denominator) looks at species evenness?
5) When using the Simpson’s Index, what does it mean as the numbers get bigger?
6) Calculate the Simpson’s Index (using the equation above) for the following data.
Species
Number (n)
n(n-1)
Woodrush
3
6
Holly (seedlings)
8
56
Bramble
2
2
Yorkshire Fog
1
0
Sedge
5
20
Total (N) = 5
19
84
Raw Data
Use the charts on the next page record your raw data
Synthesized Data – Make two data tables – one needs to contain the averages of each value from tables 4-7, for each
habitat. The second data table needs to have ALL D values for each habitat (not just the average). Data tables 1-7
included in the packet will be turned in for raw data, but not directly copied for the synthesized data section.
Data Table 1: 1st Trial. Habitat: __________________
Species (label and
describe)
Species
Total (N)
count (or other measure)
Number (n)
n(n-1)
Data Table 2: 2nd Trial: Habitat: ____________________
Species (label and
describe)
Species
count (or other measure)
Number (n)
n(n-1)
Total (N)
Data Table 3: 3rd Trial: Habitat: ____________________
Species (label and
describe)
Species
Total (N)
count (or other measure)
Number (n)
n(n-1)
Data Table 4: Class Data for Habitat 1: Forest in front of School
Group
Trial
n(n-1)
N
D
AVERAGE
Data Table 5: Class Data for Habitat 2: Forest in portable area
Group
Trial
n(n-1)
N
D
AVERAGE
Data Table 6: Habitat 3 - Grasslands on left of portables
Group
Trial
n(n-1)
N
D
AVERAGE
Data Table 7: Habitat 4- Grassland on right of portables
Group
Trial
n(n-1)
N
AVERAGE
D
Data Analysis
A. Statistics: Analyze the dot plot we did together in class – Is there any statistically significant difference between any
of the habitats? Is one significantly more biodiverse than another? Summarize class results in 2-3 sentences.
B. Calculations –
A. Show all calculation for the Simpson’s Index for each of your three group quadrat trials.
Using Simpson’s Index, calculate the Diversity Index (D) for each of the communities you have studied.
D = N(N-1) /  ni (ni – 1)
D = diversity index
N = total number different species found (if you just find fire ants and grass, you have a N=2)
ni (ni – 1) = number of each organism of a species found (if you found 3 fire ants your ni (ni – 1) = 3(3-1) = 6
 = sum of all of the total organisms of each species (add up the ni (ni – 1) for each species)
Conclusion :
1) Answer the driving question.
2) For your GROUP’S three trials, was there much variation between trials for your D values? What do you think this
indicates about the overall biodiversity of your study site?
3) Refer to your hypothesis – was it correct or incorrect?
4) Support if your hypothesis was correct or incorrect with quantitative (A) and qualitative (B) data
(A) Quantitative data: What was the overall D value for all four study sites, and what does this indicate about the
biodiversity of the study sites, especially as referenced in your hypothesis?
(B) Qualitative data: Was there support from the statistics?
5) Sources of error – what is a source of error or noticeable inconsistency?
6) Real world: List two other questions you could address using the Simpson’s Biodiversity techniques you learned here.