This exercise was created for undergraduate students in non-majors
or introductory biology courses, but could easily be adapted to
upper-level undergraduate or to high-school courses. It can be used
on any computer that has the Wolfram CDF Player or browser
plug-in installed, and takes students about two to three hours to
complete. We have tested it in both Ecology and Environmental
Science classes. These courses take place over a fifteen-week semester, with each week consisting of either a three-hour combination
lecture and laboratory block, or two, two-hour meetings per week,
with one meeting dedicated to a laboratory section. Typically, our
laboratory classes have a cap of twenty students per section. Students’ majors include art and communication fields, including film,
journalism, art, business, and music.
How to Do it
Students work in pairs within the learning management system
(LMS) at a computer that has the CDF browser plug-in installed.
The interactive CDF elements, together with background information, definitions, instructions, and other lab elements, are embedded
within an activity in the LMS. This allows students to interact with
the CDF elements and answer questions, including multiple-choice,
short-answer, and essay, within the LMS. Alternatively, the entire
lab, including both the interactive elements, text, and questions,
can be assembled into a single CDF document and used with the
stand-alone CDF Player application, but that requires students to
answer questions on paper or in a separate document.
Learning Goals and Objectives
The objectives of this exercise were to (1) understand the basics of
quantifying biodiversity using species richness, (2) graph and interpret a rank abundance curve, (3) calculate Simpson’s Diversity
Index, and (4) interpret and answer questions about a larger data set.
We defined species richness, relative abundance, a rank abundance
diagram, species evenness, and diversity indices in the introduc-
tion, as well as in the glossary of the LMS. We also provided the
Simpson’s Diversity Index is 1 ∑ip2 i, or equivalently 1 ∑ i ni N ð Þ2, where
• ni is the number of individuals of species i,
• N is the total number of individuals of all species,
• pi is the proportional abundance of species i and is defined by
pi ¼ ni N, and
• ∑ip2 i means that you add over all species.
Background Information for Students
“Is it pristine?” is often a question asked about natural environments.
When planning parks, managers want to know if the park made an
environment more natural. But these questions are really addressing
the health of the community in an area. To figure out if a community
is healthy, you can measure the biodiversity. Generally, polluted or
heavily human-impacted areas will have lower levels of biodiversity
than more pristine areas.
So, how do you measure biodiversity? The simplest way is to
count up how many individuals of each species are in a specific area.
If you are assessing a large area, this is usually done with lots of
smaller samples. Your results will be a table of species with counts
of individuals. From this table you can calculate the relative abun-
dance (pi) of each species.
Once you have the relative abundance calculations, you can
graph this as a rank abundance curve. To do this, you rank the species
by number of individuals (rank 1 has the most individuals), and
then graph the rank on the x-axis and the relative abundance on
Then you can calculate Simpson’s Diversity Index. This will give
you a number that has a minimum value of 1. If the Simpson’s Diver-
sity Index equals 1, then there is only one species in the community.
The maximum value is the number of species in the community
(species richness). This exercise will have you complete a simple cal-
culation by hand and then interpret a larger community afterward.
Overview: The first section of the exercise will walk you
through creating a rank abundance curve and calculating Simpson’s
Diversity Index using sample data. The second section will let you
explore real data from a deciduous forest in Virginia. You will be
able to manipulate the data to see how changes in the forest would
affect the diversity index and graphs.
Preliminary Protocol Notes For Instructors
We started with a sample calculation, using a hypothetical community with six species in a table. After showing students a table
with only the numbers of individuals of six species, we then
explained that the rank of a species refers to its position in the list
when the species are ordered from most abundant to least abundant, with the most abundant species having rank 1, the next
most abundant species having rank 2, etc. We showed them the
ranked data (Table 1). Then, as part of the CDF, students computed the proportional abundance, or the percentage of the total
number of individuals, of each species.
Rank Abundance Curves (for students)
1. Compute N, the total number of individuals of all species, by
adding the numbers in the Number of Individuals column.
Table 1. The species are sorted according to rank
so species A has rank 1, and species F has rank 6.
A 73 1
C 11 3