The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
For YSP Volunteers: How to Run this Activity
NOTE: THIS MODULE WORKS MOST EFFECTIVELY WITH GROUPS OF HIGHCHOOL STUDENTS,
GREATER THAN 12 STUDENTS IN THE GROUP.
(There is no student handout for the Island Biogeography module.)
Logistics
Number of Volunteers: minimum of 2 volunteers
Amount of Set-up Time: 10 minutes to arrange desks/chairs, pre-draw graphs, write concepts on
board, and arrange ropes as “islands”
Amount of Running Time: 45 minutes – 1.5 hours (depending on amount of discussion)
Module Overview
This module introduces some basic concepts of the Theory of Island Biogeography to students. The
students will actively be engaged in an exercise of island colonization, with the students themselves
representing species colonizing “islands” made by ropes shaped in circles. The topics covered in this
module tie into important themes in ecology, evolution, and conservation, such as the formation of new
species, species diversity in a fragmented landscape, and how to conserve species across a network of
protected reserves. This larger aspect of the importance of island biogeography concepts is discussed at
the end of the module.
Curriculum Links
Missouri Science Standards
Include the specific Missouri Education Standards (and put the numbers in bold). See example
below:
4.1.A Explain the nature of interactions between organisms in different symbiotic relationships
To access the standards, visit these URLs:
Biology: http://dese.mo.gov/divimprove/curriculum/GLE/documents/cur-sc-bio-cle-1108.pdf
Non-biology: http://dese.mo.gov/divimprove/curriculum/GLE/documents/cur-sc-other-cle-1107.pdf
Next Generation Science Standards
Include the national Next Generation Science Standards addressed by your kit.
http://www.nextgenscience.org/next-generation-science-standards
Goals
For the purpose of simplifying the Theory of Island Biogeography for students, we will focus on the three
better known factors influencing island species diversity:
1. The relationship between species diversity and island size.
2. The relationship between species diversity and the distance of an island from the mainland.
3. The relationship between species diversity and the age of an island.
Materials
1. At least 6 long ropes, each rope a minimum of 8 feet long.
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
2. Hawaiian leis of different colors, each color used to represent a different species. There should be
enough leis to have one per student and 3+ different colors, so that students can be divided into
equal-sized groups of different colors.
3. Blackboard or whiteboard to illustrate concepts
4. Stopwatch, watch, or clock with seconds
What to Expect
Based on past experience running this activity, you can expect…
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Clear out space in the classroom, by pushing desks and chairs to the edges of the room, to make
room for the “island colonization” activities involved in this module.
Chairs can be arranged around the blackboard or whiteboard; otherwise, students can stand during
discussion.
Students become extra excited by the physical aspects of the activity. Therefore, be sure to ask
students concept-related questions throughout the module to keep them engaged mentally as well
as physically.
Safety
Remind students to be aware of the safety of others while colonizing islands.
Background Information and Protocol
Explain to Students:
The Theory of Island Biogeography examines the factors that affect the species richness (species numbers)
on isolated communities. Robert MacArthur and E.O. Wilson coined the term in the 1960’s, and they
described the theory with regards to an archipelago (define this and draw archipelago on the board)
surrounded by water. Explain how an archipelago can form and how species reach the newly-formed
islands (by migrating from the mainland to colonize the islands).
The Theory of Island Biogeography has since been used to explain numbers of species on any isolated
habitat surrounded by unlike habitat, including mountaintops surrounded by lowlands, ponds surrounded
by terrestrial communities, organisms themselves as “islands” colonized by parasites, and fragmented
forest surrounded by farmland. We will discuss and perform an activity related to each of three factors
which affect the numbers of species on islands; the following concepts are fundamental to the Theory of
Island Biogeography.
Write on board:
A. Species numbers increase with the increased area of an island
B. Species numbers increase with the island’s closeness to the mainland
C. Species numbers increase with the increased age of the island
D. Final Discussion, after going through A, B, and C
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
A. SPECIES NUMBERS AND AREA (spend ¼ of the module time on this Part A, which includes an
approximate 5-minute illustration of the concept at the board, a 5-minute activity, and another 5-minute
discussion at the board)
1. Illustrate concept at board (approx. 5 min)
The relationship between island area and number of species has been well studied. Many archipelago have
shown that, the larger an island is, the more species it contains. This is possibly the most general pattern
found in ecology, and many explanations have been proposed. Draw on board: The Species-Area
Relationship (instructors should realize that the y-axis is on a log scale, but this should not be stressed
when explaining the relationship to the students)
Number of
Species
(on log scale)
Size of island, small to large (on log scale)
Ask students: Based on the Theory of Island Biogeography, what will the relationship between the size of
the island and the number of species look like? Students may take guesses. Tell the students that, in order
to answer this question, we will perform an activity of colonizing islands. (Instructors should know that,
because of the log scale, there should be a linear and positive relationship; for example, see below.)
Amphibian and reptile species numbers on West Indies Islands (Based on Figure 2 on page 8 of "The theory
of island biogeography" by MacArthur and Wilson.)
2. Activity (approx. 5 min.)
Divide students into at least five groups. Pass out leis, so that each groups gets one color of lei. Each group
(each color) represents a different species ready to colonize the islands. Have the students line up behind
one elongated rope, which will serve as the mainland. Show students how they will be able to move away
from the mainland so that they can colonize the islands. Students are able to move by placing ONE FOOT
IN FRONT OF THE OTHER, so that the heel of the front foot is touching the toes of the back foot as though
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
you are measuring the size of a distance with your feet. (This keeps the students moving slowly and in
control, which will become even more important later on in the module.) Make three islands of different
sizes, using the 8+ foot long ropes. One islands will be made with one rope, shaped in a circle (the smallest
island). The second island will be made with two ropes shaped in a circle (the middle island). The third
island will be made with three ropes shaped in a circle (the largest island). Orientation of the students
behind the elongated rope, ready to colonize the archipelago having three islands of different sizes:
The students start here, on the mainland:
The archipelago with 3 island sizes here:
Now, explain to the students that they will have a limited amount of time (about 15 seconds) to walk foottouching-foot to any of the islands. Using a clock, watch, or stopwatch with seconds, let the students
colonize the islands, so that you can then build a relationship between the number of species and island
size. Then have the students call out how many species (how many different colors of leis) colonized each
island.
3. Discussion at board. (approx. 5 min.) (Have one instructor carry out this discussion at the board while
the other instructor(s) prepares the set-up for the Part B2 island activity.)
Return to the board and then fill in how many species colonized each island size. On the y-axis, put a
reasonable number of minimum and maximum number of species and on the x-axis, make SMALL and
MEDIUM and LARGE be the island sizes. Then have the students help you construct the positive, linear
relationship. In case the relationship turns out to not be positive and linear, then one can explain to the
students that, if you repeated this activity several times, then you would expect the relationship to be
positive and linear. Below is the relationship, filled in with the activity results. (Put numbers and sizes on
the axes!) Now check off part A, of A-D, written on the board!
Number of
Species
(log scale)
Size of Island, small to large (log scale)
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
B. SPECIES NUMBERS AND DISTANCE (spend ¼ of the module time on this Part B, which includes an
approximate 5-minute illustration of the concept at the board, a 5-minute activity, and another 5-minute
discussion at the board)
1. Illustrate concept at the board (approx. 5 min)
The relationship between the distance of an island from the mainland and the number of species of an
island is also clearly studied in ecological research. Many archipelago have shown that, the closer an island
is to the mainland, the more species it will have.
Draw on board: the relationship between species diversity and the distance of an island from a mainland
Number of
Species
Distance of Island from mainland
Ask students: Based on the Theory of Island Biogeography, what will the relationship between the number
of species and the distance of the island from the mainland look like? Students may take guesses. Tell the
students that, in order to answer this question, we will perform an activity of colonizing islands.
(Instructors should know that this relationship should be a negative relationship; the linear aspect is less
important here because of varying island distances from mainland). *The x-axis should go from short
distances to long distances, in order to result in a negative relationship.
2. Activity (approx. 5 min.)
The activity is similar to that in part A, except that now the islands are of EQUAL size but different distances
from the mainland. Make each island out of two ropes this time, in order for each island to be of medium
size. The students must have a limited amount of time to colonize the islands, illustrating that further
islands will be less likely to be colonized with a finite amount of time (with infinite time, this would not be
the case). Allow the students a limited amount of time (about 15 seconds, or when 0-1 students are on the
far island) to colonize the islands. Remind students to safely walk foot in front of foot, heel to toe. Using a
clock, watch, or stopwatch with seconds, let the students colonize the islands, so that you can then build a
relationship between the number of species and island distance from the mainland. Then have the
students call out how many species (how many different colors of leis) colonized each island.
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
The students start here, on the mainland:
The archipelago with 3 distances from mainland:
3. Discussion at board. (approx. 5 min.) (Have one instructor carry out this discussion at the board while
the other instructor(s) prepares the set-up for the Part C2 island activity.)
Return to the board and then fill in how many species colonized each island. On the y-axis, put a
reasonable number of minimum and maximum number of species and on the x-axis, make 2 feet, 4 feet, 6
feet etc. (whatever is reasonable for the classroom set-up) be the units of the distances. Then have the
students help you construct the negative relationship. In case the relationship turns out to not be negative,
one can explain to the students that, if you repeated this activity several times, you would expect the
relationship to be negative. Below is the relationship, filled in with the activity results. (Put numbers and
distances on the axes!) Now check off part B, of A-D, written on the board!
Number of
Species
Island Distance from the Mainland
C. SPECIES NUMBERS AND THE AGE OF THE ISLAND (spend ¼ of the module time on this Part C, which
includes an approximate 5-minute illustration of the concept at the board, a 5-minute activity, and another
5-minute discussion at the board)
There is also relationship between numbers of species and the age of an island. Remember: islands form
by volcano formation, lowering of sea levels, etc. ON BOARD: Draw an archipelago and draw in new islands
that are being formed by either volcanic eruptions or the lowering of sea levels. Explain that we can date
islands through modern geologic techniques. Many archipelago have shown that, the older an island is, the
more species it contains.
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
On board, draw this new graph to complete and ask students the relationship they expect to see:
Number of
Species
Age of island (make axis from younger to older)
Tell the students that, in order to answer this question, we will perform an activity of colonizing islands.
(Instructors should know that there should be a positive relationship here.)
2. Activity (approx. 5 min.)
The activity is more complicated because, AS STUDENTS ARE COLONIZING ISLANDS, new islands will be
created by the instructors forming them through time. So that we can have a large representation of
island sizes, each island should be made of only one rope, result in a total of six islands at the end of the
activity. similar to that in part A, except that now the islands are of EQUAL size but different distances from
the mainland. Allow the students a limited amount of time (about 30 seconds this time or until all of the
islands have been “created”) to have the students colonize the islands. Remind students to safely walk foot
in front of foot, heel to toe. Using a clock, watch, or stopwatch with seconds, let the students colonize the
islands, so that you can then build a relationship between the number of species and island age. Then have
the students call out how many species (how many different colors of leis) colonized each island.
***Create at least three islands during the colonization process, so that less students end up colonizing
them by the end. After colonization, have students call out the species numbers on each island.
The students start here, on the mainland:
The archipelago with some islands created during the
colonization process:
This island created
after eg. 10 seconds
of colonization
This island created
after eg. 15 seconds of
colonization
This island created
after eg. 20 seconds of
colonization
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Washington University School of Medicine
Island Biogeography Module
3. Discussion at board. (approx. 5 min.)
Return to the board and then fill in how many species colonized each island size. On the y-axis, put a
reasonable number of minimum and maximum number of species and on the x-axis, put a reasonable
number of seconds, based on the seconds after which islands were formed. (For example, if the
colonization process went 1 minutes long, then make the x axis 0 seconds to 60 seconds.) Then have the
students help you construct the positive, linear relationship. In case the relationship turns out to not be
positive and linear, then one can explain to the students that, if you repeated this activity several times,
then you would expect the relationship to be positive and linear. Below is the relationship, filled in with
the activity results. (Put numbers and sizes on the axes!) Now check off part C, of A-D, written on the
board!
Number of
Species
Age of Island (make axis from younger to older)
D. Wrap-up discussion using the board (spend the end of the module, approximately 15 min., reviewing
the concepts in this activity and relating them to bigger-picture themes in biology and conservation)
1. So, in review, what factors have we learned today that can affect the numbers of species on islands?
The area of an island, the distance of an island to the mainland, the age of an island (time)
2. Why do you think that an increase in the area of an island would lead to an increase in the number
of species on an island? There are many reasons for this, and they are not all well known, but can
you come up with any? (i) A bigger island may allow for more resources to be exploited. (ii) A
bigger island can create more various environments that allow for different kinds of species to
inhabit each different kind of environment. (iii) A bigger island can allow for those species requiring
more space to also also occupy that island. (Larger animals and animals higher on the food chain
tend to require more space than smaller animals and animals lower on the food chain.)
3. According to the Theory of Island Bioogeography, several additional factors other than space,
distance, and the age of an island may affect the numbers of species on the island. Can you think of
what some of these additional reasons for varying species numbers may be? These may be tough
for the students to answer, so provide hints!
Additional influences of island species diversity may include habitat suitability, human activity,
ocean current directions, and chance events.
The Young Scientist Program
http://ysp.wustl.edu
Washington University School of Medicine
Island Biogeography Module
4. The concepts we covered today, that island area, island distance from the mainland, and the age of
an island all affect species diversity, refer to much more than just oceanic islands surrounded by
water (you may or may not have brought this up in the beginning of the module). What are other
island-like environments to which these concepts would apply?
All of these can function as islands: mountaintops surrounded by lowlands, ponds surrounded by
terrestrial communities, organisms themselves as “islands” colonized by parasites, fragmented
forest surrounded by farmland, each isolated tree in a forest, each isolated leaf on a tree, humandisturbed environments surrounded by undisturbed environments.
5. Can you think about why the Theory of Island Biogeography is important to conservation? (Draw on
the board a picture of Missouri and then draw approximately the parcels of National Forest
allocated across southern Missouri: see below.) What does the Mark Twain National Forest across
southern Missouri look like?
The parcels of Mark Twain National Forest across southern Missouri appear as islands of protected
forest surrounded by habitat that has been more heavily disturbed by humans, such as cities and
farmland. The numbers of species in these conserved areas depend on the concepts we covered
today. In order to conserve significant numbers of species in isolated environments such as
National Parks, National Forests, and Wilderness Areas, we have to think about the concepts related
to the Theory of Island Biogeography.
Draw on board a rough outline of the National Forest land in Missouri: Mark Twain National Forest
in green, composed of an archipelago of natural habitats surrounded by disturbed habitats