E-cology: Learning Population Dynamics with
Interactive Online Tools
Student Objectives
1) Explain what a population is in ecology.
2) Describe what r, K, and N0 are for a population.
3) Analyze how r, K, and N0 can change population
sizes over time both individually and together.
4) Devise a way to stabilize a hypothetical fish
population by varying r, K, and N0 and propose a
set of management strategies using these concepts.
5) Justify this proposal in a group presentation.
Methods & Materials
Online app: https://sites.duke.edu/ecologytools/
Students use a population model to get a sense of
how population size is determined by three important
characteristics (r, K, and N0). The online app enables
students to manipulate these characteristics and
immediately see the effect. The activity concludes
with students taking on the role of fisheries managers
and building on what they have learned to design a
healthy stock with a stable population. Best paired
with a teacher-led lecture on population
ecology.
Background
Population dynamics is the study of how a given
population of a species grows or shrinks over time.
Several processes control population size: 1)
population growth rates (r) determined by births,
deaths, and migration rates; 2) carrying capacity (K)
which is the number of organisms the environment can
support from its available resources; and 3) initial
population size (N0).
We use a classic model called the Ricker equation to
explore the effects of these three population
characteristics. Managers and scientists also use
population dynamics to understand population
dynamics of commercial species such as fishes. For
more information: sites.duke.edu/ecologytools/
Grade Level: 10-12th
Subject Areas: Biology, Ecology
NC Standards: Bio.2.1, Bio.2.2
Next Generation: HS-LS2-1, HS-LS2-6
Duration: 45 min – 1 hour
Group Size: 3-4 for group activity
Location: Indoors; computer lab
Resources Needed: Computer, Internet
Activity Procedure
1. Students will be asked to go online to a website
that has been created for this lesson. The
website will link to an interactive graph of a
population based on a classic model called the
Ricker equation. Sliding bars can be used to
change characteristics of the population.
2. From a guided worksheet, students will be
asked to look at Part 1 of the activity. In Part 1,
students will change r, the intrinsic growth
rate of a population (discussed in depth
online). Students will be asked to describe what
happens to the population.
3. Students will then move to Part 2 of the activity,
where they can change the values of r, K, and
N0. Students will be guided to change 1 or 2 of
the characteristics at a time to see how each
characteristic changes the population
individually and together. Students will be
asked to describe what happens to the
population at each stage.
4. In Part 3 of the activity, students will be
presented with a few “case study” examples,
where hypothetical fish populations are
unstable. Students will be asked to think like a
fisheries manager, and determine how to
change the population characteristics so that is
stabilizes the population and becomes a
healthier fish stock. We will provide a list of
actual management strategies that can be
taken, and will ask students to decide which
strategies pair most closely with the changes
they made to r, K, and N0. This portion can be
done as a group activity.
5. Lastly, students will present their findings to the
class as a “proposal” to a mock fisheries panel.
Evaluation
Final products:
 Completed questions from activity
 Group presentation on population
recovery proposal (with rubric)
The website will serve as both the activity to
teach ecological principles about population
dynamics as well as the main evaluation. The
website activity will be paired with a set of
questions in which students are asked to
describe what happens to populations as
characteristics are changed and why. In the
final section of the activity, students in groups
must evaluate what actions to take in order to
stabilize a hypothetical population of fish.
This activity will evaluate comprehension of
the 3 main population characteristics (r, K,
N0) and how they change the size and stability
of populations over time. In particular, the
activity in which students are asked to choose
management strategies based on changes of
r, K, and N0 will evaluate student
comprehension and application of concepts.
As a group, students will present their findings
as a “proposal” of how to stabilize a fish
population as pretend fisheries managers.
Authors: Chris Ward, Elizabeth Schrack
Duke University Marine Lab
Nicholas School of the Environment
135 Duke Marine Lab Rd.
Beaufort, NC 28516
Chris Ward: Christopher.Ward@duke.edu
http://oceanography.ml.duke.edu/hunt/lab
Elizabeth Schrack: Elizabeth.Schrack@duke.edu
http://sillimanlab.com/liz-schrack/
Note: Any changes to the lesson plan or activity
will be updated online.
Example Rubric for Group Presentations
Category
Scoring Criteria
Students introduce scenario in a clear
and well-articulated framework.
Content
Students clearly described a population
in terms of ecology.
Students explained r, K, and N0 and
showed their understanding of these
terms for ecological populations.
Students connect changes to these
parameters and describe their effects on
population dynamics.
Student’s changes to the population
parameters lead to a stabilized
population size over time.
Students use appropriate management
strategies in relation to their findings
with population parameters.
Information is presented in a logical
sequence.
Presentation
Speaker maintained good eye contact
with the audience.
Good language skills and pronunciation
are used and speaker uses a clear,
audible voice.
Length of presentation is within the
assigned time limits.
Score
Total Points
Novice
(4 pts)
Apprentice
(6 pts)
Practitioner
(8 pts)
Expert
(10 pts)