Introduction
Syllabus
Course
Information
Links & Readings
Bulletin
Board
Post
to Bulletin Board
Lecture Notes
(Will
open in new window - only use Internet Explorer)
1 - Intro Eco (html,
PPT)
2 - Pop Eco (html,
PPT)
3 - Comm Eco (html,
PPT)
4 - Ecosys Eco (html,
PPT)
5 - Cons Eco (html,
PPT)
PPT
files are zipped using WinZip
Assignments
1 - Ecol
Footprint
2 - Population
Growth
3 - Forensic
Entomology
4 - Invasion
Biology |
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Assignment:
What are the
consequences of changing population parameters? How is this useful for
conserving species?
-
Population
growth is a valuable
concept to understand thoroughly if we are to better conserve
endangered
species and manage introduced species that may be exploding in
population
size and outcompeting other native species. Of particular importance
are
the concepts of exponential growth and the logistic growth model's
carrying
capacity.
-
These concepts
are vitally important
as the basis of Population Viability Analyses. The goal of the PVA is
to
determine the minimum population size that would be necessary to ensure
that an individual population will last for a set period of time (often
100 years) at a high degree of probability (often 99%).
-
Our work today
will not directly
carry out a PVA, but our conclusions would be relevant for this type of
a study.
-
The following
are websites available
for background reading for this assignment:
- Your
Assignment:
-
Read the above webpages, particularly
the bottom three listed above.
-
Manipulate the XGROW population models, tweaking various
parameters so that you get a feel for the consequences of changing each
value. The graph will only show the 5 most recently created growth
curves at once. Stick with the following general parameters, Model:
Single, Graph Type: Arithmetic, Noise: Off. For Exponential growth
models, keep the Birth and Death Density Coefficients set to Zero. To
manipulate the growth rate (r), you could choose a different Species
Selection - those listed in the drop-down menu increase in r value from
human to T-phage in the order given. For Logistic growth, you can
increase either the Birth and/or Death Density Coefficients to a
non-zero value. If you are particularly interested in exploring the
model, you can introduce randomness, or what is called stochastic noise
into the model by turning the Noise to On.
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Answer the following questions:
-
Describe the two curves that
you obtain if you were to run the model using the same growth rate
("Species Selection" in the model) but with and without one of the
density dependent factors (birth or death) at work. Compare the two
curves and contrast what is happening in the population as it
increases. When using XGROW for humans, you need to select the
"logarithmic" button in order to see a carrying capacity for humans.
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Under what conditions could
you get oscillations in the population size in the logistic growth
model?
Explain what is happening when this occurs. What happens to the
oscillations
through time? Why does this happen? This may require some further
exploration on your part, but here's a hint - think of the carrying
capacity (a variable that is not explicitly in this model, but there in
the outcome). Answer these question using a species of your choice as
an example.
-
Explain how you could make a
rough approximation of the carrying capacity for humans, based only on
what you've learned from the comparisons of the logistic and
exponential
growth models. Feel free to make up data to support your point, rather
than relying on what passes for facts in this field. You don't need to
rely upon the graphs to answer this question.
-
DUE: Online at
Courseworks.columbia.edu before the start of the THIRD Class Session
Written 2002 by James Danoff-Burg. |