Midterm review
BSC 417
Outline
• Major points
• Question formats
• Study tips
Major topics
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Theory and purpose of environmental modeling
Systems thinking & why it is important
Basic STELLA nomenclature & structures
Mathematical relationships
– All types covered in detail
• Feedback loops, synergy
• Sensitivity analysis
• Case analysis
Concepts/things you should know
• Dimensional analysis and how it relates to
environmental modeling
– Working with units
• The basic layout (STELLA) of each behavior
pattern
• Difference equations
• Rate equations
• Key features of examples from homework/class
discussions
• Vocabulary from text
Behavior patterns
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Linear growth/decay
Exponential growth/decay
Logistic growth
Overshoot and collapse
Oscillation
• Know equations, recognize patterns, know how
patterns are influenced by the inputs, know
steady state conditions
• Be able to cite (and describe in detail) examples
for each
Linear
•Rate equation: dR(t)/dt = k
•Solution: R(t) = R0 + kt
•K is the slope
•K = sum of inflows – sum of outflows
Exponential
•Rate equation: dR(t)/dt = kR(t)
•Solution: R(t) = R0 x ekt
•K = inflow rate – outflow rate
Logistic
•Rate equation: dR(t)/dt = k(t) x R(t)
•Solution: R(t) = cc/(1+Ae-unconst.gr.rt x t)
•K(t) = unconstrained growth rate x
(1-(R(t)/cc)
•Cc = carrying capacity
•A = (carrying capacity – R0)/R0
Overshoot and collapse
•Rate equation (population): dP(t)/dt = ((B-(1R(t)/R0)) x P(t)
•Rate equation (resource): dR(t)/dt = -C x P(t)
•P(t) = population at time = t
•R(t) = resource reservoir at time = t
•B = per capita birth rate in population per unit
time
•C = per capita consumption rate of resource per
unit time
•R0 = initial value in reservoir
•Solution to rate equations: depends – system of
differential equations
Oscillation
•Rate equation (consumer): dC(t)/dt = G x R(t) D
•Rate equation (resource): dR(t)/dt = W – Q x
C(t)
•G = consumer growth rate
•D = consumer deaths per unit time
•W = resource growth per unit time
•Q = resource consumption rate
•Equilibrium oscillation for the consumer: W/Q
•Equilibrium oscillation for the resource: D/G
•Solution to rate equations: depends – system of
differential equations
Problem types you should be prepared
to face
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Short answer
Multiple choice
Simple calculations
1-2 questions involving application of systems
thinking to a hypothetical problem
– Basic model set up and analysis
Study tips
• Straightforward assessment of your
understanding of the basics of modeling
– No surprises, but comprehensive
• Application of those basics to hypothetical
problems
• Everything in Chapters 1-3 in text
• Class notes and homework
About the exam
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In room 229, Biology
Closed book/notes
Bring a calculator
One hour, 15 minutes to complete
Questions?