CS382:Predator-Prey

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<Predator Prey> ( Lynx Hare )

Overview

Some prose describing the unit.

Background Reading for Teachers and TAs

Reading Assignments for Students

  • Given the reference materials present so far, it's possible that rather than having a link to online reading assignments, we may have to create paper handouts based on the materials that we have links to.
  • A handout created from parts of the US Dept. Of Energy's guide to System Dynamics seems like a very good place to start.

Reference Material

Lecture Notes

Outline of the lectures designed to fit into 2 1:20 slots per week. This unit lasts 1 1/2 weeks, so requires 3 lectures.

Lecture 1:

  • Intro & Concepts
    • What is system dynamics?
    • What is it for?
    • What does it let you do?
      • Systems dynamics lets you sketch out the relationships between all the components of a dynamic system, and given those relationships, will allow you to predict how the system behaves over a period of time. Will it result in a fluctuating growth? Exponential growth? Perfect equilibrium? All of these questions should be answerable using this type of model.
    • Why use System Dynamics? When should you use it?
      • The answer to this question is essentially the same as why you should use any other model. It's oftentimes quicker, cheaper and safer to alter a model and run tests on that than to alter a real system and run tests on that. Additionally, a failure in a model will allow you to predict a failure in a real system.
      • Failure in a real system often has catastrophic consequences, such as the loss of lives. The failure of a model is often much less devastating, resulting in perhaps a "Darn. Well, back to the drawing board." instead of "My son/daughter was in that building!"
    • Strengths / Weaknesses
  • Basic Terminology (Building Blocks)
    • Time Paths
      • System Dynamics is interested in the behavior of systems over a period of time. Time paths are critical to expressing this.
      • Types of Time Paths
        • Linear Family
          • Growth / Decline
            • The notion that most systems grow / decline under a linear curve is in fact incorrect. A linear growth or decline indicates a system which is devoid of feedback.
            • Feedback is a crucial part for the growth or decay of any system. Any system that displays a lack of it is unrealistic.
          • Equilibrium
            • The expression of a system under which there is no pressure for change, or a system in which all variables reach their desired state at the same point in time
            • Note that this is an extremely artificial scenario, most systems do NOT reach or maintain equilibrium.
        • Exponential Family
          • Paths showing exponential growth and exponential decay. Real systems tend to grow along exponential paths rather than linear paths.
        • Goal-Seeking Family
          • Displayed in most living, and some nonliving systems
        • Oscillation Family
          • Sustained
            • Characterized by a predictable periodicity.
            • Predator-Prey relations are often characterized by this, as while the individual oscillations may vary, they often follow a predictable oscillating pattern in that the rise of the prey population indicates the rise of the predator population, and the decline of a prey population causes the decline of a predator population.
          • Dampened
            • Displayed by systems that display dissipation or relaxation processes, such as friction or information smoothing.
          • Exploding
            • Starts of smoothly, but grow until either the system settles down or is torn apart.
            • This pattern occurs infrequently in real-world situations, and doesn't last long when it does.
          • Chaos
            • A unique type of oscillation, as it basically represents a random pattern generated by a system that is devoid of randomness
        • S-Shaped Family
          • This is extremely visible in the Wolf Sheep Agent based netlogo model when the grass is taken out of the equation. The sheep population goes too high, which in turn causes the wolf population to increase too much, which leads to an irrecoverable decline in the sheep population. (Extinction)
          • This is referred to as an "Overshoot and crash" system.
    • Link
      • Feedback Loop
    • Stock
      • A stock is a quantity of objects that's variable in nature. Examples of this are the number of sheep in a pasture, the number of fish in a pond, the amount of oil left in the world, the number of tanks in the US military, etc.
    • Flow
      • This represents the flow of resources either into or out of a stock. For instance, drilling would represent a flow out of the stock of oil in Alaska, and into the stock of oil in the US Oil Reserve.


Lecture 2:

  • Review of the "Building Blocks" of a System Dynamics model
  • Applications of Basic Terminology
    • Causal Loop Diagram
      • Pictures used to convey understanding of interactions or influences within the structure. It's used specifically to show the influential interactions between two elements of a structure.
      • The main conventions that are used to display a loop are the "+", "-", "S" and "O"
      • That is to say, that if a arrow is shown from A to B with a + on it, it means that A adds to B. As A increases, it adds more and more to B, and as it decreases, it adds less and less, but still adds to B
      • With a - shown with the arrow, A subtracts from B. As A grows, it subtracts more and more from B. As A diminishes, it subtracts less and less from B (But still subtracts)
      • With a S shown with the arrow, A and B grow in the same direction. This means that as A increases, B increases, and vice versa.
      • A O indicates that A and B grow in opposite directions, I.E. as A shrinks B grows and vice versa.
      • With no label, it indicates that A is considered a constant.
      • The Causal loop diagram gives no indication as to the strength of the influence of the two elements, it just shows the nature of the influence.
      • There are, generally speaking, two types of Causal loops. A Reinforcing loop and a Balancing loop.
        • In a reinforcing loop, each action adds to the other. An action that produces a result that produces more of the same action is a reinforcing loop.
        • In a balancing loop, any action attempts to bring two things to agreement. A situation where one tries to solve a problem or achieve a goal is representative of a balancing loop.


Lecture 3:

Lab

Some prose describing the process, outcomes, etc.

Software

Bill of Materials

  • I don't think it will be practical to try and conduct a lab for this unit with anything but software.
  • So far all the software that we've found is open-source and free.

Evaluation

CRS Questions

  • Look at the graph on Lynx - Hare as a Pred/Prey model. What type of oscillation does it show?
    • A. Chaos
    • B. Explosive
    • C. Dampening
    • D. Sustained
  • What is a good example of a reinforcing loop?
    • A. Uncontrolled fishing in a lake
    • B. Spilling wine on a carpet
    • C. A Stock Market crash
    • D. Parents buying a child toys

Quiz Questions

<Predator Prey> Metadata

This section contains information about the goals of the unit and the approaches taken to meet them.

Scheduling

A note about early, late or doesn't matter, dependencies.

Concepts and Techniques

This is a placeholder for a list of items from the context page.

General Education Alignment

  • Analytical Reasoning Requirement
    • Abstract Reasoning - From the [Catalog Description] Courses qualifying for credit in Abstract Reasoning typically share these characteristics:
      • They focus substantially on properties of classes of abstract models and operations that apply to them.
        • Analysis of this unit's support or not for this item.
      • They provide experience in generalizing from specific instances to appropriate classes of abstract models.
        • Analysis of this unit's support or not for this item.
      • They provide experience in solving concrete problems by a process of abstraction and manipulation at the abstract level. Typically this experience is provided by word problems which require students to formalize real-world problems in abstract terms, to solve them with techniques that apply at that abstract level, and to convert the solutions back into concrete results.
        • Analysis of this unit's support or not for this item.
    • Quantitative Reasoning - From the [Catalog Description] General Education courses in Quantitative Reasoning foster students' abilities to generate, interpret and evaluate quantitative information. In particular, Quantitative Reasoning courses help students develop abilities in such areas as:
      • Using and interpreting formulas, graphs and tables.
        • Analysis of this unit's support or not for this item.
      • Representing mathematical ideas symbolically, graphically, numerically and verbally.
        • Analysis of this unit's support or not for this item.
      • Using mathematical and statistical ideas to solve problems in a variety of contexts.
        • Analysis of this unit's support or not for this item.
      • Using simple models such as linear dependence, exponential growth or decay, or normal distribution.
        • Analysis of this unit's support or not for this item.
      • Understanding basic statistical ideas such as averages, variability and probability.
        • Analysis of this unit's support or not for this item.
      • Making estimates and checking the reasonableness of answers.
        • Analysis of this unit's support or not for this item.
      • Recognizing the limitations of mathematical and statistical methods.
        • Analysis of this unit's support or not for this item.
  • Scientific Inquiry Requirement - From the [Catalog Description] Scientific inquiry:
    • Develops students' understanding of the natural world.
      • Analysis of this unit's support or not for this item.
    • Strengthens students' knowledge of the scientific way of knowing — the use of systematic observation and experimentation to develop theories and test hypotheses.
      • Analysis of this unit's support or not for this item.
    • Emphasizes and provides first-hand experience with both theoretical analysis and the collection of empirical data.
      • Analysis of this unit's support or not for this item.

Scaffolded Learning

Some prose.

Inquiry Based Learning

Some prose.

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