CHAPTER 4: Introduction to Systems Theory


Summary of the Lecture Topic

Scientists use systems theory to understand how things work. Systems theory suggests that you model natural and human-made phenomena as a set of interrelated components that work together to accomplish some kind of process. Systems are used by humans in every day life to describe the operation of a number of diverse phenomena. Systems or models are also generalizations of reality. One common way to present how things work is with a graphical model. In this lecture, a graphical model of how scientific understanding operates is presented as an example of a system.

Systems tend to have similarities in the way they work. Within their defined boundaries systems contain three types of properties: elements, attributes, and relationships. Elements are the things that make up the system of interest. Attributes are the perceived characteristics of the elements. Relationships are descriptions of how the various elements (and their attributes) work together to carry out some kind of process. Systems also have the same common characteristics. Seven characteristics are described.

Scientists have classified a number of different system types. These types include: isolated systems, closed systems, open systems, morphological systems, cascading systems, process-response systems, control systems, and ecosystems. The nature of each of these types of systems is defined.

We often think about systems in an isolated fashion. However, most systems have hierarchical connections and structure. These connections can be to structures that exist at smaller or larger scales. It is very important to recognize that systems generally do not exist in isolation.

An environmental system can be defined as a system where life interacts with abiotic factors. All environmental systems involve the capture, movement, storage, and use of energy. This fact also makes them energy systems. Energy is captured in the living components of environmental systems by processes like photosynthesis, biomass consumption, and biotic decomposition. Energy is also used in environmental processes that are strictly abiotic. For example, solar energy is responsible for wind, weathering, and precipitation.

Equilibrium can be defined as the average state of a system as measured through one of its attributes or elements. Scientists have defined six different types of equilibrium. Most systems maintain a steady state equilibrium through the operation of positive and negative feedback mechanisms. Negative-feedback mechanisms control the state of the system by dampening or reducing the size of the system's elements or attributes. Positive-feedback mechanisms feed or increase the size of one or more of the system's elements or attributes over time. This section concludes by showing how negative and positive feedbacks work to cause fluctuations in the population size of aphids.


List of Key Terms

Abiotic, Assimilation,

Big Bang,

Carnivores, Cascading System, Cell, Closed System, Community, Control System,

Disturbance, Dynamic Equilibrium,

Ecosystem, Element, Energy, Entropy, Environmental System,

Fermentation, Fixed, Food Chain,


Isolated System,

Metabolism, Model, Morphological System,

Negative Feedback,

Open System, Organ,

Photosynthesis, Positive Feedback, Process-Response System,


Self-Regulation, Solar System, Stable Equilibrium, Starch, Static Equilibrium, Steady State, Steady State Equilibrium, System, System Attribute, System Boundary, System Element, System Relationship, System State,

Theory, Thermodynamic Equilibrium, Thermodynamic Laws, Trophic Levels,

Universe, Unstable Equilibrium


Study Questions, Problems and Exercises

Essay Questions

(1). What is a system? How do we use them in the process of understanding?

(2). Describe the differences that exist between morphological, cascading, and process-response systems.

(3). Why does science attempt to understand systems at the process-response level?

(4). Define the three kinds of properties (elements, attributes and relationships) of systems using an ecological food chain as an example.

(5). What is an equilibrium? Describe some of the different types of equilibrium that exist in nature.

(6). Explain how do feedback mechanisms regulate natural systems?







Created by Dr. Michael Pidwirny & Scott Jones University of British Columbia Okanagan

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Copyright © 1999-2009 Michael Pidwirny

05/25/2009 9:51