Last lesson you finished the environmental movement, looking at the events and agreements that shaped it. This lesson starts a new sub-unit and a new tool. Almost everything you study for the rest of this course, from a pond to the whole planet, will be described as a system. By the end of this lesson you should be able to say what a system is, draw one as a diagram, and tell the difference between a transfer and a transformation.
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Start here. I am not with you this lesson, so this page is your teacher. Work through it in order. Everything you need is on the page.
Every question has a Check your answer toggle underneath it. Write your answer first, then open the toggle.
If you get stuck, the answer is always in the section or the video directly above the question. Go back to it before you open the toggle.
If you finish early, go to the active recall flashcards and exam-style questions at the bottom of the page.
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[21 December 2011]
1. List everything you need in order to make a cup of tea. These are the inputs.
2. The cup of tea is the output. What else leaves the kitchen that you did not set out to make?
3. Write down the steps you take, in order. These are the processes.
[4 May 2020]
You cannot fully understand something unless you view it as a whole and see it interact with its environment.
1. What does reductionism say you have to do in order to understand something?
2. The video says that leaves on their own cannot make food through photosynthesis. Why not?
3. In one sentence, what does the systems approach do that reductionism does not?
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1.2.1 Systems are sets of interacting or interdependent components.
System components are organized to create a functional whole.
1.2.2 A systems approach is a holistic way of visualizing a complex set of interactions, and it can be applied to ecological or societal situations.
A system has storages and flows, with flows providing inputs and outputs of energy and matter.
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Societal example
Ecological example Source
A system is a set of parts that interact. Those parts are the system components. What makes it a system rather than a heap is that the components are organised to create a functional whole: change one and the others respond.
A systems approach is a way of looking at something that focuses on those interactions rather than on the parts in isolation. It works for ecological situations, such as a lake, and for societal ones, such as a school or a city.
Every system has storages, which hold energy or matter, and flows, which move it. A flow that brings energy or matter into the system is an input. A flow that takes it out is an output. The edge you draw around the system, separating it from its surroundings, is the system boundary. Where you draw that line is your choice, and moving it changes what counts as an input.
Take Lac Léman. Water arrives from the Rhône and from rain, and leaves through the Rhône at Geneva. Phosphate from farmland and from sewage works enters the water, phytoplankton take it up, fish eat the plankton, and dead material settles on the lake bed. No single one of those parts tells you how the lake behaves. The interactions between them do.
1. This is the colour key we will use for system diagrams all year. Learn it now, because it comes back in every unit.
2. Now complete the table below the columns, sorting every part of Lac Léman into the right place.
Sort these eleven parts of Lac Léman into the table. Each one belongs in exactly one column.