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  • Systems and Feedback Loops

    The Big Picture • The study of Earth has been divided in to tiny pieces.

    Makes it easier to better understand

    that piece!

    • It’s important to remember that we have to not just understand how the parts work but also how they interact and connect.

    Defining a System • To simplify our studies of such a complex place such as

    Earth, scientists use the concept of a system. • A system is a portion of the universe that can be separated for

    the purpose of observing changes that happen in it.

    • By defining a system, we get a sense of how the system works internally and how it interacts with its surroundings.


    Types of Systems • Scientists categorized systems as Open or Closed based

    whether or not matter or energy can enter or leave the system.

    Energy Open! Matter Open!

    Energy Closed! Matter Closed!

    Energy Open! Matter Closed!

  • Why is this important in APES? • The balance of energy in

    an open system is important when predicting global warming and its associated climate change.

    • Things to remember when dealing with a closed matter system: • There is a finite amount of resources. • Our system provides us with our resources and

    accepts our wastes. • All parts of the systems are connected.

    System Analysis • When you analyze a system, you must know its inputs,

    outputs, and changes.

    Inputs Outputs

    Inputs Outputs

    Water Food

    Oxygen Sunlight

    Manure Methane

    Water CO2

    Water Sunlight Nutrients


    Oxygen Sugar Water

    Steady State • When you conduct a system analysis, one of the goals is to

    determine whether or not you are in a steady state situation.

    Rate of Inputs = Rate of Outputs

    • Monitoring the inputs and outputs of a system can indicate if there is a deviation from steady state. • Example is our growing concern

    that water balance in the ocean and atmosphere will be affected by global climate change.

    Feedback Systems • When the output acts as an input to the system, you have

    what is known as a feedback loop.

    Negative Feedback - System changes to minimize change and bring things back to steady state.

    Positive Feedback - System changes to enhance the change.

    Positive Amplifies Negative Resists

  • Which Is It?

    Negative Feedback Positive Feedback

    Let’s Vote!

    Feedback Loop 1 Positive Negative

    Feedback Loop 2

    Feedback Loop 3

    Feedback Loop 4

    Feedback Loop 5

    Feedback Loop 6


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