2-5 What Are Systems and How Do They Respond to Change? Concept 2-5 Systems have inputs, flows, and outputs of matter and energy, and feedback can affect their behavior.

Systems Have Inputs, Flows, and Outputs interact A System is set of components that _________________ in a regular way Examples: Human body, a river, the economy, the planet Most systems have the following key components… ________________ from the environment Flows or _________________ of matter and energy ___________________ to the environment Inputs throughputs Outputs

Inputs, Throughput, and Outputs of an Economic System Aluminum ore Mining & Manufacturing Aluminum can Figure 2.17: This diagram illustrates a greatly simplified model of a system. Most systems depend on inputs of matter and energy resources, and outputs of wastes, pollutants, and heat to the environment. A system can become unsustainable if the throughputs of matter and energy resources exceed the abilities of the system’s environment to provide the required resource inputs and to absorb or dilute the resulting wastes, pollutants, and heat. Fig. 2-17, p. 48

Systems Respond to Change through Feedback Loops Most systems are affected in one way or another by ________________...any process that increases or decreases a change to a system Positive feedback loop Causes system to change further in the ______________ direction Can cause major environmental problems Negative, or corrective, feedback loop Causes system to change in the _______________ direction feedback same opposite

Positive Feedback Loop Core Case Study Decreasing Vegetation erosion & Nutrient loss Figure 2.18: This diagram represents a positive feedback loop. Decreasing vegetation in a valley causes increasing erosion and nutrient losses that in turn cause more vegetation to die, resulting in more erosion and nutrient losses. Question: Can you think of another positive feedback loop in nature? more decreasing vegetation Fig. 2-18, p. 49

Negative Feedback Loop Figure 2.19: This diagram illustrates a negative feedback loop. When a house being heated by a furnace gets to a certain temperature, its thermostat is set to turn off the furnace, and the house begins to cool instead of continuing to get warmer. When the house temperature drops below the set point, this information is fed back to turn the furnace on until the desired temperature is reached again. Fig. 2-19, p. 50

Environmental Example of Negative Feedback Recycling Aluminum Cans! Aluminum ore must be ____________ and then manufactured for use…likely causing environmental ______________ Recycling our current supply of aluminum will… ______________ the need for ______________, manufacturing, ______________ and ______________ associated with the product mined degradation Reduce mining pollution waste

Time Delays Can Allow a System to Reach a Tipping Point A complex system will often show a ________ __________ or lack of response between the input of a feedback ________________ and the response to it Time delays can allow an environmental problem to build slowly until it reaches a tipping point or ________________ level Melting of polar ice Population growth Depletion of fish populations due to overfishing time delay stimulus threshold

System Effects Can Be Amplified through Synergy A synergistic interaction, also called ________________ occurs when… Two or more processes combine in such a way that combined effect is _______________ than the two ________________ effects Helpful Studying with a partner Harmful E.g., Smoking and inhaling asbestos particles…increased risk of lung cancer is fivefold synergy greater separate

Three Big Ideas of This Chapter There is ______________…we cannot do away with matter 2. You ___________________get something for nothing…during energy changes we cannot get more energy than we put in You ___________________________…we always end up with lower-quality energy during a transfer These laws place limits on what we can do with matter and energy resources no away Law of Conservation of Matter cannot 1st law of thermodynamics cannot break even 2nd law of thermodynamics

Review Questions What are the three key components of most systems? What is the difference between a positive and negative feedback loop? What is another term for synergistic interaction? inputs throughputs outputs positive – change continues in the same direction negative – change moves in the opposite direction synergy