entomology - Aquatic Invertebrates (Biology) Pre-Lesson One...

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Aquatic Invertebrates (Biology) Pre-Lesson One River Continuum Concept Student Outcomes: Students will: Understand the properties of a natural system Break down a river system into its primary components Discuss the importance of feedback loops and dynamic equilibrium Purpose: To develop the concept of systems as a way to analyze and understand the form, function, and interconnectedness of nature. To examine a river as a system balanced by interactions among its main components Materials/Resources: White boards and dry-erase markers Background information: Our planet consists of many complex, large-scale, interacting systems. A system is a network of relationships among a group of parts, elements, or components that interact with and influence one another through the exchange of energy , matter , and/or information . A system receives input (energy, matter, info), processes or interact with this input and responds with an output . This exchange drives a feedback loop , or circular process whereby a system’s output serves as input to that same system. The components in a system interact with each other within feedback loops. In a negative feedback loop , the output acts as an input that moves the system in the opposite direction. This compensation stabilizes the system. For example, when your brain processes an input that you are too warm, its output is too get cooler by removing a jacket or turning on the air conditioner. As you get cooler, you brain processes this new input and outputs a response to turn off the air conditioner. As a result of this opposite input vs. output, or negative feedback loop, your body system stays at a stable temperature. This alternating give-and-take cycle, or dynamic equilibrium , functions to keep a system within a healthy range. Processes in the system move in opposite directions at equivalent rates so their effects balance out. The progression of dynamic equilibrium acts to stabilize a system when it is disturbed by external forces. In a positive feedback loop , the output acts as an input that moves the system further in the same direction as the initial input. This magnification of effects destabilizes the system. For example, a desert environment can act as a system. The system’s components in this case are the living organisms. If there are no predators in this desert, such as coyotes and mountain lions, then jackrabbits can reproduce and there
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is no stopping their increase in population. The input to the desert system is more jackrabbits. Each new generation of jackrabbits can then reproduce again, increasing the overall population because the desert system void of predators responds to the new generation by allowing even more jackrabbits to survive. As a result, the number of jackrabbits will increase until another component of the desert system breaks down, such as rabbit food sources, preventing other animals to eat and survive, at which time the desert system is destabilized. The predator component had been altered in this desert
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This note was uploaded on 12/01/2009 for the course BIO BIO130 taught by Professor Goralka during the Spring '09 term at Diablo Valley College.

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entomology - Aquatic Invertebrates (Biology) Pre-Lesson One...

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