Environmental Science / Unit 1: Introduction to Environmental Science
1.2 Systems and Feedback Loops
Notes
A system is a set of parts that interact to form a whole. Earth has four major spheres: the atmosphere (air), hydrosphere (water), geosphere (rock and soil), and biosphere (life).
- Inputs enter a system and outputs leave it. A closed system exchanges energy but not matter with its surroundings. An open system exchanges both. Earth is essentially closed for matter and open for energy.
- A negative feedback loop counteracts change and keeps a system stable (a thermostat).
- A positive feedback loop amplifies change and pushes a system further in the same direction.
- Example of positive feedback: warming melts Arctic ice, dark ocean absorbs more sunlight, and warming increases.
Practice
Which Earth sphere includes all rocks, minerals, and soil?
The geosphere is the solid Earth.
A thermostat turns the heater off when a room gets warm enough. This is an example of:
It counteracts change and keeps temperature stable.
As Arctic sea ice melts, darker ocean water absorbs more sunlight, which causes more warming and more melting. This is:
Positive feedback pushes the system further in the same direction.
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