Everything is Connected
In science, we often want to study a specific part of the universe, whether it's a single cell, a forest, or a planet. To do this, we define a system. A system is a set of interacting or interdependent components that form an integrated whole. Everything outside the system is called the surroundings.
Types of Systems
We can classify systems based on how they interact with their surroundings.
1.Open System: An open system can exchange both energy and matter with its surroundings.
Example: A pot of boiling water on a stove without a lid. It is releasing heat (energy) and steam (matter) into the room. A living organism, like you, is an open system. You take in food (matter) and release heat (energy).
2.Closed System: A closed system can exchange energy but not matter with its surroundings.
Example: A sealed bottle of water. You can heat it up or cool it down (exchange energy), but no water can get in or out (no exchange of matter). The Earth as a whole is approximately a closed system (it receives energy from the sun, but very little matter enters or leaves).
3.Isolated System: An isolated system cannot exchange either energy or matter with its surroundings.
Example: A perfectly sealed and insulated thermos is a good approximation of an isolated system. In reality, a truly isolated system is a theoretical concept and very difficult to create.
Feedback Loops: The Engine of Change
Systems are not static; they are dynamic and constantly changing. These changes are often controlled by feedback loops. A feedback loop occurs when the output of a system is fed back into the system as an input, influencing the system's behavior.
Negative Feedback Loop: This is a stabilizing loop. The output of the system acts to oppose or reduce the initial change, keeping the system in a state of balance or equilibrium. Most biological and environmental systems are dominated by negative feedback.
Example: A home thermostat. If the temperature gets too hot (the initial change), the thermostat (the system) turns on the air conditioning (the output). The A/C cools the room, which opposes the initial change, bringing the temperature back down.
Example: Your body's regulation of blood sugar.
Positive Feedback Loop: This is an amplifying or runaway loop. The output of the system acts to increase or reinforce the initial change, pushing the system further and further away from its starting point.
Example: The ripening of fruit. A ripening apple releases a gas called ethylene. This ethylene gas causes nearby apples to ripen faster. Those apples then release more ethylene, which causes more apples to ripen, and so on. This creates a rapid, cascading effect.
Example: A microphone placed too close to a speaker, causing a loud, screeching sound that gets louder and louder.