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A system is in equilibrium when it is in balance and there is no net change. Equilibriums may be static with no change or movement or dynamic in which there is movement or change but these actions are equal and opposite.
An example of a dynamic equilibrium is a cell in an isotonic solution. The movement of water into the cell equals the movement of water out of the cell.
Many conditions, such as temperature and pH in an organism must be kept in an equilibrium in the body. This maintenance of a balance of these factors in the organism is called homeostasis. Different feedback loops serve as mechanisms to maintain the proper conditions in the organism.
Feedback is the process by which the output of a system causes further influence on the system.
A positive feedback loop occurs when the output leads to an increase in the output from the system.
For example, compounding interest in a bank account is an example of positive feedback, because the interest accrued adds to the amount of money in the bank which then results in more interest earned.
Be careful not to confuse the positive label with meaning that the feedback is necessarily beneficial or good. It would also be positive feedback if interest on an unpaid debt resulted in the exponential growth of a debt.
Debt
Interest
Charged

A negative feedback loop occurs when the output of a system diminishes further output of the system.
Negative feedback loops can stabilize a system. For example, a thermostat in a house exhibits negative feedback when the heat produced by the furnace causes the thermostat to shut off the furnace when the desired temperature is reached, preventing a further temperature increase.
1. Define equilibrium.
2. Compare and contrast static equilibrium with dynamic equilibrium.
3. Define homeostasis.
4. Explain the difference between positive and negative feedback loops
For questions 5- 8 identify each example as a positive or negative feedback loop and explain why.
Explanation Description of system
5 Increased births in a deer population result in a larger population size, which causes a further increase in the birth rate.
Type of Feedback
(+ or -)
6 Increased births in a deer population results in overgrazing which causes the death of many deer due to starvation.
7 A higher body temperature causes a response which includes the dilating (widening) of the blood vessel at the surface of the skin, which allows heat to be transferred out of the organism.
8 Increased temperature on earth leads to melting ice, which exposes darker surfaces that absorb more heat, leading to even higher temperatures.