Final answer:
Ripening apples release ethylene gas, signaling nearby apples to ripen, an example of positive feedback which amplifies processes, leading to exponential outcomes.
Step-by-step explanation:
When an apple ripens, it releases ethylene gas, which acts on surrounding apples, signaling them to ripen as well. This chain reaction, where one apple's ripening induces others to ripen, demonstrates a positive feedback mechanism.
Unlike negative feedback, which works to restore a system to equilibrium, positive feedback amplifies a process and leads to exponential growth or increasingly extreme conditions, as seen with ethylene and fruit ripening.
For instance, if you place a ripe banana with an unripe fruit in a closed container, the ripe banana will release ethylene, speeding up the ripening process of the other fruit.
The aging tissues and nodes of stems in plants generate ethylene, promoting not just fruit ripening but also other processes like flower wilting, leaf fall, and even the sprouting of bulbs and potatoes.
Positive feedback in biological systems is less common than negative feedback. However, in the case of ethylene and fruit ripening, the more fruit that ripens, the more ethylene gas is produced, thus causing more fruit to ripen - a classic case of positive feedback in action.