Final answer:
Positive feedback loops in biological systems amplify responses until an endpoint is reached, such as a fibrin clot in blood clotting or childbirth following oxytocin-induced uterine contractions.
Step-by-step explanation:
The question Do positive feedback loops ever stop the cycle? can be answered as follows: Positive feedback loops generally continue to amplify the biological response until a specific endpoint is reached. For instance, during blood clotting, once a clotting factor is activated in the cascade, it will activate the next factor and so on, until a stable fibrin clot forms. Additionally, in the case of childbirth, the hormone oxytocin is produced to intensify uterine contractions until delivery is achieved. Therefore, the answer would be (a) Yes, implying that positive feedback loops will stop, but only once their goal, which is usually a significant physiological event, has been accomplished.