Which of the following is an example of a positive feedback loop?

• A. Predation pressure and resource depletion
• B. Temperature changes guiding migration
• C. Breastfeeding and oxytocin
• D. Mutualism between species.

Answer: (D)

A positive feedback loop is a process where an initial change is amplified by the system, creating a self-reinforcing cycle. In mutualism between species, each partner benefits from the other, so when one species becomes more successful, it helps boost the success of its partner, and that improvement feeds back to further enhance the first species. Over time, this reciprocal boost can lead to greater abundance or activity of both, reinforcing the interaction. A clear example is a plant–pollinator relationship: more flowers attract more pollinators, which increases plant reproduction and leads to even more flowers, attracting even more pollinators. This accelerating, self-amplifying dynamic matches a positive feedback pattern. The other options do not form such reciprocal, self-reinforcing loops: predation pressure and resource depletion tend to regulate populations toward balance; temperature-driven migration is a response to environmental cues rather than a self-amplifying interaction; and while lactation involves a positive feedback mechanism within a single organism, it doesn’t illustrate a reinforcing cycle between two species.