Which term describes the protective barriers created by certain plants against pests?

The term that best describes the protective barriers created by certain plants against pests is physical defenses. Physical defenses entail structural features of plants that deter herbivory or pest infestation. These can include thorns, spines, thickened leaves, or even a tough outer bark. Such features physically hinder pests from accessing the plant, making it an effective strategy to protect against damage.

Understanding physical defenses is important as they serve as a first line of defense in the plant's survival strategy. While chemical, behavioral, and biological defenses also play roles in pest management, they operate differently. Chemical defenses involve toxins or deterrents released by the plant, behavioral defenses relate to actions taken by the plant (or sometimes pests) to avoid predation, and biological defenses may include interactions with other organisms that provide protection. However, none of these accurately capture the physical obstacles that deter pests as described by the correct answer.