What system allows only energy to pass in and out, but not matter?

A closed system is characterized by the ability to exchange energy with its surroundings while preventing the transfer of matter. This means that within a closed system, energy can enter or leave, but no physical substances can cross the boundaries of the system. This property is vital for understanding various biological and ecological processes, where energy input (such as sunlight for photosynthesis) can influence system dynamics without the introduction or loss of material.

In contrast, an open system allows both energy and matter to exchange with the surroundings, while an isolated system does not exchange either energy or matter. A dynamic system refers generally to systems that undergo change over time, which could include both energy and matter transfers. Understanding these distinctions is crucial in the study of biological systems and their interactions with the environment.