Before revision:  Here, the robustness means that the GRNs do not lose their functions when exposed to mutation or noises. Both the adaptive response and the robustness have been acquired through the evolution.
After revision:  Here, the robustness means that the GRNs do not lose their functions when exposed to disturbances such as mutations or noise, and is widely observed at many levels in living systems. Both function and robustness have been acquired through the evolution.