Building systems closely resemble a variety of biological systems. The first one that came to mind for me was how similar buildings are to trees (maybe because one is an important resource for the other). The most obvious comparison is a building’s structural foundation to the roots of a tree. Building foundations, esepcially for large structures, are typically dug into the ground to provide support just as roots reach deep into the ground. Additionally, some buildings and all trees use sunlight as a source for energy. In this way the leaves of tree can resemble PV systems on the roof of a building.