Adrian Bejan | Vegetation and Hair, from Design in Nature
The video turns to vegetation and hair, asking what flows in a tree, why plants come before animals, and why the drawing of trees in a forest looks so much like the drawing of hair and fur on the skin of animals. The main answer is that water flows from the ground into the dry wind through root, trunk, canopy, corona and forest, while stresses from the wind on the crown flow down into the ground, so vegetation transfers from high to low, from plenty to very little, and later hair and fur appear on animals to slow the flow of heat from skin to dry air by trapping a blanket of air between strands, which shows that the same kind of drawing can either facilitate flow or prevent it, depending on purpose.
The picture of the tree shows a root deep in the soil, a trunk rising, branches gathered in a canopy or corona like a crown, and the forest as a whole, so that water can reach the dry wind while stresses from the wind on the crown can reach the ground.
The first question is what flows in a tree, and the answer is water. So trees are where water is plentiful, and trees are absent in the desert. At the same time, a bundle of stresses from the wind flows down the trunk into the ground.
Vegetation happens before the rest of the biosphere, before the animate, so that later the moving animal, the tree walker, has greater access to the stationary tree, whose canopy gives access to water and access to wind at a height that a small plant does not reach.
In profile, the same kind of drawing appears again on animals, where hair and fur on the skin meet the dry air, and hair is there for the purpose of preventing the flow of heat from skin to dry air by trapping air between strands.
The forest drawing shows that trees do not like neighbors and never touch; each tree wants access to dry air all by itself, while hair on skin is dense and close so that air between filaments is slowed down and kept as an insulation blanket from which the living animal benefits.