Although organisms obey the same physical laws as inanimate objects the evolutionary implications of these laws are often neglected. Physical factors influence the fitness value of traits and play an important role in the course of evolution. These are the areas of investigation that interest us.
When I was a teenager, I liked riding my bike along the river boardwalk near my house. There were fields there, like those in the image above and video below, with tall grass that would bend and sway in the wind. The long stalks undulated almost like a fluid, and they were mesmerizing. This video gives you a higher vantage point, where you can see the larger patterns of motion. What you’re seeing, I think, are some of the large-scale turbulent variations in the wind. Rather than being uniform and laminar, the wind contains pockets of turbulent gusts, which the sway of the long grass reveals to the naked eye. In terms of physical mechanism, I suspect it’s similar to how wind imprints its patterns on water. (Video and image credit: N. Moore)