Submitted by williamj35 t3_11pmmov in askscience
When I see a video like this one of a white blood cell chasing a bacterium that is evading capture, I make an assumption that both of these organisms are *behaving* by which I mean they are doing something beyond simply reacting to the chemestry or physics of their environment.
To clarify: A dead leaf skitters across the ground when the wind blows, but that is not behavior, just a reaction of a physical body to the force of the wind. Are the white blood cell and the bacterium doing more than that? Is there some internal operation that adds something to their response to their chemical and physical environment?
To clarify further: Humans percieve their environment and then react in complex ways to it that are determined by a central nervous system. The single-celled organisms don't have such a system (right?), but do they have something more than a dead leaf has, which helps to determine their response to their environment?
What, if anything, drives the "behavior" of these organisms? What do we call it? And how does it work?