  Recent advances in nonequilibrium statistical physics have provided
unprecedented insight into the thermodynamics of dynamic processes. The author
recently used these advances to extend Landauer's semi-formal reasoning
concerning the thermodynamics of bit erasure, to derive the minimal free energy
required to implement an arbitrary computation. Here, I extend this analysis,
deriving the minimal free energy required by an organism to run a given
(stochastic) map $\pi$ from its sensor inputs to its actuator outputs. I use
this result to calculate the input-output map $\pi$ of an organism that
optimally trades off the free energy needed to run $\pi$ with the phenotypic
fitness that results from implementing $\pi$. I end with a general discussion
of the limits imposed on the rate of the terrestrial biosphere's information
processing by the flux of sunlight on the Earth.
