Information Concept in Ecology 147 



the lower end of the scale, quantum states, atoms, molecules, 

 membranes, cells and their ultrastructural components, tissues and 

 organs, to, at the upper end, individual organisms, species, popu- 

 lations, multi-specific evolutionary units (supraorganisms) (24) 

 and finally the community itself. The construction, maintenance 

 and operation of such barriers (with all the morphology and 

 physiology that this implies) are achieved by physical and chem- 

 ical processes which, in net, are endergonic. Without, therefore, 

 a continuous input of energy, the barricades would fail to function 

 and would ultimately be eroded away, with the result that com- 

 munity and environment would become one. 



This is a trivial conclusion, of course. After all, it is one of the most 

 obvious statements which could be made regarding bio-systems. 

 Yet its articulation seeins necessary to provide a basis for the follow- 

 ing restatement of the Schrodinger-Brillouin proposition: Energy 

 may be regarded as a universal currency with which organisms pur- 

 chase utility, as negative entropy, from the environment. 



COMMUNITY BIOENERGETICS 



In view of this proposition, the ultimate source of negativt 

 entropy to an ecological community may be regarded to be 

 photons. When a photon strikes an atom an electron is lifted from 

 ground state to a higher empty orbital (vertical arrow ^~ -^^* in 

 Fig. 2). For most molecules excited electrons usually drop back 

 to ground state immediately, dissipating the excess energy as 

 electromagnetic radiation (broken arrow, Fig. 2). Living systems 

 to paraphrase Szent-Gyorgi (25), have shoved themselves between 

 these two processes by shunting the excited electrons into different 

 downhill pathways in which their energy can be released slowly 

 and put to useful work. The first step in the process is excitation 

 (by photons, or indirectly via accessory plant pigments) of pi 

 electrons in the conjugated portion of chlorophyll a. In cyclic 

 photosynthetic phosphorylation (26) the chlorophyll provides these 

 electrons directly, thereby acting both as electron donor and 

 acceptor (Fig. 2). In noncyclic photophosphorylation the electrons 

 come from H2O, which the excitation energy decomposes to 

 oxygen, freed as O2, and H atoms. The hydrogen electrons sub- 



