76 



ANALYSIS OF THE ENVIRONMENT 



above zeic These conditions are furnished 

 by the earth, which rotates on an axis while 

 revolving about an energy-shedding sun. 



In general terms, the earth is a dense, 

 crusted body of sufficient size to have 

 strong enough gravitational attraction to 

 hold an extensive gaseous atmosphere, but 

 not strong enough to hold more than a 

 trace of tree hydrogen. The presence of 

 water and carbon dioxide in the atmosphere 

 seems to be a normal result of the physical 

 and chemical properties of water and car- 

 bon dioxide that have much to do with 

 regulating the general environment of hving 

 things on the earth. There is good reason to 

 beUeve that "water is the substance whose 

 movement in the organic and in the inor- 

 ganic world constitutes the first, the most 

 fundamentally important activity in the 

 world that we five in" (Henderson, 1922). 



Water has a number of remarkable quah- 

 ties that make it an important factor in the 

 environment of hving things as well as the 

 major ingredient of Hving protoplasm. It is 

 a stable chemical compound that passes 

 readily through soUd, Hquid, and gaseous 

 states at what we call ordinary tempera- 

 tures. The thermal properties of water, 

 added to its abundance and wide distribu- 

 tion, make it an important temperature 

 regulator. Its great power as a solvent, espe- 

 cially of electrolytes, and its inertness, 

 which allows many chemicals to pass into 

 and out of solution readily and without 

 change, make it an important bearer of 

 chemical suppfies. The property of expan- 

 sion before freezing has important effects 

 upon fife in bodies of water that freeze 

 over. The high surface tension of water, 

 among other things, accounts for the rise 

 of soil water through capillary attraction, 

 and is important in adsorption, which, with 

 other properties of water, makes it of high 

 value in the formation of colloids. There 

 is also a relatively high order of trans- 

 parency, mobihty, and incompressibihty. In 

 a different field, water has a markedly high 

 dielectric constant and great ionizing power, 

 Water furnishes the basic environmental 

 division into aquatic and terrestrial habitats. 



Another compound that, with water, is 

 of greatest importance in fife processes is 

 carbon dioxide. The environment-control- 

 ling properties of carbon dioxide are less 

 important than those of water. Carbon 

 dioxide enters and leaves water freely; at 

 ordinary temperatures its absorption coeffi- 



cient approaches unity; hence carbon 

 dioxide can never be wholly washed from 

 air into water or taken from water into the 

 air. In water, carbon dioxide forms a weak 

 acid that adds to the solvent power of 

 water, and since the acid is dibasic, it has 

 marked power as a chemical buffer and so 

 helps maintain a near neutraUty in the 

 acid-base relations of the environment. 



Since carbon dioxide is present as a gas 

 in the atmosphere and in solution in water, 

 and since it can readily be extracted from 

 both sources and also readily enters into 

 chemical combinations, it forms an impor- 

 tant nutrient for plants. Under the synthe- 

 siidng processes, particularly those of photo- 

 synthesis, carbon becomes the center of a 

 whole class of chemical compounds that are 

 so important chemically that they make up 

 the content of a distinct phase of chemistry, 

 so-called organic chemistry, which consists 

 of the chemistry of the carbon compounds. 

 Carbon has the remarkable abihty of com- 

 bining with itself to form the basis of 

 complex molecules which, when combined 

 particularly with hydrogen, oxygen, nitro- 

 gen, phosphorous, and calcium, to mention 

 those that, respectively, compose 1 per cent 

 or more of the organism (Fearon, 1933), 

 make a pecuHarly fit system of chemical 

 compounds for use by living organisms as 

 sources of matter and energy for the proc- 

 esses of metabohsm. 



We are accustomed to the idea that or- 

 ganisms show adaptations of fitnesses to the 

 environment in which they five, and also to 

 the more general view that, everything con- 

 sidered, hfe in the large is well adapted to 

 its generahzed environment. Despite the 

 fact that the idea is no longer new, many 

 do not yet appreciate the basic ecological 

 principle that, given matter and energy 

 and the resulting probabihty that hfe when 

 and where it develops will be a mechanism 

 (a complex mechanism, to be sure), the 

 surface of a sohd body such as the earth- 

 placed as it is in relation to a central 

 energy-giving sun— does actually provide an 

 excellent general environment for the hving 

 organism as we know it. It is possible for 

 the biochemist Henderson (1913, p. 273) 

 to maintain without successful contradic- 

 tion to date that this is actually "the best 

 of all possible environments for hfe." 



Certainly the fitness of the organisms, 

 which, as the idea of adaptation, Claude 

 Bernard urged should be the basal prin- 



