632 General and Applied Biology 



are associated with them. By eliminating large groups of organisms ol 

 certain types, the entire floral and faunal relationship of that area may 

 be affected, and thus indirectly the ecology of many forms of life may 

 be influenced. The elimination of one individual from a particular area 

 may not have a great effect, but the wholesale removal of all members 

 of a particular species may have far-reaching effects. In other words, 

 there must be a reorganization of that area in order that life may con- 

 tinue efficiently and harmoniously. 



Terrestrial and aquatic plants require water of a certain quantity 

 and quality for their particular needs. Aquatic plants usually require 

 much more than the average terrestrial type. The plants which grow 

 in arid areas require much less moisture. It can be easily seen that an 

 exchange of these various types of plants, as far as this type of environ- 

 mental factor is concerned, mav have detrimental results. Within cer- 

 tain limits the water conditions may be varied for a particular plant, 

 but beyond that the plant will refuse to develop. 



(c) Oxygen, Carbon Dioxide, and Obnoxious Gases: All living or- 

 ganisms require oxygen of a certain quantity. If this amount is insuffi- 

 cient for a certain animal, it may become extinct, or, if possible, may 

 locomote to an area in which the oxygen supply is satisfactory. Oxygen 

 is necessary for the oxidation of foods, and thus a sufficient quantity in 

 an environment is an important factor in animal ecology. Carbon 

 dioxide, if present in large quantities, is not conducive to animal life. 

 The excess of this gas may be instrumental in the distribution of many 

 types of animals, both terrestrial and aquatic. Obnoxious gases, either 

 naturally or artificially produced, may result in a redistribution of or- 

 ganisms in that particular area. In fact, certain such gases are pro- 

 duced artificially to combat many undesirable animal types, such as 

 insects, rats, moles, and gophers. 



All green plants require a certain quantity of carbon dioxide to meet 

 their needs for the process of photosynthesis. If the supply is insuffi- 

 cient, this very essential process cannot take place. If the oxygen supply 

 is limited, a plant may be unable to oxidize its protoplasmic substances 

 properly and thus be unable to liberate a sufficient amount of necessary 

 energy to supply its particular demands. Obnoxious gases of various 

 types may interfere with respiration, transpiration, and photosynthesis 

 and thus indirectly be a very important factor in the ecology of the 

 plants involved. Plants which do not possess chlorophyll (bacteria, 

 mushrooms, etc.) quite naturally would require an entirely different 

 atmosphere and consequently would be distributed accordingly. 



