CHAPTER XX 

 SOME BIOLOGICAL RELATIONS OF GREEN PLANTS 



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In the previous chapters many facts about the dependence of animals 

 and non-green plants upon green plants became evident from time to 

 time. A consideration of several of these facts in one chapter will help 

 us obtain a better perspective of their interrelations. Perhaps this can 

 best be done by reference to two concrete examples. For one example 

 we may choose the so-called balanced aquarium or microcosm; for the 

 other we may consider man on some populated island, or in some specific 

 country such as the United States. 



To understand these examples we must be able to recall and relate 

 the facts about the following processes: 



The manner in which food is obtained by plants and animals. 



The making of sugar by photosynthesis in green plants. 



The synthesis of proteins, especially the synthesis of amino acids. 



The synthesis of vitamins in plants. 



The assimilation of food to cell constituents in both plants and animals. 



The oxidation of foods in respiration in both plants and animals. 



The transformations of energy in foods and products of assimilation. 



The loss of material and energy when plants are not eaten directly 



bv man. 

 The ways in which man obtains and transforms energy. 

 The transformation of energy-containing materials to peat, coal, and 



gas. 



A microcosm. To set up a microcosm all that is necessary is to obtain 

 a 3- to 5-gallon bottle; fill it about one-fourth full of pond water; add a 

 few ounces of soil, a goldfish, and a quantity of algae that are edible by 

 fish; seal the bottle air-tight and set it in a well-lighted part of the room, 

 but not in bright sunlight and not where its temperature will often 

 exceed 70° F. The fish and algae will then continue to live and grow in 

 the bottle for months or even years (Fig. 65). 



With the pond water and soil we incidentally place numerous bac- 



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