In Brief 



Water, air, and a suitable temperature are essential conditions for the 

 germination of seeds. * 



The chemical changes that are continuously going on in living proto- 

 plasm can take place only when it is in a fluid state. 



The energy of protoplasm is derived from the oxidation of food mate- 

 rials within living cells. 



Using oxygen and liberating heat are characteristic of nearly all living 

 things. 



Living cells continually exchange materials with the fluid medium 

 which surrounds them, by osmosis, or the diffusion of fluid substances 

 through a membrane. 



In larger organisms dissolved substances reach the living cells through 

 the medium of water. 



Water filling the cells and tissues of plants stretches the outer mem- 

 branes and furnishes mechanical support. 



Organisms exposed to drying conditions often have protective coverings 

 which prevent desiccation. 



The shedding of leaves may be considered an adjustment to seasonal 

 variation in water supply. 



Living things show many adaptations to the extreme variations in the 

 moisture, light and heat of their environment. 



EXPLORATIONS AND PROJECTS 



1 To find whether carbon dioxide is discharged when ordinary fuel burns, 

 collect gases, given off by the flame of a lighted match or a candle, by holding over 

 the flame an inverted clean and dry widemouthed bottle. Test the contents of the 

 bottle for carbon dioxide and also the air in a similar bottle that has not been held 

 over a flame/ Compare the reactions in the two cases and draw conclusions. 



Incidentally, this procedure has also furnished information on the liberation 

 of water during oxidation; for, starting with a dry vessel, we could see moisture 

 condensed inside the bottle held above the flame. This can be checked by holding 

 a similar bottle over a match or candle, not lighted, under the same conditions. 



2 To see in what ways the oxidation of ordinary food substances is like that 

 of common fuel, heat some sugar, starch, bread, butter, olive oil, lard, or other 

 food material in an evaporating dish until it bursts into flame; remove the burner. 

 In each case, ascertain whether water and carbon dioxide are discharged. In what 



^A common test for carbon dioxide is a solution of slaked lime, "limewater", which turns 

 milky when carbon dioxide comes in contact with it. In this experiment pour a little lime- 

 water into the jar and shake up to mix with the air. 



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