GLOSSARY 447 



Extra-cellular digestion. Digestion that occurs outside of cells or tis- 

 sues. 



Facultative anaerobe. An organism that may under certain conditions 

 live in the absence of atmospheric oxygen and under other condi- 

 tions live normally in its presence. 



Fat. An organic substance derived from either plant or animal metabo- 

 lism, made up chiefly of esters and often having the formula: 

 C3H5(C02CqHjj)3. Not to be confused with mineral oils which are 

 mixtures of hydro-carbons. 



Fauna. The animal life of an area. 



Fermentation. A reaction catalyzed by enzymes occurring in organic 

 material. 



Fertilization. The act of combination of two cells from individuals of 

 opposite sexes; it results in the initiation of development of a new 

 individual. 



Fibrinogen. A substance in the blood that is converted to fibrin by the 

 action of thrombin in the process of blood clotting. 



Filterable virus. Bacteria so small as to be beyond the range of visi- 

 bility of the most powerful microscope; so small that they pass 

 through the pores of a porcelain filter. (There is substantial evi- 

 dence that filterable viruses may be distincdy different in character 

 from visible bacteria.) 



Flagella. Long, rotating protoplasmic fibres that are the organs of loco- 

 motion of some types of Protozoa. 



Food. Stricdy speaking, any substance that provides either energy or ma- 

 terials which may be used in metabolism is a food. 



Food balance. A condition in a community in which the holophytic nu- 

 trition of green plants and the holozooic nutrition of animals exactly 

 balance, so that all plants and animals within the community have 

 an adequate food supply. 



Food chain. The sequence in which plants and animals depend on each 

 other for food. 



Fossil. The trace, imprint or replaced tissue of an extinct animal or 

 plant. An actual skeleton or shell, for instance, is not a fossil. 



Free martin. In catde a female calf born co-twin with a male is almost 

 always sterile and is called a free martin. 



Functional adaptation. Physiological properties that are adaptive in 

 nature. 



Galvanotropism. Response to an electric current. 



