MANUAL OF ANIMAL BIOLOGY 



I. PROTOPLASM 



The world in which we live contains a great many diverse types 

 of living organisms which are known to us either as plants or as 

 animals. The study of all the phenomena of life, without regard 

 to animal or plant origin, constitutes the science of Biology. 

 Zoology, or Animal Biology, treats of living phenomena in so far 

 as they are exhibited by animals, and the companion science of 

 Botany, or Plant Biology, occupies the same sphere in the plant 

 kingdom. 



Vital phenomena have their origin in a unique substance, known 

 as protoplasm, which is the basic material — the life stuff — 

 constituting the bodies of all living organisms. It should also be 

 emphasized at once that protoplasm is never found apart from the 

 complete organized unit, that is, the individual plant or animal. 

 An additional fact of fundamental importance is revealed by 

 the microscopic examination of the tissues from any organism, 

 namely, that protoplasm does not occur in large unorganized 

 masses, but always in the form of microscopic units, termed 

 cells, which are the ultimate structural and functional units of 

 life. 



A. Cellular Organization 



In the lowest forms of life the entire organism consists of a single 

 cell which is able efficiently to perform all the processes essential 

 to life. Such organisms are termed unicellular. In the higher 

 types of living organisms, the body is composed of an almost 

 inconceivable number of cells, groups of which are specialized for 

 the various necessary functions in the life of the individual, such 

 as nutrition, respiration, reproduction, etc. Such organisms are 

 termed multicellular, and include all the familiar forms of 

 plants and animals. 



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