Properties and Activities of Living Protoplasm 101 



LIVING (ANIMATE) ORGANISMS 



NONLIVING (INANIMATE) 

 SUBSTANCES 



IRRITABILITY AND ADAPTATION 



All living protoplasm is typically sen- 

 sitive to certain environmental fac- 

 tors {irritability) and tends to react 

 or respond {adaptation) because of 

 the labile, dynamic nature of proto- 

 plasm and the extremely complex 

 interactions of physical and chemical 

 forces. Responsiveness to stimuli is 

 characteristic of living protoplasm 

 but does not seem to be limited to 

 it. By adaptation, living organisms 

 attempt to adjust themselves to their 

 environments so as to live as suc- 

 cessfully as possible. Because of ir- 

 ritability, protozoa, bacteria, the 

 various parts of animals and plants, 

 etc., tend to display variable re- 

 sponses which vary from time to 

 time and are influenced by the in- 

 herent nature of the specific proto- 

 plasm and the quantity and quality 

 of the stimuli. 



Certain nonliving materials which dis- 

 play movements also seem to display 

 something which approximates irrita- 

 bility and responsiveness under cer- 

 tain conditions. However, the type 

 of response is usually simpler and 

 more predictable than in living or- 

 ganisms. When light rays which fall 

 on a photoelectric cell are inter- 

 rupted, they may open doors, set off 

 alarms, or count cans in a commer- 

 cial cannery. Pressing a starter but- 

 ton may result in the movement in 

 an electric generator. The drop of 

 mercury in acidified water may "re- 

 spond" to contacts with certain other 

 chemicals. The movements dis- 

 played by certain inanimate objects 

 may truly resemble some of the sim- 

 pler movements of certain living or- 

 ganisms, but on the whole they are 

 less complicated and rather more 

 predictable and standardized. 



GROWTH AND DEVELOPMENT 



All living plants and animals require 

 foods and they grow, each true to 

 its type, and jrom within, through 

 intussusception. Living organisms 

 also possess the property of assimila- 

 tion (producing living protoplasm 

 from nonliving foods ) . The energy- 

 bearing molecules are taken in, re- 

 arranged, and delicately adjusted in- 

 to other more complex molecules of 

 living protoplasm under the influ- 

 ences of enzymes and catalysts. Me- 

 tabolism, which characterizes proto- 

 plasm, consists of anabolism (con- 

 structive chemical changes, with the 

 storage of energy) and catabolism 

 (destructive chemical changes with 

 a release of energy). Usually true 

 growth is accompanied by changes in 

 structure, form, and functions which 

 constitute true development. Growth 

 may be the result of an increase in 

 the number of cells, an increase of 

 the size of cells without an increase 

 in numbers, or a combination of the 

 two. Certain structures of living or- 

 ganisms may also be duplicated by 

 auto synthesis. 



Certain inanimate materials may in- 

 crease in size externally by adding 

 materials which are essentially simi- 

 lar to the original materials by the 

 process of accretion. A crystal of 

 table salt in a supersaturated solu- 

 tion of table salt will increase in size 

 by externally adding more salt. Liv- 

 ing organisms grow by producing cer- 

 tain other materials true to type, 

 while increases in size of inanimate 

 crystals are influenced by the begin- 

 ning, raw materials. In other words, 

 " the final product is the same as the 

 beginning. Certain chemicals com- 

 bined to produce the so-called 

 "chemical gardens" (crystals of 

 chemicals in water glass) may in- 

 crease in size and form beautifully 

 patterned structures which may re- 

 semble plantlike structures. How- 

 ever, are these true growth in the 

 accepted sense? 



