threads, classified with bacteria or fungi. Various kinds 

 cause decomposition, disease, or produce antibiotics such as 

 streptomycin (q.v.). 



Action 



The impingement of environmental factors such as heat 

 or light upon organisms. 



Actium 



A plant-animal community on a rocky seashore. 



Activated Sludge 



Material composed chiefly of bacteria and protozoa, used 

 in one method of sewage disposal. 



Actophilous 



Refers to organisms that grow well on rocky seashores. 



Adaptability 



Capability of an organism to make changes which fit it 

 better to its environmental conditions. 



Adaptable 



Refers to the adaptability of an organism. 



Adaptation 



(1) The process or processes by which an organism be- 

 comes apparently better suited to its environment or for 

 particular functions. (2) The structures or activities of an 

 organism, or of one or more of its parts, which tend to fit it 

 better for life in its environment. (3) The adapted form. 



Adaptedness 



The sum of genetic characters by which an organism 

 is suited to its environment. 



Adaption 



See Adaptation. 



Adaptive Radiation 



The evolution of taxa (q. v.) as they become adapted to 



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