T-3 

 TOLERANCE 



Relative capability of an organism to endure 

 or adapt to an unfavorable environmental 

 factor. 



TOLERANCE LIMIT 

 (TL 10...100 ) 



The concentration of a substance which some 

 specified portion of an experimental population 

 can endure for a specified period of time with 

 reference to a specified type of response; e.g., 

 TL 100 means tna t all test organisms endured 

 the stress for the specified time; TLiq means 

 only 10% of the test organisms could tolerate 

 the imposed stress for the specified time. 

 (See Median Tolerance Limit) 



TOLERANCE RANGE 



TOLERANT 

 ASSOCIATION 



The range of one or more environmental 

 conditions within which an organism can 

 function; range between the highest and 

 lowest value of a particular environmental 

 factor in which an organism can live. 



An association of organisms capable of 

 withstanding adverse conditions within the 

 habitat . This association is often characterized 

 by a reduction in the number of species (from 

 a clean water association ) and, in the case of 

 organic pollution, an increase in individuals 

 representing certain species. 



TOXICANT 



A substance that through its chemical or 

 physical action kills, injures, or impairs 

 an organism; any environmental factor which, 

 when altered, produces a harmful biological 

 effect. (See Pesticide) 



