EBB TIDE 



E-/ 



That period of tide between a high water and 

 the succeeding low water; falling tide. 

 (See Flood Tide) 



EC 50 



Concentration of a substance producing 50% 

 decrease in shell growth. 



ECOLOGICAL FACTOR 



Any part or condition of the environment that 

 influences the life of one or more organisms. 

 (See Biotic Factor) 



ECOLOGICAL NICHE 



The role of an organism in an ecosystem , 

 its activities and relationships to the 

 living and nonliving environment; food 

 and nutrition relationships are of primary 

 importance. (See Habitat Niche) 



ECOLOGY 



Interrelationships between organisms and their 

 environment . 



ECOSYSTEM 



A community , including all the component 

 organisms, together with the environment , 

 forming an interacting system. 



ECOTYPE 

 (Habitat Form) 



A locally adapted population of a species which 

 has a distinctive limit of tolerance to envi- 

 ronmental factors. (Individuals of the same 

 species may appear different in various 

 habitats) . 



