Alluvium 



Sediments, usually fine materials, deposited on land by 



a stream. 



Aim 



A high mountain meadow, alpine or subalpine. 



Aim's Fb Coefficient 



The relationship of fish caught per hectare to the live 

 weight of the bottom fauna per hectare. 



Alpage 



A mountain or upland pasture of natural plants grazed 

 by animals at the height of summer. See Aim. 



Alpha Particle, * Particle 



A helium nucleus, given off by nuclei of certain radio- 

 active substances. 



Alpha Radiation 



A kind of ionizing radiation (q. v.) in which alpha 

 particles are given off. 



Alpha Ray 



A stream of alpha particles (q. v.) cf. Beta ray. 



Alpine 



Refers to parts of mountains above tree growth or to 

 organisms living there. 



Alternating Communities 



See Twin communities. 



Alternation of Generations 



The alternation of different forms in the life cycle of an 

 organism, especially a sexual (gamete-producing) form with 

 a non-sexual (spore-producing) form; occurs in most plants 

 and in many animals. 



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