Assortative Breeding (mating) 



Pairing of male and female organisms that involves more 

 than chance so that mating of similar parents is favored. 



Asymptotic Population 



The maximum size reached by a population under pre- 

 vailing environmental conditions, no matter how long repro- 

 duction continues. 



Atavism 



The appearance in an organism of an ancestral character 

 after a period of several generations. 



Atlantic Period 



See Sub-boreal period. 



Atmometer 



Any instrument for measuring evaporation such as a 

 porous porcelain sphere or open pan of water. 



Atoll 



A body of water, lagoon, surrounded by a coral reef in 

 the ocean. 



ATP 



Adenosine triphosphate, an energy-rich phosphate com- 

 pound in organisms, important in the transfer of energy. 



Atrophy 



Reduction in size or contents of an organ, tissue, or cell. 



Audiogenic Seizure 



Convulsion in an animal caused by a high-pitched noise. 



Aufnahme (G) 



See Sample area, Quadrat. 



Aufwuchs (G) 



See Periphyton. 



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