Disseminule 



A detachable part of a plant which is capable of Dis- 

 persal and of giving rise to a new plant, cf. Diaspore. 



Distribution 



(1) The geographic range (continuous or discontinuous) 

 of a Taxon at any one time. (2) The pattern of occurrence of 

 individuals of a taxon in an area such as Random or Pots- 

 son (Normal) distribution; non-random or above normal, 

 Contagious dispersion (Over-dispersion, Hyperdispersion); 

 and non-random, below normal, Hypodispersion or even- 

 spaced. 



Distribution, Center of 



See Center of dispersal. 



Diurnal 



Refers to daytime in contrast to Nocturnal, cf. Diel, 

 Crepuscular. 



Divergence 



The condition in which Seres of a similar origin become 

 increasingly unlike as Succession proceeds toward the Cli- 

 max. See Convergence. 



Diversion Dam 



A dam constructed for the purpose of diverting part or 

 all of the water in a stream into a different course. 



Diversity Index 



The number of species in an area divided by the number 

 of individuals of all these species. 



Division of Labor 



The specialization of parts of an organism or members 

 of a species for carrying on certain processes, e. g., in birds 

 the wings for flying and the legs for walking, in bees the 

 workers and drones, in plants the various kinds of tissues for 

 carrying on different functions. 



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