Polytypic 



Refers to a species that occurs in various forms in differ- 

 ent parts of its range. 



Pome 



A multicarpellate fruit in which the fleshy part surround- 

 ing the ovary is formed from the receptacle, e.g., apple fruit. 



Population 



A group of interacting individuals of the same species or 

 smaller Taxa in a common spatial arrangement. 



Population Cycle 



The recurrent changes in the size of a population from 

 low to high numbers and the return to low numbers as in 

 the cycle of the snowshoe hare. 



Population Density 



The number of individuals in a population per unit area. 



Population Dynamics 



The totality of changes that take place during the life 

 of a population. 



Population Pressure 



The combined forces of the individuals of a population 

 upon the organisms in a community and upon the environ- 

 ment, cf. Biotic pressure. 



Pore Space 



The fraction of the volume of soil or rock that is not 

 occupied by solid particles. 



Porosity 



The state of matter which contains Pore spaces. 



Postadaptation 



The increase in Adaptation in a Preadapted organism 

 after its invasion into a given environment. 



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