Obligate Parasite 



A Parasite that cannot attain complete development inde- 

 pendent of its Host. 



Oceanic Province 



The portion of the ocean seaward from the Continental 

 shelf, having a depth greater than 200 meters, cf. Neritic. 



Oceanography 



The science dealing with all aspects of the ocean; physi- 

 cal conditions, plant and animal life, etc.; sometimes re- 

 stricted to the study of physical conditions only. 



Oecology 



See Ecology. 



Oesophagous 



See Esophagous. 



Oestrus (Estroys) cycle 



The period in mature females in many kinds of mam- 

 mals when the desire for mating occurs; it varies in length, 

 is controlled by hormones, and is often accompanied by 

 bodily changes. 



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