Cede ENVO:alga to PCO

[kaiiam]

ENVO: alga should be ceded to PCO.

I intend to take care of this with the help of @pbuttigieg in the next several weeks, as part a pull request I wish to make to PCO, in which I would like to add a variety of classes concerning plankton communities and population growth processes.

Cheers,
Kai

[kaiiam]

Issue to be part of pull request pending permission in issue 61

[ramonawalls]

Replaces http://purl.obolibrary.org/obo/ENVO_02500019. No definition in ENVO.

Most definitions of algae exclude Cyanobacteria, so I think we should label this class 'alga excluding Cyanobacteria'.

Similar to microbe, this will be a subclass of CARO:organism (but not organism, virus, or viroid, since it includes only cellular organisms. It should also be a subclass of NCBItaxon:cellular orgsnism, which should be a subclass of CARO:organism, but I am concerned that if I mix up the CARO and NCBItaxon hierarchies, there will be problems with people importing PCO. Will wait for CIB:organism to be released.

Proposed definition: An organism that is part of a polyphyletic group of photosynthetic Eukaryotes excluding Embriophyta (land plants). Included organisms range from unicellular microalgae, such as Chlorella and diatoms, to multicellular forms, such as the giant kelp.