Letting non-biologists browse the Tree of Life can be a dangerous thing...

So far as I can tell, bacteria and archaea never formed multicellular
structures with any sort of "pre-planned" structure, only mats.  Is
this true?

Eukaryotes, on the other hand, seem to have hit on multicellularity
multiple times; even if there is no actual cell differentiation, there
seems to be a "floor plan" of sorts: stems, flotation bladders, 
reproductive organs, etc.  The examples I have seen so far include:

Choanoflagelates -> animals
Green algae -> plants
something -> fungi
something else -> slime molds
red algae -> red seaweed
brown algae -> kelp
are there more?

Now, the first three contain many examples of species that are
exclusively multicellular; the creature does not exist in a single
celled form.  Is this true of anything in the other categories?
Do the brown algae that form kelp ever turn up alone?

Also, supposedly the same (or very similar genes) are responsible for
metamerism in all animals, from sponges to humans.  Do these genes
exist in Choanoflagelates?  Do they exist in other eukaryotes?

-- 
Please reply to:                | "All true wealth is biological"
pciszek at panix dot com        |    --Cordelia Naismith Vorkosigan
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