It is hard to distinguish between colonies of unicellular organism and multicellular organism as there is a continuum between both depending on how well integrated they cells are.
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A biological colony is an associated group of organisms or biological cells. The name alone specifies neither cell differentiation nor a particular mode of biological development. A colony can arise from related descendants or from previously separate members; see clonal development and the Queller and Strassmann discussion cited under unicellular organism.