organism; organic body
A living individual composed of organs; a biological organism. Used in scientific and general contexts.
All organisms are made of cells.
Many microscopic organisms live in this lake.
有機物 means 'organic matter' or 'organic substance', referring to material rather than a living individual.
From 有機 (organic) + 体 (body). The term is a calque from Western scientific vocabulary, likely from German 'Organismus' or English 'organism'.