noun
organism; organic body
A living individual composed of organs; a biological organism. Used in scientific and general contexts.
すべての有機体は細胞からできている。
All organisms are made of cells.
この湖には多くの微小な有機体が生息している。
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'.