Name the living organisms you know that feed on ready-made organic matter created by other living organisms.

Such organisms are found in all taxonomic categories, from unicellular protozoa to the most advanced mammals.
The simplest is the amoeba. Bacteria belong to unicellular organisms, isolated in a separate group. Polyps, corals and jellyfish. All worms. Some of them switched to the parasitic method and adapted to it as much as possible (broad tapeworm, roundworm, etc.). Fishes. Insects. Birds. Frogs, newts, lizards, crocodiles, snakes. All mammals (marmot, zebra, cheetah, elephant, seal, etc.) including humans. Such organisms are included in the kingdom of fungi.