If it's organized enough to be considered a cell it probably isn't simple. If you mean streamlined or does the work of a cell without all of the extra parts, then I would say the domain Archea or primitive prokaryotic (bacterial) cells that live in extreme conditions.
The cell is the basic unit of structure of an organism.
The simplest structure shared among all living organisms is the cell. Cells are the basic building blocks of life and are responsible for carrying out all the functions necessary for an organism to survive and reproduce.
is a cell
If tyou are speaking from an evolutionary point of view, the simplest 'complex living organism' would be an Amoeba. They are single celled organisms but carry out all the functions an organism does with that single simple but effective cell structure. However from a chemistry point of view, inside a single cell are Proteins, and they are constructed from Amino Acids. Any smaller than that and you are just talking about individual atoms so Amino Acids are often regarded as the building blocks of living organisms.
The four characteristics used to decide what organisms belong in which kingdom are cell type (prokaryotic or eukaryotic), cell structure (unicellular or multicellular), mode of nutrition (autotrophic or heterotrophic), and reproduction method (asexual or sexual).
Many people might think the answer to this question would be an atom, but not in life. The structures go like this from largest to smallest: Ecosystem, Community, Organism, Organ system, Organ, Tissue, Cell.
The cell is the basic unit of structure of an organism.
popo
The simplest structure shared among all living organisms is the cell. Cells are the basic building blocks of life and are responsible for carrying out all the functions necessary for an organism to survive and reproduce.
Amoeba sponges
* Kingdom Animalia, Phylum prokaryotae. i disagree, its kingdon prokaryote
cell
is a cell
The cell nucleus is the structure that contains most of an organism's DNA.
No they do not
The cell is the basic unit of structure and organization of organisms. Although organisms such as humans, dogs, and trees can become very large and complex, the cell remains the simplest, most basic component of any organism.
Any organism to do with the kingdom plantae just about.