Question

are organisms with one cell

are organisms with more than one cell

Answer 1

Organisms with one cell: unicellular (single-celled)
- Definition: an organism made of a single cell that carries out all life functions (metabolism, reproduction, response to environment).
- Examples: most bacteria and archaea, many protists (e.g., Amoeba, Paramecium), some fungi (yeasts), some algae.
- Key features: small size, simple organization, reproduce mainly by asexual methods (binary fission, budding), can live solitary or in loose colonies.

Organisms with more than one cell: multicellular
- Definition: an organism composed of many cells that are often specialized and organized into tissues, organs, and systems.
- Examples: animals, most plants, most fungi, many algae.
- Key features: cell specialization and coordination, larger body size, development from a single cell (zygote) by cell division and differentiation, reproduce sexually and/or asexually.

Notes:
- Some organisms form colonies of many similar cells (e.g., Volvox) that are intermediate between strictly unicellular and fully multicellular.
- Multicellularity evolved independently several times, allowing greater complexity and division of labor among cells.