Living organisms that do not have a cell wall include animals and certain types of protists. Unlike plants, fungi, and bacteria, which have rigid cell walls, animal cells are surrounded by a flexible plasma membrane. This allows for greater flexibility and movement, which is essential for the functions of animal cells.
Protists, which are a diverse group of eukaryotic microorganisms, also lack a cell wall in many cases. Instead, they may have a pellicle or other structures that provide some level of support and protection. The absence of a cell wall in these organisms allows for more dynamic shapes and movements, which can be advantageous in their environments.