It is expected that cell walls have changed before any endosymbionts could be acquired by eukaryotic cells. It is an additional barrier to the entry of materials into the cell.
The endosymbiotic theory supports the idea that a primitive eukaryotic cell engulfed other microorganisms that subsequently converted into internal organelles (i.e., chloroplasts and mitochondria).
The cell wall is a structure observed in both prokaryotic and eukaryotic cells whose primary roles include, among others, providing structural support, maintaining the shape of the cell, etc.
All prokaryotic cells (i.e. bacteria and archaea) exhibit a cell wall, which may be placed beneath a capsule.
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