Honors Biology Evolution Practice Exam 2026 – All-in-One Study Guide for Exam Success!

Peptidoglycan in cell walls is a hallmark feature of Bacteria, the group of mostly unicellular prokaryotes. This polymer forms a rigid mesh that helps give bacteria their shape and protect them. Archaea are also prokaryotes, but their cell walls typically lack peptidoglycan and use different materials instead. Eukarya includes organisms with membrane-bound cells, and when they have walls (as in plants and fungi), those walls are made of cellulose or chitin, not peptidoglycan. Protista are a diverse set of eukaryotes, and their walls, when present, aren’t built from peptidoglycan either. So the domain that contains unicellular prokaryotes with peptidoglycan in their cell walls is Bacteria.