What distinguishes diatoms from other algae?

Diatoms are specifically distinguished from other algae primarily by their unique cell wall, which is made of silica, giving it a glass-like appearance. This silica wall, known as a frustule, is composed of two halves that fit together like a petri dish and is a critical feature in identifying diatoms. Unlike other algae, which may have cell walls made from other materials like cellulose or pectin, the silica composition of diatom cell walls provides incredible strength and structural integrity. This distinctive feature also contributes to their fossilization process, resulting in diatomaceous earth deposits found in geological strata.

While all algae, including diatoms, have the ability to photosynthesize and produce oxygen as a byproduct, these traits are not unique to diatoms. Furthermore, not all algae can survive extreme conditions, nor is this characteristic exclusive to diatoms. Thus, the presence of a glass (silica) cell wall sets diatoms apart from other algal groups.