(N/A) $\rightarrow$ This group includes diatoms and golden algae (desmids).
$\rightarrow$ Habitat: They are microscopic and float passively in water currents (plankton).
$\rightarrow$ Mode of nutrition: Most of them are photosynthetic.
$\rightarrow$ Body organization: In diatoms, the cell wall forms two thin overlapping shells, which fit together like a soap box.
$\rightarrow$ The walls are embedded with silica, making them indestructible.
$\rightarrow$ Diatoms have left behind large amounts of cell wall deposits in their habitat; this accumulation over billions of years is referred to as "diatomaceous earth".
$\rightarrow$ Function: Being gritty, this soil is used in polishing and the filtration of oils and syrups.
$\rightarrow$ Diatoms are the chief 'producers' in the oceans.