Explain Pennate diatomsrole in diatoms?

Pennate diatoms have bilateral symmetry, which presents side-by-side mirror images if divided down the middle or centerline, as seen at the right.

The shells of diatoms are made of silicon dioxide, a glass-like material that is very resilient. In fact, large deposits of ancient diatoms called diatomaceous earth are mined and used in scouring powders, heat-resistant bricks used in ovens, and pool filters.

Diatoms are plankton, which means that they drift, or float, in the water column. They live in both fresh water and marine habitats, and because of their numbers and importance as photosynthetic producers in the food chain, are often referred to as the "grass of the oceans."