Protists are typically divided into three categories, including animal-like protists, plant-like protists, and fungus-like protists. Protists vary in how they move, which can range from cilia, flagella, and pseudopodia.

Some examples of plant-like protists include euglenoids, chrysophytes, diatoms, dinoflagellates, red algae, brown algae, and green algae. Plant-like protists produce 70% of the earth’s oxygen.

Multicellular protists are found within different groups of algae, and during one life stage of the slime molds. All protists have eukaryotic cells, meaning cells that have a defined nucleus enclosed in some type of membrane, but green, brown, and red algae are plant-like protists.

Diatoms are single-celled organisms with nuclei and chloroplasts. They are protists living individually or forming chains, zig zags or spirals. The first diatoms – the centrics – appeared in the Jurassic age some 200 million years ago, as combinations of yeast-like organisms and algae.

Diatom

• Diatomaceous earth.
• Phytoplankton.
• Cyclotella.
• Pennales.
• Centrales.
• Nitzschia.
• Diatomite.
• Diatom ooze.

The diatoms are the unique organisms, because of their distinctive cell walls. The walls are embedded with silica and thus the walls are indestructible. It show sculpturing and ornamentation that why Diatoms are also called as ‘Pearls of Ocean’. Diatoms are the chief ‘producers’ in the oceans.

Diatoms and desmids are inducted under chrysophytes, kingdom-Protista. These are the main producers in the ocean. They prepare food not only for themselves but also for the other life forms in the ocean. This is the reason they are also called as ‘pearls of ocean .

Diatoms are eukaryotic organism. The process of construction of cell wall in diatoms is called fruitful. The cell walls of diatoms are made up of silica. When these diatoms die and decompose, the silica returns back to the earth surface in the form of diatomaceous earth. The diatomaceous earth is quite soft and inert.