Achnanthes placentuloides, Chamaepinnularia justa and Pinnuavis aleemii are three examples of the diatoms found on Earth. Scientists believe there are anywhere from 20,000 to 2 million different species of diatom on the planet, according to the University of Colorado, Boulder.
Diatoms are a type of algae with a very distinctive cell wall. The cell wall is made of silica, giving the diatom a glasslike structure that prevents damage to the organism. Diatoms thrive in moist environments, so they are often found in damp soil, tree bark and bodies of water.
Because diatoms produce their own food via photosynthesis, many species live within the first 200 meters of lakes, oceans and other bodies of water so they can harness energy from the sun. Some diatoms exist as single-celled organisms, while others form simple colonies or filaments.
Diatoms reproduce via a process called vegetative reproduction. Instead of producing two identical cells, vegetative reproduction produces two cells that are slightly smaller than the parent cell. As a result, diatom cells continue to get smaller each time they divide. Almost all diatoms are microscopic organisms, measuring anywhere from 2 to 500 microns. Because diatoms are so small, scientists must use scanning electron microscopes or light microscopes to view their structures.