Diatom

Diatoms are a type of algae (tiny plant-like living things often found in water). Most are single cells, but some form chains or simple colonies. They usually live in the ocean, but are also found in some soils and waterways. 

 Characteristics 

 Cell walls 
Diatom cells have unique cell walls made of silica (SiO2). These walls (called "frustules") take many forms, some quite beautiful and ornate.  

The name "diatom" comes from the ancient Greek word diátomos, which means 'cut through.' Diatom cell walls are usually split (or 'cut through') into two sides. 

 Function 
Living diatoms comprise about 20 to 50 percent of the oxygen produced annually. They take in over 6.7 billion metric tons of silicon each year from the waters in which they live.

 Similar organisms 
Diatoms and coccoliths are the two great groups of single-celled organisms in the sea. They do not grow in the same places, because diatoms are silica and coccoliths are made of calcium carbonate. T.H. Huxley first discovered this on his voyage on HMS Rattlesnake in 18461850.

 Evolution 
Archeologists have found diatom fossils from as far back as the Lower Jurassic period, around 185 million years ago. However, molecular clock evidence suggests that they developed even earlier.Kooistra W.H.C.F. and Medlin L.K. 1996. Evolution of the diatoms (Bacillariophyta): IV. A reconstruction of their age from small subunit rRNA coding regions and the fossil record. Mol. Phylogenet. Evol. 6, 391-407. 

Scientists have analyzed the entire genomes of two diatom species. The analysis revealed both species had hundreds of genes that came from bacteria.Bowler C. et al. 2008. The Phaeodactylum genome reveals the evolutionary history of diatom genomes. Nature 456: 239–244.

Diatoms probably evolved some of their structure from red algae.

 Uses 
Diatoms have some practical uses. Scientists can study it to determine water quality, monitor environmental conditions like pollution, and understand what past environments were like.

Diatom communities are also of interest to nanotechnology.

 References 

Category:Protista
Category:Algae