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Based on the fact that pennate diatoms either do or do not have a longitudinal groove in the valve, called a raphe, [14] a 1990 classification by Round, Crawford & Mann [3] divides the diatoms (as Bacillarophyta) into three classes, centric (22 orders); pennate without a raphe (12 orders); and pennate with a raphe (11 orders), as follows: [15]
An exploration of the genomes of five diatoms and one diatom transcriptome led to the identification of 42 genes potentially involved in meiosis. [70] Thus a meiotic toolkit appears to be conserved in these six diatom species, [70] indicating a central role of meiosis in diatoms as in other eukaryotes.
They form a (disputed) phylum containing about 100,000 recognised species. Diatoms generate about 20 per cent of all oxygen produced on the planet each year, [26] and take in over 6.7 billion metric tons of silicon each year from the waters in which they live. [57]
John Dalton's original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed water's formula to be HO, giving the atomic weight of oxygen as eight times that of hydrogen, [ 7 ] instead of the modern value ...
Both foraminifera and diatoms have planktonic and benthic forms, that is, they can drift in the water column or live on sediment at the bottom of the ocean. Either way, their shells end up on the seafloor after they die. These shells are widely used as climate proxies. The chemical composition of the shells are a consequence of the chemical ...
Cyclotella is a genus of diatoms often found in oligotrophic environments, both marine and fresh water. It is in the family Stephanodiscaceae and the order Thalassiosirales . [ 1 ] The genus was first discovered in the mid-1800s and since then has become an umbrella genus for over 100 different species, the most well-studied and the best known ...
Pinnularia, like most diatoms, can reproduce by simple cell division. Nuclear division occurs by mitosis and cell divides into two parts. Each daughter receives one of the parent cell's thecae, which becomes that cell's epitheca. The cell then synthesizes a new hypotheca. Thus, one daughter is the same size as the parent, and one is slightly ...
The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on diatoms as pectin, a fiber most commonly found in cell walls of plants. [1] [2] This layer is actually composed of several types of polysaccharides. [3]