(Phylum Heterokontophyta formerly Chrysophyta)
make their first appearance during the Jurassic.
Diatoms are unicellular
Diatoms are the most successful of the phytoplankton in today’s
oceans in terms of biomass and net primary production. Diatoms
are encased in a two-part, asymmetrical silica cell wall. The
two halves of the silica case fit together like the parts of
dish. The diatom’s silica shell is called a frustule.
are not only major primary producers in oceans, especially
in cold marine environments, they also make up the base
food chain for many freshwater environments. The deposition
of large numbers of diatoms can create the rock diatomite or
diatomaceous earth. Diatomaceous earth is mined commercially
and used as a filtering material, mineral filler, and fine
abrasive. Fossil diatoms can be used for a multitude of purposes
1998, p 206):
Shifts In Oceanic Primary Production
Earth's oceans have
experienced two major shifts in the composition
of primary producers. Initially, cyanobacteria along with
other photosynthetic bacteria were the primary producers
Proterozoic eon. The first shift occurred during the early
Paleozoic era when eukaryotic green algae joined cyanobacteria
in being major primary producers. The second shift would
occur during the Mesozoic era when dinoflagellates and
would be joined by diatoms in the Jurassic. Diatoms, dinoflagellates,
and coccolithophores would assume their dominant role as
the base of many modern marine ecosystems by Cretaceous
(Knoll, Summons, Waldbauer, and Zumberge, 2007, p. 155).
on the word diatom to
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Science Olympiad Fossil Event
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Knoll, Summons, Waldbauer, and Zumberge. (2007). The Geological
Succession of Primary Producers in the Oceans. In Falkowski,
P.G. Knoll, A.H. [Eds] Evolution of Primary Producers in
the Sea. (pp. 133-163). China: Elsevier Academic Press.
Olney, M. (2008). MIRACLE:
Microfossil Image Recovery and Circulation for Learning
and Education: University College
London. See: http://www.ucl.ac.uk/GeolSci/micropal/foram.html
D.R. (1998). Bringing Fossils to Life: An Introduction
to Paleobiology. New York: McGraw-Hill.