Foraminifera are tiny, single-celled protozoa with pseudopodia. Most of them have a hard, mineral-formed shell with openings and numerous small pores in the shell wall. The body of a foraminifera consists of a mass of cytoplasm differentiated into two layers: an outer, thin, and transparent layer called the ectoplasm, and an inner, darker layer called the endoplasm. The ectoplasm surrounds the shell and extends numerous root-like or filamentous pseudopodia, whose main functions are locomotion, feeding, digestion, waste removal, and secretion of the exoskeleton. The endoplasm is enclosed within the shell and contains one or more nuclei, as well as food vacuoles.
Foraminifera
The vast majority of modern foraminifera are marine, with only a few living in brackish water environments such as lagoons and estuaries. A very small number are euryhaline and can live in saline water with salinity exceeding normal levels. A very few, such as certain species within the superfamily Pyrenoidea, can even live in freshwater. Most foraminifera are benthic, while a few are planktonic. Benthic foraminifera can usually move slowly along the seabed, with only a few remaining sessile.
Foraminifera have evolved over a long period from the Cambrian to the present day, with a general trend of increasing prosperity. However, they exhibit certain characteristics in different geological periods, resulting in several peaks in their development. These peaks occurred during the Carboniferous to Permian periods of the Paleozoic Era, the Cretaceous period of the Mesozoic Era, and the Eocene and Miocene epochs of the Cenozoic Era. The present day is another period of prosperity for foraminifera.
Because some groups of foraminifera evolve rapidly and have a short lifespan in geological history, they often serve as important index fossils for relevant eras. In particular, because they are small in size and numerous, and their fossils are relatively easy to collect in large quantities from drilling cores and seabed samples, foraminifera can play a significant role in areas with oil reserves, such as downhole marine stratigraphic correlation and classification, as well as in marine geological research.
