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Essay / Research Paper Abstract
This 4 page paper explores the evolutionary distinctions of the jawed fishes. The phylogeny of this superclass is explored and specific attention is devoted to the Teleostei. Bibliography lists 4 sources.
Page Count:
4 pages (~225 words per page)
File: AM2_PP674786.doc
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Unformatted sample text from the term paper:
appeared around four hundred and thirty million years ago (Raylman, 2010). These species of fish were distinguished by the fact that they had a fully formed mandibular arch that
was inclusive of the hyoid arch located behind the jaw (Miller and Harley, 2007). These specimen were already advanced enough that the hyoid arch was supporting the mandibular and
there was an intervening spiracle which was determined to be a gill slit (Miller and Harley, 2007). In contrast, he Agnathans have nothing in their fossil records to indicate
a precursor of the gill arches of the Gnathostomes (Miller and Harley, 2007). Speculation regarding the formation of the mandibular arch varies in
content. The mandibular arch may have been formed by the velum, a muscular membrane which serves as a pumping device (Miller and Harley, 2007). Research has shown that
the Agnatha velum is supplied by a system of nerves which would indicate that this is a distinct possibility (American Scientist, 1994). The identical embryonic tissue which forms the
jaws of Gnathostomes forms the velum in lampreys (American Scientist, 1994). One theory regarding the function of the velum states that
the earliest vertebrates obtained water and food by using the velum as a pump as is demonstrated in larval lampreys (American Scientist, 1994). Consequently, the velum is believed to
have undergone changes which allowed the intake of larger particles of food and structures functioning as jaws developed to allow for feeding on whole organisms (American Scientist, 1994).
The formation of functional jaws gave a distinct evolutionary advantage to those individuals who had them because they could devour larger animals, or
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