Vertebrate Evolution: Genes and Development

Abstract

The most significant differences between the vertebrates and the other chordates lie in the head. These novel features probably emerged as a result of modifications to the developmental program, and they are thought to have aided the vertebrates in assuming a predacious lifestyle. More specifically, the evolution of these characteristics must have involved extensive regionalization of the central nervous system, the evolution of neural crest and ectodermal placodes and alterations to the pharynx.

Keywords: ectodermal placodes; genome evolution; neural crest; pharyngeal segmentation; chordates; vertebrate evolution

Figure 1.

The chordate phylum consists of three subphyla: the vertebrates, the cephalochordates and the urochordates, which are united by their possession of a number of common features at the embryonic stage. These three subphyla do, however, exhibit differing degrees of anatomical complexity, with the vertebrates being the most complex.

Figure 2.

Schematic representation of a cephalochordate, Amphioxus, highlighting the typical shared characteristic chordate features: notochord, dorsal nerve cord, segmented muscle blocks and a segmented pharyngeal region.

Figure 3.

Unique features of the vertebrate head. The vertebrates differ from the other chordates in having a number of features concentrated in the head: they have an elaborate brain, numerous special sense organs, a muscularized pharynx with skeletal support, a backbone and an extensive peripheral nervous system.

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References

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Further Reading

Butler AB (2000) Sensory system evolution at the origin of craniates. Philosophical Transactions of the Royal Society of London B 355: 1309–1313.

Kardong KV (2002) Vertebrates: Comparative Anatomy, Function, Evolution. New York: McGraw‐Hill.

Lacalli TC (2001) New perspectives on the evolution of protochordate sensory and locomotory systems, and the origin of brain and heads. Philosophical Transactions of the Royal Society of London B 356: 1565–1572.

Schaeffer B (1987) Deuterostome monophyly and phylogeny. Evolutionary Biology 21: 179–234.

Web Links

The Tree of Life. A collaborative internet project containing information about phylogeny and biodiversity http://tolweb.org/tree/phylogeny.html

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How to Cite close
Graham, Anthony(Sep 2006) Vertebrate Evolution: Genes and Development. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005921]