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The Evolution of Organ Systems$
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Andreas Schmidt-Rhaesa

Print publication date: 2007

Print ISBN-13: 9780198566687

Published to Oxford Scholarship Online: September 2007

DOI: 10.1093/acprof:oso/9780198566687.001.0001

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Intestinal systems

Intestinal systems

(p.218) CHAPTER 12 Intestinal systems
The Evolution of Organ Systems

A. Schmidt-Rhaesa

Oxford University Press

Animals obtain nutrients using a two-step procedure: food collection and uptake by endocytosis. In eumetazoans, a particular intestinal tract evolved, making it possible to digest food prior to the uptake of the smallest compartments. This chapter presents models for the evolution of this intestinal tract and its further evolution. There is a general trend for evolution from a saclike system to a tubelike one-way gut. In particular, the anterior, ectodermal part of the intestinal tract can be very diverse and contains a pharynx in various forms or it contains cuticular hard structures. Feeding is discussed in the context of larvae evolution and in adults.

Keywords:   endocytosis, sac-shaped intestine, one-way gut, gastrulation, pharynx, sucking pharynx, upstream collecting system, downstream collecting system

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