rav65819_ch34_653-680

rav65819_ch34_653-680 - ;;;;;;;; 34 chapter Coelomate...

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Unformatted text preview: ;;;;;;;; 34 chapter Coelomate Invertebrates ALTHOUGH ACOELOMATES AND PSEUDOCOELOMATES have proven very successful, a third way of organizing the animal body has also evolved, one that occurs in many protostomes and in all deuterostomes. We begin our discussion of the coelomate invertebrate animals with mollusks, which include animals such as clams, snails, slugs, and octopuses. Annelids, represented by earthworms, leeches, and seaworms, also have a coelomic body cavity, as well as segmented bodies. Arthropods, such as the paper wasp pictured here, evolved segmentation and jointed appendages, and they have become the most successful of all animal groups. Echinoderms are exclusively marine animals that exhibit deuterostome development and endoskeletons, two evolutionary innovations that they share with the chordates, which are the subject of chapter 35. introduction 34.4 Phylum Arthropoda: The Arthropods concept outline 34.1 Phylum Mollusca: The Mollusks ■ Mollusks are extremely diverse ■ The mollusk body plan is complex and varied ■ Four classes of mollusks show the diversity of the phylum 34.2 Phylum Annelida: The Annelids ■ Annelids have distinct ringlike segments ■ Annelids move by contracting their segments ■ Annelids have traditionally been grouped into three main classes 34.3 The Lophophorates: Bryozoa and Brachiopoda ■ The bryozoans, phylum Bryozoa, are colonial and produce a chitinous chamber ■ The brachiopods and phoronids, phylum Brachiopoda are solitary lophophorates ■ The arthropod body plan features jointed appendages and an exoskeleton ■ Arachnids have specialized anterior appendages, the chelicerae ■ Centipedes and millipedes are segmented and have a large number of legs ■ Crustaceans are mostly aquatic and have biramous (branched) appendages ■ Insects exhibit vast diversity and exist in huge numbers 34.5 Phylum Echinodermata: The Echinoderms ■ Echinoderms undergo deuterostome development and have an endoskeleton ■ The echinoderm body plan is bilateral in the larvae but pentaradial in adults ■ Echinoderms have fve extant classes 653 rav65819_ch34_653-680.indd 653 rav65819_ch34_653-680.indd 653 12/7/06 6:11:13 PM 12/7/06 6:11:13 PM 34.1 Phylum Mollusca: The Mollusks The origin of the coelom, as was mentioned in the preceding chapter, was a significant advance in the structure of the animal body because it allowed for increased body size. Coelomates have a body design that repositions the body’s fluid and allows complex tissues and organs to develop. This new body plan also made it possible for a wide variety of different body architectures to evolve and the body to grow to much larger sizes than most acoelomate or pseudocoelomate animals. Currently, there is little doubt that coeloms evolved multiple times during animal evolution....
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This note was uploaded on 10/15/2010 for the course BIO BIO1 taught by Professor Lipke during the Fall '09 term at CUNY Brooklyn.

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rav65819_ch34_653-680 - ;;;;;;;; 34 chapter Coelomate...

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