[BIO 1306] Ch33_Lecture

[BIO 1306] Ch33_Lecture - 33 Deuterostome Animals 33...

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33 Deuterostome Animals
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33 Deuterostome Animals 33.1 What is a Deuterostome? 33.2 What Are the Major Groups of Echinoderms and Hemichordates? 33.3 What New Features Evolved in the Chordates? 33.4 How Did Vertebrates Colonize the Land? 33.5 What Traits Characterize the Primates?
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33.1 What is a Deuterostome? Deuterostomes are characterized by three early developmental patterns: Radial cleavage Mouth forms opposite the blastopore Coelom develops from mesodermal pockets that bud off from the cavity of the gastrula
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33.1 What is a Deuterostome? The first two are the ancestral states for all bilaterian animals. Evidence from DNA sequencing supports the monophyly of the deuterostomes; echinoderms, hemichordates, and chordates. There are fewer species of deuterostomes than protostomes.
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Figure 33.1 A Current Phylogenetic Tree of the Deuterostomes
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33.1 What is a Deuterostome? Deuterostomes are triploblastic, coelomate animals with internal skeletons.
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33.1 What is a Deuterostome? Recently discovered fossils of early deuterostomes in China: Homalozoans : skeleton similar to echinoderms, but also bilateral symmetry and pharyngeal gill slits. Vetulicosystids also had pharyngeal gill slits. Yunnanozoans had external gills and a segmented posterior section.
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Figure 33.2 Ancestral Deuterostomes Had External Gills
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33.1 What is a Deuterostome? Bilateral symmetry is the ancestral condition. Echinoderms evolved unique pentaradial symmetry; other deuterostomes retained bilateral symmetry.
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33.2 What Are the Major Groups of Echinoderms and Hemichordates? Only six of 23 groups of echinoderms known from fossils survive today. Nearly all are marine. Hemichordates: 95 living species Together they are known as the ambulacrarians .
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33.2 What Are the Major Groups of Echinoderms and Hemichordates? Echinoderm larvae have bilateral symmetry, as they develop into adults, it changes to pentaradial symmetry (in fives or multiples of fives). Echinoderms have no head, and move equally well in many directions. They have an oral side containing the mouth, and an aboral side containing the anus.
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Figure 33.3 Evolutionary Innovations of Echinoderms (Part 1)
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Figure 33.3 Evolutionary Innovations of Echinoderms (Part 2)
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33.2 What Are the Major Groups of Echinoderms and Hemichordates? Echinoderms have a system of internal calcified plates covered by thin layers of skin and some muscle. The plates fuse to form an internal skeleton.
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33.2 What Are the Major Groups of Echinoderms and Hemichordates? The water vascular system is a network of water-filled canals leading to the tube feet. Functions in gas exchange, locomotion, and feeding. Water enters through the madreporite , which is connected to the ring canal around the esophagus. Other canals radiate out from the ring canal.
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33.2 What Are the Major Groups of Echinoderms and Hemichordates? Crinoids
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[BIO 1306] Ch33_Lecture - 33 Deuterostome Animals 33...

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