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Chapter 32

Chapter 32. An Introduction to Animal Diversity. Welcome to Your Kingdom!. multicellular eukaryotes cells lack cell walls heterotrophs that ingest their food bodies are held together by structural proteins such as collagen Nervous tissue and muscle tissue are unique to animals

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Chapter 32

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  1. Chapter 32 An Introduction to Animal Diversity

  2. Welcome to Your Kingdom! • multicellular eukaryotes • cells lack cell walls • heterotrophs that ingest their food • bodies are held together by structural proteins such as collagen • Nervous tissue and muscle tissue are unique to animals • Most reproduce sexually, with the diploid stage usually dominating the life cycle

  3. Tissues develop from embryonic layers • Many animals have at least one larval stage • sexually immature and morphologically distinct from the adult • eventually undergoes metamorphosis

  4. Hox Gene • All animals, and only animals, have Hox genes that regulate the development of body form • Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology

  5. Symmetry • radial symmetry • bilateral symmetry • Dorsal • Anterior/posterior • Cephalization – development of head

  6. Tissues • collections of specialized cells isolated from other tissues by membranous layers • Germ layers • Ectoderm - covering the embryo’s surface • Endoderm - innermost germ layer • Mesoderm – layer in between • Diploplast vs. Triploplast organisms

  7. Body Cavities • Coelomates • True body cavity derived from mesoderm • Present in some triploblastic animals

  8. Body Cavities • Pseudocoelomates • derived from the blastocoel, rather than from mesoderm

  9. Body Cavities • Acoelomates • without body cavities

  10. Protostome and Deuterostome Development Spiral and determinate Radial and indeterminate • Protostome • cleavage is spiral and determinate • Mesoderm splits to form coelom • blastopore becomes the mouth • Deuterostome • cleavage is radial and indeterminate • Folds of archenteron forms coelom • blastopore becomes the anus mesoderm split to form coelom folds of archenteron form coelom Mouth develops from blastopore Anus develops from blastopore

  11. Animal Phylogenetic Tree: • About 35 animal phyla • two phylogenetic hypotheses • morphological and developmental comparisons • molecular comparisons

  12. LE 32-11 Ctenophora Platyhelminthes Mollusca Arthropoda Chordata Brachiopoda Phoronida Annelida Rotifera Echinodermata Ectoprocta Nemertea Nematoda Calcarea Cnidaria Silicarea “Radiata” Deuterostomia Lophotrochozoa Ecdysozoa “Porifera” Bilateria Eumetazoa Metazoa Ancestral colonial flagellate

  13. Animal Phylogenetic Tree • Agreement: • All animals share a common ancestor • Sponges are basal animals • Eumetazoa is a clade of animals with true tissues • Most animal phyla belong to the clade Bilateria • Vertebrates and some other phyla belong to the clade Deuterostomia

  14. LE 32-13 Apical tuft of cilia Mouth 100 µm Anus Structure of trochophore larva An ectoproct, a lophophorate

  15. Future Directions in Animal Systematics • Phylogenetic studies based on larger databases will likely provide further insights into animal evolutionary history

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