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Explore the fascinating journey of animal evolution and development, from the earliest ancestral colonial flagellate to the diverse and complex organisms we see today. Discover key concepts such as cleavage, gastrulation, coelom formation, and protostome and deuterostome development. Learn about the major animal phyla and their characteristic features. This comprehensive overview provides a deep understanding of the evolutionary history and developmental processes that have shaped the animal kingdom.
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Fig. 32-2-3 Blastocoel Endoderm Cleavage Cleavage Blastula Ectoderm Archenteron Eight-cell stage Zygote Gastrulation Gastrula Blastocoel Blastopore Cross section of blastula
Individual choanoflagellate Fig. 32-3 Choanoflagellates OTHER EUKARYOTES Sponges Animals Collar cell (choanocyte) Other animals
Fig. 32-7 (a) Radial symmetry (b) Bilateral symmetry
Coelom Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Digestive tract (from endoderm) (a) Coelomate Fig. 32-8 Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) (b) Pseudocoelomate Body covering (from ectoderm) Tissue- filled region (from mesoderm) Wall of digestive cavity (from endoderm) (c) Acoelomate
Deuterostome development (examples: echinoderm, chordates) Protostome development (examples: molluscs, annelids) (a) Cleavage Eight-cell stage Eight-cell stage Radial and indeterminate Spiral and determinate Fig. 32-9 (b) Coelom formation Key Coelom Ectoderm Mesoderm Archenteron Endoderm Coelom Blastopore Mesoderm Mesoderm Blastopore Solid masses of mesoderm split and form coelom. Folds of archenteron form coelom. (c) Fate of the blastopore Anus Mouth Digestive tube Mouth Anus Mouth develops from blastopore. Anus develops from blastopore.
“Porifera” Cnidaria ANCESTRAL COLONIAL FLAGELLATE Metazoa Ctenophora Eumetazoa Ectoprocta Fig. 32-10 Brachiopoda Deuterostomia Echinodermata Chordata Bilateria Platyhelminthes Rotifera Protostomia Mollusca Annelida Arthropoda Nematoda
Silicea “Porifera” Calcarea ANCESTRAL COLONIAL FLAGELLATE Metazoa Ctenophora Cnidaria Eumetazoa Acoela Fig. 32-11 Echinodermata Deuterostomia Chordata Bilateria Platyhelminthes Rotifera Ectoprocta Lophotrochozoa Brachiopoda Mollusca Annelida Nematoda Ecdysozoa Arthropoda
Common ancestor of all animals Sponges (basal animals) Metazoa Ctenophora Fig. 32-UN1 Eumetazoa Cnidaria True tissues Acoela (basal bilaterians) Deuterostomia Bilateria (most animals) Bilateral summetry Lophotrochozoa Three germ layers Ecdysozoa