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Intro to Animal Diversity. Chapter 32. What Is An Animal?. What Is An Animal?. What Is An Animal?. Multicellular Heterotrophic Eukaryotic No cell walls – held together with structural proteins, mainly collagen. Body Plans.
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Intro to Animal Diversity Chapter 32
What Is An Animal? • Multicellular • Heterotrophic • Eukaryotic • No cell walls – held together with structural proteins, mainly collagen
Body Plans • Animal phyla are categorized based on features that are either present or absent. • Features often included: • Symmetry • Tissue layers • Body cavities • Protostomes vs. deuterostomes
Body Symmetry • Asymmetrical • Radial • Bilateral • Dorsal & ventral • Anterior & posterior
Body Tissues • No true tissues (no gastrulation) • Diploblastic • Ectoderm & endoderm • Triploblastic • Also has mesoderm
Body Cavities • Acoelomate • Pseudocoelomate • Coelomate
Animal phylogenetictree • Zoologists currently recognize about 35 animal phyla • The current debate in animal systematics • Has led to the development of two phylogenetic hypotheses, but others exist as well
Rotifera Cnidaria Porifera Annelida Mollusca Chordata Phoronida Nemertea Ctenophora Nematoda Arthropoda Ectoprocta Brachiopoda Echinodermata Platyhelminthes “Radiata” Deuterostomia Protostomia Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Animal phylogenetictree • One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons
Cnidaria Chordata Mollusca Annelida Rotifera Silicarea Phoronida Nemertea Calcarea Arthropoda Ctenophora Ectoprocta Brachiopoda Nematoda Echinodermata Platyhelminthes “Radiata” Deuterostomia Lophotrochozoa “Porifera” Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Animal phylogenetictree • One hypothesis of animal phylogeny based mainly on molecular data
Points of 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 cladeBilateria • Vertebrates and some other phyla belong to the cladeDeuterostomia
Disagreement over the Bilaterians • The morphology-based tree • Divides the bilaterians into two clades: deuterostomes and protostomes • In contrast, several recent molecular studies • Generally assign two sister taxa to the protostomes rather than one: the ecdysozoans and the lophotrochozoans