Lecture 4. Metazoa PDF
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Dr. Meriem Taleb
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This document is a lecture on Metazoa, a subkingdom within the animal kingdom. It covers the classification of Metazoa based on germ layers, symmetry, and developmental patterns. The lecture notes provide definitions and examples of different groups of animals, and their characteristics.
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Subkingdom Metazoa Definition Metazoa, or multicellular animals, are classified into several major groups based on their evolutionary relationships, body plans, and characteristics. The term Metazoa refers to a major group within the animal kingdom, encompassing all multicellular anima...
Subkingdom Metazoa Definition Metazoa, or multicellular animals, are classified into several major groups based on their evolutionary relationships, body plans, and characteristics. The term Metazoa refers to a major group within the animal kingdom, encompassing all multicellular animals. The name derives from Greek roots, where "meta-" means "beyond" or "more advanced," and "zoon" means "animal." ©Dr Meriem Taleb Classification Metazoa are classified based on several key criteria, including: Germ Layers: Parazoa: Lack true tissues (e.g., Phylum Porifera). Eumetazoa: Have true tissues, further divided into: ⚬ Diploblastic: Two germ layers (ectoderm and endoderm). ⚬ Triploblastic: Three germ layers (ectoderm, mesoderm, and endoderm). Symmetry: ⚬ Asymmetrical: No specific symmetry (e.g., sponges). ⚬ Radial Symmetry: Body parts arranged around a central axis (e.g., cnidarians). ⚬ Bilateral Symmetry: Divided into two mirror-image halves (e.g., most animals, including vertebrates). Developmental Patterns: ⚬ Protostomia: Mouth develops from the blastopore (e.g., arthropods, mollusks). ⚬ Deuterostomia: Anus develops from the blastopore (e.g., echinoderms, chordates). Dr. Meriem Taleb Classification of Metazoa METAZOA Have true tissues Exhibit symmetry Eumetazoa Parazoa Lack true tissues Asymmetrical Phylum Porifera (sponges) Diploblastic Triploblastic Dr. Meriem Taleb Eumetazoa Two germ layers (ectoderm and endoderm) Radial symmetry Three germ layers (ectoderm, Phylum Cnidaria: (e.g., Diploblastic Triploblastic mesoderm, and endoderm) jellyfish, corals, sea anemones) Bilateral symmetry Phylum Ctenophora: (e.g., comb jellies) Anus develops from the blastopore first Deuterostomia Protostomia Mouth develops from Phylum Echinodermata: the blastopore first. (e.g., starfish, sea urchins) Phylum Chordata: (e.g., vertebrates) Lophotrochozoa Ecdysozoa Many have a larval stage Animals that molt their known as trochophore. exoskeleton (ecdysis) Phylum Mollusca: (e.g., Phylum Nematoda: snails, clams) (e.g., roundworms) Phylum Annelida: (e.g., Phylum Arthropoda: segmented worms) (e.g., insects, arachnids, Phylum Platyhelminthes: crustaceans) (e.g., flatworms). Dr. Meriem Taleb
