BIOL 152 1st Edition Lecture 12 Outline of Last Lecture Animal Diversity Outline of Current Lecture Animal Body Plans Current Lecture Invertebrates Animal Body Plans Grade group of animals that share the same level of organizational complexity Not necessarily equivalent in meaning with clade Animal body plans exhibit 2 Symmetry 3 Tissue layers 4 Internal cavities 5 Development 1 Body symmetry and cephalization Asymmetrical such as sponges Radial symmetry such as oral aboral Bilateral symmetry such as cephalization 2 Tissue layers Sponges lack true tissues Tissue layers form through the process of gastrulation Concentric germ layers form tissues and organs These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Animals with two embryonic tissue layers are diploblasts endoderm and ectoderm Animals with three embryonic tissue layers are tripleoblast endoderm mesoderm and ectoderm Ectoderm outer covering and forms the Central Nervous System Endoderm digestive system and is associated with the formation of organs Mesoderm formation of muscles and other organs 3 Body cavity Animals are triploblastic but not all animals are triploblastic Fluid filled space separating the digestive tract from the outer body wall True coelom forms from mesoderm Pseudocoelom forms from blastocoel and is fully functional It is gained and lost several times in the course of animal evolution Functions of the coelom cushion suspended organs hydro elastic skeleton against which muscles work allows internal organs to move and grow independently of the outer body wall 4 Mode of Development Protostome and deuterostome development Three features distinguish these modes 1 Cleavage affected by how the mitotic spindle forms Protostome eight celled spiral and determinate Dueterstome eight celled radial and intermediate 2 Coelom formation origin of mesoderm pocketing Protostome schizocoelous solid mass of mesoderm splits and forms the coelom Dueterstome enterocoelous folds of archenteron form the coelom 3 Gastrulation fate of the first pore formed Protostome mouth develops from blastopore Dueterstome first opening becomes anus Animal Phylogenetic Tree 35 Phyla relationships debated A clade represents the ancestors and offspring Two current hypotheses Morphological Molecular Points of agreement between the morphological and molecular phylogenetic tree common ancestor colonial flagellate sponges are basal radiata are basal in the Eumetazoa true animals most animals belong to Bilateria vertebrates and others are deuterostomes Points of disagreement between the morphological and molecular phylogenetic tree relationships among bilaterians there are only two main clades in morphology tree there are three main clades in molecular tree protostomes are broken up into ecdysozoa and lophotrochozoa
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