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Chapter 32 An Introduction to Animal Diversity PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kingdom Animalia • What are the characteristics of animals? Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproduction and Development • Most animals reproduce sexually, with the diploid stage usually dominating the life cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • After a sperm fertilizes an egg, the zygote undergoes cleavage, leading to formation of a blastula • The blastula undergoes gastrulation, forming embryonic tissue layers and a gastrula Video: Sea Urchin Embryonic Development Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 32-2_3 Blastocoel Cleavage Cleavage Eight-cell stage Zygote Blastocoel Endoderm Ectoderm Gastrula Blastopore Gastrulation Blastula Cross section of blastula • Many animals have at least one larval stage • A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • 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 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Paleozoic Era (542–251 Million Years Ago) • The Cambrian explosion marks the earliest fossil appearance of many major groups of living animals • There are several hypotheses regarding the cause of the Cambrian explosion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mesozoic Era (251–65.5 Million Years Ago) • During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates • Coral reefs emerged, becoming important marine ecological niches for other organisms Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cenozoic Era (65.5 Million Years Ago to the Present) • The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animals • Modern mammal orders and insects diversified during the Cenozoic Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 32.3: Animals can be characterized by “body plans” • Zoologists sometimes categorize animals according to morphology and development • A grade is a group of animal species with the same level of organizational complexity • A body plan is the set of traits defining a grade Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symmetry • Animals can be categorized according to the symmetry of their bodies, or lack of it Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 32-7a • Some animals have radial symmetry, the form found in a flower pot Radial symmetry LE 32-7b The two-sided symmetry seen in a shovel is an example of bilateral symmetry Bilateral symmetry • Bilaterally symmetrical animals have: – A dorsal (top) side and a ventral (bottom) side – A right and left side – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tissues • Animal body plans also vary according to the organization of the animal’s tissues Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Cavities • In triploblastic animals, a body cavity may be present or absent • A true body cavity is called a coelom and is derived from mesoderm Coelom Digestive tract (from endoderm) Coelomate Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) • A pseudocoelom is a body cavity derived from the blastocoel, rather than from mesoderm Body covering (from ectoderm) Pseudocoelom Digestive tract (from endoderm) Pseudocoelomate Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Muscle layer (from mesoderm) • Acoelomates are organisms without body cavities Body covering (from ectoderm) Wall of digestive cavity (from endoderm) Acoelomate Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tissuefilled region (from mesoderm) Fate of the Blastopore • In protostome development, the blastopore becomes the mouth • In deuterostome development, the blastopore becomes the anus Protostome development (examples: molluscs, annnelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Mouth Anus Digestive tube Mouth Mouth develops from blastopore Anus Anus develops from blastopore Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fate of the blastopore Concept 32.4: Leading hypotheses agree on major features of the animal phylogenetic tree • Zoologists recognize about 35 animal phyla • Current debate in animal systematics has led to the development of two phylogenetic hypotheses, but others exist as well Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 32-10 “Radiata” Deuterostomia Protostomia Bilateria Eumetazoa Metazoa Ancestral colonial flagellate • One hypothesis of animal phylogeny is based mainly on molecular data Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 32-11 “Radiata” Deuterostomia Lophotrochozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate Ecdysozoa 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 clade Bilateria • Vertebrates and some other phyla belong to the clade Deuterostomia Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings