1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 32 An Introduction to Animal Diversity

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Welcome to Your Kingdom The animal kingdom extends far beyond humans and other animals we may encounter Figure 32.1

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nutritional Mode Heterotrophs  ingest their food

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell Structure and Specialization Multicellular eukaryotes, Cells lack cell walls

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bodies are held together by structural proteins, e.g. collagen Nervous tissue and muscle tissue

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproduction Most animals reproduce sexually – Diploid stage dominating the life cycle

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Development Sperm fertilizes egg  zygote  cleavage  blastula  gastrulation  formation of embryonic tissue layers  gastrula

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Zygote Cleavage Eight-cell stage Cleavage Blastula Cross section of blastula Blastocoel Gastrula Gastrulation Endoderm Ectoderm Blastopore Early embryonic development in animals Figure 32.2 In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula, a hollow ball of cells. 3 The endoderm of the archenteron de- velops into the tissue lining the animal’s digestive tract. 6 The blind pouch formed by gastru- lation, called the archenteron, opens to the outside via the blastopore. 5 Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer). 4 Only one cleavage stage–the eight-cell embryo–is shown here. 2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage. 1

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hox genes regulate development of body form Hox family of genes has been highly conserved, yet produces a wide diversity of animal morphology

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The history of animals spans more than a billion years Great diversity of living species and even greater diversity of extinct ones

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Common ancestor of living animals – Lived ~1 billion million years ago – May have resembled modern choanoflagellates, protists that are the closest living relatives of animals Figure 32.3 Single cell Stalk

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Was probably a colonial, flagellated protist Figure 32.4 Colonial protist, an aggregate of identical cells Hollow sphere of unspecialized cells (shown in cross section) Beginning of cell specialization Infolding Gastrula-like “protoanimal” Somatic cells Digestive cavity Reproductive cells

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings (a) (b) Neoproterozoic Era (1 Billion–524 Million Years Ago) Early members of the animal fossil record Figure 32.5a, b

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Paleozoic Era (542–251 Million Years Ago) The Cambrian explosion – Earliest fossil appearance of many major groups of living animals – Several current hypotheses Figure 32.6

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mesozoic Era (251–65.5 Million Years Ago) Dinosaurs were dominant terrestrial vertebrates Coral reefs emerged, becoming important marine ecological niches for other organisms

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cenozoic Era (65.5 Million Years Ago to the Present) Mass extinctions of terrestrial and marine animals Modern mammal orders and insects diversified

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Plans Radial symmetry – Like in a flower pot Figure 32.7a Radial symmetry. The parts of a radial animal, such as a sea anemone (phylum Cnidaria), radiate from the center. Any imaginary slice through the central axis divides the animal into mirror images. (a)

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bilateral symmetry – two-sided symmetry Figure 32.7b Bilateral symmetry. A bilateral animal, such as a lobster (phylum Arthropoda), has a left side and a right side. Only one imaginary cut divides the animal into mirror-image halves. (b)

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bilateral animals – Dorsal (top) side and a ventral (bottom) side – Right and left side – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tissues Collections of specialized cells isolated from other tissues by membranous layers

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animal embryos – Form germ layers, embryonic tissues, including ectoderm, endoderm, and mesoderm Diploblastic animals – two germ layers Triploblastic animals – three germ layers

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Body Cavities In triploblastic animals – body cavity may be present or absent

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Coelom A true body cavity derived from mesoderm Figure 32.8a Coelom Body covering (from ectoderm) Digestive tract (from endoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Coelomate. Coelomates such as annelids have a true coelom, a body cavity completely lined by tissue derived from mesoderm. (a)

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pseudocoelom Body cavity not lined w/ mesoderm Figure 32.8b Pseudocoelom Muscle layer (from mesoderm) Body covering (from ectoderm) Digestive tract (from ectoderm) Pseudocoelomate. Pseudocoelomates such as nematodes have a body cavity only partially lined by tissue derived from mesoderm. (b)

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Acoelomates No body cavities Figure 32.8c Body covering (from ectoderm) Tissue- filled region (from mesoderm) Digestive tract (from endoderm) Acoelomate. Acoelomates such as flatworms lack a body cavity between the digestive tract and outer body wall. (c)

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protostome and Deuterostome Development Distinction based on early development

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cleavage Protostomes – Cleavage is spiral and determinate Deuterostomes – Cleavage is radial and indeterminate Figure 32.9a Protostome development (examples: molluscs, annelids, arthropods) Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate (a) Cleavage. In general, protostome development begins with spiral, determinate cleavage. Deuterostome development is characterized by radial, indeterminate cleavage.

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Coelom Formation Protostomes – Splitting of mesoderm  coelom (schizocoelous development) Deuterostomes – Enterocoelous development Figure 32.9b Archenteron Blastopore Mesoderm Coelom Blastopore Mesoderm Schizocoelous: solid masses of mesoderm split and form coelom Enterocoelous: folds of archenteron form coelom Coelom (b) Coelom formation. Coelom formation begins in the gastrula stage. In protostome development, the coelom forms from splits in the mesoderm (schizocoelous development). In deuterostome development, the coelom forms from mesodermal outpocketings of the archenteron (enterocoelous development).

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fate of the Blastopore Protostomes – Blastopore becomes the mouth Deuterostomes – Blastopore becomes the anus Figure 32.9c Anus Mouth Mouth develops from blastopore Anus develops from blastopore Digestive tube

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hypothesis of animal phylogeny based on anatomy Figure 32.10 PoriferaCnidaria Ctenophora Phoronida Ectoprocta Brachiopoda Echinodermata Chordata Platyhelminthes Mollusca Annelida Arthropoda Rotifera Nemertea Nematoda “ Radiata ” Deuterostomia Protostomia Bilateria Eumetazoa Metazoa Ancestral colonial flagellate

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hypothesis based on molecular data Figure 32.11 Calcarea Silicarea Ctenophora Cnidaria Echinodermata Chordata Brachiopoda Phoronida Ectoprocta Platyhelminthes Nemertea Mollusca Annelida Rotifera Nematoda Arthropoda “Radiata” “Porifera” Deuterostomia Lophotrochozoa Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate