1. LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson © 2011 Pearson Education, Inc. Lectures by Erin Barley Kathleen Fitzpatrick An Overview of Animal Diversity Chapter 32

2. There are exceptions to nearly every criterion for distinguishing animals from other life-forms Several characteristics, taken together, sufficiently define the group Concept 32.1: Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers © 2011 Pearson Education, Inc.

3. Nutritional Mode Animals are heterotrophs that ingest their food © 2011 Pearson Education, Inc.

4. Cell Structure and Specialization Animals are multicellular eukaryotes Their cells lack cell walls Their bodies are held together by structural proteins such as collagen Nervous tissue and muscle tissue are unique, defining characteristics of animals Tissues are groups of cells that have a common structure, function, or both © 2011 Pearson Education, Inc.

5. Reproduction and Development Most animals reproduce sexually, with the diploid stage usually dominating the life cycle After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage Cleavage leads to formation of a multicellular, hollow blastula The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues © 2011 Pearson Education, Inc.

6. Zygote Cleavage Eight-cell stage Figure 32.2-1

7. Zygote Cleavage Eight-cell stage Blastula Blastocoel Cross section of blastula Figure 32.2-2

8. Zygote Cleavage Eight-cell stage Blastula Blastocoel Cross section of blastula Gastrulation Cross section of gastrula Blastocoel Endoderm Ectoderm Archenteron Blastopore Figure 32.2-3

9. Many animals have at least one larval stage A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis A juvenile resembles an adult, but is not yet sexually mature © 2011 Pearson Education, Inc.

10. Most 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 © 2011 Pearson Education, Inc.

11. Concept 32.2: The history of animals spans more than half a billion years The animal kingdom includes a great diversity of living species and an even greater diversity of extinct ones The common ancestor of living animals may have lived between 675 and 800 million years ago This ancestor may have resembled modern choanoflagellates, protists that are the closest living relatives of animals © 2011 Pearson Education, Inc.

12. OTHER EUKARYOTES Choanoflagellates Sponges Animals Other animals Individual choanoflagellate Collar cell (choanocyte) Figure 32.3

13. Concept 32.3: Animals can be characterized by “body plans” Zoologists sometimes categorize animals according to a body plan, a set of morphological and developmental traits Some developmental characteristics are conservative –For example, the molecular control of gastrulation is conserved among diverse animal groups © 2011 Pearson Education, Inc.

14. Early stages of development 32-cell stage Early gastrula stage Embryos with blocked  -catenin activity 100  m Site of gastrulation RESULTS 2134 Figure 32.6

15. Symmetry Animals can be categorized according to the symmetry of their bodies, or lack of it Some animals have radial symmetry, with no front and back, or left and right © 2011 Pearson Education, Inc.

16. (a) Radial symmetry (b) Bilateral symmetry Figure 32.7

17. Two-sided symmetry is called 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 © 2011 Pearson Education, Inc.

18. Radial animals are often sessile or planktonic (drifting or weakly swimming) Bilateral animals often move actively and have a central nervous system © 2011 Pearson Education, Inc.

19. Tissues Animal body plans also vary according to the organization of the animal’s tissues Tissues are collections of specialized cells isolated from other tissues by membranous layers During development, three germ layers give rise to the tissues and organs of the animal embryo © 2011 Pearson Education, Inc.

20. Ectoderm is the germ layer covering the embryo’s surface Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron © 2011 Pearson Education, Inc.

21. Sponges and a few other groups lack true tissues Diploblastic animals have ectoderm and endoderm –These include cnidarians and comb jellies Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians –These include flatworms, arthropods, vertebrates, and others © 2011 Pearson Education, Inc.

22. Body Cavities Most triploblastic animals possess a body cavity A true body cavity is called a coelom and is derived from mesoderm Coelomates are animals that possess a true coelom © 2011 Pearson Education, Inc.

23. (a) Coelomate Coelom Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) (b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) (c) Acoelomate Body covering (from ectoderm) Wall of digestive cavity (from endoderm) Tissue- filled region (from mesoderm) Figure 32.8

24. Figure 32.8a (a) Coelomate Coelom Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm)

25. A pseudocoelom is a body cavity derived from the mesoderm and endoderm Triploblastic animals that possess a pseudocoelom are called pseudocoelomates © 2011 Pearson Education, Inc.

26. Figure 32.8b (b) Pseudocoelomate Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm)

27. Triploblastic animals that lack a body cavity are called acoelomates © 2011 Pearson Education, Inc.

28. Figure 32.8c (c) Acoelomate Body covering (from ectoderm) Wall of digestive cavity (from endoderm) Tissue- filled region (from mesoderm)

29. Coelomates and pseudocoelomates belong to the same grade A grade is a group whose members share key biological features A grade is not necessarily a clade, an ancestor and all of its descendants © 2011 Pearson Education, Inc.

30. Protostome and Deuterostome Development Based on early development, many animals can be categorized as having protostome development or deuterostome development © 2011 Pearson Education, Inc.

31. Cleavage In protostome development, cleavage is spiral and determinate In deuterostome development, cleavage is radial and indeterminate With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo Indeterminate cleavage makes possible identical twins, and embryonic stem cells © 2011 Pearson Education, Inc.

32. (a) Cleavage (b) Coelom formation (c) Fate of the blastopore Key Ectoderm Mesoderm Endoderm Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate Archenteron Coelom Blastopore Mesoderm Folds of archenteron form coelom. Solid masses of mesoderm split and form coelom. Anus Mouth Digestive tube Mouth develops from blastopore. Anus develops from blastopore. Figure 32.9

33. Figure 32.9a (a) Cleavage Key Ectoderm Mesoderm Endoderm Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate

34. Coelom Formation In protostome development, the splitting of solid masses of mesoderm forms the coelom In deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom © 2011 Pearson Education, Inc.

35. Figure 32.9b Key Ectoderm Mesoderm Endoderm Archenteron Coelom Blastopore Mesoderm Folds of archenteron form coelom. Solid masses of mesoderm split and form coelom. (b) Coelom formation Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates)

36. Fate of the Blastopore The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula In protostome development, the blastopore becomes the mouth In deuterostome development, the blastopore becomes the anus © 2011 Pearson Education, Inc.

37. Figure 32.9c (c)Fate of the blastopore Key Ectoderm Mesoderm Endoderm Anus Mouth Digestive tube Mouth develops from blastopore. Anus develops from blastopore. Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates)

38. Concept 32.4: New views of animal phylogeny are emerging from molecular data Zoologists recognize about three dozen animal phyla Phylogenies now combine morphological, molecular, and fossil data Current debate in animal systematics has led to the development of multiple hypotheses about the relationships among animal groups © 2011 Pearson Education, Inc.

39. Points of Agreement 1.All animals share a common ancestor 2.Sponges are basal animals 3.Eumetazoa is a clade of animals (eumetazoans) with true tissues 4.Most animal phyla belong to the clade Bilateria, and are called bilaterians 5.Chordates and some other phyla belong to the clade Deuterostomia © 2011 Pearson Education, Inc.

40. Progress in Resolving Bilaterian Relationships The morphology-based tree divides bilaterians into two clades: deuterostomes and protostomes In contrast, recent molecular studies indicate three bilaterian clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa Ecdysozoans shed their exoskeletons through a process called ecdysis © 2011 Pearson Education, Inc.

41. Figure 32.12

42. Some lophotrochozoans have a feeding structure called a lophophore Others go through a distinct developmental stage called the trochophore larva © 2011 Pearson Education, Inc.

43. Figure 32.13 Apical tuft of cilia Mouth Anus (a)Lophophore feeding structures of an ectoproct (b)Structure of a trochophore larva Lophophore

44. Future Directions in Animal Systematics Phylogenetic studies based on larger databases will likely provide further insights into animal evolutionary history © 2011 Pearson Education, Inc.

45. Common ancestor of all animals True tissues Bilateral symmetry Three germ layers Porifera (basal animals) Ctenophora Cnidaria Acoela (basal bilaterians) Deuterostomia Lophotrochozoa Ecdysozoa Metazoa Eumetazoa Bilateria (most animals) Figure 32.UN03