CHAPTER 32

1. CHAPTER 32 AN INTRODUCTION TO ANIMAL DIVERSITY

2. I. Concept 32.1: What is an Animal? • 95% are invertebrates • Multicellular • Eukaryotic • Heterotrophic (ingestive) • Lack cell walls • Most are mobile • Diploid with haploid gametes • Sexual reproduction (zygote  blastula  gastrula)

3. Embryology--Cleavage

4. 9. Carbohydrates stored as glycogen 10. Some produce larva which undergo metamorphosis 11. Specialized systems 12. Two unique types of tissue: nervous tissue and muscle tissue 13. Share the unique homeobox-containing family of regulatory genes know as Hox genes • Hox genes play an important role in development of animal embryos

5. II. Concept 32.2: Animal History A. Common Ancestor Such a colony is about 0.02mm high. 1. May have resembled modern choanoflagellates 2. Choanoflagellates are protists that are the closest living relatives of animals and were probably a colonial, flagellated protist.

7. III. Concept 32.3: Body Plans A. Phylogeny • Define as the evolutionary history of species • Based on general features of morphology and development • Each major branch represents a grade, (group of animal species that share the same level of organizational complexity) • A grade is not necessarily a clade or monophyletic group.

8. ANIMALS Metazoa ParazoaEumetazoa RadiataBilateria AcoelomatePseudocoelomateCoelomate DeuterostomesProtostomes

9. B. Major Branches of the Animal Kingdom 1. Subkingdom Parazoa • Simple anatomy (lack true tissues) • Phylum Porifera 2. Subkingdom Eumetazoa • True tissues • All other phyla

10. C. Body Plans • A body plan is a set of morphological and developmental traits 1.Symmetry • Animals can be categorized by body symmetry or the lack of it a. Radial symmetry (Radiata) -Characterized by a body shaped like a pie or barrel, with many equal parts radiating outward like spokes of a wheel -have oral and aboral sides but no front, back, left, or right surfaces

11. b. Bilateral symmetry (Bilateria) -Characterized by a body form with a central longitudinal plane dividing the body into two equal but opposite halves -A dorsal (top) and ventral (bottom) sides -Anterior (head) and posterior (tail) ends -Left and right sides -Exhibit cephalization (concentration of nerves and sense organs on anterior end)

12. SYMMETRY

13. 2. Tissues a. Tissues are collections of specialized cells isolated from other tissues by membranous layers b. During gastrulation(downward and inward movement of cells of blastula), three germ layers form which give rise to the tissues and organs of the animal embryo

14. c. Diploblastic • Tissues develop from two germ layers (ectoderm or endoderm) d. Triploblastic • Tissues develop from three germ layers: • Ectoderm is the outer most germ layer which develops into outer layer and central nervous system • Endoderm is the inner most germ layer and lines the developing digestive tube called the archenteron • Mesoderm is the middle layer which is located between ectoderm and endoderm • Includes all bilaterians

15. Germ Layers

16. 3. Body Cavity (Coelom) • Defined as a fluid- or air-filled space separating the digestive tract from the outer body wall a. Acoelomate • No body cavity between digestive tract and outer body wall • Area filled with cells • Phylum Platyhelminthes

17. Acoelomate

18. b. Pseudocoelomate • Body cavity lined with mesoderm and endoderm • Tube within a tube • Phyla:Nematoda Rotifera

19. Pseudocoelomate

20. c. Coelomate (true body cavity) • Body cavity lined with mesoderm • Mesenteries connect outer and inner mesoderm and suspend internal organs • Phyla:EchinodermataArthropoda MolluscaChordata Annelida • Functions of the body cavity 1. Fluid cushions the suspended organs, helping to prevent internal injury 2. In soft-bodied coelomates, functions as a hydrostatic skeleton against which muscles can work 3. Enables internal organs to grow and move independently of the other body wall

21. Coelomate

23. 4. Development--Protostomiavs. Deuterostomia • 2 evolutionary lines in coelomates • Differ in cleavage, fate of blastopore, and coelom formation • Protostomes—mollusks, annelids, arthropods • Deuterostomes—echinoderms, chordates

24. a. Cleavage Protostomes • Spiral Cleavage—cleavage diagonal to the embryo’s vertical axis Deuterostomes • Radial Cleavage—cleavage either parallel or perpendicular to embryo’s vertical axis

25. b. Determination  Protostomes • Determinate Cleavage—developmental fate of each cell determined very early -A cell from 4-cell stage will not develop fully  Deuterostomes • Indeterminate Cleavage—early cells retain ability to develop into complete embryo if isolated from other cells -Makes possible identical twins and embryonic stem cells

26. Cleavage

27. c. Coelom Formation Protostomes • Schizocoelous—the splitting of solid masses of mesoderm forms the coelom Deuterostomes • Enterocoelous—the mesoderm buds from the wall of the archenteron to form the coelom

28. Coelom Formation

29. d. Fate of Blastopore • Blastopore—first opening of archenteron (gut) which forms from blastula during gastrulation Protostomes --Blastoporebecomes the mouth Deuterostomes --Blastoporebecomes the anus

30. Fate of the Blastopore

32. IV. Concept 32.4: New Views of Animal Phylogeny • One hypothesis of animal phylogeny is based mainly on morphological and developmental comparisons

33. Morphological Characteristics

34. One hypothesis of animal phylogeny is based mainly on molecular data

35. Molecular Studies

36. A. Points of Agreement • All animals share a common ancestor • Sponges are basal animals • Eumetazoa is a clade of animals (eumetazoans) with true tissues • Most animals phyla belong to the clade Bilateria and are called bilaterians • Chordates and some other phyla belong to the clade Deuterostomia

37. B. Progress in resolving Bilaterian Relationships 1. The morphology-based tree divides bilaterians into two clades: deuterostomes and protostomes 2. In contrast, recent molecular studies indicate three bilaterian clades: Deuterostomia, Ecdysozoa, and Lophotrochozoa a. Ecdysozoansshed their exoskeletons through a process called ecdysis(Arthropoda and Nematoda) b. Some lophotrochozoanshave a feeding structure called a lophophore( Mollusca, Annelida, Rotifera, Platyhelminthes) c. Other phyla go through a distinct developmental stage called the trochophore larva(Mollusca and Annelida)

38. TERMS: • Zygote • Cleavages • Blastula • Gastrula • Ectoderm • Endoderm • Mesoderm • Blastopore • Archenteron • Metamorphosis • Radial symmetry • Bilateral symmetry • Cephalization • Acoelomate • Pseudocoelomate • Coelomate • Anterior • Posterior • Dorsal • Ventral

39. Ecdysis

40. Trochophore Larva

42. You should now be able to: • List the characteristics that combine to define animals • Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal taxa; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate grades • Compare the developmental differences between protostomes and deuterostomes • Compare the alternate relationships of annelids and arthropods presented by two different proposed phylogenetic trees • Distinguish between ecdysozoans and lophotrochozoans