The Animal Kingdom: An Introduction to Animal Diversity

1. The Animal Kingdom:An Introduction to Animal Diversity Chapter 29

2. Learning Objective 1 • What characters are common to most animals?

3. Kingdom Animalia • Eukaryotic • Multicellular • Heterotrophic • Cells specialized for specific functions

4. Structure • Body plan • basic structure and functional design of body • Animals have diverse body plans

5. Function • Most animals • are capable of locomotion at some time during life cycle • can respond adaptively to external stimuli • can reproduce sexually

6. Sexual Reproduction • Sperm and egg unite (zygote) • Zygote undergoes cleavage • cell divisions produce hollow ball of cells (blastula) • Blastula undergoes gastrulation • forms embryonic tissues

7. KEY CONCEPTS • Animals are multicellular, eukaryotic heterotrophs

8. Explore the characteristics of animals by clicking on the figures in ThomsonNOW.

9. Learning Objective 2 • Compare the advantages and disadvantages of life in the ocean, in fresh water, and on land

10. Marine Environments • Provide • relatively stable temperatures • buoyancy • readily available food • Fluid and salt balance • more easily maintained than in fresh water • Disadvantages: • currents and other water movements

11. Fresh Water • Provides • less constant environment • less food • Animals must osmoregulate • fresh water is hypotonic to tissue fluid

12. Terrestrial Animals • Have adaptations that • protect them from drying out • protect them from temperature changes • protect their gametes and embryos

13. Marine and Terrestrial Environments

14. Learning Objective 3 • Use current hypotheses to trace the early evolution of animals

15. Hypotheses • Proterozoic eon • most animal clades diverged over long period • based on molecular data • Cambrian Radiation • new body plans rapidly evolved among clades • first fossils of these animals

16. Hox Genes • Hox gene group • controls early development in animal groups • Cambrian period • many Hox genes had evolved • mutations could have resulted in rapid changes in animal body plans

17. Learning Objective 4 • How do biologists use structural characters (variations in body symmetry, number of tissue layers, type of body cavity) and patterns of early development to infer relationships among animal phyla?

18. Symmetry • Cnidarians and ctenophores are closely related • because they share radial symmetry • most other animals exhibit bilateral symmetry • Cephalization (development of head) • evolved with bilateral symmetry

19. Radial and Bilateral Symmetry

20. Radial symmetry (top view) Fig. 29-3a, p. 623

21. Radial symmetry (side view) Fig. 29-3b, p. 623

22. Dorsal Frontal section Caudal Posterior Anterior Cephalic Ventral Cross (or transverse) section Bilateral symmetry (lateral view) Fig. 29-3c, p. 623

23. Dorsal Sagittal section Medial Frontal section Lateral Ventral Bilateral symmetry (front view) Fig. 29-3d, p. 623

24. Insert “Types of body symmetry” symmetry.swf

25. Other Structural Characters • Relationships can be based on • level of tissue development • type of body cavity • Embryonic tissues (germ layers)

26. Coelom Formation

27. Schizocoely — characteristic of protostomes Enterocoely — characteristic of deuterostomes Ectoderm Ectoderm Developing mesoderm Blastopore Presumptive mesoderm Enterocoelic pouch Endoderm Mesoderm Ectoderm Endoderm Ectoderm Gut Developing coelom (Schizocoel) Ectoderm Endoderm Mesoderm Coelom (Enterocoel) Gut Gut Coelom Mesoderm Gut Endoderm Mesentery Coelom Epidermis (ectoderm) Muscle layer (mesoderm) Peritoneum (mesoderm) Gut Fig. 29-6, p. 626

28. Schizocoely — characteristic of protostomes Enterocoely — characteristic of deuterostomes Ectoderm Ectoderm Developing mesoderm Blastopore Presumptive mesoderm Enterocoelic pouch Endoderm Mesoderm Ectoderm Endoderm Ectoderm Gut Ectoderm Endoderm Developing coelom (Schizocoel) Mesoderm Coelom (Enterocoel) Gut Coelom Mesoderm Gut Endoderm Mesentery Coelom Epidermis (ectoderm) Muscle layer (mesoderm) Peritoneum (mesoderm) Gut Stepped Art Fig. 29-6, p. 626

29. Germ Layers • Outer layer (ectoderm) • gives rise to body covering, nervous system • Inner layer (endoderm) • lines the gut and other digestive organs • Middle layer (mesoderm) • gives rise to most other body structures

30. Body Plans

31. Epidermis (from ectoderm) Muscle layer (from mesoderm) Mesenchyme (gelatin-like tissue) (a) Acoelomate—flatworm (liver fluke). Epithelium (from endoderm) Fig. 29-4a, p. 624

32. Pseudocoelom Epidermis (from ectoderm) Muscle layer (from mesoderm) Epithelium (from endoderm) (b) Pseudocoelomate—nematode. Fig. 29-4b, p. 624

33. Coelom Epidermis (from ectoderm) Muscle layer (from mesoderm) Peritoneum (from mesoderm) Epithelium (from endoderm) Mesentery (from mesoderm) (c) True coelomate—vertebrate. Fig. 29-4c, p. 624

34. Insert “Types of body cavities” coelom.swf

35. Bilateral Symmetry • Acoelomate • no body cavity • Pseudocoelomate • body cavity not completely lined with mesoderm • Coelomate, (animal with true coelom) • body cavity completely lined with mesoderm

36. Bilateral Animals • Two major evolutionary branches: • Protostomia • mollusks, annelids, arthropods • Deuterostomia • echinoderms, chordates

37. Blastopore • Opening from embryonic gut to outside • In protostomes • develops into the mouth • In deuterostomes • becomes the anus

38. Cleavage 1 • Protostomes • undergo spiral cleavage • early cell divisions diagonal to polar axis • Deuterostomes • undergo radial cleavage • early cell divisions either parallel or at right angles to polar axis • cells lie directly above or below one another

39. Spiral and Radial Cleavage

40. Polar axis Top view Spiral cleavage Fig. 29-5a, p. 625

41. Top view Polar axis Radial cleavage Fig. 29-5b, p. 625

42. Cleavage 2 • Protostomes • undergo determinate cleavage • fate of each embryonic cell is fixed very early • Deuterostomes • undergo indeterminate cleavage • fate of each embryonic cell is more flexible

43. Relationships Based on Structure

44. Parazoa Eumetazoa Radiata Bilateria Coelomates Acoelomates Pseudocoelomates Protostomia Deuterostomia Choanoflagellates Platyhelminthes Echinodermata Hemichordata Onychophora Ctenophora Arthropoda Tardigrada Nematoda Nemertea Chordata Mollusca Annelida Cnidaria Rotifera Porifera Segmentation Segmentation Deuterostome development Pseudocoelom True coelom Radial symmetry Protostome development Three tissue layers (mesoderm) Bilateral symmetry Tissues (ectoderm and endoderm) Multicellularity Choanoflagellate ancestor Fig. 29-7, p. 627

45. KEY CONCEPTS • Biologists classify animals based on their body plan and features of their early development

46. Learning Objective 5 • What are three major contributions to animal phylogeny made by molecular systematics? • Identify the three major clades of bilateral animals

47. Molecular Systematics 1 • Confirmed much of animal phylogeny based on structural characters • including axiom that animal body plans usually evolved from simple to complex

48. Molecular Systematics 2 • Provided evidence for exceptions to “simple-to-complex” rule • Example • molecular data indicate flatworms and ribbon worms evolved from more complex animals, became simpler over time

49. Molecular Systematics 3 • Molecular data suggest pseudocoelomate animals do not form natural group • probably evolved from coelomate ancestors

50. Protostomes • 2 clades based on molecular data: • Lophotrochozoa • flatworms, ribbon worms, mollusks, annelids, lophophorate phyla, rotifers • Ecdysozoa (animals that molt) • nematodes and arthropods