1. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 9

2. 2 Multicellular and Tissue Levels of Organization

3. 3 Figure 9.1

4. 4 Phyla Porifera – (Parazoans) Cnidaria – (Eumatozoans) Ctenophora – (Eumatozoans)

5. 5 Origins of Multicellular Life Been around for about 600 million years Only 10% of Earth’s geological history Appeared about 100 million years before the Precambrian/Cambrian boundary (evolutionary explosion) All life we know of now + 15-20 extinct animal groups

6. 6 Colonial Hypothesis A hypothesis that states that multicellularity could have arisen as divinding cells remained together, in the fashion of many colonial protists.

7. 7 Synctial Hypothesis A synctium is a large, multinucleate cell. The formation of plasma membranes in the cytoplasm of a synctial protist could have produced a small, multicellular organism. Also, supported by formations found within the Protist kingdom.

8. 8 Animal Origins Animalia is thought to be monophyletic. The likely ancestral group has been identified as the protist group, the Choanoflagellates.

9. 9 Figure 9.2

10. 10 Figure 9.3

11. 11 Phylum Porifera Primarily marine animals consisting of loosely organized cells About 9000 species Vary in size from less than a centimeter to mass that would more than fill your arms

12. 12 Figure 9.4 (a)

13. 13 Figure 9.4 (b)

14. 14 Characteristics of the Phylum: Asymmetrical or superficially radially symmetrical Three cell types: pinacocytes, mesenchyme cells, and choanocytes Central cavity, or a series of branching chambers, through which water circulates during filter feeding No tissues or organs

15. 15 Phylum Porifera Class Calcarea – spicules composed of calcium carbonate; spicules are needle shaped or have 3 or 4 rays; ascon, leucon, or sycon body forms; all marine. Calcareous sponges. Class Hexactinellida – Spicules composed of silica and 6-rayed; spicules often fused in an intricate lattice; cup or vase shaped; sycon or leucon body form; found at 450 to 900m depths in tropical West Indies and Eastern Pacific. Glass sponges.

16. 16 Phylum Porifera (cont.) Class Desmospongiae – Brilliantly colored sponges with needle-shaped of four-rayed siliceous spicules or spongin or both; leucon body form; up to 1 m in height and diameter. Includes 1 family of freshwater sponges, Spongilladae, and the bath sponges.

17. 17 Cell Types, Body Wall, and Skeletons Pinacocytes – thin, flat cells that line the outer surface of a sponge; may be contractile vacuole; and their contraction may change the shape of some sponges. Porocytes – specialized pinacocytes that can regulate water circulation

18. 18 Cell Types, Body Wall, and Skeletons (cont.) Mesohyl – jellylike layer found just below pinatocyte layer Mesenchyme cells – amoeboid cells that move about in the mesohyl and are specialized for reproduction, secreting skeletal elements, transporting and storing food, and forming contractile rings around openings in the sponge wall.

19. 19 Cell Types, Body Wall, and Skeletons (cont.) Choanocytes – collar cells, found below the meshyl and line the inner chamber(s); flagellated; the flagellum moves in a circular motion that creates a water current that moves through the sponge. Spicules – formed by amoeboid cells, made of calcium carbonate or silica

20. 20 Figure 9.5

21. 21 Figure 9.6

22. 22 Water Currents and Body Forms 3 Sponge Body Forms –Ascon –Sycon –Leucon

23. 23 Ascon Simplest; least common; vaselike; Ostia are the outer openings of porocytes and lead directly to a chamber called the spongocoel; Water exits the sponge through the osculum (a single large opening at the top of the sponge.)

24. 24 Sycon Sponge body wall appears folded; folds into the sponge are called incurrent canals; folds out of the sponge are called radial canals; water enters through dermal pores; into the spongocoel and out the osculum

25. 25 Leucon Have extensively branched canal system; water enters the sponge through ostia, through branched incurrent canals, into choanocyte-lined chamber, into excurrent canals and eventually through oscula (multiple osculum)

26. 26 Figure 9.7

27. 27 Maintenance Functions Feed on particles that range in size from 0.1 to 50 micrometers. Food consists of bacteria, microscopic algae, protists and other suspended organic matter. Sponges do not have nerve cells to co- ordinate body functions. Therefore most reactions are the result of a single cell responding to a stimulus. Communication between cells may be possible, but we do not know for certain.

28. 28 Reproduction Both sponges are monoecious (both sexes occur in the same individual) They do not usually self-fertilize because they produce sperm and eggs at different times Both the sperm and the egg are formed by choanocytes that undergo meiosis; released through the oscula

29. 29 Reproduction (cont.) Fertilization occurs in the ocean water and planktonic larvae develop. After about 2 days the larvae will settle into the substrate and begin to develop into the adult body form. Some sponges can reproduce asexually by producing gemmules that can withstand harsh temperatures and drought in order to survive. Some sponges have shown that small portions removed from a larger sponge can grow into new individuals.

30. 30 Figure 9.8 (abc)

31. 31 Phylum Cnidaria (ni-dar’ e-ah) 9000 species Mostly marine Important in coral reef systems Radially symmetrical animals have no anterior or posterior regions; thus terms of direction are based on the placement of the mouth. Mouth end; oral Non-mouth end; aboral

32. 32 Characteristics of the Phylum Cnidaria Radial symmetry or modified biradial symmetry Diploblastic, tissue level of organization Gelatinous mesoglea between the epidermal and gastrodermal tissue layers Gastrovascular cavity Nervous system in the form of a nerve net Specialized cells, called cnidocytes, used in defense, feeding, and attachment

33. 33 The Body Wall Diploblastic –Ectoderm becomes epidermis –Endoderm becomes gastrodermis Tissue-level organization

34. 34 Figure 9.9

35. 35 Cnidocytes Cnidocytes produce cells called cnida –Cnida are fluid-filled, intracellular capsule enclosing a coiled, hollow tube –A lid-like operculum caps the capsule at one end –The cnidocyte has a modified cilium called a cnidocil –Stimulation of the cnidocil forces open the operculum, discharging the coiled tube

36. 36 Cnida & Nematocysts 30 kinds of cnida Nematocysts are a type of cnida used for food gathering and defense that may discharge a long tube armed with spines that penetrates the prey (the spines carry a paralyzing toxin) Some cnida contain unarmed tubes that wrap around prey Others produce a sticky substance to help anchor the animal Can be up to 6 different types of cnida on a single individual

37. 37 Figure 9.10

38. 38 Alternation of Generations 2 body forms –Polyp – asexual and sessile; attaches to the substrate at the aboral end; has a cylindrical body, called a column, and a mouth surrounded by food gathering tentacles –Medusa – diecious and free swimming; shaped like an inverted bowl, with tentacles dangling from its margins; mouth opening is centrally located facing downward; swims by gentle pulsations of the body wall

39. 39 Figure 9.11

40. 40 Maintenance Functions The gastrodermis lines the gastrovascular cavity –Functions in: Digestion Exchange of respiratory gases and wastes Discharge of gametes –Food, digestive wastes, and reproductive stages enter and leave the GC through the mouth

41. 41 Reproduction Most are diecious Sperm and eggs are released into the GC or to the outside of the body Embryo forms a free-swimming larvae called a planula The planula attaches to the substrate and a young polyp develops

42. 42 Class Hydrozoa Small, relatively common Mostly marine, 1 class with freshwater species Most display alternation of generations –In some medusa stage is lost –In some the polyp stage is very small

43. 43 Class Hydrozoa 3 features distinguish hydrozoans from other cnidarians: –Nematocysts are only in the epidermis –Gametes are epidermal and released to the outside of the body rather than into the gastrovascular cavity –The mesoglea is largely acellular

44. 44 Class Hydrozoa

45. 45 Figure 9.12

46. 46 Figure 9.13 (a)

47. 47 Figure 9.13 (b)

48. 48 Figure 9.14 (a)

49. 49 Figure 9.14 (b)

50. 50 Figure 9.15

51. 51 Figure 9.16

52. 52 Figure 9.17

53. 53 Figure 9.18 (a)

54. 54 Figure 9.19

55. 55 Figure 9.20

56. 56 Figure 9.21 (a)

57. 57 Figure 9.21 (b)

58. 58 Figure 9.22 (a)

59. 59 Figure 9.22 (b)

60. 60 Box Figure 9.1

61. 61 Box Figure 9.2

62. 62 Box Figure 9.3

63. 63 Figure 9.23

64. 64 EOC Figure