1. Animal Evolution –The Invertebrates Chapter 25 Part 2

2. 25.6 Flatworms—Simple Organ Systems  Flatworms (phylum Platyhelminthes) have a three-layer embryo that develops into an adult with many organ systems but no coelom  Three main classes: turbellarians, flukes (trematodes), and tapeworms (cestodes)

3. Turbellarians: Structure of a Free-Living Flatworm  Pharynx Muscular tube connecting the mouth with the gut  Nerve cords Two lines of communication along length of body  Ganglia Cluster of nerve cell bodies (simple brain)

4. Flatworm Organ Systems

5. Fig. 25-15, p. 412 nucleus rudimentary brain (pair of large ganglia in head) ovary pair of highly branched tubules that adjust water and solute levels in body cilia branching gut fluid filters through membrane folds testis oviduct pharynx; protrudes onto food, then retracts into the body between feedings genital pore pair of nerve cords that have lateral branchings flame cell opening at body surface

6. Animation: Planarian organ systems

7. Parasites: Flukes and Tapeworms  In blood flukes (Schistosoma), reproduction takes place in mammals – immature stages live in intermediate hosts (snails)  A tapeworm body consists of proglottids – repeating hermaphroditic body units that bud from a region behind the scolex

8. Fluke Life Cycle: Schistosoma

9. Fig. 25-16, p. 413 A A fluke matures and mates in a human host. F Larvae burrow into new human host, enter intestinal veins, and start a new cycle. B Fertilized eggs exit host in feces. E Fork-tailed, swimming larvae develop and leave the snail. C Eggs hatch as ciliated larvae. D Larvae burrow into an aquatic snail and multiply asexually.

10. Fig. 25-16, p. 413 A A fluke matures and mates in a human host. C Eggs hatch as ciliated larvae. D Larvae burrow into an aquatic snail and multiply asexually. Stepped Art B Fertilized eggs exit host in feces. E Fork-tailed, swimming larvae develop and leave the snail. F Larvae burrow into new human host, enter intestinal veins, and start a new cycle.

11. Beef Tapeworm Life Cycle

12. Fig. 25-17, p. 413 proglottidsscolex B A human, the definitive host, eats infected, undercooked beef, which is mainly skeletal muscle. A Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle). scolex attached to wall of intestine one proglottid D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts. C Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave the host in feces, which may contaminate water and vegetation.

13. Fig. 25-17, p. 413 B A human, the definitive host, eats infected, undercooked beef, which is mainly skeletal muscle. A Larvae, each with inverted scolex of future tapeworm, become encysted in intermediate host tissues (e.g., skeletal muscle). proglottidsscolex scolex attached to wall of intestine one proglottid C Each sexually mature proglottid has female and male organs. Ripe proglottids containing fertilized eggs leave the host in feces, which may contaminate water and vegetation. Stepped Art D Inside each fertilized egg, an embryonic, larval form develops. Cattle may ingest embryonated eggs or ripe proglottids, and so become intermediate hosts.

14. Animation: Tapeworm life cycle

15. 25.7 Annelids—Segmented Worms  Annelids (phylum Annelida) are bilateral worms with a coelom and a segmented body; typically with chaetae (chitin reinforced bristles)  Three main groups: marine worms (polychaetes), oligochaetes (including earthworms), and leeches

16. Marine Polychaetes

17. Fig. 25-18a, p. 414

18. “jaws” toothlike structures pharynx (everted) antenna palp (food handling) eyes chemical- sensing pit parapod tentacle

19. Fig. 25-18b, p. 414

20. Leeches – Bloodsuckers and Others  Leeches lack chaetae and have a sucker at either end

21. Fig. 25-19a, p. 414 before feeding

22. Fig. 25-19b, p. 414 after feeding

23. Oligochaetes  Example: earthworms Exchange gases across body surfaces Have five hearts and a closed circulatory system Nephridia regulate coelomic fluid Nervous system of ganglia and nerve cords Hydrostatic skeleton Hermaphroditic

24. Earthworm Body Plan

25. Fig. 25-20a, p. 415

26. anus nephridium dorsal blood vessel clitellum coelom intestine gizzard crop esophagus pharynx gut longitudinal muscle 2 of 5 hearts brain ventral nerve cord ventral blood vessel mouth circular muscle ventral nerve cord

27. Fig. 25-20b, p. 415

28. anus clitellumhead

29. Animation: Earthworm body plan

30. How Earthworms Move

31. Fig. 25-21, p. 415 bristles used in locomotion

32. 25.8 Mollusks—Animals With a Mantle  Mollusks (phylum Mollusca) Bilaterally symmetrical with a reduced coelom Mantle covers internal organs, secretes a shell Feed using a hard radula Have a complete digestive tract Gills for respiration in aquatic species

33. Mollusk Diversity  Chitons Eight overlapping plates  Gastropods (snails, slugs) Undergo torsion during development  Bivalves (mussels, clams, oysters) Hinged, two-part shell  Cephalopods (squids, octopuses) Large, fast and smart; closed circulatory system

34. Mollusk Groups

35. Fig. 25-22a, p. 416

36. Fig. 25-22b, p. 416

37. Fig. 25-22c, p. 416

38. Fig. 25-22d, p. 416

39. Gastropod Body Plan

40. Fig. 25-23a, p. 416

41. anus gill excretory organ mantle cavity heart digestive gland shell stomach edge of mantle that covers organs radula foot

42. Fig. 25-23b, p. 416

43. before torsion: mouth after torsion: mantle’s edge anus anus, which discharges wastes into mantle cavity

44. Animation: Snail body plan

45. Animation: Torsion in gastropods

46. Variations on the Gastropod Body Plan

47. Fig. 25-24a, p. 417

48. Fig. 25-24b, p. 417

49. mantleeye opening that leads to lung sensory tentacle foot

50. Fig. 25-24c, p. 417

51. Bivalve Body Plan: Clam

52. Fig. 25-25, p. 417 mouthleft mantleadductor muscle (cut) Water flows out through exhalant siphon Water flows in through inhalant siphon foot palpsleft gillshell

53. Animation: Clam body plan

54. 25.9 Cephalopods—Fast and Brainy  Cephalopod (“head foot”) Tentacles attached to the head are evolutionary modifications of the foot; they surround the mouth, which has a hard, horny beak  Include the fastest (squids), biggest (giant squid), and smartest (octopuses) invertebrates Jet propulsion, complex eyes, closed circulatory system, complex behavior

55. Cephalopods

56. Fig. 25-26a, p. 418

57. Fig. 25-26b, p. 418

58. Fig. 25-26c, p. 418

59. Fig. 25-26d, p. 418

60. arm beak internal shell radulamantle anus accessory heart reproductive organ tentacle siphongill heart ink sac

61. Fig. 25-26e, p. 418

62. Animation: Cuttlefish body plan

63. 25.10 Rotifers and Tardigrades— Tiny and Tough  Rotifers (phylum Rotifera) and tardigrades (phylum Tardigrada) are tiny bilateral animals  Rotifers have a pseudocoelom, but are genetically closest to annelids and mollusks  Tardigrades have a coelom and molt, and are probably relatives of roundworms and insects

64. Rotifer Body Plan

65. Fig. 25-27, p. 419 ciliated lobe mouth brain with eyespots protonephridium stomach intestine anus one of two “toes”

66. Tardigrades

67. Fig. 25-28a, p. 419 tardigrade’s mouth roundworm prey

68. Animation: Blood fluke life-cycle

69. Animation: Feeding leech

70. Animation: Marine polychaetes

71. Animation: Molluscan classes