1. Ochre sea stars, Pisaster ochraceus
Chapter 33
Introduction to Invertebrates
Ochre sea stars, Pisaster ochraceus

2. One view of animal diversity based on body-plan grades

3. Chapter 33 Outline (five concepts)
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes
Discovery Channel Video

4. Sponges – Porifera (Calcarea and Silicea)

5. Reproduction = hermaphroditic
33.4 Anatomy of a sponge
Reproduction = hermaphroditic
Sponge spicules

6. 33.7 Cnidarians: Hydrozoans (top left), jelly (top right), sea anemone (bottom left), coral polyps (bottom right)

7. 33.5 Polyp and medusa forms of cnidarians

8. 33.6 A cnidocyte of a hydra

9. 33.8 The life cycle of the hydrozoan Obelia

10. 33.8 The life cycle of the hydrozoan Obelia

11. 33.8 The life cycle of the hydrozoan Obelia

13. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

14. 33.8 A ctenophore, or comb jelly
One-way digestive tract
No nematocysts

15. Platyhelminthes: A marine flatworm (class Turbellaria)

16. Anatomy of a planarian

18. Anatomy of a tapeworm

19. 33.11 The life history of a blood fluke, Schistosoma mansoni (Trematoda)

20. Total persons infected (global): 200 million
Total persons infected (Africa): 170 million (second most prevalent parasitic disease in Africa)
Persons with associated morbidity: 120 million
Mortality Unknown, but 20 million severely infected

21. A feature of many members of the phylum of the Platyhelminthes (flatworms) is their complex life cycle. Understanding the life cycles of flatworm parasites is of great importance to human health because:
it emphasizes the beneficial relationship between humans and their environment.
although these parasites are of little importance in modern society, they must be studied before they are completely eliminated.
flatworms may secrete important chemicals for human use.
it helps us to understand the evolutionary relationships between the different parasites.
it may be possible to find a portion of that life cycle where the parasite is vulnerable and can be controlled.

22. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

23. 33.13 Rotifers (pseudo-coelomates)
Reproduction by pathenogenesis

24. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

25. Lophophorates: Bryozoan (left aka Ectoprocts), Phonorids (middle), and Brachiopod (right) – all coelomates

26. Bryozoans: Colonial animals that superficially resemble mosses

27. Nemertea – proboscis worms (pseudoceolomates)

28. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

30. Gastropods: Nudibranchs (‘sea slug’, top left and top right), terrestrial snail (bottom left), deer cowrie (bottom right)

31. 33.15 Basic body plan of mollusks

33. A chiton

34. 33.18. The result of torsion in a gastropod
(twisting of the visceral mass during embryonic development resulting in the anus being near the anterior mouth).

35. Anatomy of a clam

36. Dreissena polymorpha
Zebra mussel

38. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

40. See also Cephalopods: Squid (top left and bottom left), nautilus (top right), octopus (bottom right)

41. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

42. Annelida: External anatomy of an earthworm (note segmentation)
Tubifex sp.
Lumbricus sp.

43. 33.24. Anatomy of an earthworm

45. Annelids, the segmented worms: Polychaete (left), feather-duster worm (middle); Hirudinea (leech, right)

46. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

47. Free-living nematode
Vinegar eel

48. Two American ‘Worm People’ Win Nobel for RNA Work
This year’s Nobel Prize in Physiology or Medicine has been awarded to two American researchers, Andrew Z. Fire and Craig C. Mello, for a far-reaching discovery about how genes are controlled within living cells.
The finding by Drs. Fire and Mello made sense of a series of puzzling results obtained mostly by plant biologists, including some who were trying to change the color of petunias. By clarifying what was happening, they discovered an unexpected system of gene regulation in living cells and began an explosive phase of research in a field known variously as RNA interference or gene silencing. This natural method of switching genes off has turned out to be a superb research tool, allowing scientists to understand the role of new genes by suppressing them. The method may also lead to a new class of drugs that switch off unwanted processes in disease. Two gene-silencing drugs designed to treat macular degeneration are already in clinical trials.
Dr. Fire, now at Stanford University, worked at the Carnegie Institution of Washington when he made the discovery. Dr. Mello, a frequent collaborator, is at the University of Massachusetts Medical School in Worcester. Both are “worm people,” as scientists who do their biology in the roundworm Caenorhabditis elegans call themselves.
Prior to their discovery, plant biologists over many decades had found odd exceptions to Mendel’s laws of heredity, including some unexplained effects produced by injecting RNA, the less-well-known cousin of DNA, into plants. Both are chemicals called nucleic acids, but DNA is longer and more stable and is used by the cell for the archival function of storing genetic information. RNA is shorter and more active, and performs many of the cell’s more difficult tasks, like making copies of the genes in DNA and directing the synthesis of the proteins specified by the genes………………

49. 33.27 Parasite nematode, Trichinella spiralis in human muscle tissue
Trichinosis: may be contracted from undercooked meat – fever diarrhea, swelling, rarely fatal

50. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

51. 33.30 External anatomy of an arthropod (jointed appendages)
Exoskeleton made of chitin

52. Trachae in terrestrial arthropod species:
tiny chitin-lined airtubes that bring oxygen into the cells.
Bumblebee.org

53. A trilobite fossil

55. 33.31. Horseshoe crabs (living fossils) Limulus polyphemus (Arachnida)
Subphylum: Cheliceriformes

56. Subphylum: Cheliceriformes
Chelicerata: Claw-like feeding appendages

57. Subphylum: Cheliceriformes
Arachnids: Scorpion (left), honeybee air tube filled with parasitic mites (right)

58. Subphylum: Cheliceriformes

59. Spider anatomy

60. Subphylum Myriapoda (millipedes and centipedes)

61. 33.35 Subphylum Hexapoda: Anatomy of a grasshopper, an insect

62. Subphylum Hexapoda: beetle

63. 33.37. Subphylum Hexapoda Metamorphosis of a butterfly

66. 33.39 Subphylum Crustacea: Lobster (top left), banded coral shrimp (bottom left), barnacles (right)

67. Chapter 33 Outline
33.1 Sponges are basal animals that lack true tissues
33.2 Cnidarians are an ancient phylum of eumetazoans
33.3 Lophotrochozoans have the widest range of animal body forms (flatworms, rotifers, lophophorates, molluscs, annelids)
33.4. Ecdysozoans is the most species-rich group (nematodes, arthropods)
33.5 Echinoderms and chordates are deuterostomes

68. Echinoderm Diversity

70. Blood star, Hencricia levisuscula

71. Anatomy of a sea star

72. Ch. 33
Review
(p. 695)

73. You discover an animal that has a true coelom and an exoskeleton that includes the modified poly-saccharide chitin. Select the phylum to which this animal most likely belongs.
Nematoda (roundworms)
Porifera (sponges)
Arthropoda (crustaceans, insects, and others)
Mollusca (mollusks)
Platyhelminthes (flatworms)