1. Introduction to Invertebrates
Chapter 29
Mader: Biology 8th Ed.

2. Cnidarians and Comb Jellies Hydra Obelia Bilateral Symmetry Flatworms
Outline
Evolution of Animals
Sponges
Cnidarians and Comb Jellies
Hydra
Obelia
Bilateral Symmetry
Flatworms
Roundworms
Mader: Biology 8th Ed.

3. Classification Criteria Level of organization Cellular, tissue, organ
Evolution of Animals
All animals are multicellular heterotrophic organisms that must take in preformed food.
Classification Criteria
Level of organization
Cellular, tissue, organ
Body Plan
Sac, tube-within-a-tube
Segmentation
Segmentation leads to specialization.
Mader: Biology 8th Ed.

4. Radial - Two identical halves.
Evolution of Animals
Symmetry
Radial - Two identical halves.
Bilateral - Definite right and left halves.
Type of Coelom
Pseudocoelom
Coelom
Protostome - First embryonic opening becomes the mouth.
Dueterostome - Second embryonic opening becomes the mouth.
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5. Only level of animal to have cellular organization.
Multicellularity
Sponges
Only level of animal to have cellular organization.
Saclike bodies perforated by many pores.
Beating of flagella produces water currents that flow through pores into central cavity and out osculum.
Sessile filter feeders.
Asexual reproduction by fragmentation or budding.
Mader: Biology 8th Ed.

6. Simple Sponge Anatomy
Mader: Biology 8th Ed.

7. Total of three possible germ layers. Ectoderm, endoderm, and mesoderm
True Tissue Layers
Total of three possible germ layers.
Ectoderm, endoderm, and mesoderm
Animals in phlyum Ctenophora (comb jellies) and in phylum Cnidaria (cnidarians) develop only ectoderm and endoderm.
Diploblasts
Radially symmetrical
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8. Cnidarian and Comb Jelly
Mader: Biology 8th Ed.

9. Small, transparent, and often luminescent.
Comb Jellies
Small, transparent, and often luminescent.
Most of body composed of mesoglea.
Largest animals propelled by beating of cilia.
Capture prey with tentacles.
Mader: Biology 8th Ed.

10. Tubular animals that most often reside in shallow marine waters.
Cnidarians
Tubular animals that most often reside in shallow marine waters.
Polyp and medusa body forms.
Specialized stinging cells (cnidocytes).
Fluid-filled capsule, nematocyst.
Two-layered body sac.
Outer layer - Protective epidermis.
Inner layer - Gastrovascular cavity.
Nerve net found throughout body.
Mader: Biology 8th Ed.

11. Cnidarian Diversity
Mader: Biology 8th Ed.

12. Freshwater cnidarians.
Hydra
Freshwater cnidarians.
Small tubular poly body about one-quarter inch in length.
Gastrovascular cavity is central cavity.
Tentacles can respond to stimuli.
Can reproduce sexually and asexually.
Mader: Biology 8th Ed.

13. Hydra
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14. A colony of polyps enclosed by a hard, chitinous covering.
Obelia
A colony of polyps enclosed by a hard, chitinous covering.
Feeding polyps
Extend beyond covering
Have nematocyst-bearing tentacles.
Reproductive polyps
Budding of new polyps.
Also has sexual reproduction (medusae) stage.
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15. Obelia
Mader: Biology 8th Ed.

16. Ribbon worms (phylum Nemertea) Have distinctive proboscis
Bilateral Symmetry
Ribbon worms (phylum Nemertea)
Have distinctive proboscis
Flatworms (phylum Platyhelminthes)
Majority are parasitic
Organ-level organization
No specialized circulatory or respiratory structures.
Have undergone cephalization
Ladder-type nervous system
Mader: Biology 8th Ed.

17. Free-living Flatworms
Planarians (genus Dugesia)
Live in freshwater habitats.
Head is bluntly arrow shaped.
Auricles function as sense organs.
Two light-sensitive eye spots.
Three kinds of muscle layers:
Outer circular layer
Inner longitudinal layer
Diagonal layer
Mader: Biology 8th Ed.

18. Excretory organ functions in osmotic regulation and water excretion.
Planarians
Excretory organ functions in osmotic regulation and water excretion.
Can reproduce asexually
Hermaphroditic
Practice cross-fertilization
Mader: Biology 8th Ed.

19. Mader: Biology 8th Ed.

20. Parasitic flatworms are flukes (trematodes) and tapeworms (cestodes).
Well-developed nerves and gastrovascular cavity are unnecessary.
Flukes
Usually named for type of vertebrate organ they inhabit.
Reproductive system well developed.
Usually hermaphroditic.
Mader: Biology 8th Ed.

21. Transmission of Schistosomiasis
Mader: Biology 8th Ed.

22. Behind head region, scolex, a long series of proglottids are found.
Parasitic Flatworms
Tapeworms
Have anterior region with modifications for attachment to intestinal wall of host.
Behind head region, scolex, a long series of proglottids are found.
Segments each containing a full set of both male and female sex organs.
Complicated life cycles.
Mader: Biology 8th Ed.

23. Life Cycle of Taenia
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24. Roundworms (phylum Nematoda) Nonsegmented, generally colorless worms.
Pseudocoelom
Pseudocoelom is a false body cavity that is incompletely lined by mesoderm.
Provides a space for internal organs and can serve as hydrostatic skeleton.
Roundworms (phylum Nematoda)
Nonsegmented, generally colorless worms.
Several parasitic roundworms infect humans.
Mader: Biology 8th Ed.

25. Roundworm Anatomy
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26. Trachinella - Trichinosis Dirofilaria - Heartworms
Parasitic Roundworms
Ascaris
Trachinella - Trichinosis
Dirofilaria - Heartworms
Wuchereria - Elephantiasis
Mader: Biology 8th Ed.

27. Rotifers (phylum Rotifera)
Named for crown of cilia resembling a rotating wheel.
Serves as both as an organ of locomotion and aids direction of food to mouth.
Mader: Biology 8th Ed.

28. Rotifer
Mader: Biology 8th Ed.

29. Cnidarians and Comb Jellies Hydra Obelia Bilateral Symmetry Flatworms
Review
Evolution of Animals
Sponges
Cnidarians and Comb Jellies
Hydra
Obelia
Bilateral Symmetry
Flatworms
Roundworms
Mader: Biology 8th Ed.

30. Mader: Biology 8th Ed.