1. Biology, 9th ed, Sylvia Mader
Chapter 29
Chapter 29
Introduction to Invertebrates
Introduction to Invertebrates

2. Outline Evolution of Animals Multicellularity True Tissues
Sponges
True Tissues
Cnidarians and Comb Jellies
Hydra
Obelia
Bilateral Symmetry
Flatworms
Roundworms
Body Cavities
Acoelomates
Psuedocoelomates
Eucoelomates

3. Classification Criteria
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

4. Classification Criteria, cont
Evolution of Animals
Classification Criteria, cont
Symmetry
Radial - Two identical halves
Bilateral - Definite right and left halves
Type of Coelom
Pseudocoelom
Coelom
Early Developmental Pattern
Protostome - First embryonic opening becomes the mouth
Dueterostome - Second embryonic opening becomes the mouth

5. Animals: Multicellular, Heterotrophic Eukaryotes

6. Traditional Phylogenetic Tree of Animals

7. 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

8. Simple Sponge Anatomy

9. Total of three possible germ layers
True Tissue Layers
Total of three possible germ layers
Ectoderm
Endoderm, and
Mesoderm
phlya Ctenophora and Cnidaria develop only ectoderm and endoderm
Diploblasts
Radially symmetrical

10. Comb Jellies
Small, transparent, and often luminescent
Most of body composed of mesoglea
Largest animals propelled by beating of cilia
Capture prey with tentacles

11. Comb Jelly Compared to Cnidarian

12. 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

13. Cnidarian Diversity

14. Hydra Freshwater cnidarian
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

15. Anatomy of Hydra

16. 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

17. Obelia Life Cycle

18. Ribbon worms (phylum Nemertea) Flatworms (phylum Platyhelminthes)
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

19. Ribbon Worm, Lineus

20. 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

21. Planarian Anatomy

22. Planarians Planarians, cont.
Excretory organ functions in osmotic regulation and water excretion
Can reproduce asexually
Hermaphroditic
Practice cross-fertilization

23. Parasitic flatworms are flukes (trematodes) and tapeworms (cestodes)
Well-developed nerves and gastrovascular cavity are unnecessary
Flukes
Reproductive system well developed
Usually hermaphroditic

24. Life Cycle of Schistosomiasis

25. 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

26. Life Cycle of a Tapeworm, Taenia

27. Roundworms (phylum Nematoda)
Pseudocoelom
Pseudocoelom:
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)
Non-segmented, generally colorless worms
Several parasitic roundworms infect humans

28. Roundworm Anatomy

29. Parasitic Roundworms
Ascaris – Intestinal roundworm
Trachinella - Trichinosis
Dirofilaria - Heartworms
Wuchereria - Elephantiasis

30. Filarial Worm

31. 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

32. Rotifer

33. Review Evolution of Animals Multicellularity True Tissues
Sponges
True Tissues
Cnidarians and Comb Jellies
Hydra
Obelia
Bilateral Symmetry
Flatworms
Roundworms
Body Cavities
Acoelomates
Psuedocoelomates
Eucoelomates

34. Biology, 9th ed, Sylvia Mader
Chapter 29
Ending Slide Chapter 29
Introduction to Invertebrates
Introduction to Invertebrates