1. Chapter 28
Simple Invertebrates

2. 28-1: Sponges
Domain: Eukarya
Kingdom: Animalia
Phylum: Porifera

4. General Characteristics
No symmetry
No tissues / organs
Cells can recognize other cells
Reorganize when separated
Sessile: do not move as adults
Diameter ranges from 1cm to 2m

5. Body Characteristics Ostia: Pores on outer wall
Osculum: Large hole for water to exit
Choanocytes: cells with flagella that line internal cavity
Move water through body cavity
Trap food particles and digest
Also called Collar Cells
Amoebocytes: cells that move around in sponge body to transport nutrients / wastes

6. Pore cells = Ostia Collar cell = choanocyte

7. Sponge Feeding

8. Sponge “Skeletons”
Most have Spicules: tiny needles made of calcium carbonate or silica
Some sponges have spongin: flexible protein fibers

9. 3 Classes of Sponges Calcareous Sponges Glass Sponges Demosponges
Skeletons made of calcium carbonate spicules
Glass Sponges
Spicules made of silica
Demosponges
Skeletons made of spicules and spongin

10. Asexual Reproduction Can regenerate when cut into pieces
Fragmentation
Budding: smaller individuals grow off sides of larger individual
Form gemmules: when living conditions become too poor, amoebocytes encase in protective shells to survive

11. Sexual Reproduction Most sponges are hermaphrodites
Sperm released into water
Sperm cells from another sponge enter through pores
Larvae develop from fertilized eggs and swim away

13. Sponge Defenses Sponges are soft (easily eaten)
Sponges are sessile (can’t swim away)
Protect selves by producing chemicals
These chemicals have been used by humans for
Antibiotics
Pain killers / Sedatives
Cancer treatments

14. 28-2: Cnidarians Two body forms: Polyps are sessile…
Medusa: free-floating umbrella-like
Polyp: tubelike and attached at base
Polyps are sessile…
Attach to floor / object with Basal Disk
Both show radial symmetry
Tentacles surround mouth
Enters into gastrovascular cavity

15. 2 layers of cells Ectoderm on outside Endoderm on inside
Mesoglea: layer of “jelly” between the 2 layers
Cells arranged into tissues

17. Cnidocytes Cnidocytes: Stinging cells on tentacles
Contain Nematocysts: small, barbed harpoons
Some nematocysts have deadly toxin, some with chemicals to just stun
Used for defense and to spear prey
Tentacles pull food into mouth

19. 3 classes Hydrozoans Scyphozoans Anthozoans
Ex: Hydra, Portuguese-Man-of- War
Scyphozoans
Ex: Jellyfish
Anthozoans
Ex: Sea Anemones, Corals

20. Hydrozoans Most are Colonial
Life cycle includes both polyp and medusa forms
Live in freshwater and marine
Freshwater example: Hydra
Marine hydrozoans are among most toxic (deadly to humans)

22. Hydra: freshwater Hydrozoans
Most of life is individual polyp
Stick to surfaces with sticky secretion from basal disk (bottom)
Can glide on basal disk or tumble

23. Reproduction in Hydrozoans
Most capable of sexual reproduction
Some are hermaphrodites
Can reproduce asexually also
budding

25. Scyphozoans “True” Jellyfish
Can be small (thimble-sized) to extremely large (queen-sized mattress)
Go through polyp stage at some point in life cycle

27. Anthozoans Corals and Sea Anemones
Have symbiotic algae living in cells to help provide energy
Sea Anemones are soft-bodied
Corals secrete calcium carbonate outer skeletons
Only top layer is alive, rest is old skeletons of dead corals
Build up into reefs

29. 28-3: Flatworms & Roundworms

30. Flatworms Phylum Platyhelminthes
More complex than sponges and cnidarians
Have middle tissue layer
Tissues organized into organs
Bilateral symmetry
Cephalization

31. Since they are flat…
Each cell close enough to outside to get O2 and release CO2
Gastrovascular cavity branched and close to all tissues (nutrients to cells easily)
Still have just 1 opening

32. 3 classes
Turbellaria:
Free-living
Most marine
Freshwater: Planaria

34. Planarian Feeding Use muscular tube that extends from center of GVC
Called Pharynx
Eat small protists or dead / dying animals

35. Planaria Reproduction
Attach posterior end to rock, pull apart into 2
Regenerate
Sexually reproduce by exchanging sperm with another planarian
Hermaphrodites

36. 2. Cestoda Parasitic Commonly called Tapeworms
Hooks and suckers on head to attach inside host’s intestine
Absorb nutrients from host
Produce proglottids: string of rectangular body segments that break off in reproduction

37. Can grow to be 40 ft. long

39. 3. Trematoda AKA “Flukes” Parasites: Live in host (endoparasites)
Live on host (ectoparasites)
Ex: Schistosoma
Disease: Schistosomiasis

40. Enter through skin (hookworm) and burrows to blood vessels to lay eggs
Block blood vessels (internal bleeding and liver damage)

42. Roundworms Phylum Nematoda Have pseudocoelom
Simplest animals with one-way digestive tract (mouth and anus!)
Most microscopic
One square yard of forest soil can have 3 million nematodes

43. Pseudocoelom “False” body cavity
Filled with fluid to act as simple respiratory and circulatory systems
O2, CO2, nutrients flow through body

44. Can be human parasites…
Ascaris lumbricoides
Infects lungs, gall bladder,
pancreas
Trichinella spiralis
Infects muscles

45. Elephantitis: blockage of lymph system by nematode
enters through skin in water