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Chapter 28 Simple Invertebrates.

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Presentation on theme: "Chapter 28 Simple Invertebrates."— Presentation transcript:

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


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