invertebrates phylum porifera n.
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Invertebrates: Phylum Porifera. Sponges Multicellular; body a loose aggregate of cells All aquatic, mostly marine Body with pores ( ostia ), canals, and chambers for circulation of water Epidermis of flat cells, some with contractile fibers

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invertebrates phylum porifera
Invertebrates: Phylum Porifera
  • Sponges
  • Multicellular; body a loose aggregate of cells
  • All aquatic, mostly marine
  • Body with pores (ostia), canals, and chambers for circulation of water
    • Epidermis of flat cells, some with contractile fibers
    • Middle layer is semi-fluid, with wandering amebocytes
    • Inner layer of choanocytes-flagellated to move water
phylum porifera cont d
Phylum Poriferacont’d
  • Filter feeders- intracellular digestion
    • Cells get food from circulating water
  • Classified based on skeleton
    • Composed of spicules
      • Chalk sponges - spicules of calcium carbonate
      • Glass sponges - spicules of silica
      • Proteinaceous sponges - spongin fibers
  • Reproduction
    • asexual by budding, sexual by fusion of gametes
  • Fig. 30.3
invertebrates phylum cnidaria
Invertebrates: Phylum Cnidaria
  • Cnidarians
    • Multicellular, tubular or bell-shaped animals-radial symmetry
    • All aquatic, mostly marine
  • 2 germ layers during development
    • Organized at tissue level
  • Nematocysts
    • stinging cells unique to cnidarians
cnidarians cont d
Cnidarians cont’d
  • 2 body types-polyps and medusae
    • Life cycle alternates between both forms in some; in others one form is reduced or absent
  • Gastrovascular cavity-sac-like body plan
  • Includes corals, jellyfish, and hydrozoans
    • Corals- polyps
    • Jellyfish-medusae
    • Hydrozoans-may have both forms
cnidarians cont d1
Cnidarians cont’d
  • Hydra
    • Representative organism (Class Hydrozoa)
    • Freshwater, attaches to rocks, leaf litter
    • Small tubular polyp, sac-like body plan with a single opening
      • Outer tissue layer – epidermis from ectoderm
      • Inner layer – gastrodermis from endoderm
      • Longitudinal and circular muscle fibers present
      • Diffuse nerve net between layers
cnidarians cont d2
Cnidarians cont’d
  • Digestion begins in gastrovascular cavity, completed in cells
  • Can reproduce sexually and asexually (budding)
    • Sexual reproduction- hydra develops an ovary or testis in body wall-produces gametes
invertebrates phylum platyhelminthes
Invertebrates: Phylum Platyhelminthes
  • Flatworms
  • Bilateral symmetry, three germ layers, acoelomate
  • Mesoderm gives greater complexity
    • Muscles, excretory, reproductive, and digestive systems in some
    • Respiration by diffusion and circulation
platyhelminthes cont d
Platyhelminthes cont’d
  • Class Turbellaria - Planarians
    • Free-living flatworms
    • freshwater, feed on small living and dead organisms
    • Ladder-like nervous system
      • Ganglia and eyespots anterior
      • Auricles – chemosensitivereceptores
    • Digestion:
      • Feed through muscular pharynx
      • Specialized cells for excretion: flame cells
platyhelminthes cont d1
Platyhelminthes cont’d
  • Class Turbellaria - Planarians cont’d
    • 3 muscle layers- circular, longitudinal, and diagonal
      • Allows for more complex movements
    • Cephalization
      • Organized to have an anterior end and a posterior end
    • Hermaphroditic
  • Fig. 30.6
parasitic platyhelminthes
Parasitic Platyhelminthes
  • Class Cestoda (Tapeworms)
    • Internal parasites as adults
    • Body Structure
      • Tegument: tough outer covering
        • protect from host’s enzymes
      • Scolex - head
        • Barbs/hooks for attachment
      • Proglottids: segments
        • Each contains organs of both sexes
    • Lack a digestive system- why?
parasitic platyhelminthes cont d
Parasitic Platyhelminthescont’d
  • Class Cestoda (Tapeworms) (cont’d)
    • Reproduction
      • Fertilization is internal
        • proglottids filled with fertilized eggs are called gravid
          • Gravid proglottids drop off and pass out in feces
        • Ingested by intermediate host
          • larvae become encysted
        • Intermediate host is then eaten by definitive host
          • Larvae mature to adults
    • Representative Organism: Taneasolium
      • Pork tapeworm
parasitic platyhelminthes cont d1
Parasitic Platyhelminthescont’d
  • Class Trematoda - Flukes
    • Endoparasites of many species
    • Body Structure
      • Tegument
      • Oral sucker and posterior sucker
    • Digestion
      • Well-developed digestive canal
parasitic platyhelminthes cont d2
Parasitic Platyhelminthescont’d
  • Class Trematoda - Flukes cont’d
    • Muscles and excretory system much like free-living flatworms
      • Poorly developed sense organs- why might that be?
    • Reproduction
      • Hermaphroditic
      • Complex life cycle involving two intermediate hosts
parasitic platyhelminthes cont d3
Parasitic Platyhelminthescont’d
  • Class Trematoda - Flukes cont’d
    • Representative Organism: Clonorchis sinensis
      • Liver Fluke
      • Transmission
        • Snails ingest eggs
        • Develop in to larvae, which leave the snail and burrow into muscles of a fish
        • Humans ingest fish
          • Larvae moves into bile ducts where adults develop
        • Eggs pass out of human in feces, cycle continues
invertebrates phylum nematoda
Invertebrates: Phylum Nematoda
  • Roundworms
    • First appearance of
      • Tube-within-a-tube body plan
        • 2 openings, mouth and anus
      • Body Cavity
        • Pseudocoelomates
          • Pseudocoel -filled with fluid, acts as hydrostatic skeleton
    • Many species; some are free-living in soil and water, others are parasitic
parasitic nematodes
Parasitic Nematodes
  • Ascaris
    • Move with whip-like motion
    • Intestinal parasites in many animal species
    • Females are much longer than males and highly prolific
    • Eggs enter host in uncooked vegetables, soil, or feces
      • Larvae burrow out of intestine and migrate to heart and lungs
      • Larvae are coughed up and swallowed
      • Mature to adults in intestines
        • Estimated to infect 25% of world population
parasitic nematodes cont d
Parasitic Nematodes cont’d
  • Trichinella spiralis
    • the trichina worm
    • Causes trichinosis
    • Humans contract the worm by eating undercooked pork
    • Larvae migrate out of intestines and form painful cysts in the muscles
parasitic nematodes cont d1
Parasitic Nematodes cont’d
  • Wuchereria bancrofti
    • filarial worm that causes elephantiasis
    • Migrates into lymphatic vessels and prevents lymph drainage
    • Edema occurs
parasitic nematodes cont d2
Parasitic Nematodes cont’d
  • Pinworms and hookworms
    • Roundworm parasites which cause problems in children
    • Much more common in U.S.
      • Pinworms are primarily an annoyance
      • Hookworms cause skin irritations and in some cases debilitating disease