lab 7 animals i porifera radiata and introduction to bilateria
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Lab 7: Animals I: Porifera, Radiata, and Introduction to Bilateria

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Lab 7: Animals I: Porifera, Radiata, and Introduction to Bilateria. Part A: Sponges (Phylum Porifera). video spongin (collagen). No Symmetry (asmmetrical); no true tissue. Task A-1 : Sponges (Phylum Porifera). Slide: Scypha – look for holdfast, osculum Slide: sponge spiculues

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Part A: Sponges (Phylum Porifera)

  • video
  • spongin (collagen)

No Symmetry (asmmetrical); no true tissue


Task A-1: Sponges (Phylum Porifera)

  • Slide: Scypha – look for holdfast, osculum
  • Slide: sponge spiculues
  • body types: simple, intermediate, complex – draw arrows on Fig. 7-3; look at specimens

Part B: Phylum Cnidaria

  • have true tissues
  • radial symmetry
  • have stinging cells (cnidocytes) on tentacles and elsewhere
  • tentacles surround mouth
  • gastrovascular cavity with extracellular digestion; one opening serves as both mouth and anus
  • after larval stage (planula), polyp and/or medusa stage(s)

Part B: Phylum Cnidaria

  • three classes
    • Hydrozoa – hydroids
    • Scyphozoa – jellyfish
    • Anthozoa – sea anemones and corals

Task B-1: Phylum Cnidaria

  • Hydrozoa – hydroids
    • usually have both polyp and medusa stages
    • example: Hydra (solitary freshwater organism)
      • slides: look for tentacles, bud, cnidocytes, gastrovascular cavity, mouth, epidermis and endodermis (gastrodermis) with mesoglea between
      • living specimen – note its movement, look for external structures

Task B-1: Phylum Cnidaria

  • Hydrozoa – hydroids (continued)
    • example: Obelia (colonial marine organism)
      • slides: note structures from Fig. 7-6 (feeding polyps, reproductive polyps, medusa buds, medusae, tentacles, gonads, mouth, gastrovascular cavity, etc.)
    • example: Portuguese man-of-war (colonial)
      • note both polyps and medusae in a colony that has superficial resemblance to a large medusa

Task B-1: Phylum Cnidaria

  • Scyphozoa – jellyfish
    • dominant medusae; some have no polyp form
    • example: preserved specimen – treat it gently!
      • note tentacles, oral arms, mouth, gastrovascular cavity, gonads, thick jelly-like mesoglea

Task B-1: Phylum Cnidaria

  • Anthozoa – sea anemones and corals
    • polyp stage only
    • sea anemones – very muscular
      • some sessile, but not all (…see video)
      • example: preserved specimen (treat gently!)
        • note mouth, tentacles, pedal disc

Task B-1: Phylum Cnidaria

  • Anthozoa – sea anemones and corals (continued)
    • corals
      • most secrete calcium carbonate exoskeletons
      • look at dry coral specimens; note distinct cups indicating origins from separate polyps

Part C: Bilateria

  • Bilateria – animals with bilateral symmetry
    • associated with cephalization (forming a true head)
    • learn dorsal/ventral and anterior/posterior

Part C: Bilateria

  • different forms based on fluid-filled body cavity
    • acoelomate – no body cavity
    • pseudocoelomate – body cavity bound by mesoderm on one side, endoderm on the other
    • coelomate (or eucoelomate) – “true” body cavity, surrounded by mesoderm on both sides
  • coelom surrounded by mesodermal tissue (also called eucoelom)
  • allows for more complex organs, especially digestive system

Part C: Bilateria

  • body cavities allow many things, such as hydrostatic skeleton, internal organs, circulatory system, etc.
  • coelom allows for more specialization than pseudocoelom does

Part C: Bilateria

  • Two major clades within Bilateria: Protostomia (covered in this lab and lab 8) and Deuterostomia (covered in lab 9)
  • Within Protostomia, two major clades

Part C: Bilateria

  • non-molting protostomes (labs 7 and 8)
  • vs.
  • molting protostomes (lab 8)
  • Two selected non-molting phyla covered in this lab:
    • Phylum Platyhelminthes – flatworms
    • Phylum Annelida – segmented worms

Part C: Phylum Platyhelminthes – flatworms

  • acoelomate
  • dorsoventral flattening in most
  • incomplete digestive tract, when present (combo mouth/anus, just like Cnidarians)
  • most are parasitic; some are hunters
  • hermaphroditic
  • ….video

Task C-1: Phylum Platyhelminthes – flatworms

  • 3 classes
    • Turbellaria
    • Cestoda – tapeworms
    • Trematoda – flukes
  • examine specimens and slides, look for structures noted in Figs. 7-10, 11, and 12 such as ocellus, pharynx, intestine, scolex, proglottids

Part C: Segmented Worms (Phylum Annelida)

  • segmented – linear repetition of body parts; specialization in some (such as head); often separated by septa
  • use coelom for hydrostatic skeleton
  • closed circulatory system
  • excretory tubules (metanephridia)
  • most have chitinous bristles (setae) on most segments – for sensing, and locomotion

Task 2: Segmented Worms (Phylum Annelida)

  • 3 classes
    • Polychaeta (polychaetes)
    • Oligochaeta (earthworms)
    • Hirudinea (leeches)

Task C-2: Segmented Worms (Phylum Annelida)

  • annelid box and slide: examine the preserved specimens and slide, note the following:
    • Polychaeta – clamworm:
      • distinct head with tentacles, eyes, jaws
      • fleshy parapodia on segments – used for locomotion
      • compare to plume worm (not in box – demo only)

Task C-2: Segmented Worms (Phylum Annelida)

  • annelid box and slide:
    • Oligochaeta – earthworm:
      • rub to feel chitinous setae, used for holding to soil
      • clitellum – band used in mating; is nearer to the anterior end of the worm
      • reproductive pores anterior to clitellum (earthworms are hermaphroditic)
      • cross-section slide: compare to Fig. 7-14, note structures bolded in you manual such as coelom

Task C-2: Segmented Worms (Phylum Annelida)

  • annelid box:
    • Hirudinea – leech:
      • dorsoventral flattening
      • lack of setae and parapodia
      • less distinct segmentation
      • suckers for attaching to host for feeding (leeches are blood-sucking parasites)