npsC5AD - Cnidarians Two cell layers (diploblastic);...

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Polyp form sessile, attached to substrate at aboral end Oral end Aboral end tentacles Gastrovascular cavity Largely acellular mesoglea Two cell layers (diploblastic); hydrostatic and viscoelastic skeleton; two basic (but similar) body forms: Cnidarians Oral end Aboral end Medusa form free-swimming tentacles Three (or 4) major classes of cnidarians Hydrozoa (hydra, etc.) Complex life cycle, always with polyp form; sometimes medusa Polyp is the 'dominant' stage. Sometimes colonial with specialized individuals ( clones ) forming the complete 'animal' ("Portuguese man-o-war"). Scyphozoa ("true" jellyfish); free-swimming (now usually divided into Scyphozoa and Cubozoa ) Complex life cycle, medusa stage is dominant; feed on animals. Some can get very large (over a meter in diameter). giant green anemone and strawberry anemones coral polyps coral skeleton Three (or 4) major classes of cnidarians Anthozoa (sea anemones and corals) only have the polyp stage; can be structurally fairly complex; mesoglea more cellular than in Hydrozoans and Scyphozoans corals secrete a calcium carbonate "house"; coral reefs are the largest structures made by any form of life Reef corals have been successful largely because of symbiosis with certain unicellular algae ( zooxanthellae) . Algal cells live within the cells of coral coral provide shelter photosynthetic algae provide nutrients. In stressful conditions, coral expel algae and suffer reduced growth or death: coral ‘bleaching’ . Seems to be increasingly common worldwide as temperatures warm.
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Deuterostomia Lophotrochozoa Ecdysozoa Protistan ancestor Eumetazoa Bilateria Radiata Protostomia Parazoa levels of cell & tissue organization fundamental symmetry and number of germ layers Development patterns Cuticle presence or absence Triploblastic animals Porifera Cnidaria Platy- Annelida Mollusca Nematoda Arthropoda Echino- Chordata (Calcarea, helminthes dermata Silicea) First, the flatworms, or Platyhelminthes 15,000 -20,000 species, in most habitats (marine, freshwater, moist terrestrial, often parasitic). Major characteristics: Body solid (no cavities): ACOELOMATE triploblastic acoelomate Motile (except some parasitic forms); mesoderm provides muscle for improved locomotion hence cephalized (concentration of nervous tissue and sensors in front, creating anterior-posterior axis). No circulatory system (animal must be thin so diffusion will work) Flat (see above). FLATWORMS: phylum Platyhelminthes Basic body plan includes these features: mesoderm endoderm (gut) ectoderm ciliated epithelium gastrovascular cavity “brain” Mouth / anus gut with single opening, usually branched to get close to all parts of body gut used for digestion, nutrition, gas exchange, waste removal eat animal tissue (scavenger, predator, parasite) often hermaphroditic : contain both male and female gonads; usually cross-fertilize Top views FLATWORMS: phylum Platyhelminthes Three major classes: 1. Turbellaria (free-living flatworms), unspecialized; probably similar to ancestral flatworms. "Planarians" are
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npsC5AD - Cnidarians Two cell layers (diploblastic);...

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