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  1. Define metazoa. What are the three theories regarding metazoan ancestry?
    • Metazoans are the multicellular organisms that form tissues found in the majority of the animal kingdom.
    • Metazoa may have evolved from…
    • 1. Syncytial ciliated cells: multinucleated cells that had cilia, such as Paramecium.
    • 2. Colonial flagellated cells: flagellated cells that functioned as a colony, such as Volvox.
    • 3. Monophyletic: belief that multicellular organisms evolved from a single phylum, and not multiple phyla.
    • *#2 is most accepted due to Ribosomal RNA sequencing
  2. What are the three grades of metazoa? Describe them in detail.
    • Mesazoa: a single phylum which is entirely parasitic of invertebrates (octopuses, squids, etc). Minute, ciliated, wormlike with adults called vermiforms (“wormlike”).
    • Parazoa: Developed “parallel” to the metazoans; consists of Porifera (sponges) and Placozoa (glide over their food using digestive enzymes).
    • Eumetazoa: “True” metazoans; consists of the rest of the animal kingdom
  3. What are the major clades of bilateral symmetry? Give information about each clade.
    • Lophotrochozoans, Ecdysozoa, and Deuterostomia.
    • Information about Lophotrochozoans…
    • Bilateral symmetry
    • Triploblastic
    • Protostome (“mouth first”)
    • Some develop lophophore (ciliated tentacles or crown for feeding)
    • Some have trochophore larva
    • 18 phyla that include Platyhelminthes (flatworms), Rotifers, Mollusks (squids, clams, snails), Annelids (earthworms, leeches), Acnthocephala (spiny-headed worms), Nemertea.
    • Information about Ecdysozoa…
    • Animals that shed a tough external coat/cuticle (eg. Arthropods).
    • Process is known as molting or ecdysis
    • All invertebrates
    • 8 phyla that include Nematoda, Arthropoda, and Onychophora
    • Information about Deuterostomia…
    • Deuterostome (“mouth second”)
    • Phyla include Echinoderms (starfish, no vertebrates), Hemichordata (almost vertebrates), and Chordata (vertebrates)
  4. Phylum Porifera – Common name? Feeding style? Movement? Habitat? Special cells/structures? Reproduction?
    • Sponges
    • Filter-feeding through ostia
    • Sessile
    • Aquatic
    • Have many holes on surface (ostia)
    • Contain spicules made of Calcium Carbonate, silica, and spongin
    • Perform asexual reproduction (budding) and sexual reproduction (sperm and eggs)
    • Radial symmetry or no symmetry
  5. How are sponges classified? What are the three classes of Porifera, and what are their characteristics in detail + genera?
    • Classified based on types of spicules, shape of sponge, and DNA. NOT BY CANAL TYPES!
    • Calcarea: have calcareous spicules (calcium carbonate) which have 3-4 rays. Have tubular or vase shape. Can have asconoid, syconoid, or leuconoid canal system. (Leucosolenia, Scypha)
    • Hexactinellida: “glass sponges” have six-rayed siliceous spicules (silicon) (Euplectella aspergillum)
    • Demospongiae: “bath sponges” or “horny sponges.” Skeleton of siliceous spicules (silicon), except bath sponges which have spongin (collagen – a protein) instead. Large sponges that have only leuconoid canal system due to size and complexity. Gemmules are released through osculum, and will become a new sponge. (Spongilla, Chalina, Euspongia)
  6. Describe basic filter feeding in a sponge (not a specific canal system).
    • 1. Water enters through ostia (pores on sides of sponge)
    • 2. Microvilli of choanocytes absorb nutrients from water
    • 3. Choanocytes transfer nutrients to Amebocytes
    • 4. Amebocytes phagocytes nutrient, create spicules
    • 5. Flagella of choaocytes push water out
    • 6. Water exits through osculum (large hole at top of sponge)
  7. Describe the various cells and structures found in a sponge.
    • Amebocyte (Archaeocyte): amoeba-like cells at the base of each choanocyte. Phagocytizes the food transferred from Choanocytes, creates spicules.
    • Spicules: embedded into sponge walls to support sponge structure
    • Spongocoel: cavity within the sponge
    • Porocytes: cells at the tip of ostium that have the ability to close the ostium when the sponge is in danger (eg. Water is poisoned)
    • Pinacocyte: cells on outer surface of sponge which help to regulate surface area (look like squamous epithelial cells)
    • Choanocytes (collar cells): cells that absorb nutrients from water (via microvilli) and transfer to Amebocytes. Push water out of the osculum (via flagella)
    • Mesoglea (Mesohyl or Mesenchyme): gelatinous area found between pinacocytes and choanocytes
  8. Describe the three types of canals for sponges and the path of water for each.
    • Asconoids: flagellated spongocoel, simplest canal system (eg. Leucosolenia)
    • Ostium -> spongocoel (lined with choanocytes) -> osculum
    • Syconoids: flagellated canals, moderate canal system (eg. Scypha, Grantia)
    • Ostium -> incurrent canal -> prosopyle -> radial canal (containing choanocytes) -> apopyle -> spongocoel -> osculum
    • Leuconoids: flagellated chambers, complex canal system. All freshwater and most marine sponges. (eg. Bath sponge)
    • Ostium -> incurrent canal -> flagellated chamber (lined with choanocytes) -> excurrent canal -> osculum
  9. What are the cells that can be found in the mesoglea of a sponge?
    • Also known as Mesohyl or Mesenchyme
    • Pinacocytes: Half of cell is in mesoglea
    • Choanocytes: bulb portion is in mesoglea
    • Amebocytes: entirely in mesoglea
    • Spicules: entirely in mesoglea
  10. Types of amebocytes with function.
    • Sclerocytes: secrete spicules
    • Spongocytes: secrete spongin
    • Collencytes: secrete collagen
    • Lophocytes: secrete large amount of collagen
  11. Information about reproduction in sponges
    • Asexual: budding and regeneration
    • Gemmules are internal buds, released through osculum
    • Sexual reproduction: monoecious (hermaphroditic)
    • Sperm and oocysts formed from choanocytes
    • Some are viviparous
    • Some are Oviparous
    • NONE are Ovoviviparous
  12. Viviparous vs. oviparous vs. ovoviviparous
    • Viviparous: embryonic development within animal then give birth (mammals)
    • Oviparous: lay eggs that require an incubation period (bird)
    • Ovoviviparous: lay eggs that hatch immediately, incubation has already taken place inside animal (scorpion, shark)
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