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IB-202-2

IB-202-2. 3-10-06. Chapter 33. Invertebrates Sponges. Figure 33.1 . Overview: Life Without a Backbone Invertebrates Are animals that lack a backbone Account for 95% of known animal species. Porifera. Cnidaria. Chordata. Echinodermata. Other bilaterians (including

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IB-202-2

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  1. IB-202-2 3-10-06

  2. Chapter 33 Invertebrates Sponges

  3. Figure 33.1 • Overview: Life Without a Backbone • Invertebrates • Are animals that lack a backbone • Account for 95% of known animal species

  4. Porifera Cnidaria Chordata Echinodermata Other bilaterians (including Nematoda, Arthropoda, Mollusca, and Annelida) Deuterostomia Bilateria Eumetazoa Ancestral colonial choanoflagellate Figure 33.2 • A review of animal phylogeny

  5. Sponges are sessile and have a porous body and choanocytes • Sponges, phylum Porifera • Live in both fresh and marine waters • Lack true tissues and organs

  6. Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes. 5 Flagellum Food particles in mucus Choanocyte Collar Azure vase sponge (Callyspongia plicifera) Osculum Spongocoel. Water passing through porocytes enters a cavity called the spongocoel. 4 Phagocytosis of food particles Amoebocyte Porocytes. Water enters the epidermis through channels formed by porocytes, doughnut-shaped cells that span the body wall. 3 The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes. 6 Spicules Epidermis. The outer layer consists of tightly packed epidermal cells. 2 Water flow Amoebocyte. Amoebocytes transport nutrients to other cells of the sponge body and also produce materials for skeletal fibers (spicules). 7 Mesohyl. The wall of this simple sponge consists of two layers of cells separated by a gelatinous matrix, the mesohyl (“middle matter”). 1 • Sponges are suspension feeders • Capturing food particles suspended in the water that passes through their body Figure 33.4

  7. Choanocytes, flagellated collar cells • Generate a water current through the sponge and ingest suspended food • Most sponges are hermaphrodites • Meaning that each individual functions as both male and female Experiment: If a sponge is forced through a fine mesh screen and the cells put in a Beaker, within a few days they will reassemble and form an intact sponge. What does this mean? Do sponge cells communicate with each other?

  8. Variations in Form or Shapes of Sponges Sponges come in a variety of shapes, sizes and Colors! Since sponges are an aggregation of cells and not organized into tissues, how do they achieve this variability in structure and color??? Something to think about!

  9. Video The Shape of Life Episode 1- Origins (Sponges) The Story of Science.

  10. Cnidaria Chordata Mollusca Annelida Rotifera Silicarea Phoronida Nemertea Calcarea Arthropoda Ctenophora Ectoprocta Brachiopoda Nematoda Echinodermata Platyhelminthes “Radiata” Deuterostomia Lophotrochozoa “Porifera” Ecdysozoa Bilateria Eumetazoa Metazoa Ancestral colonial flagellate • One hypothesis of animal phylogeny based mainly on molecular data Figure 32.11

  11. Rotifera Cnidaria Porifera Annelida Mollusca Chordata Phoronida Nemertea Ctenophora Nematoda Arthropoda Ectoprocta Brachiopoda Echinodermata Platyhelminthes “Radiata” Deuterostomia Protostomia Bilateria Eumetazoa Metazoa Ancestral colonial flagellate • One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons Figure 32.10

  12. Phylum Cnidaria • Cnidarians have radial symmetry, a gastrovascular cavity, and cnidocytes • All animals except sponges • Belong to the clade Eumetazoa, the animals with true tissues • Phylum Cnidaria • Is one of the oldest groups in this clade

  13. Cnidarians • Have diversified into a wide range of both sessile and floating forms including jellies, corals, and hydras • But still exhibit a relatively simple diploblastic, radial body plan

  14. The basic body plan of a cnidarian • Is a sac with a central digestive compartment, the gastrovascular cavity • A single opening • Functions as both mouth and anus

  15. Medusa Mouth/anus Polyp Tentacle Gastrovascular cavity Gastrodermis Mesoglea Epidermis Body stalk Tentacle Mouth/anus Figure 33.5 • There are two variations on this body plan • The sessile polyp and the floating medusa

  16. Prey Tentacle “Trigger” Discharge Of thread Nematocyst Coiled thread Cnidocyte Figure 33.6 • Cnidarians are carnivores • That use tentacles to capture prey • The tentacles are armed with cnidocytes • Unique cells that function in defense and the capture of prey

  17. Table 33.1 • The phylum Cnidaria is divided into four major classes

  18. (d) Sea anemones and othermembers of class Anthozoaexist only as polyps. (b) Many species of jellies (classScyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore than 100 m long dangling from a bell-shaped body up to 2 m in diameter. (c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison,which can subdue fish andother large prey, is more potent than cobra venom. (a) These colonial polyps are members of class Hydrozoa. Figure 33.7a–d • Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa

  19. Other polyps, specialized for reproduction, lack tentacles and produce tiny medusae by asexual budding. 3 Some of the colony’s polyps, equipped with tentacles, are specialized for feeding. The medusae swim off, grow, and reproduce sexually. 2 4 Reproductive polyp Feeding polyp A colony of interconnected polyps (inset, LM) results from asexual reproduction by budding. 1 Medusa bud MEIOSIS Gonad Medusa SEXUAL REPRODUCTION Sperm Egg ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps FERTILIZATION Zygote Developing polyp Mature polyp Planula (larva) Key Haploid (n) 1 mm Diploid (2n) Figure 33.8 Hydrozoans • Most hydrozoans • Alternate between polyp and medusa forms The planula eventually settles and develops into a new polyp. The zygote develops into a solid ciliated larva called a planula. 6 5

  20. Scyphozoans • In the class Scyphozoa • Jellies (medusae) are the prevalent form of the life cycle

  21. Cubozoans • In the class Cubozoa, which includes box jellies and sea wasps. Nematocysts full of • toxic venom • The medusa is box-shaped and has complex eyes unlike scyphozoa

  22. Anthozoans • Class Anthozoa includes the corals and sea anemones • Which occur only as polyps

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