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The three grades of metazoan animals

The three grades of metazoan animals. Animalia. KINGDOM:. Mesozoa. GRADE:. Parazoa. Eumetazoa. All other animal phyla. PHYLA:. Placozoa. Porifera. Mesozoa. General Body Plan. Cellular level of organization Asymmetrical Choanocytes Mesohyl spongin/ collagen spicules.

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The three grades of metazoan animals

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  1. The three grades of metazoan animals Animalia KINGDOM: Mesozoa GRADE: Parazoa Eumetazoa All other animal phyla PHYLA: Placozoa Porifera Mesozoa

  2. General Body Plan • Cellular level of organization • Asymmetrical • Choanocytes • Mesohyl • spongin/ collagen • spicules

  3. 3 Body Types Based on the complexity of the water canals: • Asconoid • Syconoid • Leuconoid Increasing size Increasing Surface Area :Volume

  4. The three grades of metazoan animals Animalia KINGDOM: Mesozoa GRADE: Parazoa Eumetazoa All other animal phyla PHYLA: Placozoa Porifera Mesozoa

  5. Phylum Cnidaria

  6. Level of Organization Tissue • similar cells are organized into tissues that work together to accomplish a common function • Cnidarians are diploblastic: they have 2 germ layers

  7. Tissue Layers • Diploblastic = 2 germ layers • endoderm  gastrodermis (inner tissue) • ectoderm  epidermis (outer tissue) • mesoglea • gelatinous/ noncellular matrix between the 2 layers

  8. Tissue Layers epidermis gastrovascular cavity (GVC) mesoglea gastrodermis

  9. Epidermal Cell types Epitheliomuscular cell receptors neurons

  10. Epidermal Cell types • cnidocytes: epidermal cells containing stinging organelles (nematocysts). Unique to Cnidarians. cnidocyte

  11. Epidermal Cell types Cnidocil: trigger cnidocyte Undischarged

  12. Epidermal Cell types neamtocyst cnidocyte discharged

  13. Nematocysts • nematocysts are like “mini-harpoons” • cnidocil senses movement & acts like a “trigger” • can inject poison, coil around prey, or be adhesive • functions: • - prey capture; defense nematocyst cnidocil cnidocyte Undischarged Discharged

  14. Jellyfish sting

  15. Gastrodermal Cell types mesoglea gastrodermis epidermis gland cells nutritive-muscular cells (ciliated)

  16. mouth gastrodermis mesoglea epidermis General Body Plan • sac-like body (only 1 opening) oral surface Gastrovascular cavity aboral surface

  17. General Body Plan Dimorphism: 2 different body forms are usually present in the life cycle: aboral oral aboral oral

  18. General Body Plan • - Radially symmetrical: body parts are arranged concentrically around an oral-aboral axis oral aboral

  19. General Life Cycle Sexual reproduction Asexual reproduction

  20. Feeding and Digestion Feeding • nematocysts capture prey • tentacles Digestion • extracellular (in GVC) • intracellular (by gastrodermal cells) • incomplete system (no anus)

  21. Feeding and Digestion • Food and waste go in/out the same opening •  no anus! waste Food

  22. Feeding and Digestion mesoglea gastrodermis gland cells: secrete mucus, entraps food particles nutritive-muscular cells: create water currents, circulate food particles in GVC epidermis

  23. Nervous System • nerve net (no central nervous system= no brain) receptors nerve net neurons

  24. Nervous System • sense organs • statocysts (equilibrium cells) • ocelli (photosensitive cells)

  25. Nervous System ocelli statocysts

  26. Skeletal Support • water in GVC acts as a hydrostatic skeleton Muscles act against water trapped in the GVC

  27. Skeletal Support • water within GVC acts as a hydrostatic skeleton:

  28. Skeletal Support

  29. Reproduction Asexual • pedal laceration (e.g. sea anemones)

  30. Reproduction Asexual • budding Buds

  31. Reproduction Asexual • longitudinal fission

  32. Reproduction Sexual • usually dioecious (separate sexes) • monoecious (both male + female gonads in 1 individual) • results in Planula larva

  33. Phylum Cnidaria Three Classes: Class Hydrozoa Class Scyphozoa Class Anthozoa These classes differ in the prominence of the polyp and medusa stages

  34. Class Hydrozoa • medusa & polyp body forms Fire coral

  35. Class Hydrozoa • medusa & polyp body forms • most are colonial •  colonies are formed of individuals (zooids) a single zooid

  36. Class Hydrozoa • many of these colonies are polymorphic •  there are several different types of polyps/zooid and each type is specialized for a different function •  all the zooids within a colony are genetically identical and are connected by a common GVC

  37. Class Hydrozoa - a sessile colony showing polymorphism gonozooid GVC entire colony gastrozooid

  38. Class Hydrozoa - a Portugese Man-o-war is a floating hydrozoan colony showing polymorphism pneumatophore entire colony gastrozooid dactylzooid

  39. Class Hydrozoa- life cycle sexual reproduction asexual reproduction

  40. Class Hydrozoa • Hydra is an example of a solitary, freshwater hydrozoan asexual reproduction sexual reproduction gonads bud

  41. Class Scyphozoa • “true” jellyfish • medusa & polyp body forms • thick mesoglea

  42. Class Scyphozoa- life cycle adult medusa sperm and egg larva ephyra scyphistoma strobila

  43. Class Anthozoa • polyp body form ONLY • all marine

  44. Class Anthozoa • some are colonial •  colonies are formed of individual zooids (e.g. corals) • some are solitary (e.g. anemones)

  45. Class Anthozoa Sea anemones

  46. Sea pansy Class Anthozoa Soft Corals Sea pen

  47. Class Anthozoa Stony Corals

  48. Class Anthozoa- life cycle Sexual reproduction sperm egg larva

  49. Class Anthozoa- life cycle asexual reproduction fission pedal laceration fission

  50. Colony formation • colony formation is common (colonial animals) • occurs via asexual reproduction (e.g. fission) • individual polyps are connected to one another by a common GVC individual polyp

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