1. Multicellular organisms
Tissue Levels of organization

2. Origins of Multicellularity
Multicellular organisms first appeared 600 million years ago
Arose quickly 100 million years prior to the cambrian period
Two hypothesis on the origin of multicellularity
Colonial hypothesis- cells of a dividing protist remained together, cell invagination formed two cell layers, supported by the colonial organization of some protozoa with radial symmetry
Syncytial hypothesis- a large multinucleated protista developed plasma membranes separating into multiple cells, multinucleate bilateral ciliates support this hypothesis
Animal kingdom is monophyletic and the most likely protista ancestor is the Choanocyte ( collar cell )

4. Phylum Porifera
Sponges- mostly marine animals consisting of loosely organized cells
No tissues or organs, 9000 species, Asymetrical or radially symmetrical, Sessile
Filter feed by a series of canals and chambers thru body wall where water circulates
Three Classes
Calcarea- Calcium carbonate spicules, 3-4 rays
Hexactinellida – Silica spicules, 6 rays, deep water sponges
Demospongia- Brillantly colored, Siliceous spicules, needle or 4 rayed or spongin or both, Bath sponges

5. CALCAREA

6. HEXACTINELLIDA

7. DEMOSPONGIA

9. Sponge Anatomy Simple but more than colonies of independent cells
Division of labor- cells specialized for particular functions
Pinacocytes- flat cells line outer surface, can change shape ( contraction ), can regulate water circulation
Mesohyl- Jellylike layer, contains Ameboid cells which are specialized for reproduction, secrete spicules, Transport and store food, form contractile rings
Choanocytes ( collar cells)- flagellated cells with a collar like ring of microvilli forming a mesh, Line inner chambers

10. CHOANOCYTES

11. Water Currents and Body forms
Water currents created by Choanocytes beating their Flagella bring food and oxygen, carry away wastes
Food consists of bacteria, microscopic Algae, protists, and suspended organic matter, some deepwater sponges capture small crustaceans using spicule covered filaments
Large populations of sponges help reduce turbidity of coastal waters
Pinacocytes in incurrent canals may phagocytize larger food particles
Sponges absorb dissolved nutrients from seawater by active transport

12. Body forms
Ascon- Simplest, Vase shaped, Outer opening ostia lead to spongocoel chambers and then osculum inside exit
Sycon- Folded body wall, water enters thru dermal pores to incurrent canals then to radial canals with choanocytes, exits to spongocoel and out osculum
Leucon- Extensively branched canal system, water enters thru ostia to branched canals to choanocyte lined chambers, multiple exit points osculum

14. Body Functions
No nerve cells so reactions result from cells responding to a stimulus
Water circulation minimal at sunrise and maximum at sunset, light inhibitits constriction of pinacocytes
Water circulation can cease suddenly, choanocytes stop together
Internal communication is present by chemical messages

15. Reproduction
Most sponges Monocious, both sexes, no self fertilization, produce egg and sperm at different times
Some choanocytes can loose collar and flagella, or ameboid cells undergo meiosis and form sperm or eggs
Choanocytes capture sperm and transport it to egg, early development in mesohyl, Flagellated larva blastula released, 2 days settles to bottom, turns inside out
Asexual reproduction, release gemmule capsules of ameboid cells, Fragmentation of adult

17. GEMMULE

18. Cnidarians
Radial or Biradial symmetry, no anterior or posterior, direction based on mouth position, oral mouth and aboral opposite
Over 9000 species mostly marine, important ecosystems ( coral Reefs )
No Brain, nerve net system
Gastrovascular Cavity
Diploblastic tissue layers, Epidermis and Gastrodermis, mesoglea (jelly) in between

19. Cnidarian Anatomy Ectoderm, epidermis- protection, food gathering
Endoderm, gastroderm- coordination, movement, digestion, absorption and reproduction
Mesoglea- Jelly Layer, May be noncellular or contain wandering mesenchyme cells.

20. Cnidocytes Found in epiderm and gastroderm, 30 types
Used for attachment, defense and feeding
Cnidia- fluid filled intracellular capsule attached to a hollow tube
Operculum- lidlike cap on cnidia
Cnidocil- modified cilium trigger discharges ( harpoon ) using water pressure
Nematocyst- harpoon, uses spines-barbs and long tube to inject paralyzing toxins into prey, ejects from cell by inverting like a sweater sleeve

21. CNIDOCYTES

22. Scyphozoa
All marine, “True Jellyfish” because dominant stage in life is Medusa
Mesoglea contains ameboid cells
Cnidocytes in gastrodermis and epidermis
Most harmless to Humans others can cause painful stings
Gastrodermal cells possess cilia to circulate seawater and digested food

23. Scyphozoa Aurelia Libiata- very common Atlantic and Pacific
A plankton feeder, cilia on bottom carry food to mouth
Mouth leads to 4 gastric pouches then to radial canals out to margin of bell
Rhopalium (notches) along bell contain olfactory sensory pits, statocyst and photorecptors
Exhibits distinct phototaxis

24. SCYPHOZOANS

25. Hydrozoan Small common cnidarians, some freshwater
Usually anchor to bottom substrate, Polyp stage dominates in most
Nematocysts only in epidermis
Gametes epidermal released outside body
Mesoglea acellular
Many have colonial polyps, specialized for feeding, budding, or defending the colony

26. HYDROZOAN

27. Cubozoan Medusa is cuboidal, tentacles hang from each corner of bell
Active swimmers and feeders
Polyp stage very small or absent
Warm tropical waters
“Box Jellyfish” Austrailian waters
Contains photoreceptors

28. CUBOZOAN

29. BOX JELLYFISH STINGS

30. PORTUGUESE MAN OF WAR

31. PORTUGUESE MAN OF WAR

32. PORTUGUESE MAN OF WAR STING

33. Anthozoa Include Anemones, and Stony and soft corals
Are colonial or solitary and lack Medusa
Cnidocytes lack cnidocils ( triggers )
Mouth leads to pharnyx then gastrovascular cavity
Mesenteries divide gastrovascular cavity into sections
Mesoglea contains ameboid cells
Externally show radial symmetry, internally biradial

34. Sea Anemones Solitary or large colorful colonies
Attach to solid substrate, some burrow in sand, some symbiotic relationships
Attaches to substrate with pedal disk
Oral disk contains mouth and tentacles
Slitlike mouth ends have siphonoglyph “ciliated tract” to move water into gastrovascular cavity for hydrostatic skeleton

35. Sea Anemones cont.
Locomotion by gliding on their pedal disk, crawl on sides, walk on tentacles, some swim, some float with bubble in pedal disk
Feed on invertebrates and fish

36. ANTHOZOA

37. Stony and Soft Corals Similar to Anemones, lack siphonoglyphs
Calcium carbonate cup exoskeleton secreted by epithelial cells, polyps retract into cup when threatened
Symbiotic relationship with photosynthetic dinoflagellate Zooxanthellae Algae
Coral provides nitrogen and phosphorous for the Algae and get carbon compounds in return
Zooxanthellae promote calcium carbonate deposition

38. Stony and Soft Corals
Cover 0.17% of ocean bottom hold 25% of oceans species
Environmental disturbances, warm water, stress corals causing them to loose zooxanthellea and bleach
Stony corals are connected to each other under the cup, can share food
Florida and Bahama reefs are 60% degraded

39. ANTHOZOA CORALS

40. Ctenophora
Comb Jellies, Eight bands of cilia from oral to aboral sides for locomotion
Mesoglea is highly cellular, muscle cells contained here, may be triploblastic
Tentacles contain colloblasts adhesive cells to capture prey, wipe tentacles across mouth

41. CTENOPHORA

42. Additional Considerations
Sponge and Jellyfish fossils are found in the oldest fossil deposits, the Ediacaran Formation
Coral Reefs are one of the most endangered habitats on earth
Coral covers 0.17% of the ocean and yields 10% of the fish caught
Contribute $375 Billion to the worlds economy
Corals grow very slowly, are disturbed easily