Phylum Porifera: Sponges have  specialized cells but no tissues; no symmetry –Sponges are the most  primitive animals on Earth 570 million year old fossils Closely related to a  group of protists –Sponges share common characteristics: Sessile  do not move Reproduce both  sexually & asexually They are  filter feeders

–Sponges have several types of specialized cells: Pinacocytes  thin and leathery cells that form a sponge’s outer layer Choanocytes  “collar cells,” form the inner layer of a sponge –Cells have flagella surrounded by a collar of tiny hairlike structures called  microvilli –These cells pull water through the sponge by beating their flagella  trapping food particles in their mucus. Ameobocytes  mobile cells found in the jellylike material between the 2 cell layers –They  absorb & digest food particles caught by their collar cells –Transport  oxygen & waste in the sponge

Internal organization of a sponge: choanocyteamoebocyte pinacocyte

Phylum Cnidaria: Cnidarians are the  oldest existing animals that have specialized tissues; radial symmetry –Cnidarians have 2 body forms: Polyps  cylindrical tubes with mouth and tentacles facing upward (example – coral) Medusas  umbrella-shaped with their mouth and tentacles on the underside (example – free- swimming cnidarians such as jellyfish)

–Cnidarians reproduce both  sexually & asexually Polyps reproduce asexually by  budding, producing genetically identical offspring Medusa reproduce sexually by  releasing gametes into the water –Fertilized egg develops into a free-swimming larva called a  planula –The planula then develops into the  polyp stages Many cnidarian species  alternate between these two body forms

Feeding polyp Reproductive polyp Medusa bud Medusa ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps 1 mm Key Haploid (n) Diploid (2n) Gonad SEXUAL REPRODUCTION MEIOSIS FERTILIZATION Egg Sperm Zygote Planula (larva) Developing polyp Mature polyp

–Cnidarians are made up of  2 tissue layers separated by mesoglea (non- cellular jelly like material) Outer tissue layer has 3 cell types: –Contracting cells  cover the surface of the cnidarian & contain muscle fibers –Nerve cells  interconnect & form a network over the entire animal (they do not have brains) –Cnidocytes  specialized cells that contain stinging structures used for defense & capturing prey. »Found all over a cnidarian’s body but  most are on their tentacles »A nematocyst is a stinging structure found in both sea anemones & jellyfish  they contain a thin, coiled, harpoon-shaped tubule with a poisonous barb at one end

Gastrovascular cavity  sac-like digestive space through which cnidarians stuff prey –Secretes  digestive enzymes & absorbs nutrients –Also moves  oxygenated water to internal cells Polyp Mouth/anus Body stalk Tentacle Gastrovascular cavity Endoderm Mesoglea Ectoderm Tentacle Mouth/anus Medusa

–The four major cnidarian classes are defined by  their dominant body form 1)Anthozoans  polyp form is dominant, there is no medusa form; include sea anemones & coral Sea anemone (class Anthozoa)

2)Hydrozoans  alternate between polyp and medusa; include fire coral, Portuguese Man- of-War & hydras Portuguese Man-of-War HydraFire coral

3)Scyphozoans  medusa form is dominant, very short or no polyp stage; include jellyfish Jellies

4)Cubozoans  dominant medusa form; include tropical box jelly fish & sea wasps Sea wasp (class Cubozoa) Box jelly fish (class Cubozoa)