Phylum Cnidaria Jellyfish, hydra, sea anemones, & coral

Appearance Polyp: cylindrical, pine shaped animals that are usually attached to a rock or Ex. Hydras, sea anemones, corals Medusa: bell-shaped body; umbrella Ex. Jellyfish *Have 2 tissue layers: ectoderm & endoderm

Appearance (cont.)

Appearance of a jellyfish

Symmetry Radial symmetry

Skeletal/Muscle System most have primitive muscle cells; coral have external skeleton of calcium carbonate

Capturing Prey LET’S EAT!!! cnidarians are carnivores (eat meat) that use tentacles arranged in a ring around their mouth to capture prey when a “trigger” is stimulated on a stinging cell called the cnidocyte, a harpoon or nematocyst shoots out & injects poison into the prey

Capturing Prey: Cnidocyte and Nematocyst at work: Cnidocyte (stinging cell) Nematocyst (harpoon )

Digestion Sac w/ a digestive cavity (gastrovascular cavity) w/ a single opening that acts as a mouth/anus Jellyfish Hydra

Digestion (cont.) food is pushed into the gastrovascular cavity where digestion begins (extracellular digestion) then food is passed to food vacuoles of gastrodermis undigested remains leave through the mouth/anus

Nervous System Nerve Net- Cnidarians do not have a brain but they have simple sensory receptors that detect & respond to stimuli

Circulation NONE!!

Respiration Diffusion- oxygen from water moves into gastrodermal cells (high to low)

Reproduction Asexual – budding- formation of outgrowths that pinch off from parent to live independently Sexual- forms a zygote and free swimming planula that settles on ocean floor; usually have separate sexes (male & female species) but some hermaphrodites do exist *MOST ALTERNATE B/W POLYP & MEDUSA LIFE FORM

Reproduction (cont.)

Excretion mouth/anus- release waste