Transcript Phylum Cnidaria notes (coral, sea anemones, hydra, jellyfish)

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:
Nematocyst
(harpoon)
Cnidocyte
(stinging cell)
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.)
Reproduction (cont.)
Excretion
• mouth/anus- release waste