CNIDARIA
Characteristics
 Class ScyphozoaJellyfish- medusa form
 Class Antozoa- corals, sea
anemones- polyp form
 Class Hydrozoa- Hydras
 Tentacles
 2 body plans:
 Polyp- attached to ocean
floor, mouth opens up,
tentacles surround mouth
Characteristics
 Medusa- free
floating/swimming
form, mouth opens
down, tentacles trail
down, bell-shaped
 No organs
 Movement- jellyfish
swim, anemones move
slowly along ocean
floor
Anatomy
 Gas exchange
happens at cell level
 No muscle cells,
skeleton, or circulation
 Nerve Net
 Epidermis cells create
“skin”
 No excretory system
Anatomy
 Tentacles have
nematocysts – stinging
cells
 Central hollow body
cavity
 Radial symmetry
 Acoelomates
Feeding
 Uses stinging ability to
capture food
 Prey is stung and
brought to mouth by
tentacles
 Digested in central
body cavity
 Niche: Predators,
carnivores
Reproduction
 Reproduction is both
sexual and asexual
 Asexual- budding by
hydras, coral, sea
anemones
 Sexual- jellyfish have
both sexes. Females
produce eggs, males
produce sperm
Life Cycle
 Fertilized egg turns
into larvae
 Larvae settles on
ocean floor
 Polyp develops
 Medusa buds off of
polyp
 Medusa reproduces
sexually to form
fertilized egg
Habitat
 Marine/ Ocean habitat
 Polyp form lives on
ocean floor
 Medusa form swims
freely in open water
 What are some biotic
and abiotic factors?
Colony Life
 Corals reefs- coral polyp
attaches to rock or ocean
floor, secretes calcium
carbonate (CaCO3) which
is a hard skeleton. Then it
reproduces asexually.
Offspring attach on top of
same hard skeleton and
cycle goes on. This is how
a coral reef is built
Colony Life
 Portuguese Man-oWar
 Is really over 1000
polyps living together
 Some sting, some
digest, some produce
sex cells
Hydra
 Stays in polyp form
throughout life
 Only freshwater
cnidarians
 Predators- prey on
small invertebrates
 Named after Greek
mythology serpent-like
creature with many
heads
Adaptations
 Regeneration of body
parts
 Anemones have strong
adhesion in strong waves
 Asexual reproduction –
can colonize a large area
quickly
 Anemone can contract to a
tight ball to prevent drying
out in low tide