Porifera and Cnidarians
Vineet, Shiv, Kevin, Silas
Germ Layers
Germ layers a group of cells formed when the embryo is being developed. All
animals more complex than porifera have three or more primary germ layers.
Porifera
• Porifera have no germ
layers
Cnidaria
• Cnidarians mostly have two
germ layers, an
endothermic and an
ectodermic germ layer
Symmetry
Porifera
• Not symmetric
Cnidaria
• Cnidarians are radially
symmetric
Coelom
A coelom is a fluid filled body cavity that is usually in the middle germ layer or
mesoderm. The coelom allows the internal organs to develop independently of the
body wall.
Porifera
Cnidaria
• Both porifera and cnidarians are acoelomates or don’t have
coeloms
• This means that the organs are subjected to crushing forces
underwater
Digestive Tract
Porifera
• These organisms have no
digestive tract
Cnidarians
• Cnidarians have a
gastrovascular cavity for
digestion which helps the
organism digest and
distribute nutrients and
particles throughout the
body
Cephalization
Porifera
• They have no cephalization
because they have no
nervous tissue or head
Cnidaria
• These organisms have a
small degree of
cephalization although they
are radial symmetric
because they have a head
and concentrated neural
and photoreceptive cells
Segmentation
Porifera
• None
Cnidaria
• None
Neither one of these phyla are segmented
Skeleton and appendages
Porifera
• Porifera have an
exoskeleton that is made
from calcium carbonate
which help defend them
from predators.
• They have no appendages
at all
Cnidaria
• Cnidarians have a
hydrostatic skeleton which
help the organism contract
and retract against the
gastrovascular cavity
• They have some oral
appendages by the mouth
to help it feed.
Circulatory System
Porifera
• Porifera do not have
circulatory systems. By
beating their flagella, they
cause water to flow through
the animal.
Cnidaria
• Cnidarians do not need a
circulatory system because
all of their cells are already
in contact with water, which
contains all the nutrients
they need.
Respiratory System
Porifera
• Also does not have a
respiratory system. The
sponge’s cells absorb
oxygen through diffusion
from the water flow system.
Cnidaria
• Cnidarians absorb oxygen
and release carbon dioxide
into the surrounding water
through their cell layers.
They do not have distinct
respiratory organs.
Reproduction
Porifera
• Pieces of sponge are able to
respawn into whole new
sponges. Asexual
reproduction also occurs
through budding. Each bud
develops into a new sponge.
Cnidaria
• Cnidarians can undergo
both asexual and sexual
reproduction. Asexual
reproduction results in
identical clones through
budding.
Fin