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Invertebrates are animals that have no
backbone, or vertebral column.
Invertebrates make up over 95% of all
animal species.
They include sea stars, worms, jellyfishes,
and insects.
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Copyright Pearson Prentice Hall
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What is a Sponge?
 Sponges are the simplest and most
ancient animals
 in the phylum Porifera which means
“pore-bearers.”
 live their entire adult life as sessile
organisms; attached to a single spot.
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◦ Body Plan
 Sponges are asymmetrical; they
have no front or back ends, no
left or right sides.
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◦ Feeding
 Sponges are filter feeders.
 As water moves through the sponge,
food particles are trapped and engulfed
by choanocytes that line the body cavity.
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◦ Circulation
 Sponges rely on movement of water
through their bodies to carry out body
functions.
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Branching Tube Sponge
Stove Pipe Sponge
Vase Sponges
Barrel Sponges
Ball Sponges
Rope
Sponges
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What is a Cnidarian?
 Cnidarians are soft-bodied,
carnivorous animals that have
stinging tentacles arranged in circles
around their mouths.
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Body symmetry
◦ Cnidarians are radially symmetrical. They
have a central mouth surrounded by
numerous tentacles that extend outward
from the body.
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◦ Feeding
 A cnidarian pulls its food through its
mouth and into its gastrovascular cavity,
a digestive chamber with one opening.
 Food enters and wastes leave the body
through that same opening.
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◦ Circulation
 Following digestion, nutrients are usually
transported throughout the body by
diffusion.
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Portuguese
man-of-war
•Colonial Hydrozoan
(not a single
organism
•Tentacles sting prey
such as fish &
humans
•Polyps in colony feed
•Has gas-filled air float
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Anthozoans
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Hydra Feeding
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Food in
Gastrovascular
Cavity
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Scyphozoans
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Some Jellyfish Show
Luminescence
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Flatworms are acoelomates, which means
they have no coelom.
A coelom is a fluid-filled body cavity that is
lined with tissue derived from mesoderm.
The digestive cavity is the only body cavity
in a flatworm.
Flatworms have bilateral symmetry.
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◦ Feeding
 Flatworms have a digestive cavity with a
single opening through which both food
and wastes pass.
 Near the mouth is a muscular tube called
a pharynx.
 Flatworms extend the pharynx out of the
mouth. The pharynx then pumps food
into the digestive cavity.
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◦ Circulation
 Flatworms do not need a circulatory
system to transport materials they rely
on diffusion
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Copyright Pearson Prentice Hall
Roundworms
◦ Roundworms are unsegmented worms that
have pseudocoeloms and digestive
systems with two openings—a mouth and
an anus.
◦ Roundworms have bilateral symmetry.
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◦ Feeding
 Many free-living roundworms use
grasping mouthparts and spines to catch
and eat other small animals.
 There are a variety of parasitic
roundworms as well
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◦ Circulation
 They depend on diffusion to carry nutrients
and waste through their bodies.
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What Is an Annelid?
◦ Annelids are worms with segmented
bodies. They have a true coelom that is
lined with tissue derived from mesoderm.
◦ Annelids have bilateral symmetry.
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◦ Feeding and Digestion
 In carnivorous species, the pharynx
usually holds two or more sharp jaws
that are used to attack prey.
 Annelids that feed on decaying
vegetation have a pharynx covered with
sticky mucus.
 Other annelids obtain nutrients by filter
feeding.
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◦ Circulation
 Annelids typically have a closed
circulatory system, in which blood is
contained within a network of blood
vessels.
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Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall