Animal Biology and Anatomy- Exam 3
The Dichotomy of Parazoans vs. Eumetazoans
• Parazoans only include sponges (phylum Porifera).
o They do not have true tissues; you can put a sponge in a blender, place it in an
aquarium, and it will eventually come together and form a sponge again.
• Everything else are eumetazoans; these organisms have true tissues.
Bilateral vs. Radial Symmetry
Eumetazoa is divided into two major groups:
• Animals with radial symmetry
o Possess a top (aboral) and bottom (oral), but no distinct ventral, dorsal, left, or
o Their anatomy allows them to encounter the environment equally from all sides.
o Many are sessile (stay put) or planktonic (drift or swim weakly).
o Include phyla: Cnidaria, Ctenophora.
• Animals with bilateral symmetry
o Possess a dorsal, ventral, anterior, and posterior side.
o Cephalization leads to a head, a concentration of sense organs at the
anterior end. This side is the first to encounter the environment.
o Include phyla: Arthropoda, Gnathostomulida, Rotifera, Platyhelminthes,
• The only animals that have no body symmetry are sponges (phylum Porifera). Remember,
sponges are parazoa, not eumetazoa!
This term refers to a major group within the animal kingdom in which most, but not all of its
members have either a lophophore or a trochophore. • Lophophore: a filter-feeding apparatus consisting of hollow tentacles. The mouth is located
inside the ring of tentacles, and the anus is located outside. Cilia on the tentacles generate a
current of water which allows it to filter food particles.
• Trochophore: a microscopic swimmer larva. It has two bands of cilia which help it move and
• Include phyla: Mollusca, Annelida.
A coelom is a fluid-filled body cavity surrounded by mesoderm.
o Have a solid body without a cavity.
o Mesoderm fills entire space.
o Use total-body peristalsis (contracting the entire body) in order to move food through gut.
o Have a fluid-filled cavity with one side surrounded by mesoderm.
o Use total-body peristalsis in order to move food through gut.
o Have a “true coelom:” a fluid-filled cavity surrounded on both sides by
o Possess one or more mesenteries, connections of mesoderm that suspend the
endoderm and coelom within the body.
o Muscles that line the digestive tract use peristalsis to move food through the gut.
• Note: all three groups are triploblastic! They contain all three cell layers.
Animal Pathway of digestion What is happening in each area
1.Mouth Mechanical pulverization, enzymatic
decomposition of starch, & for