Today’s Objectives
TSW be able to recognize and give
examples of the three types of
symmetry found in animals.
 TSW be able to properly use directional
terms for anatomical position.
 TSW be able to draw the three types of
triploblastic body plans.

Symmetry
Asymmetry
Radial Symmetry
Bilateral Symmetry
Asymmetrical animals

Sponges
Radially Symmetrical Animals
Cnidarians
 Coelenterates
 Nematodes
 Annelids
 Ctenophorans
 Echinoderms

Bilaterally Symmetrical Animals

Platyhelminths
 Chordates
 Fishes
 Herps
 Birds
 Rotifers
 Molluscs
 Arthropods
ALLOWS FOR CEPHALIZATION!
Directional Orientation
Anterior vs. Posterior
 Dorsal vs. Ventral
 Medial vs. Lateral
 Distal vs. Proximal
 Inferior vs. Superior
 Cephalic vs. Caudal
 Aboral vs. Oral

Body Plans
Acoelomate
Pseudocoelomate
Eucoelomate
Tissue Layer Body Plans
Diploblastic – ectoderm and gastroderm
separated by mesoglea
 Triploblastic - ectoderm, mesoderm
and endoderm

– Acoelomate
– Pseudocoelomate
– Eucoelomate
Acoelomate Body Plans

Solid mass of cells between endoderm
and ectoderm (parenchyma)
Pseudocoelomate Body Plans
Body cavity not entirely lined with
mesoderm
 Pseudocoelom comes from blastocoel

Eucoelomate Body Plans
Cavity completely lined with mesoderm
(peritoneum and serosa)
 Visceral structures suspended

Review Items
Draw each type of triploblastic body
plan and label each germ layer.
 Name at least one phylum of animals
that falls into each category of
symmetry.

Anatomical Position Review

Use the proper terms to describe the
relationship between the following body
parts:
– A) hand is ____ to the elbow
– B) knee is ____ to the head
– C) bellybutton is ____ to the spinal cord
– D) heart is ____ to the lungs
– E) head is ____ to the neck (2 terms fit here)
– F) wrist is ____ to the fingers