Animal Diversity (Part 1) Lecture
Textbook Reference: Chapter 44 in Biology How Life Works (2nd ed.)
Sections 44.1 – 44.2; pp.946 to 956
Animal “Body Plans”
• Four major patterns in body plans useful in classifying animals:
1. Symmetry
2. Tissue orientation
3. Body cavities
4. Orientation of the mouth and anus
Symmetry
– Dorsal
– Ventral
– Anterior
– Posterior
– Oral
– Aboral
1
, Tissue Organization of Cnidarians and Bilaterians
How are diploblasts and triploblasts distinguished from each other?
o Diploblasts: animals that develop form embryos with two germ layers
(cnidarians)
o Triploblasts: animals that develop from embryos with three germ layers
(bilaterians)
o Diploblastic animals – 2 germ layers: endoderm + ectoderm
o Triploblastic animals – 3 germ layers: endoderm + ectoderm +
mesoderm
Triploblast Body Cavities
• Most triploblastic animals can be further subdivided based type of body cavity or
coelom
• Define coelom = space inside the body, usually fluid filled, where organs
develop, move and are cushioned from outside shocks
• Aceolomates – do not have a cavity outside the digestive tract
• Pseudocoleomates – body cavity derived from the blastocoel, rather than
mesoderm
• Coelomates – have a body cavity that completely surrounds the internal
organs
2
Textbook Reference: Chapter 44 in Biology How Life Works (2nd ed.)
Sections 44.1 – 44.2; pp.946 to 956
Animal “Body Plans”
• Four major patterns in body plans useful in classifying animals:
1. Symmetry
2. Tissue orientation
3. Body cavities
4. Orientation of the mouth and anus
Symmetry
– Dorsal
– Ventral
– Anterior
– Posterior
– Oral
– Aboral
1
, Tissue Organization of Cnidarians and Bilaterians
How are diploblasts and triploblasts distinguished from each other?
o Diploblasts: animals that develop form embryos with two germ layers
(cnidarians)
o Triploblasts: animals that develop from embryos with three germ layers
(bilaterians)
o Diploblastic animals – 2 germ layers: endoderm + ectoderm
o Triploblastic animals – 3 germ layers: endoderm + ectoderm +
mesoderm
Triploblast Body Cavities
• Most triploblastic animals can be further subdivided based type of body cavity or
coelom
• Define coelom = space inside the body, usually fluid filled, where organs
develop, move and are cushioned from outside shocks
• Aceolomates – do not have a cavity outside the digestive tract
• Pseudocoleomates – body cavity derived from the blastocoel, rather than
mesoderm
• Coelomates – have a body cavity that completely surrounds the internal
organs
2
