1. Animal Body Plans
Features of Body Plans
1. Levels of Organization
Cells Tissues Organs Organ Systems Organisms
2. Body Symmetry
a. Radial – Body parts extend outward from the center like spokes of a wheel
b. Bilateral – Single imaginary plane divides body into left and right sides that are mirror images
3. Differentiation of Germ Layers (embryologic development)
a. Ectoderm – Outer layer develops into sense organs, nerves, outer layer of skin
b. Mesoderm – Middle layer develops into muscle, circulatory, reproductive and excretory organ
systems
c. Endoderm – Inner layer develops into linings of digestive tract and respiratory system
4. Formation of Body Cavities
Fluid filled space for internal organs to grow
a. True Coelom – Develops within mesoderm and is completely lined with mesoderm
b. Pseudocoelom – Partially lined with mesoderm
c. Acoelomates – Have no body cavity

2. 5. Patterns of Embryological Development
Zygote – Fertilized egg
Blastula – A hollow ball of cells formed during early embryo development of animals
Blastopore – Single opening in the blastula
a. Protostomes – Phyla in which blastopore becomes the mouth (anus develops in opposite
end) grasshoppers
b. Deuterostomes – Phyla in which the blastopore becomes the anus (mouth develops in
opposite ends) Chordates (fishes) and Echinoderms
6. Segmentation
Body is divided into repeating parts
7. Cephalization
Sense organs and nerve cells are concentrated at the anterior end (head)
8. Limb Formation
Found in animals with bilateral symmetry and segmentation