1. 25.2 Animal Body Plans and Evolution
Miss Grant
Kaimuki Christian School

2. What is a body plan? A unique organization of structures
Features include
Levels of organization
Body symmetry
Differentiation of germ layers
Formation of body cavities
Patterns of embryological development
Segmentation
Cephalization
Limb formation

3. Levels of Organization
Body
Organ systems
Organs
Tissues
Cells
Organelles
Molecules
Atoms

4. Body Symmetry Radial symmetry (sea anemone)
Bilateral symmetry (lobster)

5. Differentiation of Germ Layers
Make up three layers of cells during embryological development
Endoderm (develop linings of digestive tract and respiratory system)
Mesoderm (muscles and most of the circulatory, reproductive, and excretory systems)
Ectoderm (sense organs, nerves, outter layer of skin)

6. Formation of Body Cavity
Fluid-filled space between the digestive tract and body wall
Space where internal organs are suspended and can grow
Most complex animals have a true coelem
Body cavity that develops within the mesoderm and is completely lined with tissues from the mesoderm
Acoelomate: lack a body cavity
Pseudocoelomate: only partially lined with mesoderm

7. Patterns of Embryological Development
Zygote: fertilized egg
Blastula: hollow ball of cells
Blastopore: single opening in the digestive tract
Efficient digestive tract needs two opening
Why?
Protostomes: blastopore becomes the mouth
Deuterostomes: blastopore becomes the anus (chordates and echinoderms)

8. Segmentation (Repeating Parts)
Worms, insects, vertebrates
At least some internal and external body parts that repeat on each side of the body
Bilateral symmetry and segmentation found in many of the most successful animal groups
How can a simple mutation in the genes of an organism affect segmentation?

9. Cephalization
Concentration of sense organs and nerve cells at the anterior end
Exhibited by most animals with bilateral symmetry
Most successful animal groups
Heads are formed by fusion and specialization of several body segments during development

10. Limb Formation
Segmented, bilaterally symmetrical animals typically have appendages on both sides
Bristles in worms
Jointed legs in spiders
Wings in dragonflies
Bird wings
Dolphin flippers
Monkey arms

11. Cladogram of Animals Based on characteristics of living species
Evidence from fossils
comparative genomic studies
Animals phyla defined according to body plans and patterns of embryological development

12. Differences Between Phyla
Cladogram shows the sequence in which body plan features evolved
Every phylum has a unique combination of ancient traits inherited from ancestors