Animal Body Plans and Evolution By: Mandie Hill

Features of Body Plans Levels of organization When first cells of most animals develop, they change into specialized cells that are organized into tissues. Tissue: group of cells that perform a similar function. Animals normally have several types of tissues, including epithelial, muscle, connective, and nervous tissues Body Symmetry: Bodies of most animals exhibit some type of symmetry. Radial symmetry: any number of imaginary planes drawn through the center of the body could divide it into equal halves

Features of Body Plans Bilateral Symmetry: A single imaginary plane divides the body into left and right sides that are mirror images of one another. Animals that contain bilateral symmetry have a definite front, end, and a back.

Features of Body Plans Differentiation of Germ Layers Endoderm: innermost layer Develop into the linings of the digestive tracts and much of the respiratory system Mesoderm: middle layer Give rise to to muscles and much of the circulatory, reproductive, and excretory organ systems. Ectoderm: outermost layer Produce sense organs, nerves, and the outer layer of the skin.

Features of Body Plans Formation of a Body Cavity Body cavity: fluid filled space between the digestive tract and body wall. Coelom: A body cavity that develops within the mesoderm and completely lined with tissue derived from mesoderm. Pseudocoelom: only being partially lined with mesoderm.

Features of Body Plans Patterns of Embryological Development Zygote: fertilized egg Blastula: a hollow ball of cells Protostomes: Blastospore becomes mouth Deuterostomes: Blastospore becomes anus.

Features of Body Plans Segmentation: Repeating Parts Segmented animals have at least a few internal and external body parts that recur on each side of the body. Segmentation is important because of the way genes control the production and growth of body segments.

Features of Body Plans Cephalization Concentration of sense organs and nerve cells at their interior end. Most successful groups (arthropods and vertebrates) exhibit cephalization. Animals with heads generally move in “head first” direction.

Features of Body Plans Limb Formation: Legs, Flippers, and Wings Appendages vary from simple groups of in worms to jointed legs in spiders, the wings in dragonflies, bird wings, dolphin flippers, and the arms of monkeys.

Cladogram of Animals Animal phyla are generally defined based on to adult body plans and patterns of embryological development.