252 animal body plans and evolution - laurelscience - ….ppt

1. 2. 3. 4. 5. 6. 7. Which numbers represent chordates and which numbers represent invertebrates? 25.2 Animal Body Plans and Evolution Features of Body Plans Each animal phylum has a unique organization of particular body structures that is often referred to as a body plan. Features of body plans include: Levels of organization Body symmetry Differentiation of germ layers Formation of body cavities Patterns of embryonic development Segmentation Cephalization Limb formation Levels of Organization Animals have specialized cells that are organized into tissues. There are several types of tissues found in animals: Epithelial tissues- cover body surfaces inside and out, are also thin and flat. Example: epithelial tissues line lungs and allow gases to easily diffuse through Muscle tissues Connective tissues Tissues combine during growth and development to form organs and organ systems to carry out complex functions Body Symmetry Bodies of most animals exhibit some sort of symmetry There are two different forms of symmetry Radial symmetry: any number of imaginary planes drawn through the center of the body could divide into equal halves. Example: Sea anemone Bilateral symmetry: a single imaginary plane divides the body into left and right sides that are mirror images of each other. Animals with bilateral symmetry have the following A definite front: also known as the anterior A definite end: also known as the posterior An upper side: also known as the dorsal side A lower side: also known as the ventral side Differentiation of Germ Layers During embryological development the cells of most animal embryos differentiate into 3 germ layers 1. Endoderm: the innermost germ layer, develops into linings of the digestive tract and much of the respiratory system 2. Mesoderm: the middle layer, gives rise to the muscles and much of the circulatory, reproductive, and excretory organ systems 3. Ectoderm: the outermost layer, produces sense organs, nerves, and the outer layer