Chapter 24 Introduction to Animals

2. Chapter 24 Introduction to Animals Section 1: Animal Characteristics Section2: Animal Body Plans Section 3: Sponges and Cnidarians

3. Introduction to Animals Chapter 24 24.2 Animal Body Plans Evolution of Animal Body Plans • Anatomical features in animals’ body plans mark the branching points on the evolutionary tree.

4. Introduction to Animals Chapter 24 24.2 Animal Body Plans Evolution of Animal Body Plans • Relationships on this tree are inferred by studying similarities in embryological development and shared anatomical features.

5. Introduction to Animals Chapter 24 24.2 Animal Body Plans Symmetry • Similarity or balance among body structures of organisms

6. Introduction to Animals Chapter 24 24.2 Animal Body Plans Symmetry TYPES OF SYMMETRY • Asymmetry – No tissue and irregular in shape • Radial symmetry – • Has a top and a bottom but no sides • Can be divided on multiple planes

7. Introduction to Animals Chapter 24 24.2 Animal Body Plans Symmetry TYPES OF SYMMETRY • Bilateral symmetry – • Can be divided on one plane to show a mirror image on each side. • Has a top, bottom and sides.

8. Introduction to Animals Chapter 24 24.2 Animal Body Plans Cephalization • Animals with bilateral symmetry tend to have a posterior (tail-end) and anterior (head-end). • They also have a tendency to concentrate nervous tissue and sensory organs at the anterior end of the animal

9. Introduction to Animals • Have a fluid-filled cavity with tissue formed from mesoderm that lines and encloses the organs in the coelom Chapter 24 24.2 Animal Body Plans Body Cavities • Coelomates

10. Introduction to Animals • Have a fluid-filled body cavity that develops between the mesoderm and the endoderm rather than developing entirely within the mesoderm Chapter 24 24.2 Animal Body Plans Body Cavities • Pseudocoelomates

11. Introduction to Animals Chapter 24 24.2 Animal Body Plans Body Cavities • Acoelomates • Have solid bodies without a fluid-filled body cavity between the gut and the body wall

12. Introduction to Animals Chapter 24 24.2 Animal Body Plans Development in Coelomate Animals • Protostomes • The mouth develops from the first opening in the gastrula. • Deuterostomes • The anus develops from the first opening in the gastrula.

13. Introduction to Animals Chapter 24

14. Introduction to Animals Chapter 24 24.2 Animal Body Plans Segmentation • Segmented animals can be “put together” from a succession of similar parts. • Can survive damage to one segment • Movement is more effective