Introduction to Animals

1. 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

2. 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

3. 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.

4. 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

5. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Sponges • Sponges do not develop tissues. • Collar cells with flagella line the inside of the sponge and whip back and forth drawing water into the body of the sponge. • Water and waste materials are expelled from the sponge through the osculum. • Asymetrical • Sessile

6. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians

7. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Filter Feeder • Food particles cling to the cells. • Digestion of nutrients takes place within each cell.

8. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Archaeocytes • Specialized cells that secrete spicules, which are the support structures of sponges • Spicules are small, needlelike structures made of calcium carbonate, silica, or a tough fibrous protein called spongin

9. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Reproduction • Reproduce asexually • Fragmentation • Budding • Gemmules • Reproduce sexually • Eggs remain within a sponge. • Sperm are released into the water. • All sponges are hermaphrodites (have both egg and sperm)

10. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Cnidarians • Have one body opening and two layers of cells • Outer layer functions in protecting the internal body • Inner layer functions mainly in digestion • Radial Symmetry • 2-way gut

11. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Feeding and Digestion • Tentacles are armed with stinging cells called cnidocytes. • A nematocyst is a capsule that holds a coiled tube containing poison and barbs. • Water inside an undischarged nematocyst is under an osmotic pressure of more than 150 atmospheres.

12. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians • As the osmotic pressure increases, the nematocyst discharges forcefully. • A barb is capable of penetrating a crab shell.

13. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians • Cells lining the gastrovascular cavity release digestive enzymes over captured prey. • Undigested materials are ejected though the mouth.

14. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Response to Stimuli • A nerve net conducts impulses to and from all parts of the body. • The impulses cause contractions of musclelike cells in the two cell layers.

15. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Reproduction • Two body forms • Polyp • Medusa

16. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians • The two body forms of cnidarians can be observed in the life cycle of jellyfishes.

17. Introduction to Animals Chapter 24 24.3 Sponges and Cnidarians Cnidarian Diversity • Hydroids • Jellyfishes • Sea anemones and corals

18. Introduction to Animals Chapter 24 Vocabulary Section 1 invertebrate exoskeleton endoskeleton vertebrate hermaphrodite zygote internal fertilization external fertilization blastula gastrula endoderm ectoderm mesoderm

19. Introduction to Animals Chapter 24 Vocabulary Section 2 symmetry radial symmetry bilateral symmetry anterior posterior cephalization dorsal ventral coelom pseudocoelom acoelomate protostome deuterostome

20. Introduction to Animals Chapter 24 Vocabulary Section 3 filter feeder sessile cnidocyte nematocyst gastrovascular cavity polyp medusa