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Invertebrates. Invertebrates. Nearly all animals are invertebrates (95%) Invertebrates are animals that lack backbones Let’s take a survey of the major phyla of animals! . Chordates. Major Animal Phyla. Echinoderms. Arthropods. Annelids. Coelomate Ancestry. Mollusks. Rotifers.

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  1. Invertebrates

  2. Invertebrates • Nearly all animals are invertebrates (95%) • Invertebrates are animals that lack backbones • Let’s take a survey of the major phyla of animals! 

  3. Chordates Major Animal Phyla Echinoderms Arthropods Annelids Coelomate Ancestry Mollusks Rotifers Roundworms Bilateral Ancestry Flatworms Radial Ancestry Cnidarians Sponges Multicelled Ancestry Figure 25.2Page 415 Single-celled, protistanlike ancestors

  4. posterior dorsal ventral anterior Symmetry Bilateral Radial Figure 25.3Page 416

  5. The Gut • Region where food is digested and then absorbed • Saclike gut • One opening for taking in food and expelling waste • Complete digestive system • Opening at both ends; mouth and anus

  6. Body Cavities - Acoelomate epidermis gut cavity no body cavity; region between gut and body wall packed with organs Figure 25.4aPage 417

  7. Body Cavities - Pseudocoel epidermis gut cavity unlined body cavity (pseudocoel) around gut Figure 25.4bPage 417

  8. Body Cavities - Coelom gut cavity peritoneum lined body cavity (coelom) Figure 25.4cPage 417

  9. Segmentation • Repeating series of body units • Units may or may not be similar to one another • Earthworms - segments appear similar • Insects - segments may be fused and/or have specialized functions

  10. Animal Origins • Originated during the Precambrian (1.2 billion - 670 million years ago) • From what? Two hypotheses: • Multinucleated ciliate became compartmentalized • Cells in a colonial flagellate became specialized

  11. Phylum Porifera • Representative organism: sponge • Have no true tissues (Parazoa) • Their cells are relatively unspecialized • Sponges are sessile (nonmotile) • Ancient Greeks believed them to be plants • Filter-feeders: • Trap food from the water that flows through them • Most sponges are hermaphrodites • Each individual produces both sperm and eggs

  12. Sponge Structure water out glasslike structural elements amoeboid cell pore central cavity semifluid matrix flattened surface cells water in Figure 25.7aPage 419 flagellum microvilli nucleus

  13. Phylum Cnidaria • Have stinging cells inside of nematocysts • On tentacles capsule’s lid at free surface of epidermal cell trigger barbed thread inside capsule Figure 25.8Page 420 nematocyst

  14. Phylum Cnidaria • Representative Organisms: Jellyfish & Sea Anemones • Have true tissues and radial symmetry • Body plan: sac with a central digestive compartment known as the gastrovascular cavity (mouth & anus) • 2 variations on the body plan: • Polyp: sessile, mouth up, waits for prey (sea anemone) • Medusa: floats, mouth down (jellyfish) • Attack prey with tentacles

  15. Two Main Body Plans Polyp outer epithelium (epidermis) mesoglea (matrix) Medusa inner epithelium (gastrodermis) Figure 25.9 Page 420

  16. Obelia Life Cycle (Hydrozoan) male medusa female medusa reproductive polyp sperm ovum zygote feeding polyp polyp forming planula Figure 25.10Page 421

  17. Phylum Platyhelminthes • Representative Organisms: • Tapeworms, flukes, & planarians • Bilateral symmetry • Acoelomates – • no body cavity enclosed by mesoderm • Many are parasitic

  18. Planarian Organ Systems flame cell nucleus pharynx cilia protonephridia fluid filters through membrane folds opening of tubule at body surface flame cell Fig. 25.11a,bPage 422

  19. Planarian Organ Systems brain nerve cord oviduct genital pore ovary testis penis Fig. 25.11cdPage 422

  20. Flukes: Class Trematoda • Parasitic worms • Complicated life cycle • Larval stage infects a mollusk • Adult infects a vertebrate Worms mate in human host Larvae bore into human skin Larvae form, leave snail Fertilized egg Asexual reproduction in intermediate host Ciliated larva Figure 25.14Page 424 Southeast Asian blood fluke

  21. Tapeworms: Class Cestoda Definitive host Larvae encysted in muscle tissue Scolex attaches to host intestinal wall Figure 25.15Page 424 Intermediate host Mature proglottid with fertilized eggs

  22. Phylum Nematoda • Representative organism: roundworms • Pseudocoelomate • have a body cavity, but not encased by mesoderm • Round worms with tapered ends • Can be parasitic (trichinosis)

  23. Roundworms (Nematoda) • False coelom (pseudocoelomate) • Complete digestive system pharynx intestine eggs in uterus gonad anus false coelom muscularized body wall Figure 25.13Page 423

  24. Two Coelomate Lineages Protostomes • Mollusks • Annelids • Arthropods Deuterostomes • Echinoderms • Chordates

  25. Cleavage Patterns Protostome embryo (spiral cleavage) Blastopore becomes mouth Deuterostome embryo (radial cleavage) Blastopore becomes anus In-text figurePage 426

  26. Phylum Mollusca • Representative organisms: • snails, slugs, oysters, clams, octopuses, squids • Coelomates • Have a true coelom • Protostomes: • Blastopore becomes mouth

  27. Phylum Mollusca • Body plan has 3 main parts: • Muscular foot used for movement • Visceral mass covering the internal organs • Mantle covers the visceral mass (may produce a protective shell)

  28. Cuttlefish Body Plan Closed circulatory system with heart and accessory heart esophagus Figure 25.22Page 429 digestive gland kidney stomach brain arm jaw mantle reproductive organ internal shell siphon ink sac heart accessory heart tentacle radula anus gill

  29. Phylum Annelida • Representative Organism: earthworm • Annelids have segmented bodies • Metanephridia (similar to kidneys) • Remove wastes from the blood • Worms are hermaphrodites • Produce both sperm and eggs • Setae provide traction for burrowing in the soil • Earthworms eat their way through the soil

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