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Animals: The Invertebrates

Animals: The Invertebrates. Chapter 25. Characteristics of Animals. Multicelled heterotrophic eukaryotes Require oxygen for aerobic respiration Reproduce sexually, and perhaps asexually Motile at some stage Develop from embryos. Chordates. Major Animal Phyla . Echinoderms. Arthropods.

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Animals: The Invertebrates

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  1. Animals: The Invertebrates Chapter 25

  2. Characteristics of Animals • Multicelled heterotrophic eukaryotes • Require oxygen for aerobic respiration • Reproduce sexually, and perhaps asexually • Motile at some stage • Develop from embryos

  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 Placozoa • One living species, Tricoplax adherens • Simplest known animal • Two-layer body, 3 mm across Figure 25.5Page 418

  12. Sponges - Phylum Porifera • No symmetry • No tissues • No organs • Reproduce sexually • Microscopic swimming larval stage

  13. 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

  14. Phylum Cnidaria • Only animals that produce nematocysts • Nerve net • Hydrostatic skeleton • Saclike gut capsule’s lid at free surface of epidermal cell trigger barbed thread inside capsule Figure 25.8Page 420 nematocyst

  15. Cnidarian Diversity • Scyphozoans • Jellyfish • Anthozoans • Sea anemones • Corals • Hydrozoans

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

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

  18. Flatworms: Phylum Platyhelminthes • Acoelomate, bilateral, cephalized animals • All have simple or complex organ systems • Most are hermaphrodites

  19. Three Classes • Turbellarians (Turbellaria) • Flukes (Trematoda) • Tapeworms (Cestoda)

  20. 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

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

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

  23. 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

  24. 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

  25. Rotifers • Bilateral • Cephalized • False coelom • Crown of cilia at head end • Complete gut Figure 25.17Page 425

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

  27. Cleavage Patterns Protostome embryo (spiral cleavage) Deuterostome embryo (radial cleavage) In-text figurePage 426

  28. Mollusks: Phylum Mollusca • Bilateral, soft-bodied, coelomate • Most have a shell or reduced version of one • Mantle drapes over body and secretes shell • Most have a fleshy foot • Many have a radula for shredding food

  29. Molluscan Diversity • Gastropods • Chitins • Bivalves • Cephalopods

  30. Torsion • Twisting of body parts during larval development • Occurs only in gastropods mouth gill anus Figure 25.18Page 426

  31. Body Plan of a Snail heart mantle cavity gill anus mantle digestive gland foot Figure 25.18Page 426 radula

  32. Body Plan of a Clam left mantle mouth retractor muscle retractor muscle foot shell left gill palps Figure 25.21Page 429

  33. Cephalopods • Only the nautilus retains external shell • Other cephalopods are streamlined, active swimmers • All move by jet propulsion • Water is forced out of mantle cavity through a funnel-shaped siphon • Have large brains relative to body size

  34. 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

  35. Annelids: Phylum Annelida Segmented, coelomate worms • Class Polychaeta • Class Oligochaeta • Class Hirudinea

  36. Polychaetes “jaws” toothlike structures • Most are marine • Bristles extend from paired, fleshy parapods on each segment • Head end is specialized pharynx (everted) antenna palp (food handling) tentacle eyes chemical-sensing pit parapod Fig. 25.24cPage 430

  37. Leeches - Class Hirudinea • Predators and parasites • Less obvious body segmentation • Most have sharp jaws

  38. Earthworm - An Oligochaete No parapodia, few bristles per segment Nerve cord Dorsal blood vessel Circular muscle Coelom Longitudinal muscle Nephridium Figure 25.25aPage 431 Seta (retracted) Nerve cord

  39. Earthworm Nephridium bladderlike storage region of nephridium nephridium’s thin loop reabsorbs some solutes, relinquishes them to blood blood vessels body wall Figure 25.25bPage 431 funnel (coelomic fluid with waste enters here) external pore (fluid containing wastes discharged here)

  40. Earthworm Circulatory System Hearts Figure 25.25cPage 431

  41. Earthworm Digestive System Coelomic chambers Crop Gizzard Esophagus Pharynx Mouth Figure 25.25dPage 431

  42. Earthworm Nervous System Brain Figure 25.25ePage 431 Nerve cord

  43. Arthropods: Phylum Arthropoda • The phylum with the greatest number of species • Four lineages: • Trilobites (all extinct) • Chelicerates (spiders, mites, scorpions) • Crustaceans (crabs, shrimps, barnacles) • Uniramians (insects, centipedes, millipedes)

  44. Adaptations for Success • Hardened exoskeleton • Jointed appendages • Fused and modified segments • Respiratory structures • Specialized sensory structures • Division of labor Do not post on Internet Figure 25.26Page 432

  45. Chelicerates • Originated in seas • A few are still marine: horseshoe crabs, sea spiders • The arachnids are all terrestrial Spiders Mites Scorpions Chiggers “Daddy longlegs” Ticks

  46. Body Plan of a Spider eye brain heart digestive gland Malpighian tubule poison gland book lung ovary silk gland anus pedipalp mouth sperm receptacle spinners chelicera Figure 25.28Page 433

  47. Crustaceans • Most are marine, some freshwater, a few terrestrial • Head has two pairs of antenna, three pairs of food-handling appendages • Copepods • Crayfish • Barnacles • Lobsters • Shrimps • Crabs • Isopods (pillbugs)

  48. Lobster Body Plan one of two eyes segments of abdomen fused segments of cephalothorax antennae (two pairs) food-handling appendages (three pairs) swimmerets tail fin first leg Figure 25.29aPage 434 five walking legs (five pairs total)

  49. Crab Life Cycle Larval and juvenile stages molt repeatedly and grow in size egg Figure 25.30Page 435

  50. Millipedes and Centipedes • Segmented bodies with many legs • Millipedes • Two pairs of legs per “segment” • Scavengers • Centipedes • Flattened, with one pair of legs per segment • Predators

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