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Chapter 18

Chapter 18. 0. The Evolution of Animal Diversity 18.5,18.6,18.7,18.10, 18.9,18.11. What Am I? ~1.5 million species known to science Over two-thirds are animals! Humans have a long-studied animal diversity classifying an animal isn’t always easy….

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Chapter 18

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  1. Chapter 18 0 The Evolution of Animal Diversity 18.5,18.6,18.7,18.10, 18.9,18.11

  2. What Am I? • ~1.5 million species known to science • Over two-thirds are animals! • Humans have a long-studied animal diversity • classifying an animal isn’t always easy…

  3. Imagine you were the first person to encounter the animal pictured here • With all of its varying characteristics, what would you think it is?

  4. A Tasmanian tiger, 1928 • Biologists often encounter classification problems • When evolution creates organisms with similar characteristics

  5. Figure 18.1A ANIMAL EVOLUTION AND DIVERSITY 18.1 What is an animal? • eukaryotic, multicellular heterotrophs • ingest their food

  6. http://media.pearsoncmg.com/bc/bc_campbell_essentials_3/discvids/_html/index.htm?info_text=cc5_invertebrateshttp://media.pearsoncmg.com/bc/bc_campbell_essentials_3/discvids/_html/index.htm?info_text=cc5_invertebrates

  7. Figure 18.5A–C INVERTEBRATES 18.5 Sponges - relatively simple, porous body • Phylum • Porifera • simplest animals; no true tissues

  8. Pores Choanocyte Amoebocyte Waterflow Skeletalfiber Centralcavity Flagella Choanocytein contactwith anamoebocyte Figure 18.5D • Flagellated choanocytes • Filter food from the water passing through the porous body

  9. 18.6 Cnidarians - radial animals w/tentacles & stinging cells • Phylum • Cnidaria • true tissues; radial symmetry

  10. Figure 18.6A–C • 2 body forms: • Polyps, such as hydra • Medusae, the jellies

  11. Capsule(nematocyst) Coiledthread Tentacle “Trigger” Dischargeof thread Prey Cnidocyte Figure 18.6D • gastrovascular cavity • & cnidocytes on tentacles that sting prey

  12. 18.7 Flatworms = simplest bilateral animals • Phylum • Platyhelminthes • bilateral animals w/no body cavity

  13. Gastrovascularcavity Nerve cords Mouth Eyespots Nervoustissueclusters Figure 18.7A Bilateral symmetry • A planarian’s gastrovascular cavity & simple nervous system

  14. Units withreproductivestructures Scolex(anteriorend) HooksSucker Colorized SEM 80 • Flukes & tapeworms • parasitic flatworms, complex life cycles Figure 18.7B

  15. Visceral mass Reproductive organs Coelom Heart Kidney Digestive tract Mantle Shell Digestive tract Mantle cavity Radula Radula Anus Mouth Gill Mouth Foot Nerve cords Figure 18.9A 18.9 Phylum?? • Mollusca • All have muscular foot & mantle • may secrete shell that encloses visceral mass • Many feed with a “rasping radula”

  16. Figure 18.9B, C Class Gastropoda • largest mollusc group • snails & slugs

  17. Figure 18.9D Class Bivalvia • shells in 2 halves • clams, oysters, mussels, scallops

  18. Figure 18.9E, F Class Cephalopoda • adapted to be agile predators • Squids, octopuses

  19. 18.10 segmented worms • Phylum • Annelida • added mobility for swimming & burrowing

  20. Epidermis Anus Circular muscle Segment wall (partition between segments) Segment wall Longitudinal muscle Dorsal vessel Excretory organ Mucus-secreting organ Intestine Bristles Bristles Dorsal vessel Coelom Nerve cord Ventral vessel Excretory organ Digestive tract Brain Segment wall Blood vessels Giant Australian earthworm Mouth Nerve cord Pumping segmental vessels Annelids: Earthworms and Their Relatives • Earthworms • Eat their way through soil • closed circulatory system Figure 18.10A

  21. Figure 18.10B, C Annelids: Polychaetes • largest group of annelids • Search for prey on seafloor or • live in tubes, filter food particles

  22. Figurer 18.10D Annelids: Leeches • Most leeches • Are free-living carnivores, but some suck blood

  23. Cephalothorax Abdomen Thorax Antennae (sensory reception) Head Swimming appendages Walking legs Figure 18.11A Mouthparts (feeding) Pincer (defense) 18.11 segmented animals w/jointed appendages and exoskeleton • Phylum? • arthropoda

  24. Colorized SEM 900 A black widow spider (about 1 cm wide) A dust mite (about 420 µm long) A scorpion (about 8 cm long) Figure 18.11B, C Arthropods: Chelicerates • Horseshoe crabs • Arachnids (spiders), scorpions, mites, ticks

  25. Figure 18.11D Arthropods: Millipedes and Centipedes identified by # of jointed legs per body segment

  26. Figure 18.11E Arthropods: Crustaceans • nearly all aquatic • crabs, shrimps, barnacles

  27. Chordates Craniates Vertebrates Jawed vertebrates Tetrapods Amniotes Lobe-fins Lancelets Reptiles Hagfishes Mammals Tunicates Lampreys Amphibians Sharks, rays Ray-finned fishes Milk Amniotic egg Legs Lobed fins Lungs or lung derivatives Jaws Vertebral column Head Brain Ancestral chordate VERTEBRATES 18.15 Derived characters define major clades of chordates • A chordate phylogenetic tree • based on a sequence of derived characters Figure 18.15

  28. ANIMAL PHYLOGENY AND DIVERSITY REVISITED 18.22 phylogenetic tree is work in progress! • Molecular-based phylogenetic trees Molluscs Sponges Annelids Cnidarians Echinoderms Chordates Flatworms Arthropods Nematodes Deuterostomes Ecdysozoans Lophotrochozoans Bilaterians Radial symmetry Bilateral symmetry Eumetazoans True tissues No true tissues Ancestral colonial protist Figure 18.22

  29. Animal development • May include a blastula, gastrula, and lar val stage Key Haploid (n) Diploid (2n) Sperm 2 1 Egg Meiosis Zygote(fertilized egg) 3 Eight-cell stage Adult 8 Metamorphosis 4 Blastula(cross section) Digestive tract Ectoderm 5 Larva 7 Early gastrula(cross section) 6 Endoderm Futuremesoderm Figure 18.1B Internal sac Later gastrula(cross section)

  30. 18.2 The ancestor of animals was probably a colonial, flagellated protist • Cells in these protists • Gradually became more specialized and layered Somaticcells Digestive cavity Reproductivecells 2Hollow sphere of unspecialized cells (shown in cross section) 3Beginning of cell specialization (cross section) 4Infolding (cross section) 1Colonial protist, an aggregate of identical cells 5Gastrula-like “proto-animal” (cross section) Figure 18.2A

  31. Figure 18.2B • Animal diversity • Exploded during the Cambrian period

  32. Top Dorsal surface Anterior end Posterior end Ventral surface Bottom Figure 18.3A 18.3 Animals can be characterized by basic features of their “body plan” • Animal body plans • May vary in symmetry

  33. Tissue-filled region (from mesoderm) Body covering (from ectoderm) Digestive tract (from endoderm) Body covering (from ectoderm) Muscle layer (from mesoderm) Digestive tract (from endoderm) Pseudocoelom Body covering (from ectoderm) Coelom Tissue layer lining coelomand suspendinginternal organs(from mesoderm) Digestive tract(from endoderm) • Vary in body cavity Figure 18.3B–D

  34. Development as either protostomes or deuterostomes

  35. Molluscs Annelids Sponges Flatworms Chordates Arthropods Cnidarians Nematodes Echinoderms Deuterostomes Protostomes Bilaterians Radial symmetry Bilateral symmetry Eumetazoans No true tissues True tissues Figure 18.4 Ancestral colonial protist 18.4 The body plans of animals can be used to build phylogenetic trees • One hypothesis of animal phylogeny • Is based on morphological comparisons

  36. 18.8 Nematodes have a pseudocoelom and a complete digestive tract • Nematodes, phylum Nematoda • Have a pseudocoelom and a complete digestive tract • Are covered by a protective cuticle

  37. Muscle tissue Trichinella juvenile Mouth Colorized SEM 400 LM 350 Figure18.8A, B • Many nematodes are free-living • And others are plant or animal parasites

  38. 18.12 Insects are the most diverse group of organisms • Insects have a three-part body consisting of • Head, thorax, and abdomen • Three sets of legs • Wings (most, but not all insects)

  39. Many insects undergo • Incomplete or complete metamorphosis

  40. Abdomen Head Thorax Antenna Forewing Eye Mouthparts Hindwing A. Order Orthoptera • The order orthoptera includes • Grasshoppers, crickets, katydids, and locusts Figure 18.12A

  41. Figure 18.12B B. Order Odonata • The order odonata includes • Dragonflies and damselflies

  42. Figure 18.12C C. Order Hemiptera • The order hemiptera includes • Bedbugs, plant bugs, stinkbugs, and water striders

  43. Figure 18.12D D. Order Coleoptera • The order coleoptera includes • Beetles

  44. Figure 18.12E E. Order Lepidoptera • The order lepidoptera includes • Moths and butterflies

  45. Haltere Figure 18.12F F. Order Diptera • The order Diptera includes • Flies, fruit flies, houseflies, gnats, and mosquitoes

  46. Figure 18.12G G. Order Hymenoptera • The order hymenoptera includes • Ants, bees, and wasps

  47. Tube foot 18.13 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement • Echinoderms, phylum Echinodermata • Includes organisms such as sea stars and sea urchins • Are radially symmetrical as adults Tube foot Spine Figure 18.13B, C

  48. Anus Spines Stomach Tube feet Canals Figure 18.13A • The water vascular system • Has suction cup–like tube feet used for respiration and locomotion

  49. 18.14 Our own phylum, Chordata, is distinguished by four features • Chordates, phylum Chordata have • A dorsal hollow nerve cord • A stiff notochord • Pharyngeal slits • A muscular post-anal tail

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