Emergence of the Animal Kingdom

1. Emergence of the Animal Kingdom • Animals are: • multicellular • heterotrophic • no cell walls • highly differentiated • tissues • organ systems • nervous systems • reproduce sexually

2. Organization into tissues • radiata • bilateral symmetry • flatworms • cephalization • flatworms • body cavities • roundworms

3. segmentation • molluscs, annelids, arthropods • internal skeleton • echinoderms, chordates

4. Phylogenycontainsmajor morphologicalinnovations

5. Animals evolved along several major plans • parazoa • sponges • colonial • no symmetry • no tissues • flagellated feeding cells = collar cells • filter feeders

6. radiata • sea anemones, jellyfishes, corals • radial symmetry • 2 tissues: • ectodermis • gastrodermis • simple nervous system • ecologically important • reef builders

7. bilateria • flatworms • bilateral symmetry • no body cavity • cepalization - head • organ systems • digestive • nervous • three tissue layers • predators • detritivores • parasites • liver flukes

8. Roundworms • body cavity • fluid filled • false cavity = pseudocoel • complete digestive system • detritivores • in soil & water • parasites • most diverse • parasitize nearly all other organisms • body cavities • support - fluid pressure • protect organs • house gut & reproductive • allow flexibility

9. PROTOSTOMES • “first mouth” • first opening in gut becomes mouth • segmented worms • earthworms, polychaetes, leeches • true body cavity • internal segmentation • closed circulation • detritivores • filter feeders • predators (parasites)

10. Molluscs • segmentation • head • foot • visceral mass - internal organs • snails, bivalves (clams, etc), octopi • octopi highly evolved • closed circulation • vision • nervous system - behavior

11. Arthropods • joint foot • segmented • exoskeleton • chitin • flight • able to colonize long distances • tolerate dry habitats • 98 % of animal kingdom • insects > 85% of species

12. Deuterostomes • second opening becomes mouth • echinoderms - sea stars, sea urchins • early separation from protostomes • radial symmetry • except for larva which is bilateral • endoskeleton • grazers / carnivores • water vascular system • hydraulic system for movement • tube feet • primitive nervous network

13. Chordates • 4 characteristics • notochord - support • post-anal tail • pharyngeal gill slits • dorsal hollow nerve cord • sea squirts • sponge like - filter feeder • larva free swimming, bilateral with all chordate traits • macroevolution through paedogenesis (neoteny) of larval stage to become ancestral chordates

14. Chordate Characteristics

15. Vertebrates • chordate traits plus: • tetrapods - four limbs • backbone • cranium (bony protection for brain • fishes • first jaws - from modified gill arches • limbs - lobe-finned fishes • lungs - primitive (sturgeons, lungfishes) • amphibians • lungs

18. Reptiles, birds, mammals • complete separation from water habitats • scales, fur, feathers • amniote egg • membranes surround egg for respiration, water retention

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