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

Organization into tissues –radiata bilateral symmetry –flatworms cephalization –flatworms body cavities –roundworms

segmentation –molluscs, annelids, arthropods internal skeleton –echinoderms, chordates

Phylogeny contains major morphological innovations

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

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

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

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

–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)

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

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

–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

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

Chordate Characteristics

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

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

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