Evolution of Animals (Metazoa) BIOL 1407 Animal Body Plan вЂў Tissues вЂ“ Absent = Parazoa вЂ“ Present = Eumetazoa Radial Symmetry вЂў Encounter environment equally from all sides вЂў Sessile, sedentary or planktonic вЂў Sea Anemone Feeding Video вЂў вЂў http://www.mbayaq.org/efc/video_library/vid eo_library.aspx Then click on вЂњAnemone FeedingвЂќ вЂў Jellyfish Swimming вЂў http://www.youtube.com/watch?v=760lUxyle6I Bilateral Symmetry вЂў Central nervous system in head вЂў Active movers вЂў Frilled lizard video вЂў http://video.nationalgeographic.com/video/pl ayer/animals/reptilesanimals/lizards/lizard_frilled_ontherun.html?f s=animals.nationalgeographic.com вЂў Crocodile gallop video вЂў http://www.flmnh.ufl.edu/natsci/herpetology/ brittoncrocs/images/cj-gallop2.mpg Number of Germ Layers вЂў Diploblastic: has two germ layers вЂ“ Endoderm вЂ“ Ectoderm вЂў Triploblastic: has three germ layers вЂ“ Endoderm вЂ“ Mesoderm вЂ“ Ectoderm Question? Body Cavities вЂў What is a body cavity? вЂ“ Fluid-filled cavity separates digestive tract from body wall Body Cavities вЂў Advantages: вЂ“ Fluid cushions organs вЂ“ Acts as hydrostatic skeleton вЂ“ Allows internal organs to move independently of body wall вЂ“ Allows internal organs space for folding Development вЂў Protostome вЂ“ Fate of blastopore вЂ“ Type of cleavage: spiral and determinate вЂ“ Coelom formation вЂў Deuterostome вЂ“ Fate of blastopore вЂ“ Type of cleavage: radial and indeterminate вЂ“ Coelom formation Animation of Spiral and Radial Cleavage http://worms.zoology.wisc.edu/urchins/rad_spir.html Schizocoelous Enterocoelous Sister Taxon Model of Early Animal Evolution Evolution of Animals вЂў Earliest animal fossils вЂў Fossilized embryos from China вЂў 575 mya Ediacaran Fauna вЂў 565-550 mya вЂў Australia вЂў Soft-bodied animal fossils вЂў What type of symmetry? Ediacaran Fauna вЂў вЂў вЂў вЂў Animal fossil Many body segments Head What type of symmetry? Cambrian Explosion вЂў 535-525 mya вЂў Animal diversity в†‘в†‘ вЂў 50% extant animal phyla in fossil record Burgess Shale Fossils Cambrian Explosion вЂў First animals with hard mineralized skeletons вЂў 1st arthropods, chordates & echinoderms Hypotheses for Cambrian Explosion (1) Predator-prey coevolution (2) Rise in atmospheric oxygen levels пѓ в†‘ metabolic rate and body size (3) Evolution of Hox genes пѓ developmental flexibility Traditional Phylogenetic Tree вЂў Was based on body plans вЂ“ Tissues absent or present вЂ“ Type of symmetry вЂ“ Types of body cavities вЂ“ Protostomes versus deuterostomes Modern Phylogenetic Tree вЂў Based on molecular data Modern Phylogenetic Tree вЂў Reinforces some of traditional tree вЂ“ Parazoa vs. Eumetazoa вЂ“ Radial vs. Bilateral вЂ“ Deuterostomes are a clade Modern Phylogenetic Tree вЂў Radical affects on other parts вЂ“ Body cavity characteristics are analogous вЂ“ Two main lineages for most invertebrates вЂў Lophotrochozoa вЂў Ecdysozoa Lophotrochozoa вЂў Clade named for presence of either a: вЂ“ Lophophore (horse-shoe shaped ciliated feeding apparatus) вЂ“ Trochophore larva Lophotrochozoa Ecdysozoa вЂў Clade was named for presence of вЂў Ecdysis = molting вЂў Produce an exoskeleton вЂў Must be shed as animal grows The End Unless otherwise specified, all images in this presentation came from: Campbell, et al. 2008. Biology, 8th ed. Pearson Benjamin Cummings. Slides 19 and 28 are from Campbell, et al. 2005. Biology, 7th ed.