Sponges?. Sponge-like Protists?. Flatworms?. Earthworms?. Clams, snails, squid?. Roundworms?. Starfish? Vertebrates? Jellyfish?. -Embryonic tissue layers -Symmetry, cephalization, directed movement -Body cavity (coelom) -Key embryonic processes and events. -Segmentation Insects, Crustaceans, Arachnids?. Key innovations set the stage for adaptive radiation of triploblastic coelomate animals * * * Evolution of tissues and developmental program Evolution of bilaterally symmetric body plan ? directed movement, cephalization Evolution of body cavity between digestive tract and body wall Cnidarians (and Ctenophores) (secondarily evolved in one lineage of Deuterstomes) Porifera Protostomes and Deuterstomes Symmetry, Directed Movement, and Cephalization -rRNA -cell junctions -matrix proteins Evolution of Bilateral Symmetry, Directed Movement, cephalization Radially symmetric Cnidarian Asymmetric sponge (Poriferan) Bilaterally symmetric flatworm (platyhelminthes) Settled sponge larva Origin of cell specialization, tissues, developmental program Hypothesis on evolution of animals with specialized cells arranged in two layers Colonial flagellated protist with unspecialized cells Certain cells became specialized for feeding & other functions A developmental reorganization produced a two-layered animal with a sac-within-a-sac body plan Gastrulation Embryo (blastula) gastrulates giving rise to embryonic tissue layers and the onset of morphogenesis Important events & processeses germ layers body plans inductive interactions "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life.? Lewis Wolpert (1986) Tissues & Embryonic Tissue Layers Embryonic Tissue Layers Endoderm Mesoderm Ectoderm Tissue Group of similar cells organized into a functional unit and usually integrated with other tissues to form part of an organ Sea Pen a ctenophore Hydra A sea anemone that swims. When attacked by a predatory sea star Dermasterias, the anemone Stomphia didemon detaches from the bottom and rolls or swims spasmodically to a safer location. Contractile cells, nerve cells, hydrostatic skeletons Hydrostatic skeleton Mechanism in many soft-bodied invertebrates consisting of a fluid-filled cavity surrounded by muscles or contractile fibers Pressure of the fluid and action of the surrounding muscles are used to change an organism's shape and produce movement, such as burrowing or swimming. Contractile cells, nerve cells, hydrostatic skeletons Epitheliomuscular and nerve cells in Hydra Daphnia Daphnia consumed by Hydra Cross section of Hydra Animations and Videos on hydrostatic skeletons Nematode: http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/INT-ANIMA-v inegar.htm Annelids http://www.biology.ualberta.ca/courses.hp/zool250/animations/Earthworm.swf http://www.biology.ualberta.ca/courses.hp/zool250/animations/Polychaete.swf Cnidarians, Annelids http://www.biol.wwu.edu/204/Video%20Files.html.html click on: -earthworm movement -jellyfish swim -hydra eats waterflea Triploblasts with & without Coeloms Coelom functions -hydrostatic skeleton -circulation -protected 3D space to suspend organs -body flexibility -locomotion -burrowing -feeding The tube-within-a-tube body plan of triploblastic coelomates Three events in early development differ in protostomes and deuterostomes; cleavage, gastrulation (mouth formation), and mesodermal coelom formation Protostome and Deuterostome Patterns of Development
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