CH_23_STUDENT_OUTLINE

CH_23_STUDENT_OUTLINE - Chapter 22: Animal Diversity I,...

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Chapter 22: Animal Diversity I, Invertebrates
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Key Features of Animals Animals possess all of the following Characteristics: Multi-cellular Heterotrophic (obtain energy from organic molecules) Cells lack a cell wall Are able to respond rapidly to external stimuli Most animals populating the earth were present by the Cambrian period (544 million yrs ago)
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Animal Evolution Certain features represent evolutionary milestone the appearance of tissue the appearance of body symmetry protostone and deuterostome development The features mark major branching points on the animal revolutionary tree
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Porifera (sponges) Cnidaria (jellyfish, corals, anemones) Ctenophora (comb jellies) Arthropoda (insects, arachnids, crustaceans) Platyhelminthes (flatworms) Annelida (segmented worms) Mollusca (clams, snails, octopods) Echinodermata (sea stars, sea urchins) Chordata (lancelets, vertebrates) cuticle molted protostome development deuterostome development bilateral symmetry radial symmetry no tissues tissues Nematoda (roundworms) PRIMITIVE ANCESTOR
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The Appearance of Tissues Tissue are groups of similar cells that carry specific functions (e.g. muscle) The earliest animals had no tissue Sponges are the only modern day animals that lack tissue Individual cells may be specialized, but act independently Sponges and other phyla arose from an ancient common ancestor without tissues 3 types of layers
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Animal Tissues Ectoderm (top) Mesoderm (middle) Endoderm (bottom)
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The Appearance of Body Symmetry Symmetrical animals have an upper (dorsal) surface and a lower (ventral) surface Animals with tissues exhibit either radial or bilateral symmetry 3 types Radial, bilateral, asymmetric (no symmetry)
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Radial Symmetry Can be divided into roughly equal halves by any plane that passes through the central axis Have two embryonic tissue (germ) layers: Ectoderm (outer layer, covers the body) Endoderm (inner layer, lines most hollow organs) Tend to be either sessile (fixed to one spot) or drift around on currents cnidarians, hydra, and anemones
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Radial symmetry central axis plane of symmetry
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radial symmetry
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Bilateral Symmetry Can be divided into mirror-image halves only along one plane that runs down the midline Have an additional germ layer: Mesoderm (middle layer, forms muscle & circulatory/skeletal system) Exhibit cephalization (concentration of sensory organs & brain in a well-defined head) Defined anterior (head) and posterior (tail regions) Example: humans
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Bilateral symmetry anterior plane of symmetry posterior
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d o r s a l n t e i p v bilateral symmetry
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Body Cavities Most bilateral animals have a body cavity Serve many functions Skeleton: provides support and a framework against which muscles can act Protection: buffer between internal organs and outside world 3 types Coelomate (eucoelomate), pseudocoelomate and acoelomate
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CH_23_STUDENT_OUTLINE - Chapter 22: Animal Diversity I,...

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