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8/11/2019 Chapter 32: An Overview of Animal Diversity
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Sio 2014
Chapter 32: An Overview of Animal Diversity
Term Definition
Animal multicellular, heterotrophic eukaryotes with tissuesthat develop from embryonic layers
Tissues groups of cells that have a common structure,function, or both; collections of specialized cellsisolated from other tisues by membranous layers
Cleavage rapid cell division undergone by the zygote after asperm fertilizes an egg
Blastula multicellular, hollow; formed from the cleavage
Gastrulation undergone by the blastula; forms a gastrulawithdifferent layers of embryonic tissues
Larva sexually immature and morphologically distinctfrom the adult; eventually undergoes
metamorphosisJuvenile resembles an adult, but is not yet sexually mature
Hox genes that regulate the development of body form;can produce a wide diversity of animalmorphology
Choanoflagellates may have resemblance to common ancestors ofliving animals; protists that are the closest livingrelatives of animals
Neoproterozoic Era (1 billion542 million years ago)
Ediacaran biota included in the early members of the animal fossilrecord; dates from 565 to 550 million years ago
Paleozoic Era (542251 million years ago)Cambrian explosion (535 to 525 million years ago) marks the earliest
fossil reappearance of many major groups of livinganimals
Several hypotheses regarding the cause of theCambrian explosion and decline of Ediacaranbiota:
- New predator-prey relationships- A rise in atmospheric oxygen-
The evolution of the Hox gene complex
Mesozoic Era (25165.5 million years ago) coral reefsemerged; ancestors of plesiosaurs were reptilesthat returned to the water; dinosaurs were thedominant terrestrial vertebrates; the first mammalsemerged; flowering plants and insects diversified
Cenozoic Era (65.5 million years ago to the present) beginningfollowed mass extinctions of both terrestrial andmarine animals which included the large, nonflyingdinosaurs and the marine reptiles; mammals
increased in size and exploited vacated ecologicalniches; global climate cooled
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Body plan a set of morphological and developmental traits
Radial symmetry no front and back, or left and right
Bilateral symmetry two-sided symmetry; often move actively andhave a central nervous system
Dorsal top
Ventral bottomAnterior head
Posterior tail
Cephalization development of a head
Sessile planktonic; drifiting or weakly swimming
Ectoderm germ layer covering the embryos surface
Endoderm innermost germ layer and lines the developingdigestive tube (archenteron)
Diploblastic have ectoderm and endoderm; include cnidariansand comb jellies
Triploblastic have an intervening mesodermlayer; include allbilaterans
Body cavity possessed by most triploblastic animals
Coelom a true body cavity; derived from mesoderm
Coelomates animals that possess a true coelom
Pseudocoelom a body cavity derived from mesoderm andendoderm
Pseudocoelomates triploblastic animals that possess apseudocoelom; belong to the same grade ascoelomates
Acoelomates triploblastic animals that lack a body cavity
Grade a group whose members share key biologicalfeatures; not necessarily a clade. An acestor andall of its descendants
Protostome development cleavage is spiraland determinate; splitting ofsolid masses of mesoderm forms the coelom
Deuterostome development Cleavage is radial and indeterminateeach cellin the early stages of cleavage retains thecapacity to develop into a complete embryo;makes possible identical twins, and embryonicstem cells; mesoderm buds from the wall of thearchenteron to form the coelom
Blastopore forms during gastrulation and connects thearchenteron to the exterior of the gastrula;becomes the mouthin protosome development;becomes the anusin deuterosome development
Eumetazoa a clade of animals with true tissues
Bilaterians most animal phyla belonging to the clade Bilateria;the morphology-based tree divides bilaterians intodeuterostomes and potostomes; molecular studiesindicate bilaterian clades Deuterostomia,Ecdysozoa, and Lophotrochozoa
Deuterostomia chordates and some other phylaEcdysozoans shed their exoskeleton through a process called
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