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Cambrian Keywords.docx

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CambrianAcoelomate a body plan of bilaterally symmetrical animals that lack a body cavity coelom between the gut and the body wall p 581ex flatworm fluke tapeworm ribbon worm all exhibit bilateral symmetry and possess one internal space the digestive cavityAlgal matslayers of usually filamentous algae on marine or fresh water soft bottomsa dense mass of algae ex green algae which blankets the substratum in a littoral or shallowwater environment often in areas of freshwater influence or where eutrophication occursPrior to the Cambrian start of the Cambrian the ocean bottom is believed to be covered by impenetrable algal mats and one of the innoative feeding strategies of the Cambrian was being able to penetrate the mats and feed on the substrate underneath Amebocytea cell having amoeboid form or motionany cell having properties similar to an amoeba such as shape mobility and ability to engulf particlesex leukocyteArcheocytea type of ovoid amebocyte in sponges characterized by large nucleolate nuclei and blunt pseudopodiagives rise to germ cellscapable of developing into other types of cells especially reproductive cellsAssymetric body planBody plan the layout and structure of an organisms body asymmetrical animals have no general body plan or axis of symmetry that divides the body into mirrorimage halves Within the animal kingdom this appears to be a primitive conditionBilateral symmetry body plana basic body plan in which the left and right sides of the organism can be divided into approximate mirror images of each other along the midline ex crayfish humancan divide the animal through one plane through the centre of our axis from the oral to the aborral sideadvantagescephalization concentrating sensory tissues at the anterior end of the animalthis is a major innovationthese organisms move through their environment lookingsmellins where theyre going looking for foodpredatorsdirected instead of passive motionorientationtriploblastic innovation of muscles allowing for more precise directed movement more efficient to move in one direction resulting in cephalizationhave a headBivalvean animal that has two hinged shells shells are formed of calcium carbonatemollusk that has a shell consisting of two hinged valvesexamples clams mussels oysters scallopsBlastopore The opening at one end of the archenteron in the gastrula that gives rise to the mouth in protostomes and the anus in deuterostomes p 579the opening of an embryos central cavity in the early stage of developmentthe opening into the archenteron formed by the invaigination of the blastula to form a gastrulaBlastulaThe hollow ball of cells that is the result of cleavage divisions of a fertilized ovumzygote in an early embryo p 825consists of a spherical single layer of cells surrounding a fluidfilled cavityan animal embryo at the early stage of developmentalso called blastosphereBryozoaaquatic invertebrate of the phylum Bryozoa moss animalsreproduce by budding usually form permanently attached branched or mossy coloniesBurgess Shale fossilssignificant fossil discoveryagefrom the Cambrian period 505 million years ago shortly after an astonishing burst of biodiversity occured in the ancient oceansexquisite preservation amazing fine details of the structure of the animals are seen in the fossils which tell paleontologists much more detail about what the ancient animals looked like and how they livedonot only were the hard parts of their bodies bones shells teeth preserved but also the muscles gills digestive systems and other soft body parts were preserved allowing scientists an opportunity to observe not only these details but also the way the creatures lived and interactedthe fossils reveal important clues to the nature of evolution all the major types of animals phyla known today are represented in the Burgess Shale plus others that cannot be placed in our modern classification systemCambriana period of the Paleozoic Era 570 million to 500 million years agoalgae and marine invertebrates were the predominant form of lifethe Cambrian comes to an end with a major extinction event where many of the weird and unusual animals that appear in the Cambrian disappear from the planet foreverCambrian burrowersCambrian explosion
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