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Cambrian and Ordovician Key Words

Cambrian and Ordovician Key Words - Cambrian and Ordovician...

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Cambrian and Ordovician Periods Term Definition Key Points Acoelomate Animals without a body cavity that seperates the gut from the muscles of the body wall. Instead a mass of cells derived largely from mesoderm, packs the region between the gut and the body wall ( a = without; koiloma = cavity) Example: flatworm Algal mats Prevented the earliest animals from burrowing into the sediment Precambrian ocean bottom was covered in these Amebocyte Archeocyte Become eggs in sponges Assymetric body plan Body plan that is irregular in shape and cannot be divided into equal parts Example: Sponges Bilateral symmetry body plan A body plan that has left and right sides that are mirror images of each other on either side of the body's midline Also have front and back ends, as wells as upper and lower surfaces Start to develop motion Bivalve Class that includes clams, scallops, oysters, and mussels ( Bi = two; valv = folding door) Muscle relaxes, opens shell; muscle contracts closing shell Clams Burrow in substrate Filter feed Blastopore The opening at one end of the archenteron in the gastrula that gives rise to the mouth in protstomes An opening that connects to a developing gut Later in
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and the anus in deuterostomes development, a second opening at the opposite end of the embryo transforms the pouchlike gut into a digestive tube Blastula The hollow ball of cells that is the result of cleavage divisions in an early embryo Bryozoa Live in colonies lorophorates (feeding structures) Build reefs Reefs; Prime productivity area Burgess Shale fossils Fossil's that can be found at Yoho national park in BC Discovered by Charles Walcott in 1909 Formed from a mudslide that buried the animals in a fine silt preserving the fossils Trilobites Most complete set of soft invertebrate fossils Cambrian Period that began about 540MA Beginning of continents Animals start to diversify in Oceans Multicellular animals,; invertebrates Cambrian burrowers Priapulids Eat food in the substrate; bottom of ocean Burrows Organisms can now penetrate benthic zone to access its nutrients New habitat causes an explosion in new life More trophic levels appear Cambrian explosion During the Cambrian period when many bizarre Snowball Earth Burrowing
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creatures began to appear Shelled arms race more Ca and CO2 dissolved in water; CaCO3 which is used to make shells bigger animals prey on smaller ones Developmental hox genes Cambrian Swimmers Carnivores An animal that primarily eats other animals Cephalization The development of an anterior head where sensory organs and nervous system tissue are concentrated In bilateral shaped organisms, natural selection favoured this Cephalopod Class that includes octopuses and squids ( cephal = head; pod =foot) Body has a fused head and foot; head comprises mouth and eyes, “foot” forms a set of arms which are equipped with suction pads or hooks.
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