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BIO2135 Definitions.docx

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University of Ottawa

Porifera KeywordsAboral side Opposite the end or side on which the mouth is locatedAmebocyte A cell in a multicellular organism that moves using amoeboid movement Amebocytes often are involved in transporting materials defending against invading organisms or cleaning up dead debris and materialsApomorphiesA relatively derived or advanced or unique character state cf autapomorphy synapomorphy plesiomorphy symplesiomorphyAquiferous systemThis type of system is found in sponges and consists of the canals and chambers through which water flows Water is pumped through the system by the choanocytesArcheocyteCell capable of a variety of functions or of differentiating into a variety of cell types with different functions Examples include the wandering amebocytes in the mesohyl of a spongeAsconoidOf the three different sponge architectures this is the simplest It consists of a central choanocyte lined spongocoel that opens to the outside directly through the osculum Water enters the spongocoel after passing through the dermal poresAssymetric body planThere are a number of reasons why the sponge body plan is considered asymmetric some that are obvious and another that isnt as obvious and is more technical Its quite clear that an encrusting sponge has no symmetry but why is the cylindrical sponge also asymmetric The reason is that a single finger is not the whole sponge and when you look at the whole organism the symmetry disappears The large barrel sponges appear to have a radial symmetry but the barrel structure is formed from a sheet of sponge cells that is folded into the barrel shape again there is no symmetry in the underlying structure Technically body symmetry is defined by the oral to aboral axis of the animal and occurs when any line drawn through this axis will result in identical halves If it can only be done once we end up withbilateral symmetry if it can be done in a number of ways then the result is radial symmetry Because a sponge doesnt have a mouth or digestive tract it doesnt have an oral to aboral axis to define any form of symmetry and is technically asymmetricAssymetric body Animals that have no axis of symmetry Examples are sponges and gastropods Autapomorphies An apomorphy in a terminal taxon diagnoses the terminal but is uninformative about relationships to other terminals therefore of no use for cladistic treebuildingBilaterally symmetric body In organisms that have a bilaterally symmetric organization there is only one way that the axis of symmetry can pass through the longitudinal axis and create two identical halvesBuddingA form of asexual reproduction where a small part of the body separates from the parent and develops into a complete organismCellular gradeOrganisms with this type of cellular organization are referred to as the Parazoa They have distinct cells that function independently of each other even though some cells may take on specialized functions Groups of cells never work together and function as a tissue L cella cell or chamberChoanocyteThis unique collarshaped cells whose flagella are responsible for generating the water current in the sponge As the flagella beat food particles are trapped against the microvilli that form the collar Choanocytes are also found in some colonial protistsChoanocyte chamber ny cavity lined by choanocytes and located between inhalant and exhalant systems
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