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symmetry
similarity of form or arrangement on either side of a dividing line or plane
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how many types of symmetry?
- four:
- asymmetry, spherical, radial, bilateral
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Asymmetry
- any line or plane through the center does not result in equivalent parts
- ex: protists
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Spherical
- al lines or planes passing through the center result in the same two equivalent parts
- (many objects like basketablls and some protists [some algae[)
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Radial
- any cut passing through the center results in two halves that are essentially idental; cuts usually through the medial axis which pass through the mouth of hte organism; the object or organism doesn't have radial symmetry as viewed from teh side
- ex: cylinder, starfish, etcl
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bilateral
- most common in animal kingdom
- only one cut that can be made which will yield two essentially alike peices; vertical cut that passes through the center of the organism or object and extends the length of the organism or object
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Section/ plane
surface passing through the body that divides it into two parts
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Bilaterally symmetrical organisms have which planes
- median (midsagittal)
- sagittal
- parasagittal
- frontal/ coronal
- cross
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Median plane
- vertical longitudinal plane passing through the organism
- divides organism into two essentially identical halves, right and left
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sagittal
any vertical longitudinal plane through the organism that is the median plane or any plane parallel to it
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parasagittal
sagittal planes other than the median plane
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frontalĀ
any longitudinal plane which occurs at right angles to the sagittal plane
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cross
any plane or section that is at right angles to both the sagittal and frontal planes
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radially symmetrical planes
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radial plane
any plane or section that passes through teh center adn along the central axis; infinite number of cuts that can be made, all of which result in two identical portions
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tangential
any plane or section that is parallel to the central axis but does not pass through the center
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cross
a plane or section at right angles to the radial and tangential planes
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__ relates to the determination of the position of one point in relation to another
orientation
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Terms referring to the head end adn rear end fall into three major groups
- superior and inferior (not four-legged animals)
- cranial and caudal (all animals with brain case and tail, respectively)
- anterior and posterior (part of body that goes forward or backward in locomotion)
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Terms referring to the back side and the belly side
- Dorsal and Ventral
- Anterior and Posterior
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Terms referring to points on or away from the midline or center
- medial and lateral
- central and peripheral (spheroidal part or organ)
- superficial and deep
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Terms desribing appendages or partsz
proximal and distal
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