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 Labs
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Homology and Analogy List
NOTE: In the lists below an "equals sign" (=) indicates a homologous
relationship while the "is not equal to" sign (≠) represents
a relationship that is NOT homologous. The "tilda" (~) is used to
indicate an analogous relationship.
Homologies:
In general, the major organs can be considered to be homologous among the
vertebrates. This means that the liver of the lamprey is homologous to the
livers in all the "higher" taxa up through the rat. This is also true of the
heart (as a whole structure), pancreas, spleen, gall bladder, stomach, intestine,
and lungs (when present).
A growing list of other homologies follows:
- crop (bird) = esophagus in other groups
- proventriculus (bird) = cardiac region of stomach
- gizzard (bird) = pyloric region of stomach
- shark scales = teeth (not keratin "teeth" of lamprey) = bony
fish scales
- reptile scales = feathers (bird) = scales on rat tail ≠ hair
- epididymis (amniotes) = genital portion of kidney (shark, Necturus)
- swim bladder (bony fish) = lungs (tetrapods)
- lamprey, shark, and bony fish gills (internal) ≠ adult Necturus gills
(external)
- lobe-finned fish pectoral and pelvic fins = tetrapod limbs
- notochord (lamprey) = gel-like core of intervertebral discs (mammals)
Analogies:
- mammalian hair ~ feathers (insulatory function)
- ureter (amniotes) ~ urinary duct (lamprey, Necturus, dogfish)
(carries urine away from kidney)
- shark liver ~ accessory bladders (turtle) ~ swim bladder (bony fish) (buoyancy
control function)
- clasper (shark) ~ hemipenis (turtle), penis (rat) (sperm delivery)
- bony fish scales ~ reptilian scales (osmoregulation or abrasion resistance
function)
- ostracoderm scales ~ echinoderm calcium carbonate endoskeleton ~ vertebrate
endoskeletal bone (mineral reservoir)
- notochord ~ vertebral column (body support, not as protection
for nerve cord)
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