Most chordates are vertebrates. Invertebrate chordates, which belong to two of the subphyla of chordatesâCephalochordata and Urochordata, also have a dorsal tubular nerve cord, a notochord, pharyngeal pouches, a postanal tail, and, possibly, an ancestral thyroid gland.They ha ve no backbone, however.ost chordates are vertebrates. Invertebrate chordates, which belong to two of the subphyla of chordatesâCephalochordata and Urochordata, also have a dorsal tubular nerve cord, a notochord, pharyngeal pouches, a postanal tail, and, possibly, an ancestral thyroid gland. They ha ve no backbone, however.
Quadratic Equation. An equation where the highest exponent of the variable (usually x) is a square (2). It is usually written ax2+bx+c = 0 Example: 2x2+5x-3 = 0. See: Exponent. Quadratic Equations.
A quad (pronounced KWAHD ) is a unit in a set of something that comes in four units. The term is sometimes used to describe each of the four numbers that constitute an Internet Protocol ( IP ) address.