24 agosto 2014
One fundamental question in biology is what constitutes the basic type of the animal body plan and how did all the more complex forms, including that of humans, evolve from it. At the simplest level, this body plan can be described by the three axes. These three axes — the familiar X, Y and Z axes from geometry — are the anterior-posterior axis, which determines the position of the mouth in front and the anus at the rear, the dorsal-ventral axis, which in vertebrates separates the front of the body from the back, and the left-right axis, which creates a mirror-like symmetry of our extremities and left-right asymmetry of the organs.
http://feeds.sciencedaily.com/~r/sciencedaily/~3/2HkFhm1Vxro/140824152247.htm
