Page 144 - Engineering in Nature
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Engineering in Nature

               tubule from moving away from its neighboring tubule more than a
               very short distance. When the loose nexin connectors extend to the
               final row, the greater movement of the dynein protein makes the
               nexin connectors to contract from the micro-tubule. The tension rises
               as the dynein movement continues. Since the micro-tubules are flexi-
               ble, the sliding movement caused by the dynein protein in the tubule
               opposite gradually turns into a bending movement.


                  The Micro-Hairs' Mechanical System Cannot Have
                  Formed by Chance
                  As we've seen so far, a mechanical system, all of whose parts work
               interdependently, has been designed in the micro-hairs and is far
               more difficult than one might imagine. All the elements in the system
               must be exactly right, and all their features must be fully present,
               since the slightest deficiency will harm the outcome.
                  In order to understand this, look at any child's moving toy. If one
               of the parts that permit it to move is missing, the toy will not work.
               The absence of just one of its components will reduce it to just a col-
               lection of plastic and metal parts that serve no purpose.
                  To review, these are the parts necessary in order for the micro-hairs
               to move:
                  Micro-tubules comprise the main structure of the hairs. They are
               just as essential as walls are to a building. Were it not for the micro-tu-
               bules there would be no part for the engine rod to slide over.
                  The engine has to be present in order for the hairs, and therefore
               the micro-tubules, to move.
                  The links cause neighboring tubules to move. The separation
               movement is turned into a bending one, and the connectors prevent
               the entire structure from falling apart.
                  In order for the system to move successfully, the components'


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