Did a giraffe's neck grow to great lengths for the animal to survive or because organisms with increasingly longer necks reproduced more effectively and, hence, had a greater chance of passing on their genes than the short-necked variety? This is an interesting question with many answers; you will know the correct one soon.
This section may save you the trouble of stretching to become taller; it will also present you with one of the great dilemmas that is still with us. Hopefully you can solve it. Darwin's theories are presented in a historical context so you can develop the sense of understanding in incremental, sequential units that may stay with you for a while, at least through the next test. You will also be able to visualize the effects of natural selection on population trends. This is good stuff!
Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. Moulton, Ed.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.