摘要（這是新的工商服務 xD）：植物葉脈的分布提供了一具較佳效率的運輸模式參考模型。

如果大家接受「一般而言，演化的產物（即天擇作用後存活的個體）為一較適於環境之個體」的說法，那麼要猜測某些現存動植物的運輸模式為該物種所能支持的最具效率選項，應該就不會是什麼難事。

模型（models）常常在實驗室裡被建造，目的是為了驗證學說或找出針對某情況的最佳應對方案。但如果將現存的生物視為自然生成的模型（事實上，模型的建造本來就是為了「模擬真實的情況」！），那麼天擇不就已經幫我們把所有可能的變因給實驗過了嗎？

有些最佳模式，也許就在現存的生物身上。此即一例。

原文出自於此：
http://www.sciencenews.org/view/generic/id/55984/title/Leaf_veins_loopy_for_a_reason，video不長，但還滿值得一看的。


    Leaf veins loopy for a reason   
        Circular networks are best for getting around a bad spot, varying load
                    By Laura Sanders        
                        Web edition                 : Tuesday, February 2nd, 2010        

Enlarge
Avoiding a bad spotVeins’ looped network allows water and nutrients to flow around an injury (green dot) on the main vein of a lemon leaf. E. Katifori et al/PRL 2010


Treebranches have inspired efficient transit networks, but a new studyfinds inspiration in leaves. The curvy, connected leaf veins found insome plants are an efficient way to circumvent damaged areas andchannel nutrients, report researchers led by Eleni Katifori of theRockefeller University in New York City.
“It’s obvious that ifyou look at leaves, they have a lot of loops,” Katifori says. To findout how the looped networks may be beneficial for the plants, theresearchers created a computer model to compare how efficientlydifferent branching patterns could do the job of leaf veins, which movewater and nutrients around. “The question we’re asking is, what’s thebest network we can build?” Katifori says.
In the simulations,the looped network performed better than nonlooped ones in severalimportant ways, the team reported January 29 in Physical Review Letters.Damage from hungry insects, cold weather or parasites can interruptleaves’ normal venation patterns. Connected circular veins allowed theflow of water and minerals to circumvent areas where veins weredestroyed, the team shows. The looped network also allowed leaves toeasily adjust the flow rate of water through veins, which can helpleaves conserve water on a hot day, Katifori says.
Loop networksaren’t found just in tree leaves. Blood vessels in the retina,structural veins in insect wings and the architecture of certain coralsare all based on loops, the researchers write. Understanding thebenefits of such networks might lead to more efficient man-made networkdesigns.

[ 本帖最後由 Chao33 於 2010-2-8 00:13 編輯 ]