请Zinal同学确认下哦——北京吉面考古到了本月42篇：化学物质。谢谢

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（Sap树液，类似植物的“血液”，它存在于木质部和韧皮部，用来输送营养物质和遗传物质。有些昆虫以Sap为食，例如知了？Resin树脂基本相当于绷带，位于表皮，当植物受伤时分泌出来修补伤口，有时也用来防虫和杀虫。Resin是Amber琥珀的原料）
琥珀amber最早不被人们了解，甚至放在矿石的教科书里，但琥珀其实是resin在某种情况下变硬形成的。因为缺乏一种检测方法，所以它总是被confused认为是SAP或gum。但是resin和gum及sap不同。因为sap对于plant是有功能function的，能transport还水、养料和荷尔蒙。
Resin是怎样形成的呢？ 1）有研究表明，植物产生resin或gum等物质，以驱除repel其他昆虫的，但是对于一些昆虫来说，反而形成吸引attraction。2）又有研究说，这是一种chemical XXX(注意，新理论名词)，意思是互相依赖interdependence of 植物的chemical和食草昆虫的习性。
很久以来科学家研究动物与植物的进化。没有多大进展。最近有学者发现他们之间的关系可作为研究动植物进化的很重要的证据。举例： 如 蝴蝶和P植物之间存在一种特殊的关系。蝴蝶吃p的叶子和嫩芽bud。导致p的新芽不能成长。于是p逐渐进化改变自己叶子的形状为蝴蝶不敏感植物的叶子形状。但是蝴蝶采取了一种反侦察的方式，进化自己的嗅觉，通过P发出的化学气味辨清真P假P。
P发现改变叶子的方式不能让蝴蝶晕菜后，又努力进化自己，改变自己的叶子，使之出现像疱疹一样的小粒状物-黄色。因为蝴蝶喜欢在叶子上产卵，但是母蝴蝶间非常绅士。从不侵略以被其他蝴蝶占领的植物，从而P保护了自己。最近发现2%的植物P用这种方式防虫成功。科学家预测这个成功导致了今后蝴蝶与P共生进化链关系的结束。
题目：
主题。（对共同进化的概述并例举蝴蝶和植物关系；详细分析蝴蝶和植物共同进化关系）
P植物有什么特点？（细节定位在第三段，选：在P的生长过程中变化很大。干扰选项：P的叶子与其它植物区别很大）
细节题问sap的描述哪个不对。（第一段讲sap的地方，sap的功能）
下列哪个研究跟文章中的东西（chemical XXX）最有关。（找寻类似的化学共生共进化关系）
文中提到2%的目的是什么？（这种新的关系刚刚开始。新一轮攻防战的开始？）

背景知识1：
Weeping sap are plants displaying a natural defense against an insect infestation. Sap, also referred to as resin or sticky pitch, typically flows when insects attempt to enter the tree's bark（树皮）. The sap blocks the hole and often saturates and kills the insect。
Some defensive compounds are produced internally but are released onto the plant’s surface; for example, resins树脂, lignins木质素, silica硅, and wax cover the epidermis表皮 of terrestrial plants and alter the texture质地 of the plant tissue. The leaves of holly plants, for instance, are very smooth and slippery making feeding difficult. Some plants produce gummosis流胶 or sap that traps insects.
Mimicry模仿 and camouflage伪装：Some plants mimic the presence of insect eggs on their leaves, dissuading劝阻 insect species from laying their eggs there. Because female butterflies are less likely to lay their eggs on plants that already have butterfly eggs, some species of neotropical vines of the genus Passiflora (Passion flowers) contain physical structures resembling the yellow eggs of Heliconius butterflies on their leaves, which discourage oviposition by butterflies.[37]

背景知识2：
Sap is a fluid transported in xylem cells (tracheids or vessel elements) or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant. Fluid found in the vacuoles of other cells is sometimes referred to as "cell sap".[citation needed]

Xylem sap consists primarily of water, with hormones, mineral elements and other nutrients dissolved in it. Transport of sap in xylem is characterized by movement from the roots toward the leaves. Over the past century, there has been some controversy regarding the mechanism of xylem sap transport; today, most plant scientists agree that the cohesion-tension theory, along with evapotranspiration best explains this process.

Phloem sap consists primarily of water, with sugars, hormones, and mineral elements dissolved in it. It flows from where carbohydrates are produced or stored to where they are used. The pressure flow hypothesis proposes a mechanism for phloem sap transport.

Maple syrup is made from reduced sugar maple xylem sap. In some countries (e.g., Russia, Latvia, Estonia or Finland) it is common to collect the early spring sap of birch trees (so called "birch juice") for human consumption; the sap can be used fresh or fermented and contains xylitol