程序代写：植物和昆虫长期共存下的防御途径
植物和昆虫已经共存了上亿多年。这种长期共存使它们建立起一个复杂的觅食和防御互动系统。自近百万年以来，植物的防御系统不断进化，同时，昆虫的觅食模式也在不断进化，从而扩大了它们的食性。这些现象有力地证明了昆虫与植物的相互作用是植物与昆虫共同进化的结果。此外，昆虫是自然界中最富有的生物体之一，有80多万种昆虫，其中近一半以植物为食。然而，这些植物几乎覆盖了整个地球。
植物可能受到来自不同物种的大量食草动物和疾病的侵袭。为了更好的生活，获得高水平的防守是很重要的。说到植物防御，这个定义是指植物进化出一系列的适应能力，通过减少食草动物的影响来提高它们的生存能力。有不同的防御机制，这有助于对寄主昆虫的负面影响。对于防御目标，可以划分为直接防御和间接防御两种类型。直接防御使植食动物成为目标，间接防御则是提高植物对植食动物天敌的吸引力水平。
Plant and insects have co-existed for more than hundred million years. This long term co-existence makes them set up a complex interaction system about foraging and defensing. Since almost a millions years, plant defense evolved, and at the same point of time, the insects foraging mode evolved further resulting to widen their diet. These phenomena showed strong proof that insect-plant interactions are developed by co-evolution of both plant and insect. Also, insects are one of the richest organisms group in nature, which have more than 800,000 species, and nearly half of them feed on plants. Yet, the plants can be seen covered nearly all across the planet.
Plants could be attacked by a large amount of herbivores and diseases as carried from different species. It is important to get high level defense to have a better life. Speaking of plants defense, the definition would be to describe plants evolved a series of adaptions to improve their survival by reducing the impact of herbivores. There are different defensive mechanisms, which contribute to a negative influence on host insects. For the target of the defense, two types can be drawn, direct defense and indirect defense. Direct defense make the herbivores target, and indirect defense means to enhance the attractive level of the plant to the nature enemies of herbivores.
程序代写 ：植物和昆虫长期共存下的防御途径
对于不同的防御途径，可以归纳为以下两类:1。既存防卫或构成防卫是指防卫系统的第一防卫。它由防御成分组成，如:刺、蜡层、毛状体、一些有毒的次生代谢物(萜类、酚类和含氮化合物如生物碱、氰苷等)、产生的胶等。诱导防御，进化的结果，只有在攻击时才能被激活。对于直接诱导防御，它们具有改变蛋白质等相关成分结构的能力，具有高度的可塑性，可以根据食草动物的不同刺激灵活地改变表型。对于间接诱导防御，它们可以释放挥发物作为化学信息，帮助食草动物的天敌更有效地工作。
由于长期共存，植物的防御进化了，而在同一时间点，昆虫作为最多样化的群体之一，通过改变觅食行为进化了。共生关联是共同进化的结果之一。不同生物之间的联系可以归结为共生、寄生和捕食-被捕食系统。在自然选择的过程中，共生关系的产生是因为它是一种关联，参与其中的有机体都能从中获益。昆虫、微生物、植物等整个生物体或多或少都会有共生关系。例如，一些植物有古老的光合细菌。即使是我们人类，也有细菌和病毒存在于我们的身体系统中，比如线粒体。昆虫作为多细胞生物，似乎对外来生物具有最高的适者生存能力，它们可以以多种形式与体内和体外的生物共存。共生关系可能通过作为一个功能单元参与改变宿主机体的正常代谢途径。长期以来，人们就知道共生细菌可以帮助昆虫扩展它们的饮食范围，并促进它们在新的进食环境中定居下来。
For different pathways of defense, following two catalogues can be concluded: 1. Preexisting or constitutive defenses are referred to the first guard of defense system. It consist of defensive components, for example: thorns, waxy layers, trichomes, some toxic secondary metabolites (terpenoids, phenolics and nitrogen-contained compounds like alkaloids, cyanogenic glycosides), gum-produced and etc. 2. Inducible defenses, result of evolution, only can be activated upon attack. For direct inducible defenses, they have ability to change the structure of associated components such as protein, and they have highly plastic trait, which can change phenotype flexibly based on different stimulation coming from the herbivores. For indirect inducible defenses, they can release volatiles as chemical information to help the natural enemies of herbivores working more efficient.
By long- term co- existence, the plant defense evolved, and at the same point of time, the insects as one of the most diverse groups evolved by changing foraging behavior. Symbiotic association is one of the co-evolution results. Associations between different organisms can be concluded as symbiosis, parasitism and predator-prey system. During natural selections, symbiosis sparked for it is a kind of associations that both of the participating organisms get benefits. The entire organism like insect microorganism, and plant, will more or less have symbiosis associations with each other. For instance, some of the plant have ancient bacteria for photosynthetic. Even we human-beings, there are bacteria and virus exists in our body system like mitochondria. Insects as multicellular are seems to have the highest stand ability for foreign organisms, which can live with the organisms inside and outside the body in large amount of forms. Symbiotic associations will probably change the host organism’s regular metabolic pathways by involving in as a function unit. It has been known for a long time that symbiotic bacteria can help the insects expending their range of diets and facilitating colonization of new feeding niches.
