1. 定义（What is foraging？）
Foraging behavior includes all the methods by which an organism acquires and utilizes sources of energy and nutrients. This includes the location and consumption of resources, as well as their retrieval and storage, within the context of the larger community. Foraging theory seeks to predict how an animal would choose to forage within its environment, based on the knowledge of resource availability, competition, and predation risk.
觅食行为包括生物体获取和利用能量和营养源的所有方法。包括资源的位置和消耗，以及在更大的环境中能量的检索和存储。觅食理论旨在根据资源可用性、竞争和环境的知识，预测动物将如何选择在其环境中觅食捕食风险。
必要条件
The purpose of foraging is to create a positive energy budget for the organism. In order to survive, an organism must balance out its energy spent with energy gained. In order to also grow and reproduce, there must be a net gain in energy. The major theoretical statement of this concept is Optimal Foraging Theory (Pyke et al., 1977; Stephens and Krebs, 1986; Brown, 2000), which assumes that an organism will optimize its energy budget by maximizing energy intake and minimizing energy expenditure.
觅食的目的是为生物体创造正能量预算。为了生存，有机体必须平衡其消耗的能量和获得的能量。为了生长和繁殖，必须有能量的净增益。（即觅食所获取的能量>觅食所消耗的能量）这一概念的主要理论陈述是最佳觅食理论（Pyke等人，1977年；Stephens和Krebs，1986年；Brown，2000年），该理论假设生物体将通过最大化能量摄入和最小化能量消耗来优化其能量预算。
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3. 为适应环境所做的调整
Changes in foraging behavior can increase the food-finding ability. In the darkness of caves, a food-searching behavior concentrated on only the two-dimensional bottom or other surface areas can be much more economic in time and cost than a food search in a three-dimensional space, as exhibited by most surface animals in light and what they also try to do in darkness. Several cave animals have abandoned the shoaling or grouping behavior and adopted a continuous moving mode as a consequence of darkness and food scarcity in the cave habitat. The amblyopsid cavefish have developed a different swimming behavior, referred to as glide-and-rest swimming. This behavior, also enabled by the larger fins, not only conserves energy but also results in a reduction of interference noise for neuromast receptors, thus improving prey detection.
觅食行为的改变可以提高觅食能力。在洞穴的黑暗中，集中在二维底部或其他表面区域的觅食行为在时间和成本上比在三维空间中的食物搜索要少得多，正如大多数地面上的动物在光线下以及在黑暗中所做的那样。由于洞穴栖息地比较黑暗而且食物匮乏，一些洞穴动物已经放弃了群居行为，采取了不断移动的生活模式。弱视洞穴鱼进化出一种不同的游泳行为，称为滑翔和游泳。这种行为，可以通过较大的鳍实现，不仅可以节省能量，还可以减少神经肥大受体的干扰噪声，从而提高对猎物的检测。
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综合上述两篇文章，不难发现：在细菌话题中，最常见的就是定义式结构；且考察的内容无非是细菌常见的几个好处。
不过，这篇文章中：X细菌对worm（蠕虫）的影响其实只是本文的一个片段，而并非全文主旨。通过instruction这句：The class is discussing symbiosis. 我们可以判断，这篇lecture重点强调共生关系。所以，如果同学们在生物类话题中遇到与细菌相关的内容片段，需要留意，此处可能会有多选题出没。
而细菌话题的多选题一般涉及的都是细菌的好处，大多是为了检测考生是否能够捕捉到明显的并列逻辑词、对比词或序数词（也就是我们常说的多选题出题信号词）。
比如这篇文章中的For one thing和Also，就是两个非常明显的并列信号词。
《动物的觅食行为及细菌功能》资料片段展示[/caption]
