第一篇 生命的形成
原文回顾：地球早期火山爆发使得地球上有很多大气，后来形成了一些简单的植物。这些 植物吸收了甲烷和二氧化碳进行光合作用，光合作用产生了氧气和水(于是就有了海)，一些简单生物就在海里形成了。氧气多了以后形成了一个氧气保护膜，使得地球气温不太高，生物不受紫外线伤害。太阳系上其他行星因为没有这个氧气保护层，所以没有办法形成生命。
解析：生物进化类的文章，单词已经不陌生了，句子结构也比较清楚，是容易出分的文章。
相关背景学习：
Timeline of evolutionary history of life
This timeline of evolution of life represents the current scientific theory outlining the major events during the development of life on planet Earth. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules, such as DNA and proteins. The similarities between all present day organisms indicate the presence of a common ancestor from which all known species, living and extinct, have diverged through the process of evolution. Although more than 99 percent of all species that ever lived on the planet are estimated to be extinct, there are currently 10–14 million species of life on the Earth.
第二篇 树木脱落
原文回顾：树木自己会脱落树枝，原因有好几个：细小的树枝吸收了碳水化合物超过了自己能生产的。或是因为有些地方太干燥缺水。还有因为自然灾害。
解析：生物类的文章，文章结构清晰，按照原因分布进行阅读。
相关背景学习：
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines, and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner bark, which in older stems is living tissue, includes the innermost area of the periderm. The outer bark in older stems includes the dead tissue on the surface of the stems, along with parts of the innermost periderm and all the tissues on the outer side of the periderm. The outer bark on trees is also called the rhytidome.
Products used by people that are derived from bark include: bark shingle siding and wall coverings, spices and other flavorings, tanbark for tannin, resin, latex, medicines, poisons, various hallucinogenic chemicals and cork. Bark has been used to make cloth, canoes, and ropes and used as a surface for paintings and map making. A number of plants are also grown for their attractive or interesting bark colorations and surface textures or their bark is used as landscape mulch.
Bark tissues make up by weight between 10-20% of woody vascular plants and consists of various biopolymers, tannins, lignin, suberin, suberan and Polysaccharides. Up to 40% of the bark tissue is made of lignin which forms an important part of a plant providing structural support by crosslinking between different polysaccharides, such as cellulose.
Condensed tannin, which are in fairly high concentration in bark tissue, is thought to inhibit decomposition. It could be due to this factor that the degradation of lignin is far less pronounced in bark tissue than it is in wood. It has been proposed that, in the cork layer (the phellogen), suberin acts as a barrier to microbial degradation and so protects the internal structure of the plant.
Analysis of the lignin in bark wall during decay by the white-rot fungi Lentinula edodes (Shiitake mushroom) using 13C NMR revealed that the lignin polymers contained more Guaiacyl lignin units than Syringyl units compared to the interior of the plant. Guaiacyl units are less susceptible to degradation as, compared to syringyl, they contain fewer aryl-aryl bonds, can form a condensed lignin structure and have a lower redox potential. This could mean that the concentration and type of lignin units could provide additional resistance to fungal decay for plants protected by bark.
第三篇 种植业的形成
原文回顾： 由于农业给人们提供了充足的营养，所以形成了农业种植业。农业种植业的发展，导致商业的发生和发展，所以更多的人就开始种植而不是涉猎。种植业的发展有好处也有坏处，比如人口增长，分配不均，饥荒等等。
解析：历史发展类的文章。按照时间顺序进行解读，注意段落之间的联系。
相关背景学习：
Agriculture
Agricultural practices such as irrigation, crop rotation, application of fertilizers and pesticides, and the domestication of livestock were developed long ago, but have made great progress in the past century. The history of agriculture has played a major role in human history, as agricultural progress has been a crucial factor in worldwide socio-economic change. Division of labour in agricultural societies made commonplace specializations rarely seen in hunter-gatherer cultures, which allowed the growth of towns and cities, and the complex societies we call civilizations. When farmers became capable of producing food beyond the needs of their own families, others in their society were free to devote themselves to projects other than food acquisition. Historians and anthropologists have long argued that the development of agriculture made civilization possible. According to geographer Jared Diamond, the costs of agriculture were: "the average daily number of work hours increased, nutrition deteriorated, infectious disease and body wear increased, and lifespan shortened."
Prehistoric origins
Forest gardening, a plant-based food production system, is thought to be the world's oldest agroecosystem. Forest gardens originated in prehistoric times along jungle-clad river banks and in the wet foothills of monsoon regions. In the gradual process of a family improving their immediate environment, useful tree and vine species were identified, protected and improved whilst undesirable species were eliminated. Eventually superior foreign species were selected and incorporated into the family's garden.
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