2015年10月11日大陆托福阅读解析

词汇篇：

　　第一篇：

　　生物演替

　　1. 概念介绍，分为初生演替和次生演替，主要区别，初始环境不一样，次生是在已有生物的基础上。

　　2. 演替的群落种类一般都是可以耐极端天气，少水分，苔藓地衣之类，他们不需要太多的营养物质，直接从裸露的岩石中吸收，同时还可以帮助分解岩石成小颗粒。

    解析：本文属于生态类文章，关注的是生物演替类别以及演替的过程。生态演替类文章在托福里属于常考话题，学员应该不太陌生，不过由于演替类文章涉及到的学科术语较多，而且讲述内容偏抽象，对学员的理解速度和程度都有一定的挑战，在备考时需要额外关注。

    参考阅读：

In the late nineteenth century, ecology began to grow into an independent science from its roots in natural history and plant geography. The emphasis of this new "community ecology" was on the composition and structure of communities consisting of different species. In the early twentieth century, the American ecologist Frederic Clements pointed out that a succession of plant communities would develop after a disturbance such as a volcanic eruption, heavy flood, or forest fire. An abandoned field, for instance, will be invaded successively by herbaceous plants (plants with little or no woody tissue), shrubs, and trees, eventually becoming a forest. Light-loving species are always among the first invaders, while shade-tolerant species appear later in the succession.

Clements and other early ecologists saw almost law like regularity in the order of succession, but that has not been substantiated. A general trend can be recognized, but the details are usually unpredictable. Succession is influenced by many factors: the nature of the soil, exposure to sun and wind, regularity of precipitation, chance colonizations, and many other random processes.

The final stage of a succession, called the climax by Clements and early ecologists, is likewise not predictable or of uniform composition. There is usually a good deal of turnover in species composition, even in a mature community. The nature of the climax is influenced by the same factors that influenced succession. Nevertheless, mature natural environments are usually in equilibrium. They change relatively little through time unless the environment itself changes.

For Clements, the climax was a "superorganism," an organic entity. Even some authors who accepted the climax concept rejected Clements' characterization of it as a superorganism, and it is indeed a misleading metaphor. An ant colony may be legitimately called a superorganism because its communication system is so highly organized that the colony always works as a whole and appropriately according to the circumstances. But there is no evidence for such an interacting communicative network in a climax plant formation. Many authors prefer the term "association" to the term "community" in order to stress the looseness of the interaction.

Even less fortunate was the extension of this type of thinking to include animals as well as plants. This resulted in the "biome," a combination of coexisting flora and fauna. Though it is true that many animals are strictly associated with certain plants, it is misleading to speak of a "spruce-moose biome," for example, because there is no internal cohesion to their association as in an organism. The spruce community is not substantially affected by either the presence or absence of moose. Indeed, there are vast areas of spruce forest without moose. The opposition to the Clementsian concept of plant ecology was initiated by Herbert Gleason, soon joined by various other ecologists. Their major point was that the distribution of a given species was controlled by the habitat requirements of that species and that therefore the vegetation types were a simple consequence of the ecologies of individual plant species.

With "climax," "biome," "superorganism," and various other technical terms for the association of animals and plants at a given locality being criticized, the term "ecosystem" was more and more widely adopted for the whole system of associated organisms together with the physical factors of their environment. Eventually, the energy-transforming role of such a system was emphasized. Ecosystems thus involve the circulation, transformation, and accumulation of energy and matter through the medium of living things and their activities. The ecologist is concerned primarily with the quantities of matter and energy that pass through a given ecosystem, and with the rates at   which they do so.

Although the ecosystem concept was very popular in the 1950s and 1960s, it is no longer the dominant paradigm. Gleason's arguments against climax and biome are largely valid against ecosystems as well. Furthermore, the number of interactions is so great that they are difficult to analyze, even with the help of large computers. Finally, younger ecologists have found ecological problems involving behavior and life-history adaptations more attractive than measuring physical constants. Nevertheless, one still speaks of the ecosystem when referring to a local association of animals and plants, usually without paying much attention to the energy aspects.

    第二篇：

　　第二个是农耕方式变化带来的gender role change。

　　最开始的时候，是刀耕火种，耕作面积小，所以女的种地和男的打猎提供的食物一样，status没差别。

　　后来plow出现以后，男女分工出现，男的种地，女的负责maintain这个耕种，然后做一些secondary的事情，比如农耕用的牛可以做奶制品，纺织也出现了，和照看老幼同时进行然后因为农耕依赖男劳动力，所以偏好男孩而不是女孩。

　　解析：本文属于人文类和农业类跨学科文章，讲述的是农业与女性社会角色之间的关系。农业类文章自2014年以来一直属于偏高频学科，但是因为TPO里相关文章较少，而学员对农业类词汇概念理解不够，出现后对部分同学而言有较大挑战，在备考托福时需要专门准备。

   参考阅读：

For most of human history, we have foraged (hunted, fished, and collected wild plants) for food. Small nomadic groups could easily supply the necessities for their families. No one needed more, and providing for more than one' s needs made little sense. The organization of such societies could be rather simple, revolving around age and gender categories. Such societies likely were largely egalitarian,beyond distinctions based on age and gender, virtually all people had equivalent rights, status, and access to resources.

Archaeologist Donald Henry suggests that the combination of a rich habitat and sedentism (permanent, year-round settlement) led to a dramatic increase in human population. In his view, nomadic, simple foragers have relatively tow levels of fertility. Their high-protein, low-carbohydrate diets result in low body-fat levels,which are commonly associated with low fertility in women. High levels of physical activity and long periods of nursing, which are common among modem simple foragers, probably also contributed to low levels of female fertility if they were likewise common among ancient foragers.

In Henry's view, the adoption of a more settled existence in areas with abundant food resources would have contributed to higher fertility levels among the sedentary foragers. A diet higher in wild cereals produces proportionally more body fat, leading to higher fertility among women. Cereals, which are easy to digest, would have supplemented and then replaced mother's milk as the primary food for older infants. Since women are less fertile when they are breast-feeding, substituting cereals for mother s milk would have resulted in closer spacing of births and the potential for a greater number of live births for each woman. A more sedentary existence may also have lowered infant mortality and perhaps increased longevity among the aged. These more vulnerable members of society could safely stay fixed village rather than be forced regularly to move great distances as part of a nomadic existence, with its greater risk of accidents and trauma.

All of these factors may have resulted in a trend of increasing size among some local human populations in the Holocene (since 9600 B C E) Given sufficient time,even in very rich habitats, human population size can reach carrying capacity, the maximum population an area can sustain within the context of a given subsistence system. And human population growth is like a runaway tram once it picks up 5 speed, it is difficult to control. So even after reaching an area s carrying capacity.Holocene human populations probably continued to grow m food-rich regions,overshooting the ability of the territory to feed the population, again within the context of the same subsistence strategy. In some areas, small changes in climate or minor changes in plant characteristics may have further destabilized local economies.

One possible response to surpassing the carrying capacity of a region is for a group to exploit adjoining land However, good land may itself be limited-for example, to within the confines of a river valley Where neighbors are in the same position, having filled up the whole of the desirable habitat available in their home territories expansion is also problematic. Impinging on the neighbors' territory can lead to conflict, especially when they too are up against the capacity of the land to provide enough food.

Another option is to stay in the same area but to shift and intensify the food quest there. The impulse to produce more food to feed a growing population was satisfied m some areas by the development of more-complex subsistence strategies involving intensive labor and requiring more cooperation and greater coordination among the increasing numbers of people. This development resulted in a change in the social and economic equations that defined those societies.Hierarchies that did not exist in earlier foraging groups but that were helpful in structuring cooperative labor and in organizing more-complex technologies probably became established, even before domestication and agriculture, as pre-Neolithic societies (before the tenth millennium B C E) reacted to the population increase.

    第三篇：

　　这个是海洋mammal怎么保持体温:

　　第一个是ratio of body size and body surface一般bigger body size, lower ratio, lower heat loss。

　　第二个是fat layer beneath skin越厚越好，热带和寒带的动物也有不同厚度。

　　第三个是一些比较容易冻坏的地方怎么保护，blood slow中的某些物质可以怎样待定。

　　最后是overheating怎么缓解，某些像狗，吐舌头，有些跳水里。

    解析：本文属于生物类文章，关注的是海洋哺乳动物保持体温的方式。从机经来看，本文结构比较清晰，分别从三个方面来讨论保持体温的方式，对学员而言理解上难度不大。动物保温方面的内容，在TPO中也有相关讨论，可以参考TP015的A Warm-blooded Turtle。

参考阅读：

When it comes to physiology, the leatherback turtle is, in some ways, more like areptilian whale than a turtle. It swims farther into the cold of the northern and southern oceans than any other sea turtle, and it deals with the chilly waters in a way unique among reptiles.

A warm-blooded turtle may seem to be a contradiction in terms. Nonetheless, an adult leatherback can maintain a body temperature of between 25 and 260C (77-790F) in seawater that is only 80C (46.40F). Accomplishing this feat requires adaptations both to generate heat in the turtle' s body and to keep it from escaping into the surrounding waters. Leatherbacks apparently do not generate internal heat the way we do, or the way birds do, as a by-product of cellular metabolism. A leatherback may be able to pick up some body heat by basking at the surface; its dark, almost black body color may help it to absorb solar radiation.However, most of its internal heat comes from the action of its muscles.

Leatherbacks keep their body heat in three different ways. The first, and simplest, is size. The bigger the animal is, the lower its surface-to-volume ratio; for every ounce of body mass, there is proportionately less surface through which heat can escape. An adult leatherback is twice the size of the biggest cheloniid sea turtles and will therefore take longer to cool off. Maintaining a high body temperature through sheer bulk is called gigantothermy. It works for elephants, for whales, and, perhaps,it worked for many of the larger dinosaurs. It apparently works, in a smaller way, for some other sea turtles. Large loggerhead and green turtles can maintain their body temperature at a degree or two above that of the surrounding water, and gigantothermy is probably the way they do it. Muscular activity helps, too, and an actively swimming green turtle may be 70C (12.60F) warmer than the waters it swims through.

Gigantothermy, though, would not be enough to keep a leatherback warm in cold northern waters. It is not enough for whales, which supplement it with a thick layer of insulating blubber (fat). Leatherbacks do not have blubber, but they do have a reptilian equivalent: thick, oil-saturated skin, with a layer of fibrous, fatty tissue just beneath it. Insulation protects the leatherback everywhere but on its head and flippers. Because the flippers are comparatively thin and blade-like, they are the one part of the leatherback that is likely to become chilled. There is not much that the turtle can do about this without compromising the aerodynamic shape of the flipper. The problem is that as blood flows through the turtle' s flippers, it risks

losing enough heat to lower the animal' s central body temperature when it returns. The solution is to allow the flippers to cool down without drawing heat away from the rest of the turtle' s body. The leatherback accomplishes this by arranging the blood vessels in the base of its flipper into a countercurrent exchange system.

In a countercurrent exchange system, the blood vessels carrying cooled blood from the flippers run close enough to the blood vessels carrying warm blood from the body to pick up some heat from the warmer blood vessels, thus, the heat is transferred from the outgoing to the ingoing vessels before it reaches the flipper itself. This is the same arrangement found in an old-fashioned steam radiator, in which the coiled pipes pass heat back and forth as water courses through them. The leatherback is certainly not the only animal with such an arrangement; gulls have a countercurrent exchange in their legs. That is why a gull can stand on an ice floe without freezing.

All this applies, of course, only to an adult leatherback. Hatchlings are simply too small to conserve body heat, even with insulation and countercurrent exchange systems. We do not know how old, or how large, a leatherback has to be before it can switch from a cold-blooded to a warm-blooded mode of life. Leatherbacks reach their immense size in a much shorter time than it takes other sea turtles to grow. Perhaps their rush to adulthood is driven by a simple need to keep warm.