8月20日托福閱讀第一篇 人口增長

　　原文回顧：因為農(nóng)業(yè)發(fā)展，公元前8000年人口就忽然增長。然后，因為農(nóng)業(yè)讓媽媽可以生更多的孩子。而且嬰兒可以喂谷物，而不是像以前那樣，只喝奶;大孩子也可以照顧小孩，還可以分擔一些農(nóng)活。所以，人類出生率就變高了。農(nóng)業(yè)人口再語言上和其他一些方面上都優(yōu)于漁獵人口。所以，漁獵人口逐漸開始向農(nóng)業(yè)人口學習。

　　8月20日托福閱讀第二篇 鳥類的起源

　　原文回顧：鳥類是不是從恐龍進化的，之前普遍認為是從樹上飛下來而不是在陸地上。之后發(fā)現(xiàn)鳥類和恐龍有很多共同點，不過和現(xiàn)在脊椎動物不同，這些都還在研究中，參考的是中國發(fā)掘保存好的化石，說很多不飛的恐龍也有羽毛，所以羽毛只有鳥類有不對，而且羽毛是地面恐龍和飛行鳥類的一個過渡。

　　8月20日托福閱讀第三篇 美國鐵路的發(fā)展和影響

　　原文回顧： 美國的鐵路線數(shù)量幾乎超過了世界其余國家的鐵路線總量，鐵路的發(fā)展使美國成為僅次于英國的第二大工業(yè)國家。除了促進交通業(yè)的發(fā)展，鐵路的發(fā)展還促進了鋼鐵業(yè)，采煤業(yè)的發(fā)展。鐵路的發(fā)展更促進了電報業(yè)的發(fā)展。

　　2016年8月20日托福閱讀詞匯題：

　　likewise=similarly

　　lucrative=profitable

　　surge=sudden increase

　　might=strength

　　compile=put together

　　prevail=accepted

　　coexist=live together

　　exquisitely=perfectly

　　predominate=mainly

　　adopting=start to use

　　2016年8月20日托福閱讀第一篇 人口增長

　　原文回顧：因為農(nóng)業(yè)發(fā)展，公元前8000年人口就忽然增長。然后，因為農(nóng)業(yè)讓媽媽可以生更多的孩子。而且嬰兒可以喂谷物，而不是像以前那樣，只喝奶;大孩子也可以照顧小孩，還可以分擔一些農(nóng)活。所以，人類出生率就變高了。農(nóng)業(yè)人口再語言上和其他一些方面上都優(yōu)于漁獵人口。所以，漁獵人口逐漸開始向農(nóng)業(yè)人口學習。

　　相關(guān)背景學習： Population genetics

　　In population genetics a sexual population is a set of organisms in which any pair of members can breed together. This means that they can regularly exchange gametes to produce normally-fertile offspring, and such a breeding group is also known therefore as a gamodeme. This also implies that all members belong to the same of species, such as humans. If the gamodeme is very large (theoretically, approaching infinity), and all gene alleles are uniformly distributed by the gametes within it, the gamodeme is said to be panmictic. Under this state, allele (gamete) frequencies can be converted to genotype (zygote) frequencies by expanding an appropriate quadratic equation, as shown by Sir Ronald Fisher in his establishment of quantitative genetics.

　　This seldom occurs in nature: localisation of gamete exchange – through dispersal limitations, or preferential mating, or cataclysm, or other cause – may lead to small actual gamodemes which exchange gametes reasonably uniformly within themselves, but are virtually separated from their neighbouring gamodemes. However, there may be low frequencies of exchange with these neighbours. This may be viewed as the breaking up of a large sexual population (panmictic) into smaller overlapping sexual populations. This failure of panmixia leads to two important changes in overall population structure: (1) the component gamodemes vary (through gamete sampling) in their allele frequencies when compared with each other and with the theoretical panmictic original (this is known as dispersion, and its details can be estimated using expansion of an appropriate binomial equation); and (2) the level of homozygosity rises in the entire collection of gamodemes. The overall rise in homozygosity is quantified by the inbreeding coefficient (f or φ). Note that all homozygotes are increased in frequency – both the deleterious and the desirable. The mean phenotype of the gamodemes collection is lower than that of the panmictic "original" – which is known as inbreeding depression. It is most important to note, however, that some dispersion lines will be superior to the panmictic original, while some will be about the same, and some will be inferior. The probabilities of each can be estimated from those binomial equations. In plant and animal breeding, procedures have been developed which deliberately utilise the effects of dispersion (such as line breeding, pure-line breeding, back-crossing). It can be shown that dispersion-assisted selection leads to the greatest genetic advance (ΔG = change in the phenotypic mean), and is much more powerful than selection acting without attendant dispersion. This is so for both allogamous (random fertilization) and autogamous (self-fertilization) gamodemes.

　　2016年8月20日托福閱讀第二篇 鳥類的起源

　　原文回顧：鳥類是不是從恐龍進化的，之前普遍認為是從樹上飛下來而不是在陸地上。之后發(fā)現(xiàn)鳥類和恐龍有很多共同點，不過和現(xiàn)在脊椎動物不同，這些都還在研究中，參考的是中國發(fā)掘保存好的化石，說很多不飛的恐龍也有羽毛，所以羽毛只有鳥類有不對，而且羽毛是地面恐龍和飛行鳥類的一個過渡。

　　相關(guān)背景學習： Feathers, plumage, and scales

　　Feathers are a feature characteristic of birds (though also present in some dinosaurs not currently considered to be true birds). They facilitate flight, provide insulation that aids in thermoregulation, and are used in display, camouflage, and signaling. There are several types of feathers, each serving its own set of purposes. Feathers are epidermal growths attached to the skin and arise only in specific tracts of skin called pterylae. The distribution pattern of these feather tracts (pterylosis) is used in taxonomy and systematics. The arrangement and appearance of feathers on the body, called plumage, may vary within species by age, social status, and sex.

　　Plumage is regularly moulted; the standard plumage of a bird that has moulted after breeding is known as the "non-breeding" plumage, or—in the Humphrey-Parkes terminology—"basic" plumage; breeding plumages or variations of the basic plumage are known under the Humphrey-Parkes system as "alternate" plumages. Moulting is annual in most species, although some may have two moults a year, and large birds of prey may moult only once every few years. Moulting patterns vary across species. In passerines, flight feathers are replaced one at a time with the innermost primary being the first. When the fifth of sixth primary is replaced, the outermost tertiaries begin to drop. After the innermost tertiaries are moulted, the secondaries starting from the innermost begin to drop and this proceeds to the outer feathers (centrifugal moult). The greater primary coverts are moulted in synchrony with the primary that they overlap. A small number of species, such as ducks and geese, lose all of their flight feathers at once, temporarily becoming flightless. As a general rule, the tail feathers are moulted and replaced starting with the innermost pair. Centripetal moults of tail feathers are however seen in the Phasianidae. The centrifugal moult is modified in the tail feathers of woodpeckers and treecreepers, in that it begins with the second innermost pair of feathers and finishes with the central pair of feathers so that the bird maintains a functional climbing tail. The general pattern seen in passerines is that the primaries are replaced outward, secondaries inward, and the tail from center outward. Before nesting, the females of most bird species gain a bare brood patch by losing feathers close to the belly. The skin there is well supplied with blood vessels and helps the bird in incubation.

　　Red parrot with yellow bill and wing feathers in bill

　　Red lory preening

　　Feathers require maintenance and birds preen or groom them daily, spending an average of around 9% of their daily time on this. The bill is used to brush away foreign particles and to apply waxy secretions from the uropygial gland; these secretions protect the feathers' flexibility and act as an antimicrobial agent, inhibiting the growth of feather-degrading bacteria. This may be supplemented with the secretions of formic acid from ants, which birds receive through a behaviour known as anting, to remove feather parasites.

　　The scales of birds are composed of the same keratin as beaks, claws, and spurs. They are found mainly on the toes and metatarsus, but may be found further up on the ankle in some birds. Most bird scales do not overlap significantly, except in the cases of kingfishers and woodpeckers. The scales of birds are thought to be homologous to those of reptiles and mammals.

　　2016年8月20日托福閱讀第三篇 美國鐵路的發(fā)展和影響

　　原文回顧： 美國的鐵路線數(shù)量幾乎超過了世界其余國家的鐵路線總量，鐵路的發(fā)展使美國成為僅次于英國的第二大工業(yè)國家。除了促進交通業(yè)的發(fā)展，鐵路的發(fā)展還促進了鋼鐵業(yè)，采煤業(yè)的發(fā)展。鐵路的發(fā)展更促進了電報業(yè)的發(fā)展。

　　相關(guān)背景學習：Rail transport

　　Rail transport is a means of conveyance of passengers and goods on wheeled vehicles running on rails, also known as tracks.

　　It is also commonly referred to as train transport. In contrast to road transport, where vehicles run on a prepared flat surface, rail vehicles ("rolling stock") are directionally guided by the tracks on which they run. Tracks usually consist of steel rails, installed on ties (sleepers) and ballast, on which the rolling stock, usually fitted with metal wheels, moves. Other variations are also possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface.

　　Rolling stock in railway transport systems generally suffers lower frictional resistance than road vehicles, and the passenger and freight cars (carriages and wagons) can be coupled into longer trains. The operation is carried out by a railway company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway electrification system or produce their own power, usually by diesel engines. Most tracks are accompanied by a signalling system. Railways are a safe land transport system when compared to other forms of transport.[Nb 1] Railway transport is capable of high levels of passenger and cargo utilization and energy efficiency, but is often less flexible and more capital-intensive than road transport, when lower traffic levels are considered.

　　The oldest, man-hauled railways date back to the 6th century BC, with Periander, one of the Seven Sages of Greece, credited with its invention. Rail transport blossomed after the British development of the steam locomotive as a viable source of power in the 18th and 19th centuries. With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution. Also, railways reduced the costs of shipping, and allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships. The change from canals to railways allowed for "national markets" in which prices varied very little from city to city. The invention and development of the railway in Europe was one of the most important technological inventions of the 19th century; in the United States, it is estimated that without rail, GDP would have been lower by 7% in 1890.

　　In the 1880s, electrified trains were introduced, and also the first tramways and rapid transit systems came into being. Starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being almost complete by 2000. During the 1960s, electrified high-speed railway systems were introduced in Japan and later in some other countries. Other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. Following decline after World War II due to competition from cars, rail transport has had a revival in recent decades due to road congestion and rising fuel prices, as well as governments investing in rail as a means of reducing CO2 emissions in the context of concerns about global warming.