词汇题：

negligible = minor, constraint = limit, commence = begin,

unexpectedly = surprisingly, enormous = huge, cluster = group

第一篇

TOPIC Distribution of Plants and Animals

讲地球上植物之间的相似性要远大于动物。以下阐明原因。原因一是植物很早以前就开始大范围传播，在大陆板块分开之前就分布到各处，而动物出现得较晚；原因二是动物曾经历了多次大灭绝，且之后出现的新物种代替了旧物种与原来很不相同，而植物则很长寿；原因三是动物群不如植物群一样分散广，每一个地方都有特定的动物种类，只有当大陆相连接的时候，动物才能进行传播。植物群分散比较广，并且即便是由于大陆漂移，植物也可以越过海洋进行种子的传播。所以人们能看到各个地方相似的植物群出现。最后转折，在亚洲和非洲两地的动物相似性却很高，是因为当时一度亚非板块相连。

解析：

本文属于生物学中的生物地理学biogeography范畴，从文章结构来看是典型的因果类文章，先说明结果，下面分别写几个原因，最后一段则是极具托福特色的转折。其中，关于大灭绝的部分可以参照TPO阅读文章Meteorite Impact and Dinosaur Extinction，关于植物传播的部分可以参照TPO阅读文章The Arrival of Plant Life in Hawaii。以下是与物种分布有关的内容扩展。

Species distribution

Species distribution is the manner in which a biological taxon is spatially arranged. Species distribution is not to be confused with dispersal, which is the movement of individuals away from their area of origin or from centers of high population density. A similar concept is the species range. A species range is often represented with a species range map. Biogeographers try to understand the factors determining a species' distribution. The pattern of distribution is not permanent for each species. Distribution patterns can change seasonally, in response to the availability of resources, and also depending on the scale at which they are viewed. Dispersion usually takes place at the time of reproduction. Populations within a species are translocated through many methods, including dispersal by people, wind, water and animals. Humans are one of the largest distributors due to the current trends in globalization and the expanse of the transportation industry. For example, large tankers often fill their ballasts with water at one port and empty them in another, causing a wider distribution of aquatic species.

There are three basic types of population distribution within an area. From top to bottom: uniform, random and clumped. Biogeography is the study of the distribution of biodiversity over space and time. It is very useful in understanding species distribution through factors such as speciation, extinction, continental drift, glaciation, variation of sea levels, river capture and available resources. This branch of study not only gives a description of the species distribution, but also a geographical explanation for the distribution of particular species. The traditional biogeographic regions were first modeled by Alfred Wallace in The Geographical Distribution of Animals (1876). These were based on the work of Sclater's terrestrial biogeographic regions. Wallace's system was based on both birds and vertebrates, including non-flying mammals, which better reflect the natural divisions of the Earth due to their limited dispersal abilities.

第二篇

TOPIC Determining the Age of Planets and Universe

宇宙里面组成的物质都是一样的，形成的时间也比较相仿。科学家发现不同的的星球上留下的遗迹通过科学测量，月球和岩石形成的时间都是一样的，得出结论，所有星球形成时间相仿。地球上有很多水，有腐蚀，不能作为参数进行比较。但是月球和小行星进行比较，目前人类史上没出现小行星撞击地球，但宇宙爆炸产生的小行星碎片已陨石的状态掉落到地球上。

解析：

本文属天文学内容，讲解如何测量行星及宇宙的形成时间，文中谈到各行星形成时间相同，这部分内容可以参照TPO阅读文章Planets in our Solar System。以下为文中提到的几个学术概念的解释。

Big Bang Theory

Big Bang Theory, currently accepted explanation of the beginning of the universe. The big bang theory proposes that the universe was once extremely compact, dense, and hot. Some original event, a cosmic explosion called the big bang, occurred about 13.7 billion years ago, and the universe has since been expanding and cooling.

The theory is based on the mathematical equations, known as the field equations, of the general theory of relativity set forth in 1915 by Albert Einstein. In 1922 Russian physicist Alexander Friedmann provided a set of solutions to the field equations. These solutions have served as the framework for much of the current theoretical work on the big bang theory. American astronomer Edwin Hubble provided some of the greatest supporting evidence for the theory with his 1929 discovery that the light of distant galaxies was universally shifted toward the red end of the spectrum (see Redshift). Once "tired light" theories-that light slowly loses energy naturally, becoming more red over time-were dismissed, this shift proved that the galaxies were moving away from each other. Hubble found that galaxies farther away were moving away proportionally faster, showing that the universe is expanding uniformly. However, the universe's initial state was still unknown.

Expanding Universe Experiment

One way to understand the concept of an expanding universe is to draw dots, representing galaxies, on a balloon. As the balloon is inflated, each dot moves away from all the others. To a person viewing the universe from a galaxy, all other galaxies would seem to be receding. The distant galaxies appear to be moving away faster than the near ones, which demonstrates Hubble's law. Most astronomers now believe that this expansion will continue forever.

Redshift

Redshift, change, or shift, in the light radiated by an object, such as a star or galaxy, that indicates the object's motion. Scientists have used redshifts to measure the velocities (speed and direction) of distant galaxies. Knowing the velocities of galaxies helps astronomers understand how the universe is changing. This knowledge allows scientists to interpret the distant past of the universe and to predict the universe's distant future. See also Light.

Redshift only occurs when an object is moving. Another mechanism can also redden the light of astronomical objects, but it is not considered to be the same as redshift. Dust particles between stars are just the right size to scatter light with short wavelengths more than they scatter light with long wavelengths. As the light of a star passes through a cloud of dust on the light's way to Earth, more of the long, red wavelengths get through the dust than the short, blue wavelengths do. This makes the star appear redder than it really is, but the light that reaches Earth is the true red light of the star and has not actually shifted. See also Interstellar Matter.

Redshifts of galaxies allow astronomers to measure the distance from Earth to the galaxies. Knowing the distances to galaxies gives astronomers an idea of the way the universe is expanding and provides clues to the origin, evolution, and future of the universe. The relationship between the redshift (and therefore velocity) and distance of a galaxy is called Hubble's law, which was named after American astronomer Edwin Hubble.

第三篇

TOPIC Agriculture and Settlement around the Nile

有图有真相：尼罗河流域地图

主要讲撒哈拉沙漠和尼罗河对居民的影响。大家都认为尼罗河对于居民的定居是积极意义的，沙漠有着消极的影响。但实际上两个方面是相互影响。在很多年前，当时撒哈拉沙漠还是一片比较富裕的土地，土壤比较适宜，但是随着气候逐渐变干，撒哈拉沙漠已经不适宜人们居住，人们被迫迁移到尼罗河周围，尼罗河那里比较适宜人类的居住，但是大洪水在尼罗河的泛滥导致在溪流边上的人民到达介于河流和沙漠的一片土地上躲避洪水，退却后，人们恢复正常的生活。随着气候的变化，越来越多额游牧主义社群开始定居下来sedentary lifestyle，以庄稼的种植和农业的发展来不断的提供稳定的食物来源，其中谈到非洲农作物源于东亚。

解析：本文属于非洲农业史内容，讲解尼罗河地区农业的特点，文章的重点在于理解造成农业发展的原因，类似讲解农业发展原因的文章可以参照TPO阅读文章The Origins of Agriculture。同时文章给出关于尼罗河和沙漠的比较和对比。以下为对于尼罗河地区农业的特点的介绍。

Nile River

The Greek historian Herodotus wrote that "Egypt was the gift of the Nile". An unending source of sustenance, it provided a crucial role in the development of Egyptian civilization. Silt deposits from the Nile made the surrounding land fertile because the river overflowed its banks annually. The Ancient Egyptians cultivated and traded wheat, flax, papyrus and other crops around the Nile. Wheat was a crucial crop in the famine-plagued Middle East. This trading system secured Egypt's diplomatic relationships with other countries, and contributed to economic stability. Far-reaching trade has been carried on along the Nile since ancient times. The Ishango bone is probably an early tally stick. It has been suggested that this shows prime numbers and multiplication, but this is disputed. In the book How Mathematics Happened: The First 50,000 Years, Peter Rudman argues that the development of the concept of prime numbers could only have come about after the concept of division, which he dates to after 10,000 BC, with prime numbers probably not being understood until about 500 BC. He also writes that "no attempt has been made to explain why a tally of something should exhibit multiples of two, prime numbers between 10 and 20, and some numbers that are almost multiples of 10." It was discovered along the headwaters of the Nile (near Lake Edward, in northeastern Congo) and was carbon-dated to 20,000 BC.

Water buffalo were introduced from Asia, and Assyrians introduced camels in the 7th century BC. These animals were killed for meat, and were domesticated and used for ploughing-or in the camels' case, carriage. Water was vital to both people and livestock. The Nile was also a convenient and efficient means of transportation for people and goods. The Nile was an important part of ancient Egyptian spiritual life. Hapy was the god of the annual floods, and both he and the pharaoh were thought to control the flooding. The Nile was considered to be a causeway from life to death and the afterlife. The east was thought of as a place of birth and growth, and the west was considered the place of death, as the god Ra, the Sun, underwent birth, death, and resurrection each day as he crossed the sky.