2014年3月16日中国大陆地区
第一篇
TOPIC 群居动物和独居动物
讲群居和独居动物的cost和benefit比较。群居动物更易觅食产卵，但配偶竞争压力大(有题)，而且容易互相感染疾病。举了燕子和蜜蜂的例子。工蜂用某些方式清理hive里的fungus防止疾病。独居动物一般自己能够应对捕食者predator(有题)，而群居动物是一起来对付predator。举了鱼的例子。一种鱼联合一起对抗catfish，防止它们的蛋被吃掉。
解析：本文属生物学话题中动物学内容，是
Why do some animals live alone and others form societies?
The success of living alone vs. in a group depends on the environment and they type of animal.
Some animals live alone because it is easier to find food and shelter for themselves in rough climates. Cheetahs and leopards in the Savannah live alone because feeding one leopard takes 50 pounds of meat every few days to live. There hunting styles are also not suited for group hunting. If they changed there hunting style they would compete with outer hunters, like the lion. other animals like the rhinoceros is a solitary animal because there is not enough resources for more then one adult animal in a given area. That is why many animals have territories were they feed and live where no other animals of the same species lives except during breeding season.
Those animals that live in groups tend to do so for one or more of the following reasons:
1) “Safety in numbers” In a large herd, a predator can only take a few individuals. By staying with others of their own kind, each animal is lowering its personal odds of being chosen. Also, there are more eyes watching for predators. This is part of the reason why birds form mixed foraging flocks.
2) “It takes a village” Many animals group together to raise their young. For some, this is a subset of #1 above – if all the young are being born at the same time and place, each individual’s risk of being prey is lower. For others, it is a way to pool resources, with adults sharing the protection, defense or feeding of the young. In many bird species, young birds live with their parents in family groups for a season or two before trying to mate on their own – they use this time to learn parenting skills, and their contributions to nestling care increases their parents’ success as well.
3) Greater success in finding, killing or defending prey items. Wolves are actually more successful as lone hunters than in a pack, but cannot defend their kills from bears and even ravens when they are alone. This was a fascinating recent study on why some predators hunt in groups even when they are more successful as single predators.
4) Very large ranges make finding mates difficult. Some animals live together in small groups because finding one another across large territories with low population densities is difficult.
第二篇
TOPIC 彗星
有图，彗星图片。讲彗星靠近太阳的时候表面物质会蒸发，形成一个尾巴tail。通常有两个tail，一个是蒸发气体一个是金属物质particle。远离太阳后，气体就凝结condense，尾巴会消失。彗星每次靠近太阳都会损失，但不会消失，因为只剩一个core的时候就不再继续蒸发了。还有一个long-period和short-period彗星的对比。讲长周期卫星，很久不会靠近一次太阳，但可能会被其他天体影响轨道的改变。最后提到哈雷彗星，周期76年，从240BC到现在出现30多次，后来科学家才知道这原来都是同一个彗星(有句子插入题)。还提到彗星会受到太阳风Solar Wind和射线的影响。
解析：本文属天文学话题，介绍彗星的各方面情况，。文章各段内容相对独立，都围绕彗星主题。天文学文章一般学术词汇较多，是一大障碍，但这些词汇不是考点，只是会影响阅读的流畅度，平常训练时要注意提高自己在有生词的情况下理解文章的能力。
Comets: Formation, Discovery and Exploration
Comets – Overview
A comet is an icy body that releases gas or dust. They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs. Comets contain dust, ice, carbon dioxide, ammonia, methane and more. Some researchers think comets might have originally brought some of the water and organic molecules to Earth that now make up life here.
Comets orbit the sun, but most are believed to inhabit in an area known as the Oort Cloud, far beyond the orbit of Pluto. Occasionally a comet streaks through the inner solar system; some do so regularly, some only once every few centuries. Many people have never seen a comet, but those who have won't easily forget the celestial show.
The solid nucleus or core of a comet consists mostly of ice and dust coated with dark organic material, with the ice composed mainly of frozen water but perhaps other frozen substances as well, such as ammonia, carbon dioxide, carbon monoxide and methane. The nucleus might have a small rocky core.
As a comet gets closer to the sun, the ice on the surface of the nucleus begins turning into gas, forming a cloud known as the coma. Radiation from the sun pushes dust particles away from the coma, forming a dust tail, while charged particles from the sun convert some of the comet's gases into ions, forming an ion tail. Since comet tails are shaped by sunlight and the solar wind, they always point away from the sun.
The nuclei of most comets are thought to measure 10 miles (16 km) or less. Some comets have comas that can reach nearly 1 million miles (1.6 million kilometers) wide, and some have tails reaching 100 million miles (160 million kilometers) long.
We can see a number of comets with the naked eye when they pass close to the sun because their comas and tails reflect sunlight or even glow because of energy they absorb from the sun. However, most comets are too small or too faint to be seen without a telescope.
Comets leave a trail of debris behind them that can lead to meteor showers on Earth. For instance, the Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes through the orbit of the Swift-Tuttle comet.
Orbital Characteristics
Asteroids classify comets based on the durations of their orbits around the sun. Short-period comets need roughly 200 years or less to complete one orbit, long-period comets take more than 200 years, and single-apparition comets are not bound to the sun, on orbits that take them out of the solar system. Recently, scientist have also discovered comets in the main asteroid belt — these main-belt comets might be a key source of water for the inner terrestrial planets.
Scientists think short-period comets, also known as periodic comets, originate from a disk-shaped band of icy objects known as the Kuiper belt beyond Neptune's orbit, with gravitational interactions with the outer planets dragging these bodies inward, where they become active comets. Long-period comets are thought to come from the nearly spherical Oort cloud even further out, which get slung inward by the gravitational pull of passing stars.
Some comets, called sun-grazers, smash right into the sun or get so close that they break up and evaporate.
Naming
In general, comets are named after their discoverer, either a person. For example, comet Shoemaker-Levy 9 got its name because it was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy. Spacecraft have proven very effective at spotting comets as well, so the names of many comets incorporate the names of missions such as SOHO or WISE.
Astronomers think comets are leftovers from the gas, dust, ice and rocks that initially formed the solar system about 4.6 billion years ago.
History
In antiquity, comets inspired both awe and alarm, "hairy stars" resembling fiery swords that appeared unpredictably in the sky. Often, comets seemed to be omens of doom — the most ancient known mythology, the Babylonian "Epic of Gilgamesh," described fire, brimstone, and flood with the arrival of a comet, and Emperor Nero of Rome saved himself from the "curse of the comet" by having all possible successors to his throne executed. This fear was not just limited to the distant past — in 1910, people in Chicago sealed their windows to protect themselves from what they thought was the comet’s poisonous tail.
For centuries, scientists thought comets traveled in the Earth's atmosphere, but in 1577, observations made by Danish astronomer Tycho Brahe revealed they actually traveled far beyond the moon. Isaac Newton later discovered that comets move in elliptical, oval-shaped orbits around the Sun, and correctly predicted that they could return again and again.
Chinese astronomers kept extensive records on comets for centuries, including observations of Halley's Comet going back to at least 240 BC, historic annals that have proven valuable resources for later astronomers.
A number of recent missions have ventured to comets. NASA's Deep Impact collided an impactor into Comet Tempel 1 in 2005 and recorded the dramatic explosion that revealed the interior composition and structure of the nucleus. In 2009, NASA announced samples the Stardust mission returned from Comet Wild 2 revealed a building block of life. The European Space Agency's Rosetta is scheduled to orbit Comet Churyumov-Gerasimenko in 2014 and deploy a probe to make the first landing on a comet.
Famous Comets
Halley's Comet is likely the most famous comet in the world, even depicted in the Bayeux Tapestry that chronicled the Battle of Hastings of 1066. It becomes visible to the naked eye every 76 years when it nears the sun. When Halley's Comet zoomed near Earth in 1986, five spacecraft flew past it and gathered unprecedented details, coming close enough to study its nucleus, which is normally concealed by the comet's coma. The roughly potato-shaped, nine-mile-long (15 km) contains equal part ice and dust, with some 80 percent of the ice made of water and about 15 percent of it consisting of frozen carbon monoxide. Researchers believe other comets are chemically similar to Halley's Comet. The nucleus of Halley's Comet was unexpectedly extremely dark black — its surface, and perhaps those of most others, is apparently covered with a black crust of dust over most of the ice, and it only releases gas when holes in this crust expose ice to the sun.
The comet Shoemaker-Levy 9 collided spectacularly with Jupiter in 1994, with the giant planet's gravitational pull ripping the comet apart for at least 21 visible impacts. The largest collision created a fireball that rose about 1,800 miles (3,000 km) above the Jovian cloudtops as well as a giant dark spot more than 7,460 miles (12,000 km) across — about the size of the Earth —and was estimated to have exploded with the force of 6,000 gigatons of TNT.
A recent, highly visible comet was Hale-Bopp, which came within 122 million miles (197 million kilometers) of Earth in 1997. Its unusually large nucleus gave off a great deal of dust and gas — estimated at roughly 18 to 25 miles (30 to 40 kilometers) across — appeared bright to the naked eye.
When Earth crosses the path of a comet, even if the comet hasn't been around for a few years, leftover dust and ice can create increased numbers of meteors in what's known as a meteor shower.
第三篇
TOPIC 18世纪新英格兰地区农业Agriculture in British America
讲新英格兰地区农业变化情况。先是北部农业发展好，人们伐木、造船、耕种等，然后中部土壤比北部好，很肥沃，但种几年会休耕7年，所以还要向北部进口粮食。后来人口增多，土地不够用，人们改为种2年休2年，土地逐渐不好了，人们离开而去其他地方，并且除了农业还做其他事情。
解析：本文属农业话题，也属于美国历史范畴。关于农业的各方面知识是生活在城市中的同学比较缺乏的，通过广泛阅读一些农业相关文章，要补充一些农业词汇和农业相关实践和历史的知识。
Industrialization & Agriculture
The half-century period before the Civil War, more generally between 1800 and 1900, saw the “development of New England manufactures and the rise of new factory villages and towns”. This brought about significant changes to the agricultural system in the region, specifically through new demands for raw materials and food. Though demand was quick to change, supply remained fixed for a long period of time due to the “inherent inflexibility of the agricultural industry”. However, with the development of railroads by 1840, supply was pretty much forced to change and meet demand. This occurred due to the sudden drop in transportation costs, and thus how competitive the agricultural sector became as a result of the newer farms utilizing newer technologies in the New York area. Farmers elsewhere in New England had to institute similar changes in capital to match the increase in competition by making farming in plantations more efficient and productive. Though such changes were made reluctantly, they were the steps that resulted in what would thereafter be referred to as an agricultural revolution.