歷屆托福考試閱讀機經(jīng)內(nèi)容解析

第一篇 駱駝的耐旱耐熱能力

【機經(jīng)回憶】

還有篇是關(guān)于駱駝為什么耐炎熱，說駱駝可以缺水20%-25%都沒事，血液中的一種細胞也沒事，但人類到12%就要掛了，這尿性的駱駝NB!還說了同樣生活在沙漠里的其他物種，但都沒駱駝耐熱。駱駝皮膚下有一種什么東西（那詞我不認識），好像是能減少熱量散發(fā)還是干什么（忘了）

還說了駱駝確實能在體內(nèi)存水，但沒有證據(jù)表明是存在駝峰里的（那次我不認識，但我猜的應該是駝峰吧）。反正就是在它的體內(nèi)（PS：camel niubility）

【過往機經(jīng)】駱駝，為什么可以在沙漠生存，和他的skin，fat，hump 等等有關(guān)，我覺得這篇不是太難，但是細節(jié)挺多的

【重點詞匯解析】

Camel 駱駝

Hump駝峰

Skin 皮膚

Fat 脂肪

Dehydration 缺水

Store water 儲水

Drought enduring 耐旱

Heat resisting 耐熱

【機經(jīng)解析】

駱駝的抗旱儲水能力

Camel Eco-behavioral adaptations

Camels do not directly store water in their humps as was once commonly believed. The humps are actually reservoirs of fatty tissue: concentrating body fat in their humps minimizes the insulating effect fat would have if distributed over the rest of their bodies, helping camels survive in hot climates. When this tissue is metabolized, it yields more than one gram of water for every gram of fat processed. This fat metabolization, while releasing energy, causes water to evaporate from the lungs during respiration （as oxygen is required for the metabolic process）： overall, there is a net decrease in water.

A camel's thick coat is one of their many adaptations that aid them in desert-like conditions.

The Horn of Africa has the world's largest population of camels.

Camels have a series of physiological adaptations that allow them to withstand long periods of time without any external source of water. Unlike other mammals, their red blood cells are oval rather than circular in shape. This facilitates the flow of red blood cells during dehydration and makes them better at withstanding high osmotic variation without rupturing when drinking large amounts of water: a 600 kg （1,300 lb） camel can drink 200 L （53 US gal） of water in three minutes.

Camels are able to withstand changes in body temperature and water consumption that would kill most other animals. Their temperature ranges from 34 °C （93 °F） at dawn and steadily increases to40 °C （104 °F） by sunset, before they cool off at night again. Camels rarely sweat, even when ambient temperatures reach 49 °C （120 °F）。 Any sweat that does occur evaporates at the skin level rather than at the surface of their coat; the heat of vaporization therefore comes from body heat rather than ambient heat. Camels can withstand losing 25% of their body weight to sweating, whereas most other mammals can withstand only about 12-14% dehydration before cardiac failure results from circulatory disturbance.

When the camel exhales, water vapor becomes trapped in their nostrils and is reabsorbed into the body as a means to conserve water. Camels eating green herbage can ingest sufficient moisture in milder conditions to maintain their bodies' hydrated state without the need for drinking.

Camels are used as draft animals inPakistan.

The camels' thick coats insulate them from the intense heat radiated from desert sand, and a shorn camel has to sweat 50% more to avoid overheating. During the summer the coat becomes lighter in color, reflecting light as well as helping avoid sunburn. Its long legs help by keeping them farther from the hot ground, which can heat up to 70 °C （158 °F）。

Camels' mouths have a thick leathery lining, allowing them to chew thorny desert plants. Long eyelashes and ear hairs, together with nostrils that can close, form a barrier against sand. If sand gets lodged in their eyes, they can dislodge it using their transparent third eyelid. The camels' gait and widened feet help them move without sinking into the sand.

The kidneys and intestines of a camel are very efficient at reabsorbing water. Camel urine comes out as a thick syrup, and camel feces are so dry, the Bedouins use it to fuel fires.

Camels' immune system differs from those of other mammals. Normally, the Y-shaped antibody molecules consist of two heavy （or long） chains along the length of the Y, and two light （or short） chains at each tip of the Y. Camels, in addition to these, also have antibodies made of only two heavy chains, a trait that makes them smaller and more durable. These "heavy-chain-only" antibodies, discovered in 1993, are thought to have developed 50 million years ago, after camelids split from ruminants and pigs.

第二篇 達爾文進化論

【機經(jīng)回憶】

有一篇是講達爾文進化理論的，說達爾文visited了一個島（是一個chain型的島），然后通過觀察物種，得出了自然選擇的結(jié)論。文章后說達爾文和另外一個人同時得出了這個結(jié)論，只是達爾文的有更多的數(shù)據(jù)（地理上的+生物上的）做支持

【過往機經(jīng)】達爾文的進化論，他是在航行的時候發(fā)現(xiàn)的，有化石和現(xiàn)存的生物作為例子，但是他不敢發(fā)表好象是因為他覺得可靠的data 不夠，同時有一個什么HC 人跟他一起發(fā)現(xiàn)了進化論，但是達爾文的得到了更多的認可。

【重點詞匯解析】

Darwin 達爾文

Evolution Theory 進化論

Natural Selection 自然選擇

Chain Island 島鏈

Fossil 化石

Species 物種

Data 數(shù)據(jù)

【機經(jīng)解析】

達爾文和加拉帕戈斯群島

Darwin & The Galapagos Islands

The tiny volcanic island chain of the Galapagos has played a huge role in the formation of Charles Darwin's 'theory of evolution'. Darwin visited the Galapagos aboard the HMS Beagle in 1835, as part of a five year navigational mission to chart the coast of South America for the British Royal Navy. Under the command of Captain Robert Fitzroy, the expedition was drawing to a close when the Beagle landed in the Galapagos on Isla San Cristobal.

In his early 20's at the time, Darwin was a young and unknown naturalist interested in joining the ministry. However, after doing extensive research and making a number of astute observations about the flora and fauna found on the four islands he had visited, Darwin became more interested in the natural sciences. He also became very keen on understanding the differences between the animal and plant species found on each of the islands, namely Isla Isabela, the Isla Floreana, the Isla Santiago and the Isla San Cristobal. He additionally noted that on each of these islands closely akin species behaved differently, which made him wonder how all of this was possible.

After years of endless research, he came to the conclusion which resulted in his theory of evolution by natural selection, which was published in his book The Origin of Species in 1859. Putting forward the concept that evolution and not God was responsible for the creation of human beings, Darwin shook society as we know it, to its very core. This book raised a number of important scientific questions and changed the way life was once viewed through the eyes of the church.

The best example of Darwin's theory of evolution in action was explained based upon his research of the various finches found in the Galapagos. He noted that on each of the islands the finches were all slightly different from each other, with shorter or longer beaks, a different diet and fuller or less plumage. In honor of his research of these birds, the finches of the Galapagos are now known as Darwin's finches.