2013年1月13日
第一篇 骆驼的耐旱耐热能力
【机经回忆】
还有篇是关于骆驼为什么耐炎热，说骆驼可以缺水20%?25%都没事，血液中的一种细胞也没事，但人类到12%就要挂了，这尿性的骆驼NB!还说了同样生活在沙漠里的其他物种，但都没骆驼耐热。骆驼皮肤下有一种什么东西(那词我不认识)，好像是能减少热量散发还是干什么(忘了)
还说了骆驼确实能在体内存水，但没有证据表明是存在驼峰里的(那次我不认识，但我猜的应该是驼峰吧)。反正就是在它的体内(PS：camel niubility)
【过往机经】骆驼，为什么可以在沙漠生存，和他的skin，fat，hump 等等有关，我觉得这篇不是太难，但是细节挺多的
【重点词汇解析】
Camel 骆驼
Hump驼峰
Skin 皮肤
Fat 脂肪
Dehydration 缺水
Store water 储水
Drought enduring 耐旱
Heat resisting 耐热
【机经解析】
骆驼的抗旱储水能力
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.#p#副标题#e#
第二篇 达尔文进化论
【机经回忆】
有一篇是讲达尔文进化理论的，说达尔文visited了一个岛(是一个chain型的岛)，然后通过观察物种，得出了自然选择的结论。文章最后说达尔文和另外一个人同时得出了这个结论，只是达尔文的有更多的数据(地理上的+生物上的)做支持
【过往机经】达尔文的进化论，他是在航行的时候发现的，有化石和现存的生物作为例子，但是他不敢发表好象是因为他觉得可靠的data 不够，同时有一个什么HC 人跟他一起发现了进化论，但是达尔文的得到了更多的认可。
【重点词汇解析】
Darwin 达尔文
Evolution Theory 进化论
Natural Selection 自然选择
Chain Island 岛链
Fossil 化石
Species 物种
Data 数据
【机经解析】
达尔文和加拉帕戈斯群岛
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.