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  3. Here’s a question about chickens and eggs you may not have heard before: How is it that an egg can be so hard to break from the

Here’s a question about chickens and eggs you may not have heard before: How is it that an egg can be so hard to break from the

admin2022-08-27  36
问题     Here’s a question about chickens and eggs you may not have heard before: How is it that an egg can be so hard to break from the outside, yet so easy for a weak little chick to peck through from the inside?
    It’s a tough question to crack. Eggshells are thought to change as the chick grows inside. As the creature develops, parts of the inner eggshell dissolve and the fuzzy little bird incorporates some of that calcium into its bones. But it remained unclear how this process influenced eggshell microstructure. Now, As Nicola Davis at The Guardian reports, a new study in Science Advances suggests that it’s all about the structure of the egg and how it develops with the growing creature inside.
    To solve the mystery and study egg structures, researchers at McGill University used a new method that allowed them to cut extremely thin sections of shell. They then analyzed these thin sections using a microscope to study shell structure.
    The team examined the shell of fertilized (受精的) eggs and compared that to unfertilized eggs. As Laurel Hamers at ScienceNews reports, they discovered that the key to the eggs’ toughness appeared to be the formation of microstructures, guided into place by proteins. They focused their analysis on one particular protein, which is found throughout the shell and is believed to be vital in the organization of mineral structure.
    As Davis explains, the special protein seems to act as a "scaffold (脚手架)" that guides the structure and density of minerals in the shell, in particular calcium. In a developed egg, the minerals in the outer layer of the shell are densely packed and rich with such special protein. But inner egg layers have a different structure, which has less of such special protein and lower density of mineral packing.
    In non-incubated eggs, the nanostructure didn’t change. But in the fertilized eggs, the structure of the inner egg appeared to shift over time. Calcium was transferred to the chicks and the inside of the shell grew weaker, making it easier for the chick to crack through. The inner shell also became bumpier (更崎岖不平的), which the researchers believe provides more surface area for chemical reactions that release calcium to the chicks.
    Knowing the structure of the egg could lead to new types of materials, says Lara Estroff, a Cornell engineer who was not involved in the study, Hamers reports. The researchers think it could even improve food safety for eggs. About 10 to 20 percent of chicken eggs crack in transport, which could lead to contamination. Understanding why some eggs are stronger than others could help breed chickens with tougher eggs.
What do we know about the inside of eggshells and the outside of eggshells?
选项 A、The inner shell of fertilized eggs is harder to break than that of unfertilized eggs.
B、The outer layers of the shell are more densely packed with minerals than the inner egg layers.
C、The inner shell and the outer shell of an egg are made up of different proteins.
D、It is easier for chemical reactions to occur if the inner shell becomes flatter.
答案C
解析 根据题干中的信息词the inside of eggshells和the outside of eggshells，可以把答题线索定位到第五段。第五段提到，在发育成熟的鸡蛋中，蛋壳外层的矿物质密集堆积，富含这种特殊的蛋白质。但蛋壳内层结构不同，这种特殊蛋白质的含量较少，矿物质堆积密度较低。由此可推断，蛋壳外层矿物质密度比内层矿物质密度更大，本题应选C。
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