哎呀,来晚了~~~来确认几个段落和题目啦! 50、紫外线对两栖类孵化情况的影响:2.段落大意:P1:提出一种现象,并实验证明:环境变化导致的紫外线变化会对两栖类造成伤害,但是酶可以repair基因(Q2)。两个科学家做蛙类卵的孵化率field study,三个品种(species)的卵拿来照紫外线:一个是H,一个是R,一个是B。品种不同,对于UV(紫外线)造成影响的反应也不同。H的卵比较厉害,UV射线照也不会影响fertility;H因为含有某种酶,此酶的activity很活跃因此抵挡紫外线,所以孵化成功率(hatching)仍然很高。另外其他两种R和B,酶activities较低,所以孵化率就不行了,要减少紫外线照射孵化率才会回升(如果R和B被cover了,那么它们受到的保护就会increase)。所以证明这个酶跟孵化率有关。(Q1)。P2:提出进一步说明:同时酶也和免疫力有关,酶比较活跃的,不容易得一种病(Q4)。讲了这三种eggs的免疫力的问题,说他们的免疫力强的时候也能提高孵化率。但是人类活动不断deplete ozone,使更多紫外线能够到达地球,影响了eggs的免疫力,因为这样会使得青蛙更容易被一种真菌感染,所以孵化率就降低了。**三种蛙类Hyla regilla 太平洋树蛙Rana cascadae 红腿蛙Bufo boreas 巴氏蟾蜍3.题目:Q1. hatching时R和B会怎样Q2. 酶的featureQ3.主旨题参考答案:解释说明实验现象Q4. 下列哪个选项能weaken专家关于免疫力的观点?英文背景知识(非原文,但接近原文背景):Many amphibian species, in widely scatteredlocations, currently show population declines and/or reductions in range, butother amphibian species show no such declines. There is no known single causefor these declines. Differential sensitivity to UVB radiation among speciesmight be one contributing factor. We have focused on amphibian eggs,potentially the most UVB-sensitive stage, and compared their resistance to UVBcomponents of sunlight with their levels of photolyase, typically the mostimportant enzyme for repair of the major UV photoproducts in DNA, cyclobutanepyrimidine dimers. Photolyase varied 100-fold among eggs/oocytes of 10 species.Among three species—Hyla regilla, Rana cascadae, and Bufo boreas—for whichresistance of eggs to solar UVB irradiance in their natural locations wasmeasured, hatching success correlated strongly with photolyase. Two additionalspecies, Rana aurora and Ambystoma gracile, now show similar correlations. Amongthe low-egg-photolyase species, R. cascadae and B. boreas are showing declines,and the status of A. gracile is not known. Of the two high-photolyase species,populations of H. regilla remain robust, but populations of R. aurora areshowing declines. To determine whether levels of photolyase or other repairactivities are affected by solar exposures during amphibian development, wehave initiated an extended study of H. regilla and R. cascadae, and of Xenopuslaevis, laboratory-reared specimens of which previously showed very lowphotolyase levels. Hyla regilla and R. cascadae tadpoles are being reared tomaturity in laboratories supplemented with modest levels of UV light or lightfiltered to remove UVB wavelengths. Young X. laevis females are being rearedindoors and outdoors. Initial observations reveal severe effects of both UVAand UVB light on H. regilla and R. cascadae tadpoles and metamorphs, includingdevelopmental abnormalities and high mortalities. Assays of photolyase levelsin the skins of young animals roughly parallel previous egg/oocyte photolyasemeasurements for all three species.-- by 会员 zxfjacob (2012/11/24 0:15:11)
Q1.Q3我确定有! |