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托福听力的背景知识很重要，出国留学网托福栏目小编整理了相关的资料，希望可以帮助考生度过考试的难关，下面是小编搜集的托福听力生物学背景知识的相关资讯，欢迎参考!
托福听力生物学背景知识：痕量金属
Introduction：
Trace Metal
痕量金属,是指只含量极少的金属。一般是指水中、气体中的微量金属。
Background information：
Trace metals are metals in extremely smallquantities that are present in animal and plant cells and tissue. They are anecessary part of nutrition and physiology. Ingestion of, or exposure to,excess quantities is often toxic. However, insufficient plasma or tissue levelsof certain trace metals can cause pathology as well; as is the case with iron.
Trace metals are depleted through theexpenditure of energy by various metabolic processes living organisms. They arereplenished in animals through diet as well as environmental exposure, and inplants through the uptake of nutrients from the soil in which the plant grows.
Human vitamin pills and plant fertilizersboth contain trace metals as additional sources for trace metals. The harderyou work to expend energy, the more trace metals you will lose. These metals needto...
托福听力涉及不少知识，出国留学网托福栏目小编整理了相关的资料，希望可以帮助考生度过考试的难关，下面是小编搜集的托福听力背景知识：红光和远红光的相关资讯，欢迎参考!
托福听力背景知识：红光和远红光
Introduction：
Red and Far-red
光环境是植物生长发育不可缺少的重要物理环境因素之一,通过光质调节,控制植株形态建成是设施栽培领域的一项重要技术。红光和远红光的吸收比率对植物的生长有重要影响。
Background information：
Light isan important environmental factor in most ecosystems. Photosynthetic organismsin particular must sense and respond to light cues to optimize their growth andmetabolism. The quantity, direction and spectral make-up (the color or'quality') of the light sensed by an organism conveys information regarding theabiotic and biotic environment and can be used to control adaptive responses.One superfamily of photosensory receptors comprises the phytochromes ('plantcolor'), which absorb in the red/far-red part of the spectrum. These receptorswere first discovered in plants in the 1950s, but have more recently beenidentified in a broad spectrum of eukaryotic and prokaryotic phyla.
Far-redlight is light at the extreme red end of the visible spectrum, between red andinfra- red light. Usually regarded as the region...
托福听力的背景知识很多，出国留学网托福栏目小编整理了相关的资料，希望可以帮助考生度过考试的难关，下面是小编搜集的托福听力背景知识：古埃及历法的相关资讯，欢迎参考!
托福听力背景知识：古埃及历法
Introduction：
Ancient Egyptian Calendar
古埃及的历法包括太阴历和准太阴历等,大体上将每年分为 3 个季节:泛滥季、长出五谷季、收割季。同时以 365 天为 1 年,1 年 12 个月,每月 30 天,年终另外再加 5 天作为节日。比现行的阳历只少 1/4 天。古罗马的儒略历就是在此基础上修订的。
Background information：
The ancient Egyptian calendar was inventedover 5000 years ago. It was originally based on the lunar cycle of 12 months,which the Egyptians grouped into three seasons of four months each to coincidewith the rise and fall of the waters of the Nile. However, although theflooding of the Nile began each year around the end of June, the floodsoccurred within a range of 80 days and were not accurate enough to base acalendar on. So the ancient Egyptians, having noticed that the Nile’s risingcoincided with the heliacal rising of the star Sirius, the brightest star inthe sky, based the year on the cycle of its reappearance.
The beginning of the year, also called"the opening of the year", was determined by the appearance of thestar Sirius, in the constellation ...
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托福听力背景知识：太阳
关于太阳
太阳的位置(Solar Position)
太阳的构成(Solar Structure)
1、太阳对流区以外(Visible Sun)
2、太阳的内部(Solar Interior)
3、太阳的构成(Composition)
太阳活动 (Solar Activity)
1、太阳黑子(Sunspot)
2、太阳耀斑(Solar Flare)
3、太阳风(Solar Wind)
太阳的位置(Solar Position)
太阳是太阳系(Solar System)的中心天体，占有太阳系总体质量(total mass)的99.86%。太阳系中的八大行星(eight planets)、小行星(asteroid)、流星(metero)、彗星(comet)、外海王星天体(trans-neptunian objects)以及星际尘埃(interstellar dust)等，都围绕着太阳公转，而太阳则围绕着银河系(milky way)的中心公转。
太阳的构成(Solar Structure)
1、太阳对流区以外(Visible Sun)
包括了光球(Photosphere)，色球层(Chromosphere)，过渡区(Transition Region)和日冕(Solar corona)。光球(Photosphere)即我们平时看到的太阳圆面，色球层(Chromosphere)指的是紧贴光球的大气，过渡区(Transition region)是太阳大气(the Sun's atmosphere)的一个非常不规则的薄层，将炽热(100万摄氏度)的日冕(Solar Corona)与凉得多(2万摄氏度)的光球层分开。日冕(Solar corona)是太阳大气的最外层。
2、太阳的内部(Solar Interior)
从内向外分为4个区域：核心(Core)、辐射区(Radiative Zone)、界面层(Interface Layer)和对流区(Convective Zone)
3、太阳的构成(Composition)
从化学组成来看，现在太阳质量的大约四分之三是氢(hydrogen)，剩下的几乎都是氦(helium)，包括氧(oxygen)、碳(carbon)、氖(neon)、铁(iron)和其他的重元素质量少于2%，采用核聚变的方式向太空释放光和热。
太阳活动 (Solar Activity)
1、太阳黑子(Sunspot)
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