雅思练习总结（十八）

雅思练习总结（十八）

本文章是雅思练习总结（十八），总结了文章《The effects of light on plant and animal species》，内容包括原文精翻，文章脉络总结，单词扩展学习3个部分

1 文章原文及翻译

The effects of light on plant and animal species

翻译：光对动植物的影响

Light is important to organisms for two different reasons. Firstly it is used as a cue for the timing of daily and seasonal rhythms in both plants and animals, and secondly it is used to assist growth in plants.

翻译：光，对有机体都十分重要的，原因有二：一是光可作为植物和动物每日和季节规律的提示；其次，光可帮助植物的生长。

Breeding in most organisms occurs during a part of the year only, and so a reliable cue is needed to trigger breeding behaviour. Day length is an excellent cue, because it provides a perfectly predictable pattern of change within the year. In the temperate zone in spring, temperatures fluctuate greatly from day to day, but day length increases steadily by a predictable amount. The seasonal impact of day length on physiological responses is called photoperiodism, and the amount of experimental evidence for this phenomenon is considerable. For example, some species of birds’ breeding can be induced even in midwinter simply by increasing day length artificially (Wolfson 1964). Other examples of photoperiodism occur in plants. A short-day plant flowers when the day is less than a certain critical length. A long-day plant flowers after a certain critical day length is exceeded. In both cases the critical day length differs from species to species. Plants which flower after a period of vegetative growth, regardless of photoperiod, are known as day-neutral plants.

翻译：大多数生物的繁殖只发生在一年中的某个时间段，因此需要一个可靠的线索来触发他们的繁殖行为。日照长度就是一个很好的线索，因为它提供了动植物的生存环境在一年中完全有迹可循的变化模式。在春季的温带地区，气温每天都在大幅波动，但日照长度却稳步增加，且幅度是有迹可循的。日照长度对生理反应的季节性影响称为光周期现象，这种现象的实验证据数量相当可观。例如，某些鸟类物种即使在隆冬也能通过人工增加日照长度来诱导繁殖（Wolfson 1964）。光周期现象的其他例子出现在植物中。短日植物在日照长度小于某个临界长度时开花。长日植物在超过某个临界日照长度后开花。这两种植物的临界日照长度，因物种而异。而无论光周期如何变化，始终在营养生长期后才开花的植物被称为日中性植物。

Breeding seasons in animals such as birds have evolved to occupy the part of the year in which offspring have the greatest chances of survival. Before the breeding season begins, food reserves must be built up to support the energy cost of reproduction, and to provide for young birds both when they are in the nest and after fledging. Thus many temperate-zone birds use the increasing day lengths in spring as a cue to begin the nesting cycle, because this is a point when adequate food resources will be assured.

翻译：经过不断的进化，鸟类等动物的繁殖季节现在是一年中后代存活率最高的时期。在繁殖季节开始之前，必须建立食物储备以支持繁殖的能量消耗，并为幼鸟在巢中和离巢后提供食物。因此，许多温带鸟类利用春季日照长度的增加作为开始筑巢周期的提示，因为这个时期可以保证充足的食物资源。

The adaptive significance of photoperiodism in plants is also clear. Short-day plants that flower in spring in the temperate zone are adapted to maximising seedling growth during the growing season. Long-day plants are adapted for situations that require fertilization by insects, or a long period of seed ripening. Short-day plants that flower in the autumn in the temperate zone are able to build up food reserves over the growing season and over winter as seeds. Day-neutral plants have an evolutionary advantage when the connection between the favourable period for reproduction and day length is much less certain. For example, desert annuals germinate, flower and seed whenever suitable rainfall occurs, regardless of the day length.

翻译：光周期对植物的适应性也是意义非凡。温带地区春季开花的短日植物适宜生长季节最大限度地促进幼苗生长。长日植物则需要昆虫授粉或种子成熟期较长的情况。温带地区秋季开花的短日植物能够在生长季节和冬季以种子的形式积累食物储备。当繁殖适宜期与日照长度之间的联系不太确定时，中性植物具有进化优势。例如，沙漠一年生植物无论日照长度如何，只要有合适的降雨就会发芽、开花和结籽。

The breeding season of some plants can be delayed to extraordinary lengths. Bamboos are perennial grasses that remain in a vegetative state for many years and then suddenly flower, fruit and die (Evans 1976). Every bamboo of the species Chusquea abietifolia on the island of Jamaica flowered, set seed and died during 1884. The next generation of bamboo flowered and died between 1916 and 1918, which suggests a vegetative cycle of about 31 years. The climatic trigger for this flowering cycle is not yet known, but the adaptive significance is clear. The simultaneous production of masses of bamboo seeds (in some cases lying 12 to 15 centimetres deep on the ground) is more than all the seed-eating animals can cope with at the time, so that some seeds escape being eaten and grow up to form the next generation (Evans 1976).

翻译：此外，有些植物的繁殖季节可能会被推迟到极长的时间。竹子是多年生草本植物，可以保持营养状态多年，然后突然开花、结果并死亡（Evans 1976）。牙买加岛上的 Chusquea abietifolia 竹子在 1884 年开花、结籽并死亡。这些竹子的下一代，则在 1916 年至 1918 年间开花并死亡，这表明这些竹子的营养周期约为 31 年。这一开花周期的气候触发因素尚不清楚，但其适应性意义是显而易见的。同时产生的大量竹子种子（在某些情况下，种子位于地面 12 至 15 厘米深）超过了所有以种子为食的动物吃饱肚子还要多得多的数量，因此一些种子没有被吃掉，而是长大形成下一代（Evans 1976）。

The second reason light is important to organisms is that it is essential for photosynthesis. This is the process by which plants use energy from the sun to convert carbon from soil or water into organic material for growth. The rate of photosynthesis in a plant can be measured by calculating the rate of its uptake of carbon. There is a wide range of photosynthetic responses of plants to variations in light intensity. Some plants reach maximal photosynthesis at one-quarter full sunlight, and others, like sugarcane, never reach a maximum, but continue to increase photosynthesis rate as light intensity rises.

翻译：光对生物体很重要的第二个原因是光合作用。光合作用是植物利用太阳能将土壤或水中的碳转化为有机物质以供生长的过程。植物的光合作用速率可以通过计算其碳吸收速率来测量。随着光照强度的变化，植物的光合作用效率变化也范围也很广。一些植物在四分之一份充足阳光下达到最大光合作用，而其他植物，如甘蔗，则永远不会达到最大值，但随着光照强度的增加，光合作用速率会继续增加。

Plants in general can be divided into two groups: shade-tolerant species and shade-intolerant species. This classification is commonly used in forestry and horticulture. Shade-tolerant plants have lower photosynthetic rates and hence have lower growth rates than those of shade-intolerant species. Plant species become adapted to living in a certain kind of habitat, and in the process evolve a series of characteristics that prevent them from occupying other habitats. Grime (1966) suggests that light may be one of the major components directing these adaptations. For example, eastern hemlock seedlings are shade-tolerant. They can survive in the forest understorey under very low light levels because they have a low photosynthetic rate.

翻译：植物通常可分为两类：耐荫植物和不耐荫植物。这种分类广泛应用于林业和园艺。耐荫植物的光合速率较低，因此生长速率也低于不耐荫植物。植物会在适应某种栖息地生存的过程中，会进化出一系列特征。这种特征会阻止他们占据其他栖息地。Grime (1966) 认为光可能是指导这种适应性的主要因素之一。例如，东部铁杉幼苗耐荫。由于它们的光合作用速率较低，它们可以在光照水平较低的森林下层中生存。

2 文章结构分析

这篇的脉络可总结如下

1. 第一段是总体说明，光对生物们有着非凡的意义，可以作为植物和动物每日和季节规律的提示，并可帮助植物的生长。

2. 第二段、第三段、第四段是说光对植物和动物繁殖时间的影响，因为生物都会在自己认为适宜的时间段来进行繁殖，并会在确定时间后，开展一段时间的准备，而光就可以提供这种适宜时间的提前确定，比如，日照长度小于某个临界长度时开花的短日植物，日照长度大于某个临界长度时开花的长日植物，不受光照影响，只会在营养期后开花的日中性植物，以及在繁殖季节前长期准备的温带鸟类、不同种类日照植物的开花季节选择

3. 第五段是一个特例，竹子，他们会保持营养状态多年，然后突然开花、结籽并死亡。牙买加岛上的 Chusquea abietifolia 竹子，在第二代时，营养周期保持了 31 年，并在开花后，产出了大量的种子。

4. 第六段、第七段是说，植物的光合作用对他们影响，一些植物在四分之一份充足阳光下达到最大光合作用，而其他植物，如甘蔗，则永远不会达到最大值，但随着光照强度的增加，光合作用速率会继续增加。光和速率较低的耐荫植物和光合速率较高的不耐阴植物占据着不同的栖息地，且因为其分别具备的特性，井水不犯河水

文章整体结构如下