原文：It is animals and plants which lived in or near water whose remains are most likely to be preserved, for one of the necessary conditions of preservationis quick burial, and it is only in the seas and rivers, and sometimes lakes, where mud and silthave been continuously deposited, that bodies and the likecan be rapidly covered overand preserved.

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只有生活在水中或水边的动植物尸体最有可能被保存下来，因为保存的必要条件之一是迅速掩埋，所以只有在泥沙不停淤积的海洋和江河里，有时在湖泊里，尸体之类的东西才能被迅速地覆盖而保存下来。

1) 该句结构比较复杂,整个段落为一个句子。这个句子的基本结构是两个并列复合句。这两个并列句都是强调句,第 1个是 It is animals and plants..., for ...burial, 第2 个是and it is only in the seas and ...preserved。

第1个强调句所强调的是animals and plants which...water，该句还原为非强调句后，其结构应该是The remains of animals and plants which lived in or near water are most likely to be preserved for... burial。

第2个强调句所强调的部分是地点状语 in the seas and rivers。将该句还原为非强调句后，其结构应该是 and bodies and the like can he rapidly covered over and preserved in the seas and rivers, and sometimes lakes, where mud and silt...deposited

which lived in or near water 作定语从句，修饰animals and plants

for one of the necessary conditions burial作原因状语从句，作补充说明。

where mud and silt have been continuously deposited 作非限定性定语从句，修饰 the seas and rivers, and sometimes the lakes.

2) preservation [ˌprezəˈveɪʃn] n. 保护；保养；维护；保全；保存；保留；留存

eg: Water is essential to the preservation of the ecology of the steppe.

水对维持大草原的生态环境是绝对必要的。

silt [sɪlt] n. 泥沙；淤泥；泥沙层；粉砂尘；粉砂 v.泥沙；淤泥；泥沙层；粉砂尘；粉砂

eg: The waterway is clogged with silt.水道被泥沙壅塞。

deposit [dɪˈpɒzɪt] n. 存款；保证金；定金；沉积物；沉淀；放置；押金；竞选押金

v. 放置；安置；把…委托他人保存；使…沉积；下；在银行（或建房互助会中）存；付（一定金额）作为首期分期付款

eg: They deposit waste on unapproved sites. 他们在未经批准的地点抛垃圾。

the like， 相当于such like, 类似的东西

eg: He examined how many times people were first authors on influential studies, and the like.

他研究了很多次那些做过有影响力研究的第一作者，还有类似的。

cover over 遮没

eg: Here's a way you can accelerate and establish a beautiful green moss cover over your garden rocks and concrete features.

这里的方法可以加快建立绿色青苔盖了你们美丽花园岩石和具体特点。

原文：But even in the most favourable circumstances only a small fraction of the creatures that die are preserved in this way before decaysets inor, even more likely, before scavengerseat them. 

即使是在最有利的环境中，死去的生物中也只有一小部分能在开始腐烂前，或更可能在被食腐动物吃掉之前，被这样保存下来。

3) that die作定语，饰 creatures。

set in(常用来表示不好的事情)开始,到来  set in stone 确定；一成不变；板上钉钉的

eg:  We need to have the roof repaired before the bad weather sets in.

我们需要在坏天气到来之前把屋顶修好

scavenger[ˈskavɪn(d)ʒə] n. 食腐动物；清道夫；净化剂；捡破烂的人；清扫工；清除剂

eg: The First Order wants the map. Finn is with the Resistance. I'm just a scavenger.

第一秩序想要那张地图，芬恩是抵抗组织成员，我只是一个拾荒者。

原文：After all, all living creatures live byfeeding onsomething else, whether it be plant or animal, dead or alive, and it is only by chancethat such a fate is avoided. 

因为一切生物都是靠吃别的东西来活命的，不管这种东西是植物还是动物，死的还是活的，因此，生物偶尔才能避免被吃掉的命运。

4) whether it be plant or animal, dead ar alive 是一个让步状语从句, 用的是虚拟语气。it 指 something else. 

and it is only bychance that...为强调句，被强调的部分是状语 by chance。还原为非强调句应该是 and such a fate is avoided only by chance。 

such a fate 指“被吃掉的命运”

5）live by... 靠…生存；靠…生活; 遵循

eg: All my children live by their own labour. 我的几个孩子都自食其力了。

feed on 以…为食

eg: There are huge clusters of organic waste they can feed on.

它们可以以大量的有机废料为食。

by chance 偶然

eg: She has a mental toughness that did not come about by chance.

她的坚韧不是偶然产生的。

原文：The remains of plants and animals that lived on land are much more rarely preserved, for there is seldom anything to cover them over. 

曾在陆地上生活过的动植物的遗体被保存下来的更为罕见，因为陆地上几乎没有什么东西覆盖它们。

原文：When youthink ofthe innumerable birds that one sees flying about, not to mention the equally numerous small animals like field mice and voleswhich you do not see, it is very rarely that one comes acrossa dead body, except, of course, on the roads. 

你可以想象出天上有看得见的飞来飞去、数不清的鸟，地上有不显眼的无数的老鼠和田鼠之类的小动物，但是，除非在路上，很少有人遇到这些动物的尸体。

6) that one sees flying about 为定语从句，修饰 birds。 one 泛指“人们”。flying about 作宾语补足语。

it is very rarely that... roads 中的it是先行主语, that 引导的是真正的主语。

not to mention...为补充说明部分。not to mention 为固定词组，意即“更不用说”“更不屑说”,主要用来强调所要补充说明的部分。

eg:  We cannot afford a house, let alone/not to mention a car.

我们连房都买不起，更不消说买汽车了。

注意该词组与 don't mention it 的区别。don't mention it 用于别人对你表示感谢而进行回答时,意即“不必客气”, eg: 

-Thanks for your help 十分感谢你的帮助。

-Not at all, don't mention it 没什么,不必客气。

7) think of 想起，想象

eg: Think of failures as milestones towards success.

把失败看作通向成功的里程碑。

come across 遇到，偶然碰到 

eg: When you come across such words, check a dictionary to confirm their exact pronunciations.

当你偶然遇到这样的单词时，查字典来确认它们的确切发音。

vole[vəʊl] n. 田鼠，仓鼠

eg:  As he watched, a mink pounced on the vole.

在他观察的时候，一只貂朝那只田鼠猛扑过去。

原文：They decomposeand are quickly destroyed by the weather or eaten by some other creature.

因为它们腐败之后很快就被风化掉，或被别的动物吃掉了。

8) decompose [ˌdiːkəmˈpəʊz] v. 腐败；腐烂；使变质；使腐烂；分解；使…分解

eg: Many chemicals decompose rapidly under high temperature.

许多化学制品在高温下很快分解。

原文：It is almost always due to some very special circumstances that traces of land animals survive, as by falling into inaccessiblecaves, or into an ice crevasse, like the Siberian  [saɪ'bɪərɪən]  mammoths  [ˈmaməθ] , when the whole animal is sometimes preserved, as in a refrigerator. 

几乎总是由于某些特殊的条件，陆地动物的遗体才被存下来，如掉进难以到达的洞穴，或掉进冰河裂缝里，或者像西伯利亚长毛象那样掉进冰窟中，有时整个动物像被放在冰箱里一样被保存下来.

9) 该句为强调句，强调部分是原因状语 almost always... circumstances。

as 引导方式状语从句，as 后面省略了 they survive。

when 意即“这时”补充说明动物掉进冰河裂缝里有时就像被保存在冰箱里一样。

as in a refrigerator 的as后面省略了it is preserved

10) inaccessible  [ˌɪnækˈsesəbl] adj. 达不到的；难以到达的；得不到的；不可接近的；难以理解的；欣赏不了的；不能被看见的；不能被使用的；不接受别人示好的；不易感化的

eg: The city centre is inaccessible to traffic in most places.

市中心许多地方都不通车。

crevasse  [krɪˈvas] n.  裂隙；冰隙；决口

eg: The unfortunate hiker fell into a crevasse.

这个不幸的徒行者落进了裂口处.

原文：This is what happened to the famous Beresovka mammoth which was found preserved and in good condition. 

著名的那林索夫卡长毛象就是这样被保存下来的，而且保存得很好。

11) what引导表语从句。

which 引导定语从句，修饰 the famous Beresovka mammoth 

preserved and in good condition 作主语补足语。

原文：In his mouth were the remains of fir trees[fə:triː] - the last meal that he had before he fell into the crevasse and broke his back. 

它嘴里还留着冷杉 -- 它掉进冰河裂隙折断脊椎柱之前的最后一顿饭。

12) In his mouth were the...是倒装句。该句之所以倒装，是因为主语即 the remains of fir trees 及后面由破折号出的同位语 the last meal 和其定语从句 that he had before ... back 过长

原文：The mammoth has now been restored in the PalaeontologicalMuseum in St. Petersburg. Other animals were trapped in tar pits, like the elephants, saber-toothedcats and numerous other creatures that are found at Racho La Brea, which is now just asuburbof Los Angeles. 

这头长毛象已被修复，现存于圣彼得堡古生物学博物馆。有的动物掉进天然沥清坑里被保存下来，如在兰桥.拉.布里 -- 现在是洛杉矶的郊区发现的大象、剑齿虎和许多其他动物。

13) palaeontological [pælɪɒntə'lɒdʒɪkəl] adj. 古生物学的

tar  [tɑː] n. 柏油；水手；焦油 v. 用柏油覆盖

pit [pɪt] n.  坑；穴；洼；地洞；为特定活动预留或圈围起来的地方；凹；窝；床；腋窝；果核

v. 使互斗；使相斗；使对抗；使竞争；使对立；使有坑；使凹陷；开入检修加油站；除去…的果核；起凹陷

saber-toothed adj. 长着锐利的长犬牙的

suburb [ˈsʌbɜːb] n. 郊区

eg: People planted thousands of trees in the suburb of the city, Urumqi.

人们在乌鲁木齐市郊种植了数千棵树。

原文：Apparently what happened was that water collected on these tar pits, and the bigger animals like the elephants venturedout on to the apparently firm surface to drink, and were promptly boggedin the tar. 

显然，事情的经过是这样：沥青坑里积存了水，大象那样的大动物冒险到似乎坚固的水面上去饮水，立即掉进了沥青坑。

14) what happened 为主语从句, that 引导的是表语从句

15) venture  [ˈventʃə] n. 冒险旅行；冒险行动；企业

v. 敢于冒险；敢做；敢去；敢说；冒昧；冒失去…的风险

eg： We were encouraged by the success of this venture.

这次冒险的成功使我们受到了鼓舞。

promptly [ˈprɒmptli] adv. 迅速地；立即地；敏捷地；准时地

eg: All the daily business has been promptly dealt with.

所有日常工作都得到了及时处理。

bog  [bɒg] v. 使（车辆；人；动物）陷入泥沼 n. 泥沼；沼泽；厕所；酸性泥炭湿地

eg: You must not get bogged down in detail. 你不必纠缠于细节之中。

原文：And then, when they were dead, the carnivores, like the sabre-toothed cats and the giant wolves, came out to feed and suffered exactly the same fate. There are also endless numbers of birds in the tar as well.

大象死后，一些食肉动物，如剑齿虎和大灰狼就来吃大象，结果遭到了同样的命运。沥青坑里还有无数只鸟的尸体。

16) the same fate 指 were promptly bogged in the tar, 意即“也掉进沥青坑”。

carnivore [ˈkɑːnɪvɔː] n. 食肉动物；食肉目哺乳动物