[00:02.35]地球
[00:04.70]READING THE PROPERTIES OF WATER
[00:07.29]阅读 水的特性
[00:09.87]Earth is an ocean planet.
[00:11.76]地球是个水球。
[00:13.64]About three billion years ago,life on our planet began in the deep blue seas.
[00:17.32]大约有三十亿年以前，在我们的星球上，生命从蓝色的海洋深处开始。
[00:21.00]Ninety-nine percent of the living space on earth is in the oceans.
[00:24.28]地球上99%的生存空间是在海洋中，
[00:27.56]Marine life is incredibly rich and varied.
[00:30.38]海洋生物非常丰富。
[00:33.20]There are about five million species in the oceans
[00:35.88]海洋中大约有五百万种生物，
[00:38.56]and we have yet to learn much about them.
[00:40.69]还有很多有待我们去研究。
[00:42.81]Life in the oceans ranges from the tiniest plankton
[00:45.30]海洋中的生物种类包括最小的浮游生物
[00:47.78]all the way up to giants like sharks and whales.
[00:50.51]和像鲨鱼和鲸等最大的动物。
[00:53.24]What makes the ocean such a great place to live?The answer is water.
[00:56.57]是什么使海洋成为一个如此大的居住地呢？答案就是水。
[00:59.90]CHEMICAL STRUCTURE
[01:01.37]水的化学结构
[01:02.85]The chemical structure of water makes it an excellent medium for life.
[01:05.93]水的化学结构使它成为极好的生命介质。
[01:09.02]Water is actually quite simple,but the way the water molecule if formed
[01:12.29]水实际上很简单，但水分子的构成方式赋予了它的独特的性质。
[01:15.57]gives water its unique properties.
[01:19.73]The water molecule is made up of two hydrogen atoms and one oxygen atom.
[01:23.36]水分子是由两个氢原子和一个氧原子组成。
[01:26.99]They form a polar molecule,that is,
[01:29.56]两个氢原子形一个有阴阳极的微粒子，
[01:32.13]one with a slightly positive end and a slightly negative end.
[01:35.36]即一个氢原子稍微带有阳极，另一个带有阴极。
[01:38.59]Because water is polar,it can break down both solids and gases.
[01:42.27]因为水是有阴阴极的，它可以分解或溶解气体和固体。
[01:45.95]The nutrients in whatever falls into the ocean
[01:48.37]无论什么物质中的营养成分落入海洋中，
[01:50.79]quickly become available to other living creatures.
[01:53.31]就会让其了生物得到。
[01:55.83]The chemical structure of water
[01:59.77]also makes it different from almost everything else on earth.
[02:02.96]水的化学结构使得它几乎与世界所有其它物质不同。
[02:06.15]Water is a liquid at room temperature and has a relatively high freezing point.
[02:10.12]水在室温下成液体状态，它且具有相对高的冰点。
[02:14.09]SALINITY
[02:15.52]盐度
[02:16.96]When dissolved gases and solids mix with pure water,
[02:19.89]当净水和可溶解的气体与固体混合时，
[02:22.81]the result is sea water,or salt water.
[02:25.79]结果就是海水或盐水。
[02:28.77]The salinity of the earth's oceans is about thirty-five per thousand,
[02:32.05]海洋的含盐量是35%。
[02:35.32]meaning that there are about thirty-five grammes
[02:37.81]即在1千克水中含有35克被溶解的气体和固体。
[02:40.29]of dissolved solids and gases in one kilogramme of water.
[02:43.62]尽管净水赋予了水的主要特性，
[02:46.95]Even though the pure water is what gives sea water its main properties,
[02:50.19]但是海水的盐度影响它的重要及冰点。
[02:53.43]the salinity of sea water affects both its weight and freezing point.
[02:56.76]但是海水的盐度影响它的重要及冰点。
[03:00.09]Salt water has a lower freezing point and is heavier than pure water.
[03:03.51]盐水比净水具有更低的冰点，比净水更重。
[03:06.93]DENSITY
[03:08.46]密度
[03:09.99]Density is the relationship between mass and volume
[03:12.88]密度是质量与体积之间的关系，
[03:15.76]and is measured in kilogrammes per cubie metre.
[03:18.24]密度用千克每立方米做单位（千克每立方米）
[03:20.72]The density of pure water is 1,000 kg/m3,
[03:24.06]水的密度是1000千克/米3。
[03:27.39]meaning that one cubic metre of water weighs one thousand kilogrammes.
[03:31.02]即一立方米水重一千千克。
[03:34.65]If a substance has a higher density,say 5,000 kg/m3,it will not float on water.
[03:39.57]如果某种物质有更高的密度，如5,000知克/立方米，它就不会浮在水面上。
[03:44.50]Marine animals and plants take a advantage of the density of water
[03:47.76]海洋生物利用水密度。
[03:51.03]With the right kind of body,it is possible to float around in the ocean
[03:54.31]有合适的体形，在海洋中就能四处漂浮，
[03:57.58]and let the water do the work.
[03:59.62]让海水发挥作用。
[04:01.66]When water freezes,its density decreases.
[04:04.30]当水结冰时，它密度会减少。
[04:06.94]If it did not,the oceans would be frozen solid.
[04:09.76]若不是这样，整个海洋就会冻结成固体。
[04:12.58]HEAT CAPACITY
[04:14.05]热容
[04:15.53]Heat capacity is the amount of energy it takes to raise the temperature of a substance
[04:19.25]热容指的是一种物质的温度升高一摄氏度所需要的能量。
[04:22.97]by one degree centigrade.
[04:26.81]The heat capacity of water is relatively high.
[04:29.44]水的热容相对很高。
[04:32.07]Water can absorb and give off a lot of heat without big changes in temperature,
[04:35.89]温度改变不大，
[04:39.72]thus creating a stable environment.
[04:41.94]这样形成了稳定的环境。
[04:44.16]Most animals and plants are sensitive to large or sudden changes in temperature,
[04:47.70]大多数动物和植物对于巨大的或突然的温度变化很敏感，
[04:51.24]so the ocean is a safe and comfortable habitat.
[04:53.72]因而海洋是一既安全又舒适的栖息地。
[04:56.20]The water in the oceans also keeps the temperature of the earth steady
[04:59.32]海洋中的水也通过吸收或释放热量使地球的温度保持稳定。
[05:02.45]by absorbing and giving off heat.
[05:06.89]OCEAN MOTION
[05:08.41]海洋运动
[05:09.94]Since changes in slainity and temperature affect water's density,
[05:13.42]由于盐度和气温变化影响水的密度，
[05:16.89]the water in the ocean is always moving.
[05:19.37]海洋中的水一直在运动。
[05:21.85]Dense water sinks and less dense water is pushed to the surface.
[05:25.28]密度大的水下沉，密度较小的水被推到海面。
[05:28.70]This circulation adds energy to the marine ecosystems and moves nutrients around.
[05:32.93]这种循环为海洋生态系统增加了能量并使营养成分四处游动。
[05:37.16]Isn't it amazing that a single substance can be so important to our planet
[05:44.53]and even the whole universe?
[05:48.00]Water,which seems so simple and common,is what makes life possible.
[05:55.37]Of all the resources on earth-oil,gas,gold and so on
[06:04.12]-nothing is as precious as a drop of rain.
[06:09.08]Learning about the properties of water helps us understand life on our planet.
[06:16.45]The most important thing we can learn about water,however,
[06:21.91]is that we must protect it and use it wisely.
[06:27.06]Our future depends on it.
[06:30.92]INTEGRATING SKILLS
[06:34.15]综合技巧
[06:37.37]Reading NATURE'S NURSERY:ESTUARIES
[06:40.05]阅读 自然的保育院：入海口
[06:42.73]As the oceans are the source of life ib earth,
[06:47.30]the estuaries are our planet's nurseries.
[06:52.06]An estuary is the body of water where a river meets the ocean.
[06:54.88]入海口就是一条河与海洋交汇的有很多水的地方。
[06:57.70]Salt water from the ocean and fresh water from the river
[07:00.43]从海中来的盐水和河流中来的淡水在入海口混合在一起。
[07:03.16]mix together in an estuary.
[07:07.23]This mixing of fresh and salt water
[07:09.41]这种盐水和淡水的混合
[07:11.60]creates a unique environment filled with life of all kinds-
[07:14.38]形成了一具独一无二的、充满各种生物的环境-
[07:17.16]a zone between the land and the sea.
[07:19.38]位于陆地与海洋之间的一个过渡的区域。
[07:21.60]Estuaries are the homes of thousands of animals and plants.
[07:24.40]入海口是成千上万种动植物的栖息地。
[07:27.19]Many cities and towns are built near estuaries,
[07:29.62]很多城市和城镇入海口建起，
[07:32.05]and a lot of fish is caught in estuaries.
[07:34.37]大量的鱼在入海口被捕捞。
[07:36.70]Estuaries are great places for nature's young ones.
[07:39.34]入海口对于自然中的细小生命来说是非常重要的地方。
[07:41.98]Here,animals can enjoy all the many of the benefits of teh oceans
[07:44.91]在这里，动物可以避开很多危险
[07:47.85]without having to fact many of the dangers.
[07:50.03]从而尽情享受海洋给其带来的益处。
[07:52.22]Tides provide energy for the ecosystems,
[07:54.54]潮汐为生态系统提供了能量，
[07:56.87]but estuaries are protected from waves and storms by islands,mud or sand
[08:00.73]但入海口受到保护使其免于受到波浪及岛屿、泥沙的袭击。
[08:04.60]Nutrients arrive in estuaries from both the land and the ocean.
[08:07.58]从陆地和海洋来的营养成分到达入海口。
[08:10.55]The density of living creatures is higher than in any other habitat on earth.
[08:13.83]生物的密度比地球上其他栖息地要高。
[08:17.11]The diversity of life in estuaries is incredible-birds,fish,marine mammals,
[08:21.04]入海口生物的多样性是惊人的-鸟、鱼、海洋哺乳动物、
[08:24.97]shellfish and other species all come here to live,feed and reproduce.
[08:28.85]贝类以及其它物种都来这和生活、捕食及繁殖。
[08:32.73]Estuaries are also important because they absorb nutrients
[08:35.60]入海口还非常重要是因为他们吸引从内陆来的水中的营养成分
[08:38.48]and pollutants from water coming from inland sources,
[08:41.14]与污染物，
[08:43.81]thus cleaning our water.Unfortunately,
[08:46.18]这样就净化了水，不幸的是，
[08:48.56]this function also makes estuaries very sensitive to environmental pollution.
[08:51.94]这种功能也使入海口对于环境污染特别敏感。
[08:55.33]Since estuaries protect animals and plants from storms and floods
[08:58.46]既然入海口保护动植物不受风暴及洪水侵袭，
[09:01.60]and prevent erosion,protecting estuaries is very important.
[09:04.57]防止侵蚀，对其保护就非常重要。
[09:07.55]Finally,estuaries provide both recreation and education for human beings.
[09:11.24]最后，入海口既为人类提供了娱乐活动又提供了救育资源。
[09:14.92]Most of us enjoy fishing,swimming and having fun on the beach,
[09:17.95]我们大都喜欢在海滨钓鱼、游泳和游玩。
[09:20.98]and scientists and students have endless opportunities
[09:23.55]科学家们和学生有无数的机会研究
[09:26.13]to study a variety of life in the habitat.
[09:28.61]在这个地方的多种生物。
[09:31.09]Estuaries also contribute to the economy through tourism and fishing.
[09:34.32]入海口可通过旅游业和渔业促过经济的发展。
[09:37.54]INTEGRATING SKILLS
[09:50.81]Reading LIFE IN THE OCEAN
[09:55.28]The earth's oceans can reach depths of up to 11,000 metres.
[10:01.94]That is deep enough to cover Mt Qomolangma!
[10:06.67]The oceans are incredibly large and contain several different habitats.
[10:13.51]To make it easier to describe the various parts of the oceans,
[10:19.26]marine scientists usually divide the oceans into five zones.
[10:26.23]Each zone is different mainly as a result of how much sunlight reaches it.
[10:32.89]Most of the life in the ocean can be found in the first zone,
[10:38.96]which begins at the surface and goes down about 200 metres.
[10:45.51]Because there is sunlight at this level,plants are able to grow.
[10:51.57]Marine animals such as dolphins,sharks,sea turtles and sea lions,
[10:59.12]and of course a variety of fish,
[11:03.09]live in the sunlit part such as dolphins,
[11:07.45]It is difficult to hide from other animals in this area,
[11:12.73]but many species have adapted by becoming dark on the top
[11:18.58]and light on the bottom.
[11:21.95]This makes it diffucult to see them against the dark water below
[11:27.91]and the blue sky above.
[11:32.17]The second zone starts at 200 metres and goes down to about 1,000 metres.
[11:39.72]Some sunlight can reach this level,but it is not enough for plants to grow.
[11:47.08]Because this zone is relatively dark,
[11:51.73]may of the creatures that live here are able to make light with their body.
[11:59.10]The light from these animals makes the water look like a sky
[12:04.66]with moving stars in it.
[12:08.42]The third zone of the ocean is dark.
[12:12.87]This place,about 3,000 metres deep,may not seem a likely habitat,
[12:20.31]but there are more creatures here than one might think.
[12:25.67]Most of the animals that live here are black or red because of the lack of light.
[12:33.42]At this depth,a slow shower of what looks like snow is falling.
[12:40.40]This phenomenon,called"marine snow",
[12:45.65]is actually nutrients falling towards the bottom of the ocean.
[12:51.71]It is important source of food for the creatures that live in the deep.
[12:57.59]Below 4,000 metres,
[13:01.24]the temperature is near freezing and there is no light at all
[13:07.12]In fact,the zone is so dark and empty
[13:12.76]that scientists named this zone after the Greek word for"no bottom".
[13:19.01]There is not much life to be found
[13:23.24]in this cold and unpleasant part of the ocean,
[13:27.78]but some small creatures still manage to survive here
[13:33.35]despite the high water pressure.
[13:37.19]Few of the animals inthe ocean can dive this deep.
[13:42.23]One exception is the sperm whale,
[13:46.78]which slows its heartbeat in order to reach this zone as it hunts for food.
[13:53.85]The very deepest part of the ocean if found 2,000 metres further down.
[14:00.93]At this depth,the water pressure is extremely high
[14:06.68]and life is very difficult for the few creatures that live here.
[14:12.45]Compared to the other zones,this one has very little life.
[14:18.62]Since there is no light here,
[14:22.38]some of the animals do not have eyes.
[14:27.84]When scientists explored the very deepest parts of the ocean,
[14:33.40]they did not expect to find any life at all.
[14:38.58]However,it turned out that there are creatures
[14:43.54]that can live even in habitats as far down as 10,000 metres.
[14:51.12]They usually survive by living close to deep sea vents,
[14:57.46]"chimneys"that send out gases from within the earth.
[15:03.11]Unlike all other living things on the earth,
[15:07.76]which get their energy from the sun,
[15:11.73]the creatures that live here use chemicals from the vents to stay alive.
[15:18.99]Next time you look at the ocean from the beach or on a map,
[15:24.13]remember that what you are seeing is only the surface
[15:29.59]-Only the beginning of the large and caried adventure that is ocean |