史上最瘋狂的六次生物大滅絕：英語精讀講義

Over 99% of the animal species that have ever lived are now extinct. 文法

曾經存在過的動物物種中，如今已有超過99%滅絕。

And sometimes an event occurs causing changes so drastic 文法

而有時，一場事件會帶來極其劇烈的變化，

that most species are completely wiped out within a short period of time. 片語動詞

讓大多數物種在短時間內徹底消失。

So here are the five most incredible mass extinctions ever to occur

以下就來看看史上最不可思議的五次大滅絕，

and a look at whether the sixth might be happening right now. 文法

以及第六次大滅絕是否可能正在此刻發生。

440 million years ago was the Ordovician extinction.

4億4千萬年前發生了奧陶紀大滅絕。

At that time most creatures swam or crawled in shallow seas.

當時，多數生物都在淺海中游動或爬行。

As newly created volcanic rock was worn down by water and wind, 片語動詞

新形成的火山岩在水與風的侵蝕下逐漸風化，

it reacted with carbon dioxide and absorbed it.

會與二氧化碳產生反應並將其吸收。

As a result, carbon dioxide levels dropped, 表達脈絡

因此，二氧化碳濃度下降，

temperatures fell and water got locked away as ice.

氣溫降低，水則以冰的形式被封存。

This caused ocean levels to drop and shallow seas to drain 文法

這使海平面下降、淺海乾涸，

and after several cycles of growing and shrinking glaciers,

而在冰河經過數次擴張與消退後，

about 86% of species were lost forever.

約86%的物種永遠消失了。

Then over millions of years the oceans slowly repopulated with fish

隨後數百萬年間，魚類慢慢重新遍布海洋，

and the land was colonized by early plants. 用詞

早期植物也開始占據陸地。

These plants were then eaten by the first crawling and flying insects.

接著，最早的爬行與飛行昆蟲開始以這些植物為食。

Then 374 million years ago

到了3億7千4百萬年前，

these new plants contributed to the next mass extinction. 片語搭配

這些新植物促成了下一次大滅絕。

The plants absorbed enough carbon dioxide to create another round of global cooling.

這些植物吸收了足夠多的二氧化碳，引發新一輪全球降溫。

They changed soil causing nutrients to wash into the ocean

它們改變土壤，使養分被沖入海洋，

creating enormous amounts of algae which sucked up oxygen. 片語動詞

催生出大量藻類，而藻類又吸光了氧氣。

More than half of the ocean species essentially choked to death.

超過一半的海洋物種幾乎都是窒息而死。

Although somewhere in the world a small family of fish with foot-like fins and lungs managed to scrape by. 片語動詞

不過，在世界某個角落，一小群長著足狀鰭和肺的魚勉強存活下來。

Over the next 100 million years these creatures would evolve into amphibians, 文法

接下來1億年間，這些生物逐漸演化成兩棲類、

reptiles, and nearly all modern land animals.

爬蟲類，以及幾乎所有現代陸生動物。

250 million years ago is the Permian extinction.

2億5千萬年前發生了二疊紀大滅絕。

The single worst mass extinction in history,

這是史上最嚴重的一次大滅絕，

70% of life on land and over 95% of life in the oceans was wiped out.

70%的陸地生命與超過95%的海洋生命被徹底消滅。

Billions of tons of volcanic gases destroyed the ozone layer

數十億噸火山氣體摧毀了臭氧層，

and the average ocean temperature hit 40 degrees Celsius 用詞

海洋平均溫度達到攝氏40度，

which is hotter than most hot tubs.

這比大多數熱水浴缸的水還燙。

Acid rain fell all over the planet devastating life on land.

酸雨席捲全球，重創陸地生命。

Life had only 50 million years to recover until the fourth mass extinction came.

生命只有5千萬年的恢復時間，第四次大滅絕便接踵而來。

At this time early small dinosaurs roamed the land.

當時，早期的小型恐龍已在陸地上四處遊蕩。

A huge volcanic rift opened in the middle of the planet

地球中部裂開了一道巨大的火山裂谷，

eventually splitting the Americas from Europe and Africa and forming the Atlantic Ocean.

最終將美洲與歐洲、非洲分開，並形成大西洋。

The volcanoes spewed out carbon dioxide increasing temperatures 片語動詞

火山噴出大量二氧化碳，使氣溫升高，

and killing about 80% of the species around at that time.

並殺死當時約80%的物種。

Yet in this newly emptied world dinosaurs did extremely well

然而，在這個重新變得空曠的世界中，恐龍卻極為興盛，

and during the next 135 million years

而在接下來的1億3千5百萬年間，

they grew to become some of the largest land animals

牠們逐漸成為體型最龐大的陸生動物之一，

the world had ever seen. 文法

是這個世界前所未見的龐然大物。

But all good things must come to an end. 慣用語

但再美好的時代也終會落幕。

Many scientists believe that the extinction of dinosaurs

許多科學家認為，恐龍的滅絕

was caused by an asteroid

是由一顆小行星造成的。

the size of a small town 片語搭配

這顆小行星有一座小鎮那麼大，

crashing into what is now Mexico's Yucatan Peninsula. 文法

撞上如今墨西哥的猶加敦半島。

The impact shot millions of tons of dust into the atmosphere

撞擊將數百萬噸塵埃轟入大氣層，

blocking out sunlight and spelling an end to all large dinosaurs. 片語搭配

遮蔽陽光，也宣告所有大型恐龍的末日。

The small ones that survived evolved into birds.

倖存下來的小型恐龍後來演化成鳥類。

The world was now primed for a small scuffling rat-like creature, 用詞

世界就此為一種四處竄動的鼠狀小生物準備好舞台，

the ancestor of all modern mammals.

牠正是所有現代哺乳動物的祖先。

Within 50 million years its descendants

在5千萬年內，牠的後代

from wildebeest and whales to horses and us humans

從牛羚、鯨魚到馬和我們人類，

have diversified and grown to dominate

不斷分化壯大，最終主宰了

nearly every available environment on Earth.

地球上幾乎所有可利用的環境。

So where does that leave us now 65 million years later? 表達脈絡

那麼，6千5百萬年後的今天，我們又處於什麼境地？

Well, human dominance of Earth has led to big changes too

人類對地球的主宰同樣帶來巨大改變，

except the changes of today are happening over decades not millennia. 表達脈絡

只不過，今天的變化以數十年而非數千年為尺度發生。

Carbon dioxide levels implicated in so many of the past extinctions 用詞

在過去多次大滅絕中都被視為重要因素的二氧化碳濃度，

have climbed at least 25% in just the last 50 years,

光是過去50年間就至少上升25%，

almost no time in geological terms. 片語搭配

從地質尺度來看，幾乎只是一瞬間。

In addition to climate change we've exterminated hundreds of species

除了氣候變遷，我們還使數百個物種滅絕，

by hunting, fishing, habitat destruction, and pollution.

方式包括狩獵、捕魚、棲地破壞與污染。

It's been estimated that the current species extinction rates 文法

據估計，目前的物種滅絕速度

are between 100 and 1,000 times higher 文法

要高出100至1,000倍——

than the natural background rate

這是與自然背景滅絕率相比；

and that if all the species that are currently threatened

而且，如果目前所有因族群數量下降

by declining populations actually do go extinct, 文法

而受到威脅的物種真的全部滅絕，

we may reach the level of a true mass

我們或許就會達到真正的大滅絕級別，

extinction in just a few hundred years.

而這只需要短短幾百年。

And while all the mass extinctions of the past have had some survivors,

儘管過去每次大滅絕都有一些倖存者，

it's worth remembering that the creatures at the top of the food chain 講解

但值得記住的是，位於食物鏈頂端的生物

are usually hit the hardest.

通常遭受的打擊最為沉重。

We may just be setting the stage for history to repeat itself 慣用語

我們或許正在為歷史重演搭好舞台，

and for some small unexpected organism to replace us

讓某種出乎意料的小生物取代我們，

as the planet's dominant form of life.

成為這顆星球上的主導生命形式。

Curious about the coolest animals that existed during these mass extinctions?

想知道這些大滅絕時期有哪些最酷的動物嗎？

Check out our new video

快來看看我們的新影片

Five Insane Creatures we wish still existed 文法

《我們真希望還沒滅絕的五種瘋狂生物》，

over on our AsapTHOUGHT channel

就在我們的AsapTHOUGHT頻道上，

which explores some of the neatest and most absurd creatures

影片將帶你探索一些最奇特、最荒謬的生物，

through history that are no longer with us. 慣用語

牠們曾存在於歷史長河中，如今卻已不復存在。

There's a link in the description for that video.

影片連結就在說明欄中。

And subscribe for more weekly science videos.

別忘了訂閱，收看每週更新的更多科學影片。