シャドーイング練習: The First Mass Extinction as Explained by Lindsay Nikole - 動画で英語スピーキングを学ぶ
レッスンを作成中...
1
Extinction is a fact of life on Earth.
2
Our planet is always changing, and not every species can handle the changes.
3
So it's pretty normal for a handful of species to go extinct every year.
4
But sometimes, huge changes cause lots of extinction, and tons of species disappear in a relatively short time all over the world.
5
A mess.
6
Extinction.
7
These events are terrifying and fascinating.
8
By studying mass extinctions, we learn how our world got the way it is now, and where it's headed.
9
Right now, rates of extinction are so high that we might be on the verge of a modern mass extinction.
10
Experts predict that if this trend continues, we could lose up to 50% of all species on Earth by 2050.
11
So, for this video series, I'm partnering with Colossal, the de-extinction company, working to prevent the next mass extinction.
12
Throughout Earth's history, there have been five famous mass extinction events, the Big Five.
13
In each one, more than 70% of life on Earth died out.
14
In this series, we're going to explore the causes and effects of each of them, one by one, to lay out what we know about mass extinctions of the past so we can prevent another one.
15
First up is the oldest of the big five, the Ordovician mass extinction.
16
The Ordovician period was from 485 to 444 million years ago.
17
During this time, the Earth was like an alien world.
18
There were no familiar shapes among the continents or oceans.
19
Most of the land masses were in the southern hemisphere, like the supercontinent Gondwana.
20
The world was very warm and had very high sea levels, which created lots of warm, shallow ocean habitats.
21
Those warm oceans are where we find Ordovician life, like Eurypterid sea scorpions crawling along the ocean floor.
22
Some of them got to almost six feet long.
23
Squid-like cephalopods with massive shells drifted through the water.
24
The biggest ones, like Endoceros, were almost 20 feet long.
25
I like those cones a lot.
26
There were ancient corals, sea lilies, sponges, lamp shells, et cetera.
27
This was also the time of the trilobites.
28
Big ones, small ones, smikey, smikey, spiky and smooth, crawling and swimming and burrowing all over the ocean.
29
There were also fish, too.
30
They were strange, jawless species, including eel-like conodonts, and also ones like Sacobambaspis, a tiny jawless fish that had armored plates on their heads.
31
Almost all life at this time lived in the water.
32
The land was almost completely barren, except for some of the earliest land plants that were just starting to creep up.
33
Fossil spores provide evidence that simple non-vascular plants, similar to like mosses and liverworts, forming green carpets over the rocks, very mid-century.
34
At the end of the Ordovician, in the last two million years or so of the period, this alien world was rocked by a global mass extinction.
35
In the fossil record, we see about 85% of species disappear.
36
Trilobites, corals, fishes.
37
Every group experienced major loss.
38
This is the first time that animal life on Earth experienced a global collapse of this scale.
39
That mean Noah.
40
But a mass extinction doesn't happen for no reason.
41
Rocks and fossils from the late Ordovician contained clues to the cause of this catastrophe.
42
Specifically, changes in the chemical makeup of certain minerals reflect a massive climate fluctuation.
43
First, the Earth got slapped with a global cooling, and then slapped with a global warming.
44
A one-two punch of destruction.
45
It starts with an event called the Hernantian Glaciation, the Ordovician Ice Age.
46
Scientists have identified geologic evidence of ice sheets at the South Pole, kind of like the ice that covers Antarctica today.
47
Also, a drop in sea level of about 300 feet, while that water was frozen into ice.
48
Global temperatures dropped at least 5 degrees Celsius, disrupting the formation of certain minerals and leaving telltale evidence in rocks and fossils.
49
All of this was bad for sea life.
50
Colder temperatures were a big problem for any species that got very cozy in those warm waters.
51
And also, as sea levels fell, the water drained away from coastlines and shallow seas.
52
So, their habitats were done-zo anyway.
53
Changes to sea level and water temperature also disrupt ocean chemistry and circulation, which can mess with animal migrations, reproduction, even down to the basic finding food and breathing properly.
54
But an ice age doesn't happen for no reason either.
55
The cause of the cooling was a change in the atmosphere.
56
Minerals from the late Ordovician period show a change in their carbon composition, the kind of change that happens when atmosphere is running low on carbon dioxide.
57
Carbon dioxide is a greenhouse gas, which means it traps heat in the atmosphere.
58
Less CO2 in the air means less trapped heat, means cooler global climate.
59
Exactly why CO2 levels plummeted in the late Ordovician is hard to say for sure, but there are two prime suspects that were suspiciously active at this time in Earth's history.
60
Volcanoes and plants.
61
Volcanoes are where baby rocks come from as lava cools, it forms new solid rock.
62
And if that rock is exposed to the air, it can experience chemical weathering, which is a process that pulls CO2 out of the atmosphere.
63
Lava rocks from the late Ordovician provide evidence that volcanoes were erupting at that time, producing lots of new rocks that were weathering away.
64
But you know what else draws CO2 out of the air?
65
Yeah, plants.
66
Like I said before, land plants were just getting started in the Ordovician, just like we breathe in oxygen to fuel our bodies, plants breathing carbon dioxide to power their photosynthesis.
67
As plants became more common on land, they pulled more and more carbon dioxide from the atmosphere.
68
Land plants also churn up the ground, pulling up mineral nutrients that end up getting washed into the oceans.
69
Similar nutrients can also be released from volcanic eruptions and from weathering rocks.
70
As those nutrients concentrate in shallow waters, they can become fuel for massive blooms of algae, cyanobacteria, which also suck up carbon dioxide.
71
So some combination of land plants, volcanoes, and algal blooms was pulling lots of carbon out of the Ordovician atmosphere.
72
And once the cooling trend got started, it snowballed.
73
As water freezes into ice, sea levels drop, which exposes more land to weathering, which draws down more CO2, which means more cooling.
74
And on, and on, and on.
75
Ice is also very reflective, so sunlight bounces off of it, taking some heat with it.
76
In the late Ordovician, the giant continent Gondwana sat right over the South Pole, so there was lots of room for massive ice sheets.
77
As the ice sheets grew, they reflected more and more heat, and the air got colder and on and on and on.
78
Freezing water also acts as a trap for carbon dioxide.
79
Rain pulls carbon dioxide down with it.
80
When the water freezes the CO2 gets stuck in the ice.
81
This is called a positive feedback loop, a series of events that reinforce themselves.
82
But if you were to ask the Ordovician species they'd say it was very negative for them.
83
Some species were pretty quick to adapt to the changing climate.
84
Certainly the Ordovician fossil sites are full of cold adapted species that establish new ecosystems in these cooler conditions.
85
But then the second slap.
86
Right before the end of the Ordovician the Ice Age All those trends we see in the rocks and fossils become reversed, reflecting new trends of rising temperatures,
87
rising sea levels, and rising carbon dioxide in the atmosphere.
88
Ocean habitats got messed up again.
89
Those cold-adapted ecosystems that had literally just settled were destroyed by warming temperatures.
90
And once again, there were global changes to ocean chemistry and circulation, as well as the shape of shallow ocean habitats.
91
Rising temperatures and CO2 in the ocean can also lead to ocean acidification a change in seawater chemistry
92
that dissolves the shells and skeletons of species like corals and plankton, which form the foundation of ocean ecosystems.
93
The rock record of the latest Ordovician also contains deposits of black shale, a type of rock that forms from sediment deposited in oxygen-poor water.
94
Ocean circulation is responsible for carrying oxygen from the atmosphere down to deeper waters.
95
When that circulation changes, certain waters can become deprived of oxygen.
96
Also, when those massive blooms of algae die, they decompose, which is a chemical process that sucks up oxygen from the water.
97
So, between changing circulation patterns and lots of decomposing microbes, oxygen levels were dropping all over the ocean, suffocating marine life and leaving behind those black shales.
98
And just like ice ages don't start for no reason, they also don't end for no reason.
99
In this case, the reason is most likely those volcanoes.
100
I said before that volcanoes can lead to cooling, which is true, especially on short time scales, but volcanic gases also contain lots of carbon dioxide.
101
So when When volcanic eruptions continue for a long time, they release tons of CO2 into the atmosphere.
102
Then we get those runaway processes again, in reverse.
103
More CO2 traps more heat, so the climate gets warmer.
104
Warmer temperatures melt more ice, which reflects less heat, releases trapped carbon dioxide, leading to more warming.
105
Melting ice also floods the seas, raising sea levels, flooding exposed to land, protecting the rocks from weathering, so less CO2 is being pulled out of the air, and so on, and so on, and so on.
106
And before you know it, the ice age is over.
107
The world is warm again, and ecosystems are in shams.
108
By the time it's all done, about 443 million years ago, most of that alien ordovician biodiversity is gone.
109
About 85% of species became extinct.
110
Some of the hardest hit groups were temperature-sensitive species like corals, sponges, and plankton.
111
And so many other species rely on these animals for food and shelter that with them gone, entire ecosystems collapsed.
112
Some groups eventually recover pretty well.
113
Sea lilies and fish go on to become highly diverse and successful again.
114
Other groups never regain their former glory.
115
Trilobites got hit pretty hard, and they're never again as widespread or varied as they were in the Ordovician.
116
And some groups vanished completely, like those giant Endoceracephalopods.
117
And in case you're wondering, land plants were fine.
118
They were pretty much barely affected.
119
They're probably responsible for this whole fiasco, but it's everyone else that suffered for it, as that's just the way it works.
120
But life on Earth goes on.
121
After the Ordovician comes the Silurian Period.
122
Recovery starts off slow, but gradually, plants and animals develop all new ecosystems throughout the seas, and eventually on land too.
123
And soon the world is once again home to an incredible diversity of life.
124
Until the next Mass Extinction.
125
This is the first episode of a six-part series on mass extinctions.
126
Make sure to follow the Colossal YouTube channel for the next episode, where we're gonna go over the confusing mess of the Devonian Mass Extinction.
127
See ya!
📺 同じチャンネル
✨ おすすめ動画
C13
37 文
The Megatsunami That Struck the Entire Planet
IELTS PrepTOEFL PrepUniversity Students
C12
58 文
Listening part four (THE EXTINCTION OF THE DODO BIRD) @ieltslisteningpro.24
IELTS PrepTOEFL PrepUniversity Students
C12
47 文
We Found Galaxies Too Old for the Universe
IELTS PrepTOEFL PrepUniversity Students
C11
114 文
There's a Giant Hole In Earth's History
IELTS PrepTOEFL PrepUniversity Students
C14
204 文
The Insane Biology of: The Octopus
IELTS PrepTOEFL PrepUniversity Students
C111
52 文
The Most Gruesome Parasites – Neglected Tropical Diseases – NTDs
IELTS PrepTOEFL PrepUniversity Students
C195 文
Paleoworld- Loch Ness Secrets (Part 1)
IELTS PrepTOEFL PrepUniversity Students
C15
87 文
Why Meat is the Best Worst Thing in the World 🍔
IELTS PrepTOEFL PrepUniversity Students
C11
33 文
Join Kai, protect the night sky. Light pollution is hurting cultural knowledge and biodiversity
IELTS PrepTOEFL PrepUniversity Students
C13
22 文
How The Universe Could Destroy Life On Earth
IELTS PrepTOEFL PrepUniversity Students
C14
50 文
IELTS Listening Practice Test 2026 | Section 4 | Coral Reefs | Questions 31-40 | With Answers
IELTS PrepTOEFL PrepUniversity Students
この動画で身につけるスピーキングスキル
英語シャドーイングに最適なこの動画では、2つの重要なスキルが身につきます。まず、科学的な内容を明快に説明するためのリズムとペースのコントロール。講師が「mass extinction」や「Ordovician period」などの専門用語を使いながらも自然に話す様子を観察し、真似ることで、難しい単語でも流れるように発音できるようになります。もう一つは、情報を分かりやすく伝えるための強調の仕方。「85% of species disappear」のような重要なデータを強調する際の声のトーンやストレスを学ぶことで、IELTS スピーキング対策にも役立つ説明力が向上します。
聞き取りに注意すべき発音のポイント
YouTubeで英語学習をする際、ネイティブの発音の繋がりや縮約形に慣れることが大切です。この動画では特に、連結音と弱められた発音が多く見られます。例えば、「a handful of」は「a hɑːndfʊləv」ではなく「a hændfʊləv」と繋がって発音され、「it's pretty normal」は「it's prɪti nɔːrml」と「pretty」の「y」の音が弱まります。また、「tons of species」では「tons of」が「tʌnzəv」となり、「of」の音がほとんど聞こえなくなります。これらのポイントを捉えることで、シャドーイングの精度が上がります。
ネイティブのように話すコツ
shadow speechのコツは、講師のリズムとストレスを徹底的に真似ることです。この動画の講師は、「These events are terrifying and fascinating」のように、重要な形容詞にストレスを置き、文の流れを作っています。また、「First up is the oldest of the big five」のようなフレーズでは、「First up」を軽く発音し、「oldest」を強調することで、聞き手の注意を引きます。シャドーイングをする際は、まず動画を何度も聴き、そのリズムを体で覚えてから、声を出して真似てみてください。shadowing siteなどを利用して、自分の発音とネイティブの発音を比較することも効果的です。
この動画の文法
話し手がよく使っている文型を、動画の実際の表現とともに紹介します。
| 文型 | 動画での表現 |
|---|---|
| 受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる | was rocked · was frozen · were done |
| 関係詞節 who / which + 節 — 人や物について情報を加える | circulation, which can · gas, which means · weathering, which is |
| 現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している | have been · have identified |
シャドーイングとは？英語上達に効果的な理由
シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。