シャドーイング練習: Why Are There No Holes Around Trees? - 動画で英語スピーキングを学ぶ

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Trees are the heaviest and largest living things on Earth, with the most massive tree weighing almost 2,000 tons – as much as ten blue whales.

But instead of floating weightlessly in the ocean it reaches 25 stories into the sky, held in place by surprisingly shallow roots.

You’d think trees grow from the ground because, well, they are made of stuff and there is stuff in the ground – but if something so massive and huge ate something down below, it would have to leave holes.

Instead trees are growing by literally eating thin air!

But this is only half of the story because down in the ground, roots are mining rocks in ways weirder than you can imagine.

How does this work?

How to Eat Air to Grow Huge Carbon is the most valuable material for living things.

A chemical multi tool you can make almost everything from – and a good amount of it just floats around in the air and the oceans.

What makes plants so incredibly successful is that over a billion years ago their ancestors became better than any other living thing at harvesting carbon.

They used it to grow and grow and grow.

Today plants make up 80% of the biomass on earth and are the basis for all complex life – all animals eat either plants or animals that eat plants, to get the carbon they need.

Trees are an especially ingenious way plants found to harvest massive amounts of carbon.

Trees are big and heavy and so they need a lot of material.

But the atmosphere is only about 0.04% CO₂.

425 CO₂ molecules per million molecules in the air.

To get a single tonne of carbon a tree has to process 6000 tons, or 5 million cubic meters of air!

This is a lot.

So trees developed sophisticated biological industrial megalopolises: Their crowns.

A huge industrial park network, made from dozens of branches, subbranches and hundreds of thousands of twigs that can sense the sun and shape the tree to grow towards it in slow motion.

They are carrying up to a million leaves, the industrial parks where a tree eats and builds, consuming extreme amounts of resources from the air and fed by the roots down below while vomiting waste and changing the climate around them.

Let’s zoom into a single leaf.

It is made from hundreds of millions of factory cells and optimized to have as much surface area and be as thin as possible to harvest sunlight.

While your skin is hundreds of cells thick, a leaf can be just ten cells top to bottom.

On their top leaves have only a single, ultra thin layer of protective transparent “skin” cells that let light through and keep water in.

Below them are layers of factory cells, filled to the brink with chloroplasts that do the actual work.

Beneath them a spongy layer of loose cells enables gases to travel around.

The whole leaf is traversed by a network of vein-like superhighways, that carry sugars back down and bring water and minerals up from the roots.

At the bottom is another protective layer of cells interrupted by hundreds of thousands of stomata – tiny mouths opened and closed by two guard cells that look a bit like lips.

Each day an adult tree pulls up dozens of liters of water all the way from its roots in the ground to these veins, where about 95% of it is sweated out through hundreds of billions of these tiny mouths.

This cools the leaf factories, which need to stay in direct sunlight as long as possible, and the air around the tree.

And it surrounds the tree with an invisible mist.

The vapor from a forest of billions of trees can seed clouds and create rain.

Rainforest is literal – without the trees the amazon would be a sad dry shrubland or desert.

The other 5% of the water is used to keep the cells alive and to power the factories where the magic happens: Photosynthesis.

We are not going to explain the details here, but in a nutshell, with the energy from the sun, water molecules are split into hydrogen and oxygen.

The oxygen is ejected, while the leftover hydrogen and CO2 are forged and reduced into glucose – a simple sugar that’s both battery and building block.

And the source of most carbon in the world for most animals.

Oxygen is not just garbage to the tree though.

To actually use the energy stored in the glucose, the tree has to burn the sugar, just like we humans do, with cellular respiration.

So all living cells in the tree suck in oxygen – through the tiny leaf mouths, cracks in the bark, and even root tips tapping into tiny air pockets hidden in the soil.

This respiration runs nonstop, and especially at night when the leaf factories stop production.

Trees actually reabsorb some of the oxygen they produce and almost all of the rest gets used up by microbes and everything else breathing nearby.

Most of the world's free oxygen doesn't come from trees but from algae and cyanobacteria in the oceans.

But this is only half of the story because the even more insane parts of trees are the second invisible crown: the underground empire of the roots.

Most of the water a tree needs comes from rainfall, which soaks mainly into the upper layers of soil.

Annoyingly for trees their crowns are big umbrellas, so their roots need to spread out far and wide towards the side.

About 50% of their roots are packed into the top 25 centimeters of soil.

They are not a mirror image of the crown, but a dense, tangled mat, deeply intermingled with their neighbours’.

Only if it’s very dry do roots grow straight down to tap hidden water reserves, in extreme cases more than 20 stories deep.

But this is a rare exception.

Most roots reach down 7m.

But roots have a far more complex job than just catching water.

Just like you can’t build a city from only bricks and steel, trees also need some rare materials: phosphorus to build DNA, nitrogen for proteins and many more.

And all of these are stealthily buried underground.

Rocks, dry patches, nutrients, and rival roots are all scattered unpredictably and chaotically.

To navigate this shifting maze, roots evolved a specialized sensor at their very tip: the root cap.

Each cap is filled with gravity-sensing cells, in which tiny dense particles sink like pebbles settling in a jar of water.

So the root always knows which way is down.

As it pushes forward, specialized cells detect moisture, temperature, chemical gradients and the smallest vibrations from water.

This raw data flows into the root’s command center just behind the tip, where cells produce electrical pulses and move transmitter chemicals around.

Signals from the soil are processed, interpreted and turned into decisions about where to grow.

A single tree has hundreds of thousands of these command centers and they seem to share information with each other.

Once a root has chosen a path, fuzzy little drinking straws called root hairs, loaded with enzymes and transport proteins, begin soaking up water and dissolved minerals.

But many essential nutrients are locked away in solid rock.

So roots evolved to move into the finest cracks.

Once in, they fill with water and swell like tiny hydraulic jacks, creating enough pressure to break even the hardest rock.

Next they release a mix of acids that seep into the fractures and dissolve the bonds that hold nutrients in place.

Claw-like molecules grab them and pull them in before they can slip away.

This sophistication really is stunning but it gets even wilder.

Even with all these tools, to really thrive, the tree needs allies.

And it found them: fungi.

The underground networks of fungi can stretch for kilometers.

They are so small that they can go where roots can’t, slipping between grains of soil to reach distant pockets of nutrients.

But they need food.

So hundreds of millions of years ago roots and fungi formed a trade alliance.

The trees provide a cut of the sugars they produce far up in the sky and fungi collect and give them nutrients and water in return. Some fungi grow directly into the root’s cells, building tiny trade posts, where sugars and minerals change hands.

Others wrap themselves around root tips, weaving between their outer layers, insulating delicate tissues and protecting them against microorganisms.

Today there are thousands of fungal tree ally species, each with its own specialties.

Some only partner with specific tree species, while others are happy to work with almost anyone.

These connections often knit the roots of many trees together into vast underground networks.

Their scale is gigantic.

In just one cubic meter of healthy forest floor, fine tree roots can stretch for several kilometers and for every kilometer of root, there can be hundreds of kilometers of fungal networks.

It’s one of the largest and most intricate living structures on Earth, and may even connect whole forests.

We are only beginning to understand how complex and intricate the relationships between trees, their offspring, relatives and rivals, microbes and fungal networks are.

But the more we’ve learned over the last few decades, the clearer one thing has become: Trees are just so incredibly wild.

And we have so much more to learn.

People once believed that all fungi — even those allied with trees — were just strange plants.

But then, some incredible minds discovered that they were actually an entirely different life form!

This breakthrough in understanding was powered by a combination of technical knowledge and problem-solving skills.

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To explore everything Brilliant has to offer for free for a full 30 days, go to brilliant.org/nutshell, scan the QR code on the screen, or click on the link in the description.

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このレッスンの語彙とスピーキングのポイント

このC1レベルのスピーキングレッスンは、動画「Why Are There No Holes Around Trees?」を教材にしています。繰り返し出てくる語は次のとおりです：tree, root, cells, grow, hundreds。この動画には、シャドーイング用の文が98文、単語が1791語あります。音声の長さは11:04です。話す速さは1分あたり約162語で、日常会話に近い自然なペースです。英語の頻出3,000語に含まれる単語は77%だけなので、語彙は難しめです。

この動画の重要語彙

動画の中で特に難しい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
nutrient 名詞	/ˈnuː.tɹi.ənt/	栄養, 栄養素
molecule 名詞	/ˈmɑ.lɪ.kjul/	分子
mineral 名詞	/ˈmɪn.ə.ɹəl/	鉱物
harvest 名詞	/ˈhɑɹ.vəst/	収穫
microbe 名詞	/ˈmaɪkɹoʊb/	微生物
nutshell 名詞	/ˈnʌt.ʃɛl/	木の実の殻
respiration 名詞	/ɹɛspɪˈɹeɪʃən/	呼吸
intricate 形容詞	/ˈɪn.tɹɪ.kət/	複雑
glucose 名詞	/ˈɡluː.kəʊz/	ブドウ糖, 葡萄糖
vein 名詞	/veɪn/	静脈
breakthrough 名詞	/ˈbɹeɪk.θɹuː/	突破
sunlight 名詞	/ˈsʌnˌlaɪt/	日光, 太陽光
hydrogen 名詞	/ˈhaɪdɹəd͡ʒ(ə)n/	水素
dense 形容詞	/ˈdɛns/	濃い, 密
invisible 形容詞	/ɪnˈvɪzəb(ə)l/	目に見えない, 不可視の

動画に出てくる句動詞

単語	発音	意味
pull up 動詞	/ˌpʊl ˈʌp/	引き上げる

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	are made · is made · is traversed
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	has chosen · we've learned

注意したい発音

話し手はcan't, doesn't, we'veなど、短縮形や弱形を7回使っています。聞こえたとおりの短い形で発音しましょう。

「th」の音: breakthrough /ˈbɹeɪk.θɹuː/, thrive /θɹajv/, algorithm /ˈælɡəɹɪðm̩/
「sh」と「zh」の音: nutshell /ˈnʌt.ʃɛl/, respiration /ɹɛspɪˈɹeɪʃən/, specialize /ˈspɛʃəˌlaɪz/, shallow /ˈʃæloʊ/, subscription /səbˈskɹɪpʃən/
長い単語（アクセントの位置に注意）: respiration /ɹɛspɪˈɹeɪʃən/, invisible /ɪnˈvɪzəb(ə)l/, annoyingly /ʌˈnɔɪjɪŋli/, personalize /ˈpɜː.sə.nə.laɪz/, interactive /ˌɪn.tɚˈæk.tɪv/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: mineral /ˈmɪn.ə.ɹəl/, hydraulic /haɪˈdɹɔːlɪk/, literal /ˈlɪt(ə)ɹəl/, algebra /ˈæl.d͡ʒɪ.bɹə/, particle /ˈpɑɹtək(ə)l/
/v/ — /b/ にならないように、上の歯を下唇に当てる: harvest /ˈhɑɹ.vəst/, vein /veɪn/, evolve /ɪˈvɑlv/, invisible /ɪnˈvɪzəb(ə)l/, dissolve /dɪˈzɑlv/
/f/ — 「フ」ではなく、上の歯と下唇で出す: fungi /ˈfund͡ʒi/, fungal /ˈfʌŋɡəl/, fuzzy /ˈfʌzi/, fracture /ˈfɹæk.t͡ʃʰəː/, offspring /ˈɔfspɹɪŋ/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
まず0.75倍速で一文ずつシャドーイングし、慣れてきたら通常の速度に戻します。
自分の声を録音して元の音声と比べます。nutrient, molecule, mineralなどの単語に特に注意しましょう。

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。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Why Are There No Holes Around Trees? - 動画で英語スピーキングを学ぶ

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