Prática de Shadowing: The Hunters: Sundews & the Venus Flytrap - Aprenda a falar inglês com vídeo
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A plant that hunts.
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A leaf that snaps shut in a tenth of a second and counts to two before it does.
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This is not a single weird mutation in a single weird species.
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It is a whole family, a small one, that turned its leaves into traps and runs on electrical signals like a nerve.
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Welcome to Droseraceae.
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About 250 species, give or take.
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Almost all of them carnivorous, and almost all of them living where the soil is too poor to feed an honest plant.
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It is a small family doing something enormous.
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The famous one is the Venus flytrap, Dionea massipula, the leaf that closes in roughly 100 milliseconds.
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But the family also built the sundews, Drosera, which catch insects on sticky tentacles, and Aldrovanda, the water wheel plant,
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which does the fly trap trick underwater, with no roots at all.
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Three genera, three different traps, one impossible idea.
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Stop eating dirt and start eating the things that crawl across it.
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It is also the family that engineers study when they want a machine that grabs without a motor.
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Charles Darwin thought this family was wonderful.
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He spent years dropping bits of meat and egg onto sundew leaves and watching them curl.
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And in 1875, he published a whole book about it called Insectivorous Plants.
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He was right to be delighted.
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This is the family that proved a plant can move, can count, and can digest its own prey.
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all with no muscles and no brain.
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Let's start with the snap.
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The Venus Flytrap does not close because it is fast.
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It closes because it is loaded.
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The open trap is a leaf held concave, bent outward like a bowstring drawn and waiting.
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That shape is unstable.
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The leaf is storing elastic energy the way a spring stores it, and it is held there by turgor pressure,
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the water pressure that keeps every plant cell rigid.
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When the right signal arrives, the pressure changes, the leaf buckles, and it flips from concave to convex,
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from open to closed, in roughly 100 milliseconds.
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That is the fastest movement any plant makes.
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But the trap is not a hair trigger.
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Each half of the leaf carries a few trigger hairs, and a single touch does almost nothing.
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The plant needs two touches within about 20 seconds of each other before it will spend the energy to close.
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The two touches can land on the same hair or on different ones.
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A raindrop will not fool it because a raindrop does not struggle and it does not tap twice.
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One touch the plant remembers.
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A second touch it acts.
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A living timer with no clock.
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And if the second touch never comes, it forgets and resets.
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Once it closes, the trap narrows and only seals tight if it keeps feeling the prey move.
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Then it forms a sealed pocket, a kind of stomach, and the leaf opens again days later, empty.
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It is a counting plant, and what it is counting is electrical.
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A Venus flytrap fires an action potential, a spike of electrical voltage, the same kind of signal that fires down your own nerves.
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When an insect touches a trigger hair, ion channels in the cell membrane open, calcium floods in, and a voltage wave races across the leaf.
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This is the clearest demonstration we have that plants have excitable cells.
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They have no nerves and no brain, but they speak the same electrical language your neurons use.
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The first person to measure it was doctor named John Burden Sanderson who wired up a flytrap in the 1870s
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and watched the voltage jump.
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Two spikes, about 20 seconds apart, and the leaf buckles shut.
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The signal is all or nothing, just like a nerve, and a weak touch fires the same size spike as a strong one.
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The sensitive plant, mimosa, folds its leaves the same way, on the same kind of electrical fire engineers have noticed.
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The flytrap's snap is a bi -stable mechanism, a structure with two stable shapes that flips between them,
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and that is exactly the trick people want for soft robots.
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Copy the buckling leaf and a gripper can grab fast with almost no motor
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and almost no power because the leaf does the work and the energy is already stored.
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And if you put electrodes on a plant and read its action potentials, you have a living sensor,
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a plant cyborg that fires when it is touched or stressed or thirsty.
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Farmers are already wiring crops this way to catch drought before the wilt shows.
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The plant is already wired.
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We are just listening to it.
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The sun dews, Drosera, do not snap.
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They stick.
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A sundew leaf is covered in tentacles, each one tipped with a bead of glistening mucilage, the dew that gives the plant its name.
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To a fly, it looks like water or nectar.
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It is glue.
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The insect lands, touches a droplet and is caught.
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The nearby tentacles sense the struggle and slowly curl inward, holding over the prey and pressing it against the leaf.
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The movement is not fast, it is patient.
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A sundew can take hours to close around a fly.
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Then the leaf secretes enzymes, proteases that break down protein,
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phosphatases, esterases and the sundew digests its meal right there, on the surface and absorbs what it needs through the leaf itself.
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The whole leaf becomes a temporary stomach and when the meal is done, it resets, unfurls and waits for the next visitor.
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With roughly 240 species, Drusera is the most diverse group of carnivorous plants on Earth and it grows on every continent except Antarctica.
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Australia is its great stronghold, with species that survive dry summers as underground tubers.
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Darwin called the sundew one of the most wonderful plants in the world.
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The chemists have noticed too.
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The same digestive enzymes and the same wet, sticky, self -cleaning surface are exactly the properties people want for biomimetic materials,
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adhesives that grip, digest, and let go without leaving a residue.
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And then there is the family's strangest member, Aldrovanda vesculosa, the waterwheel plant.
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It is a Venus flytrap that gave up on land.
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It lives underwater, floating free,
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with no roots at all and its traps are tiny snap traps strung along a stem like the blades of a wheel,
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which is where the name comes from.
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Each trap is only a few millimeters across, and it snaps shot on small aquatic creatures, water fleas and mosquito larvae,
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in a fraction of a second.
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It is among the fastest movements any plant makes underwater.
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Same family, same snap, a different medium.
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With no roots, Aldrovanda takes its minerals straight from the prey it catches.
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It overwinters as a tight little bud called a turian resting on the bottom until the water warms.
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What is remarkable is that the snap trap evolved more than once, even within this one small family.
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Dianaea on land, Aldravanda in the water, and the flypaper trap of the sundews is a third design entirely.
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Three genera reinventing the trap again and again, as if the family could not stop solving this same problem.
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Aldravanda is a single species, and it is now rare, scattered across the old world and declining almost everywhere it still survives.
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It has already vanished from large parts of its old range.
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Carnivory, though, is not a Drosaraceae invention.
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It evolved independently, over and over, in at least six separate lineages of flowering plants.
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The tropical pitcher plants, Nepenthes, belong to a separate family, Nepenthesae.
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The American pitcher plants, the trumpet pitchers of Saracenia, the cobra lily, Darlingtonia, the sun pitchers,
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Heliamphora, belong to another separate family, Saraseniaceae.
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The Australian pitcher plant, Cephalotus, sits in a family of its own.
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And the corkscrew plants, Genlicia, and the bladderworts, Utricularia, are yet another family,
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Lentibulariaceae, with traps that suck prey in underwater.
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Different ancestors, different traps, the same answer.
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Why does it keep paying?
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Because these plants do not live where food is easy.
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They live in bogs, wet, acidic, nutrient -poor ground, where the nitrogen and phosphorus a plant needs are locked away or washed out.
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A normal plant starves there.
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A plant that can fly trap or glue trap or pitfall trap the insects wandering through gets its minerals from the air.
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One bug at a time time.
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It still photosynthesizes for energy.
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The trap is not for calories.
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It is for fertilizer.
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But carnivory is not free.
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Building a trap and making digestive enzymes costs the plant something.
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So it only pays where the soil is poor and the sun and water are good enough to keep the leaf alive.
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And the pitcher plants do not even move.
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They just wait with a pitfall full of fluid at the bottom of a slippery tube.
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The worse the dirt, the better the trap has to be.
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Which is exactly why convergent carnivory is not an accident.
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It is a solution that evolution keeps arriving at.
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And here is the part that should not be true.
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The Venus flytrap, the most famous carnivorous plant in the world is native to a range you can almost drive across in an afternoon.
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It grows wild in a thin strip of the Carolinas, within about 75 miles of Wilming to North Carolina,
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and in a sliver of South Carolina beside it.
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That is almost the entire wild range of the species.
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And it is being stolen.
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Wild flytraps are dug up by the thousands and sold because a poached plant is cheaper than a grown one.
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In North Carolina, digging them up is a felony, and still they disappear.
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On top of that, the bogs they need are drained, paved, and fire -suppressed until there is nothing left to come back to.
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The flytrap depends on fire the way a pine forest does to clear the competition and let the bog stay open.
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By any honest accounting, it is an endangered plant, protected by law and still declining,
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with a wild population that is a small fraction of what it once was.
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So here is the only ask.
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If you want a Venus flytrap, buy one that was grown in a nursery.
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There is no reason to buy a wild one.
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Nurseries propagate these plants by the millions, by tissue culture, for a few dollars each, and a cultivated flytrap is healthier,
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legal, and not stolen out of a bog.
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If you ever see one in the wild, look, take a photograph, and leave it exactly where it is.
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The plant that eats insects should not be eaten by us.
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Subscribe.
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There is a lot more weirdness down here.
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Vocabulário e dicas de fala para esta lição
Esta aula de conversação usa o vídeo “The Hunters: Sundews & the Venus Flytrap”. As palavras que mais se repetem: plant, trap, leaf, flytrap, snap. Este vídeo tem 141 frases e 1774 palavras para praticar shadowing. A fala dura 12:24. O falante mantém um ritmo estável de cerca de 143 palavras por minuto, confortável para o shadowing. Apenas 71% das palavras estão entre as 3.000 mais comuns do inglês, por isso o vocabulário é exigente.
Vocabulário principal deste vídeo
15 palavras do vídeo que vale a pena aprender, com pronúncia e significado:
| Palavra | Pronúncia | Significado |
|---|---|---|
| trap substantivo | /tɹæp/ | armadilha, arapuca |
| leaf substantivo | /lif/ | folha |
| prey substantivo | /pɹeɪ/ | presa |
| insect substantivo | /ˈɪn.sɛkt/ | inseto |
| nerve substantivo | /nɝv/ | nervo |
| underwater adjetivo | /ʌndɚˈwɔtəɹ/ | submarino, subaquático |
| wire substantivo | /ˈwaɪɚ/ | arame |
| roughly advérbio | /ˈɹʌf.li/ | rudemente, precariamente |
| trigger substantivo | /ˈtɹɪɡɚ/ | gatilho |
| voltage substantivo | /ˈvəʊltɪd͡ʒ/ | tensão, voltagem |
| spike substantivo | /spaɪk/ | espinho, cravo |
| enzyme substantivo | /ˈɛn.zaɪm/ | enzima |
| digest verbo | /daɪˈd͡ʒɛst/ | digerir |
| buckle substantivo | /ˈbʌkəl/ | fivela |
| meal substantivo | /ˈmiːl/ | refeição |
Gramática neste vídeo
As estruturas que o falante mais usa, com as palavras exatas do vídeo:
| Estrutura | No vídeo |
|---|---|
| Voz passiva be + particípio passado — o foco está no que acontece, não em quem faz | is loaded · is held · is already stored |
| Present perfect have/has + particípio passado — uma ação passada que ainda importa agora | have noticed · has already vanished |
Pronúncia para ficar de olho
- Os sons de “th”: thin /ˈθɪn/, tenth /tɛnθ/, thirsty /ˈθɝs.ti/
- Os sons de “sh” e “zh”: fraction /ˈfɹæk.ʃən/, wash /wɑʃ/, evolution /ˌiːvəˈluːʃ(ə)n/, tissue /ˈtɪʃ.(j)u/, demonstration /dɛmənˈstɹeɪʃən/
- Palavras longas — acerte a sílaba tônica: electrical /ɪˈlɛktɹɪkəl/, underwater /ʌndɚˈwɔtəɹ/, temporary /ˈtɛmp(əˌɹ)ɛɹi/, evolution /ˌiːvəˈluːʃ(ə)n/, mechanism /ˈmɛk.ə.nɪ.zəm/
Sons difíceis para falantes de português:
- Consoante final — sem acrescentar um “i” depois: trap /tɹæp/, snap /snæp/, insect /ˈɪn.sɛkt/, spike /spaɪk/, digest /daɪˈd͡ʒɛst/
- /l/ final — a língua toca o céu da boca, não vira “u”: electrical /ɪˈlɛktɹɪkəl/, buckle /ˈbʌkəl/, meal /ˈmiːl/, stable /ˈsteɪ.bəl/, soil /sɔɪl/
- s + consoante no início — sem um “i” antes: snap /snæp/, spike /spaɪk/, stable /ˈsteɪ.bəl/, stomach /ˈstʌmək/, steal /stiːl/
Como praticar com este vídeo
- Ouça o vídeo inteiro uma vez sem falar e anote as palavras que você não conhece.
- Faça shadowing frase por frase na velocidade normal, repetindo cada uma até o seu ritmo ficar igual ao do falante.
- Grave a sua voz e compare com o original, prestando atenção a palavras como trap, leaf, prey.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.