शैडोइंग अभ्यास: How Feathered Dinosaurs Accidentally Invented Flight (We Tested It!) - वीडियो के साथ अंग्रेजी बोलना सीखें
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- Thank you to Delete Me for supporting PBS.
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Hey smart people, Joe here, and this is a chicken.
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This humble bird and some of her friends are gonna help us solve one of evolution's greatest mysteries.
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How fluffy feathered dinosaurs became today's masters of the sky.
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At least, that's what we hope is gonna happen.
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Okay? Today, we are gonna use chickens to remake a genius and rather hilarious experiment that helped unlock the answer to how the first feathered dinosaurs started to fly.
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Why chickens?
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Because today's birds are the only surviving lineage of the dinosaurs, the incredible creatures that dominated our planet for tens of millions of years.
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More than a century of fossil discoveries have shown us that like today's birds, many extinct dinosaurs had feathers.
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But when and how did feather covered arms become fully functional wings capable of flight?
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This is a puzzle that's captivated and confused scientists for more than a century.
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In fact, that question was one of the first great challenges Charles Darwin himself faced after publishing his theory of natural selection.
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The evolutionary transition from feathers to flight is one of the most important and amazing mysteries in evolution.
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And these chickens, well, hopefully they're gonna help us solve it today, aren't you?
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Big news, dino lovers, a brand new Walking With Dinosaurs just launched on PBS 25 years after the original series.
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Head to the link in the description to learn more.
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Bird flight is, without a doubt, one of the most incredible feats of any animal on earth.
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Flight has created blazingly fast and agile hunters.
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Others can fly standing perfectly still.
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Some can so as high as jet airliners over the Himalayas or glide over the sea for months without landing.
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And the secret to flight are these feather covered arms we call wings.
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Inside a bird's wing are the same bones you have in your arm with fused fingers near the tip.
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Extending from the back of that hand and arm are the flight feathers, the incredibly light but stiff nature of these lets them not only provide thrust through the air.
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They also turn the shape of the arm into an air foil capable of creating lift.
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The arms and flight feathers we find in different birds today are specialized and adapted to the different ways that birds fly, from sorting to hovering to aerobatics.
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But all of the incredible and varied forms that flight takes today can trace their origin to some ancient bird ancestor.
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The moment a feather dinosaur first used its wings to fly.
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Until 1861, the only animals with feathers we knew of were birds.
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For that year, a single isolated fossil feather was found in Germany.
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Its discoverer, Hermann Von Meyer noted it was indistinguishable from a bird's feather.
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Later that year, a near complete skeleton of that feathered animal was found and given the name, Archaeopteryx.
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The rocks in which Archaeopteryx was found date to the Jurassic, around 150 million years ago.
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Yet this mysterious creature possessed features of both dinosaurs and modern birds.
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Just two years before Archaeopteryx' discovery, a British naturalist named Charles Darwin had published a revolutionary new theory about how species change over time.
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Darwin's theory states that evolution's creativity plays out in tiny doses of change with natural selection as the great filter deciding which changes let an organism survive and reproduce better in its environment.
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One of the predictions of Darwin's theory is that between some ancestral trait and its modern form, we'd expect to find an intermediate form, what some people call a transitional fossil.
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Archaeopteryx appeared to be exactly the transitional fossil that Darwin's theory predicted.
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And as early as 1868, Thomas Huxley, one of Darwin's most vocal supporters, was the first to claim dinosaurs like Archaeopteryx were ancestors of modern birds, but not everyone was convinced.
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In 1871, one English biologist reportedly challenged Darwin with a simple question, what good is half a wing?
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In other words, it's easy to understand why a normal arm with claws for grasping would be good for ancestral dinosaurs.
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And how later, fully feathered bird-like wings would be an evolutionary advantage for flying dinosaurs, AKA birds, but complex structures like wings don't just pop into existence fully formed.
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In between, we'd have some not quite bird dino with a feathered limb that's not exactly an arm, but less than a wing.
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What possible evolutionary advantage could that provide?
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You can't fly with a fraction of a wing.
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So how can natural selection explain those in-between forms?
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Well, Darwin himself came up with the solution.
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What if that half a wing is an advantage for something other than flying?
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This is precisely the question I'm hoping to answer with the chicken experiment I'm going to do later.
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We're doing some science here.
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Even though the first fossil evidence of Jurassic era feathers was found more than 150 years ago, the link between birds and dinosaurs was largely ignored for a century.
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That's because early on, most known dinosaurs were gigantic sora pods and carnivores.
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These supposedly slow cold-blooded clumsy branches of the dinosaur family tree couldn't have led to birds.
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Other than Archaeopteryx, small bird-like dinosaur fossils were still hidden in the rocks.
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And in the 1920s, influential scientists declared that since no one had found fossil wishbones, one of the key skeletal characteristics of birds, dinosaurs couldn't be their ancestors.
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But decades later, researchers realized that many fossils they already had were in fact dinosaur wishbones mislabeled as other bones.
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And beginning in the 1960s, the link between birds and dinosaurs was revived.
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Paleontologist John Ostrom discovered Deinonychus.
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- The evil robot shackled the deinonychus.
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- Gray fox on attack!
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- A fast moving, warm blooded dinosaur with bird-like feet that Steven Spielberg renamed Velociraptor in Jurassic Park, even though there's already a different dinosaur named Velociraptor.
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- Clever girl.
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- Anyway, Ostrom later described many more bird-like traits in other fossil species.
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His work proved once and for all that modern birds are a living subgroup of theropod dinosaurs that survived the giant space rock, mass extinction, and diversified into the forms we see today, even chickens.
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But we still have to solve Darwin's dilemma.
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What mechanism could explain how a perfectly good arm evolved into a feathered flying wing?
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What was half a wing actually useful for?
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New fossil discoveries began to fill in the blanks.
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In the 1990s, Sinosauropteryx was unearthed in China.
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It was the first non-avian dinosaur found to have feathers.
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The color pattern of those feathers was even preserved, showing stripes on its tail.
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But Sinosauropteryx' feathers were primitive, more like short filaments or bristles.
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Since feathers had now been found in two different branches of the dinosaur family tree, it's a good hint that they evolved in some ancestor of both branches.
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In other words, feathers showed up long before flight and other feathered fossils were found with more complex feathers, like those of modern birds arranged on wing like arms.
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But mathematical analyses showed that the shape and size of these feathered arms couldn't create lift.
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But since these species were also in branches outside of birds, it was more evidence that a bird-like wing structure first arose in dinosaurs that weren't flying.
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So what was the purpose of these non-flying half wings?
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Feathers located far away from the body.
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The tips of early wings or tails could have been used for communication or attracting mates.
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You know, think of birds with mohawks or those guys at the airport, waving planes in.
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There are plenty of examples today of bird feather structures and patterns that evolved thanks to sexual selection and communication.
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Also, right around when feathered wings first appear in the fossil record, there's evidence many dinosaurs began to sit on their eggs rather than bury them.
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Feathered arms would be helpful in covering or keeping eggs warm.
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It's also likely that theropod dinosaurs, the group of dinosaurs that contains birds and their ancestors as well as others, they were warm blooded and small, warm blooded animals have to have insulation to hold in their heat or else it's too energetically costly to be warm blooded.
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Feathers could help with that too.
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These were all examples of how half a wing could be useful in the evolutionary journey toward birds, but none of these put wings on a pathway toward flight.
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What if these feathered proto wing structures first evolved for communication and thermal regulation, but then just happened to also have some small benefit in helping bird-like dinosaurs move?
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Well, it wasn't until the 21st century that researchers began to finish this story.
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Now, one campus scientists noticed that the theropod dinosaurs, birds are closely related to, they look like they run on the ground.
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So maybe flight began as a series of running jumps with longer and longer hang time as wings and feathers grew more complex.
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It's called the Ground-Up Theory of Flight.
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Another group of scientists said, no, you'd never want to evolve flying going against gravity.
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It's way too hard!
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So the half wing ancestors of birds - Geromino!
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- must have been living in trees already.
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They were climbers and they started gliding down, a Trees-Down Theory of Flight.
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Neither camp could assemble definitive evidence to prove their case, but then came a third model, and that is what our chicken experiment set out to demonstrate.
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In the early 2000s, a biologist named Ken Dial noticed that young birds before their full feathers come in, they basically have half a wing.
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They could be a living stand-in for those extinct transitional dinosaurs.
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So what do young birds do with their half wings?
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I found a farm with some young chickens so we could put them to the test.
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The birds are going to make their way up a ramp placed at various inclines so that we can observe if they're non-flying wings are able to help them move.
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Not exactly a calculus exam, but hey, they're chickens.
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- The enormity of of their flat brain, the enormity of their stupidity is just overwhelming.
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- We're gonna see what this bird does, ready?
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Yeah! For an easy incline, the birds just walk because why fly if you don't have to?
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That was easy mode.
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I think it's time to level up.
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Chicken didn't have to use its wings that time, but we made this a little bit steeper and we're gonna see what happens.
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Okay, go to your friend, do some science.
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As the incline gets steeper, the bird is still mostly walking.
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Then it's starts to engage its wings to help it get up.
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But is it creating lift or are those wings doing something else?
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Let's make it even steeper and then see what the chicken does.
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This is your gold medal moment.
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Ready? As the incline gets nearly vertical, the chicken has to flap hard to make the climb, but what's really cool is it's flapping its wings in a different way than birds do when they're flying.
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Don't tell the chickens, but they're not really great flyers.
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That's why there's such a great model for that transition from feathered wings to flight.
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Now, you might think that a bird would try to push itself up with its wings, but what shots like this and experiments like this have shown scientists is that instead of flapping themselves up, they're pushing themselves toward what they're trying to climb.
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When a bird is in the air, it flaps its wings almost perpendicular to align between the beak and tail in order to create lift.
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But up the incline, the young chicken's wing is instead flapping down and behind it, pushing its body toward the surface to increase climbing traction, not simply pushing its body up.
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What I've done here on the farm is basically a very silly and non-scientific replication of some very rigorous and very scientific research by Ken Dial.
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He found that young birds with immature wings will climb steep or even vertical surfaces by using the force of their wings to increase traction.
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He called it Wing-Assisted Incline Running or W.A.I.R.
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If you wanna avoid predators on the ground, wing-assisted incline running is a great way to get yourself up to safety.
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And we still see many birds climb this way today.
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We know from fossil skeletons that transitional bird-like dinosaurs wouldn't have been able to flap their wings with the full range of motion that modern birds can, but they would have been able to move their wings the way young birds do when using W.A.I.R.
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Today, where is one of the most accepted theories for how those transitional half wings, those intermediate forms between fluffy dinosaur arms and fully developed flying wings on modern birds could have provided their own evolutionary advantage along that journey from feathers to flight, Darwin's dilemma solved with a chicken.
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Later on, it was shown that baby birds will also flap to slow down a fall.
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So, when it comes to the trees down versus ground up versus W.A.I.R. camps, it's not all or nothing.
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More than one answer can be correct.
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This is still new science in just the last 10 to 15 years, which is basically brand new as paleontology is concerned, and a more definitive answer may lie in future fossil discoveries that continue to fill in the blanks.
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This whole process is known as exaptation when evolution takes an existing structure and hijacks it for some new purpose.
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And when you think about it, it's a pretty logical way for change to occur in nature because every organism has to be fully functional as it is in the moment it's alive on its own evolutionary journey.
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It has to be able to feed and move and get away from predators and reproduce, all of those things.
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So any organism that survives is already pretty darn advanced and specialized for its environment.
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Really, almost the only way for new structures and abilities to arise is for them to evolve from something that already exists.
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Flight has evolved in different organisms on earth many different times, but the way that birds took to the sky is one of the most fascinating stories in the history of life.
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Thankfully, we still got a few dinosaurs left over that helped us solve that mystery.
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High five. High wing?
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Stay curious.
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Good chicken, good time.
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Want more dinosaurs?
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Head to the PBS app or PBS.org to watch Walking With Dinosaurs.
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25 years ago, the original Walking with Dinosaurs took us on a journey into deep time, and now, we're going back again.
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The new Walking with Dinosaurs uses state-of-the-art visual effects and the latest research to reconstruct how these iconic creatures lived and died.
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Check out the link in the description to watch this incredible show.
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If you'd like to become a supporter of our show and help us make these episodes directly, check out the link down in the description to join the club.
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Up here, up here, ready, go.
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You're startin' to get a little feisty.
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Go! You're done.
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संदर्भ एवं पृष्ठभूमि
इस वीडियो में, जो एक वैज्ञानिक और शैक्षिक प्रयोग पर आधारित है, प्रस्तुतकर्ता ने पक्षियों और पूर्वज डायनासोर के बीच के संबंध को उजागर किया है। खासतौर पर, कैसे पंखदार डायनासोर ने उड़ान का आविष्कार किया। वीडियो में बताया गया है कि चिकन कैसे वैज्ञानिक प्रयोगों के माध्यम से हमें इस विकासात्मक प्रक्रिया को समझने में मदद करेगा। पक्षियों के विकास के पीछे की जटिलता और प्राकृतिक चयन के सिद्धांत को समझाना इस विषय का मुख्य उद्देश्य है।
दैनिक संचार के लिए शीर्ष 5 वाक्यांश
- “यह एक अद्भुत प्रयोग है!” - जब आप किसी दिलचस्प वैज्ञानिक प्रयोग की बात कर रहे हों।
- “क्या आप जानते हैं कि?” - जानकारी साझा करने के लिए उत्तम।
- “पक्षियों का उड़ना अद्भुत है।” - जब आप किसी पक्षी की विशेषता पर चर्चा कर रहे हों।
- “यह कैसे होता है?” - जिज्ञासा दिखाने के लिए उपयोगी।
- “विकास के सिद्धांत पर आधारित।” - जब आप किसी वैज्ञानिक सिद्धांत की बात कर रहे हों।
स्टेप-बाय-स्टेप शैडोइंग गाइड
इस वीडियो से अंग्रेजी सीखने के लिए, आप निम्नलिखित तरीकों का पालन कर सकते हैं:
- प्रस्तुतकर्ता को ध्यान से सुनें: पहले वीडियो को बिना रुके सुनें और समझें कि वह क्या कह रहा है।
- इसके बाद, शैडोइंग तकनीक अपनाएं: जैसे ही आप सुनते हैं, उसके बोलने के तुरंत बाद आप उसी शब्दों का उच्चारण करें। यह अंग्रेजी शैडोइंग की एक उत्कृष्ट तकनीक है।
- विभिन्न वाक्यांशों का अभ्यास करें: ऊपर दिए गए शीर्ष 5 वाक्यांशों का कई बार अभ्यास करें ताकि आप उन्हें बेहतर तरीके से याद कर सकें।
- खुद को रिकॉर्ड करें: अपने बोलने के दौरान सुनें और तय करें कि आपको किस भाग का अभ्यास करने की आवश्यकता है। यह आपको अपने उच्चारण में सुधार करने में मदद करेगा।
- रिपीट करें: वीडियो में प्रयोग की गई संज्ञानात्मक अवधारणाओं को फिर से समझें और अपने रूपांतरण का अभ्यास करें। यदि संभव हो, तो shadowspeaks जैसे अन्य संसाधनों का भी उपयोग करें।
इन चरणों का पालन करके, आप न केवल अपनी अंग्रेजी बोलने की क्षमता को मजबूत कर सकते हैं, बल्कि विज्ञान और इतिहास के विषयों पर संवाद करने की क्षमता भी विकसित कर सकते हैं। इस प्रकार, shadow speech और shadow speak तकनीकों का उपयोग करें और अपनी अंग्रेजी कौशल को निखारें।
इस वीडियो का व्याकरण
वक्ता जिन संरचनाओं का सबसे अधिक प्रयोग करता है, वीडियो के असली शब्दों के साथ:
| संरचना | वीडियो में |
|---|---|
| Passive voice be + past participle — ज़ोर इस पर कि क्या होता है, न कि कौन करता है | are specialized · was found · were still hidden |
| Present perfect have/has + past participle — बीता हुआ काम जिसका असर अभी भी है | have shown · has created · I've done |
| Relative clauses who / which + उपवाक्य — व्यक्ति या वस्तु के बारे में अतिरिक्त जानकारी | years, which is · everyone who supports |
शैडोइंग तकनीक क्या है?
शैडोइंग (Shadowing) एक विज्ञान-समर्थित भाषा सीखने की तकनीक है जो मूल रूप से पेशेवर दुभाषिया प्रशिक्षण के लिए विकसित की गई थी। विधि सरल लेकिन शक्तिशाली है: आप मूल अंग्रेज़ी ऑडियो सुनते हैं और तुरंत इसे ज़ोर से दोहराते हैं — जैसे वक्ता की छाया 1-2 सेकंड की देरी से। शोध से पता चलता है कि यह उच्चारण सटीकता, स्वर, लय, जुड़ी हुई ध्वनियाँ, सुनने की समझ और बोलने की प्रवाहशीलता में काफ़ी सुधार करता है।