Shadowing Practice: How Feathered Dinosaurs Accidentally Invented Flight (We Tested It!) - Learn English Speaking with Video
בחר מצב תרגול
כל מצב פותח חדר תרגול במסך מלא.
161 משפטים
אם המשפטים קצרים או ארוכים מדי, לחץ על ערוך כדי להתאים אותם.
1
- Thank you to Delete Me for supporting PBS.
2
Hey smart people, Joe here, and this is a chicken.
3
This humble bird and some of her friends are gonna help us solve one of evolution's greatest mysteries.
4
How fluffy feathered dinosaurs became today's masters of the sky.
5
At least, that's what we hope is gonna happen.
6
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.
7
Why chickens?
8
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.
9
More than a century of fossil discoveries have shown us that like today's birds, many extinct dinosaurs had feathers.
10
But when and how did feather covered arms become fully functional wings capable of flight?
11
This is a puzzle that's captivated and confused scientists for more than a century.
12
In fact, that question was one of the first great challenges Charles Darwin himself faced after publishing his theory of natural selection.
13
The evolutionary transition from feathers to flight is one of the most important and amazing mysteries in evolution.
14
And these chickens, well, hopefully they're gonna help us solve it today, aren't you?
15
Big news, dino lovers, a brand new Walking With Dinosaurs just launched on PBS 25 years after the original series.
16
Head to the link in the description to learn more.
17
Bird flight is, without a doubt, one of the most incredible feats of any animal on earth.
18
Flight has created blazingly fast and agile hunters.
19
Others can fly standing perfectly still.
20
Some can so as high as jet airliners over the Himalayas or glide over the sea for months without landing.
21
And the secret to flight are these feather covered arms we call wings.
22
Inside a bird's wing are the same bones you have in your arm with fused fingers near the tip.
23
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.
24
They also turn the shape of the arm into an air foil capable of creating lift.
25
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.
26
But all of the incredible and varied forms that flight takes today can trace their origin to some ancient bird ancestor.
27
The moment a feather dinosaur first used its wings to fly.
28
Until 1861, the only animals with feathers we knew of were birds.
29
For that year, a single isolated fossil feather was found in Germany.
30
Its discoverer, Hermann Von Meyer noted it was indistinguishable from a bird's feather.
31
Later that year, a near complete skeleton of that feathered animal was found and given the name, Archaeopteryx.
32
The rocks in which Archaeopteryx was found date to the Jurassic, around 150 million years ago.
33
Yet this mysterious creature possessed features of both dinosaurs and modern birds.
34
Just two years before Archaeopteryx' discovery, a British naturalist named Charles Darwin had published a revolutionary new theory about how species change over time.
35
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.
36
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.
37
Archaeopteryx appeared to be exactly the transitional fossil that Darwin's theory predicted.
38
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.
39
In 1871, one English biologist reportedly challenged Darwin with a simple question, what good is half a wing?
40
In other words, it's easy to understand why a normal arm with claws for grasping would be good for ancestral dinosaurs.
41
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.
42
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.
43
What possible evolutionary advantage could that provide?
44
You can't fly with a fraction of a wing.
45
So how can natural selection explain those in-between forms?
46
Well, Darwin himself came up with the solution.
47
What if that half a wing is an advantage for something other than flying?
48
This is precisely the question I'm hoping to answer with the chicken experiment I'm going to do later.
49
We're doing some science here.
50
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.
51
That's because early on, most known dinosaurs were gigantic sora pods and carnivores.
52
These supposedly slow cold-blooded clumsy branches of the dinosaur family tree couldn't have led to birds.
53
Other than Archaeopteryx, small bird-like dinosaur fossils were still hidden in the rocks.
54
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.
55
But decades later, researchers realized that many fossils they already had were in fact dinosaur wishbones mislabeled as other bones.
56
And beginning in the 1960s, the link between birds and dinosaurs was revived.
57
Paleontologist John Ostrom discovered Deinonychus.
58
- The evil robot shackled the deinonychus.
59
- Gray fox on attack!
60
- 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.
61
- Clever girl.
62
- Anyway, Ostrom later described many more bird-like traits in other fossil species.
63
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.
64
But we still have to solve Darwin's dilemma.
65
What mechanism could explain how a perfectly good arm evolved into a feathered flying wing?
66
What was half a wing actually useful for?
67
New fossil discoveries began to fill in the blanks.
68
In the 1990s, Sinosauropteryx was unearthed in China.
69
It was the first non-avian dinosaur found to have feathers.
70
The color pattern of those feathers was even preserved, showing stripes on its tail.
71
But Sinosauropteryx' feathers were primitive, more like short filaments or bristles.
72
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.
73
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.
74
But mathematical analyses showed that the shape and size of these feathered arms couldn't create lift.
75
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.
76
So what was the purpose of these non-flying half wings?
77
Feathers located far away from the body.
78
The tips of early wings or tails could have been used for communication or attracting mates.
79
You know, think of birds with mohawks or those guys at the airport, waving planes in.
80
There are plenty of examples today of bird feather structures and patterns that evolved thanks to sexual selection and communication.
81
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.
82
Feathered arms would be helpful in covering or keeping eggs warm.
83
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.
84
Feathers could help with that too.
85
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.
86
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?
87
Well, it wasn't until the 21st century that researchers began to finish this story.
88
Now, one campus scientists noticed that the theropod dinosaurs, birds are closely related to, they look like they run on the ground.
89
So maybe flight began as a series of running jumps with longer and longer hang time as wings and feathers grew more complex.
90
It's called the Ground-Up Theory of Flight.
91
Another group of scientists said, no, you'd never want to evolve flying going against gravity.
92
It's way too hard!
93
So the half wing ancestors of birds - Geromino!
94
- must have been living in trees already.
95
They were climbers and they started gliding down, a Trees-Down Theory of Flight.
96
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.
97
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.
98
They could be a living stand-in for those extinct transitional dinosaurs.
99
So what do young birds do with their half wings?
100
I found a farm with some young chickens so we could put them to the test.
101
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.
102
Not exactly a calculus exam, but hey, they're chickens.
103
- The enormity of of their flat brain, the enormity of their stupidity is just overwhelming.
104
- We're gonna see what this bird does, ready?
105
Yeah! For an easy incline, the birds just walk because why fly if you don't have to?
106
That was easy mode.
107
I think it's time to level up.
108
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.
109
Okay, go to your friend, do some science.
110
As the incline gets steeper, the bird is still mostly walking.
111
Then it's starts to engage its wings to help it get up.
112
But is it creating lift or are those wings doing something else?
113
Let's make it even steeper and then see what the chicken does.
114
This is your gold medal moment.
115
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.
116
Don't tell the chickens, but they're not really great flyers.
117
That's why there's such a great model for that transition from feathered wings to flight.
118
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.
119
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.
120
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.
121
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.
122
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.
123
He called it Wing-Assisted Incline Running or W.A.I.R.
124
If you wanna avoid predators on the ground, wing-assisted incline running is a great way to get yourself up to safety.
125
And we still see many birds climb this way today.
126
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.
127
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.
128
Later on, it was shown that baby birds will also flap to slow down a fall.
129
So, when it comes to the trees down versus ground up versus W.A.I.R. camps, it's not all or nothing.
130
More than one answer can be correct.
131
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.
132
This whole process is known as exaptation when evolution takes an existing structure and hijacks it for some new purpose.
133
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.
134
It has to be able to feed and move and get away from predators and reproduce, all of those things.
135
So any organism that survives is already pretty darn advanced and specialized for its environment.
136
Really, almost the only way for new structures and abilities to arise is for them to evolve from something that already exists.
137
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.
138
Thankfully, we still got a few dinosaurs left over that helped us solve that mystery.
139
High five. High wing?
140
Stay curious.
141
Good chicken, good time.
142
Want more dinosaurs?
143
Head to the PBS app or PBS.org to watch Walking With Dinosaurs.
144
25 years ago, the original Walking with Dinosaurs took us on a journey into deep time, and now, we're going back again.
145
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.
146
Check out the link in the description to watch this incredible show.
147
And thank you to Delete Me for supporting PBS.
148
Delete Me was built to safeguard its members from data brokers, companies that compile detailed interconnected profiles by scraping public records, mining social media, and purchasing commercial data.
149
These profiles are then sold to various industries, usually without the individuals ever knowing.
150
How does Delete Me work?
151
Their platform searches through hundreds of data broker sites, identifies where your information is exposed, and issues official removal requests.
152
It also provides continuous monitoring to quickly catch and address any resurfacing data as well as protect and prevent things like doxing, harassment, or identity theft.
153
With a family plan, Delete Me extends these protections to linked individuals to help minimize household exposure by disrupting how brokers infer relational connections.
154
You can get 20% off any Delete Me consumer or family plan at joindeleteme.com/besmart with promo code BESMART.
155
There's a link down in the description.
156
And as always, thank you to everyone who supports the show on Patreon, including these fine folks at our top tier.
157
We couldn't make episodes like this one without you.
158
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.
159
Up here, up here, ready, go.
160
You're startin' to get a little feisty.
161
Go! You're done.
הורד אפליקציה
כל מה שאתה צריך כדי לדבר בשטף
הגיית AIציון לכל משפט
תרגול IPAשלוט בכל צליל
אוצר מיליםבנה את מאגר המילים שלך
משחק אוצר מיליםלמד תוך כדי משחק
אותו ערוץ
B218
Why don't you remember being a baby?
American AccentIELTS PrepTOEFL PrepUniversity Students
B29
How Habits Can Change Your Life (and Your Brain)
American AccentBusiness EnglishUniversity StudentsWorking Adults
B22
Scientists Finally Figured Out What Love Is For
American AccentDaily ConversationUniversity StudentsWorking Adults
B21
Why Is Blue So Rare In Nature?
American AccentDaily ConversationUniversity Students
B24
Mars Used to Be Blue... Then Something Happened
American AccentIELTS PrepTOEFL PrepUniversity Students
C14
The Unbelievable Science of How We Read
American AccentIELTS PrepTOEFL PrepUniversity Students
C19
The Strange Science of Why We Dream
American AccentIELTS PrepTOEFL PrepUniversity Students
B25 Weird Involuntary Behaviors Explained!
American AccentDaily ConversationUniversity StudentsWorking Adults
B2Evolution FAILS in the Human Body
American AccentDaily ConversationUniversity StudentsWorking Adults
FOR YOU
המלץ על סרטון
C116
48 משפטים
Why birds don't crash (and what humans can learn from them)
British AccentIELTS PrepTOEFL PrepUniversity Students
C17
110 משפטים
World’s Most Advanced Artificial Egg Hatches Chicks
IELTS PrepTOEFL PrepUniversity Students
C147
90 משפטים
How do bees make honey?
American AccentIELTS PrepTOEFL PrepUniversity Students
C1118
15 משפטים
Could Humans Evolve Flight?
Daily ConversationUniversity StudentsWorking Adults
C12
23 משפטים
Phát âm chuẩn - Anh ngữ đặc biệt: Migrating Birds (VOA)
American AccentIELTS PrepTOEFL PrepUniversity Students
C17
127 משפטים
The Day the Dinosaurs Died – Minute by Minute
IELTS PrepTOEFL PrepUniversity Students
B22
108 משפטים
Every Dodo You’ve Ever Seen Is Probably Wrong. These Aren’t.
IELTS PrepTOEFL PrepUniversity Students
C11
138 משפטים
Chaos: The Science of the Butterfly Effect
IELTS PrepTOEFL PrepUniversity Students
B254
38 משפטים
Why Birds Migrate: A Chat with an Ornithologist
American AccentBritish AccentIELTS PrepUniversity StudentsWorking Adults
C19
77 משפטים
How High Can Birds Fly?
IELTS PrepTOEFL PrepUniversity Students
C25
98 משפטים
Why Over 600,000 Bird Specimens Are Preserved At The Smithsonian | Colossal Collections
IELTS PrepTOEFL PrepUniversity Students
B26
155 משפטים
Why Ancient Humans Were The Most TERRIFYING Animal Alive
IELTS PrepTOEFL PrepUniversity Students
אוצר מילים והערות הגייה לשיעור הזה
שיעור הדיבור הזה ברמה C1 מבוסס על הסרטון “How Feathered Dinosaurs Accidentally Invented Flight”. המילים שחוזרות הכי הרבה: bird, wing, dinosaur, feather, chicken. בסרטון הזה יש 161 משפטים ו-2745 מילים לתרגול Shadowing. הדיבור נמשך 18:11. הדובר מדבר בקצב טבעי של כ-151 מילים בדקה, קרוב לשיחה יומיומית. רק 78% מהמילים נמצאות בין 3,000 המילים הנפוצות ביותר באנגלית, כך שאוצר המילים מאתגר.
אוצר מילים מרכזי בסרטון הזה
15 המילים המתקדמות ביותר בסרטון, עם ההגייה והמשמעות שלהן:
| מילה | הגייה | משמעות |
|---|---|---|
| dinosaur שם עצם | /ˈdaɪnəsoɹ/ | דִּינוֹזָאוּר |
| feather שם עצם | /ˈfɛðə/ | נוצה, נוֹצָה |
| fossil שם עצם | /ˈfɑsl̩/ | מְאוּבָּן, מְאֻבָּן |
| evolutionary שם תואר | /ˌiː.vəˈluː.ʃən.ɛɹ.i/ | אבולוציוני |
| organism שם עצם | /ˈɔɹ.ɡəˌnɪz.əm/ | אוֹרְגָּנִיזְם, יְצוּר |
| steep שם תואר | /stiːp/ | תָּלוּל |
| broker שם עצם | /ˈbɹoʊkɚ/ | בְּרוֹקֶר |
| biologist שם עצם | /baɪˈɒləd͡ʒɪst/ | ביולוג \ בִּיוֹלוֹג |
| reproduce פועל | /ˌɹi.pɹəˈdus/ | התרבה |
| extinct שם תואר | /ɪkˈstɪŋkt/ | כבוי |
| trait שם עצם | /tɹeɪt/ | מאפיין, תכונה |
| predator שם עצם | /ˈpɹɛd.ə.tɚ/ | טוֹרֵף |
| dilemma שם עצם | /daɪˈlɛmə/ | דילמה |
| stripe שם עצם | /stɹaɪp/ | פַּס |
| assemble פועל | /əˈsɛm.bəl/ | אסף |
Phrasal verbs שתשמעו
| מילה | משמעות |
|---|---|
| check out פועל | בדק |
| get up פועל | קָם |
משפטים שכדאי לחזור עליהם
משפטים קצרים ושלמים מהסרטון שאפשר להשתמש בהם בשיחה יומיומית:
- At least, that's what we hope is gonna happen.
- You can't fly with a fraction of a wing.
- We're doing some science here.
- I think it's time to level up.
- We couldn't make episodes like this one without you.
דקדוק בסרטון הזה
המבנים שהדובר משתמש בהם הכי הרבה, עם המילים המדויקות מהסרטון:
| מבנה | בסרטון |
|---|---|
| סביל (Passive voice) be + past participle — הדגש הוא על מה שקורה, לא על מי שעושה את הפעולה | are specialized · was found · were still hidden |
| הווה מושלם (Present perfect) have/has + past participle — פעולה שקרתה בעבר ועדיין יש לה חשיבות או השפעה עכשיו | have shown · has created · I've done |
| משפטי זיקה (Relative clauses) who / which + clause — מידע נוסף על אדם או דבר | years, which is · everyone who supports |
הגייה ששווה לשים לב אליה
הדובר משתמש ב-40 קיצורים וצורות מקוצרות, כמו they're, gonna, couldn't. אמרו אותם בצורה הקצרה, כפי שאתם שומעים אותם.
- הצלילים של “th”: feather /ˈfɛðə/, theropod /ˈθɪɚ.əˌpɑd/, pathway /ˈpæθˌweɪ/, thrust /θɹʌst/, thermal /ˈθɜːməl/
- הצלילים של “sh” ו-“zh”: evolutionary /ˌiː.vəˈluː.ʃən.ɛɹ.i/, transitional /tɹænˈzɪʃənəl/, specialize /ˈspɛʃəˌlaɪz/, wishbone /ˈwɪʃˌboʊn/, traction /ˈtɹæk.ʃən/
- מילים ארוכות — שימו לב להטעמה: evolutionary /ˌiː.vəˈluː.ʃən.ɛɹ.i/, transitional /tɹænˈzɪʃənəl/, organism /ˈɔɹ.ɡəˌnɪz.əm/, ancestral /ænˈsɛs.təɹ.əl/, biologist /baɪˈɒləd͡ʒɪst/
צלילים שדוברי עברית מתקשים בהם:
- /w/ — שפתיים מעוגלות, לא /v/: squawk /skwɔːk/, wishbone /ˈwɪʃˌboʊn/, overwhelm /ˌoʊ.vɚˈwɛlm/, pathway /ˈpæθˌweɪ/
- /æ/ — פתוח יותר מה-“אֶ” העברית, לא כמו “a” ב-“cup”: flap /flæp/, ancestor /ˈæn.sɛs.tɚ/, transitional /tɹænˈzɪʃənəl/, ancestral /ænˈsɛs.təɹ.əl/, traction /ˈtɹæk.ʃən/
- /r/ — הלשון לא נוגעת בשום מקום, לא ה-“ר” הגרונית: dinosaur /ˈdaɪnəsoɹ/, evolutionary /ˌiː.vəˈluː.ʃən.ɛɹ.i/, transitional /tɹænˈzɪʃənəl/, organism /ˈɔɹ.ɡəˌnɪz.əm/, broker /ˈbɹoʊkɚ/
איך לתרגל עם הסרטון הזה
- הקשיבו לכל הסרטון פעם אחת בלי לדבר, ורשמו את המילים שאתם לא מכירים.
- התחילו במהירות 0.75×, תרגלו Shadowing משפט אחר משפט, וחזרו למהירות רגילה כשזה מרגיש קל.
- הקליטו את עצמכם והשוו למקור, תוך תשומת לב למילים כמו dinosaur, feather, fossil.
מהי טכניקת השאדואינג?
שאדואינג היא טכניקת למידת שפה מבוססת מדע שפותחה במקור להכשרת מתורגמנים מקצועיים ופופולרית על ידי הפוליגלוט ד"ר אלכסנדר ארגואלס. השיטה פשוטה אך עוצמתית: אתה מקשיב לאודיו באנגלית ילידית וחוזר עליו בקול רם מיד — כמו צל העוקב אחרי הדובר עם עיכוב של 1–2 שניות בלבד. בניגוד להאזנה פסיבית או תרגילי דקדוק, שאדואינג מכריח את המוח והשרירים בפה לעבד ולשחזר דפוסי דיבור אמיתיים בו זמנית. מחקרים מראים שזה משפר משמעותית את דיוק ההגייה, האינטונציה, הקצב, הדיבור המחובר, הבנת השמיעה ושטף הדיבור — מה שהופך אותו לאחת השיטות היעילות ביותר להכנה לIELTS Speaking ולתקשורת באנגלית בעולם האמיתי.