7月16日CNN聽力：科學家揭開變色龍變色秘密
Time for the Shoutout.
What is not a characteristic of a chameleon?
If you think you know it,shout it out.
Is it independent eye movement,zygodactylousfeet,projectile tongues or regenerative tails?
You've got three seconds.Go.
Chameleons are lizards that share all of thesecharacteristics except the ability to regenerate lost or injured limbs or tails.
That's your answer and that's your Shoutout.
Zygodactylous means their toes are grouped together.
There are more than 150 known species of chameleons.
They're reptiles.They prefer to live in trees.
Their tongues are as long or longer than they are.
But the most famous characteristic,of course,is that they're able to change color,some ofthem.
How and why exactly might they do that?
How Chameleons Change Colors
A chameleon can change the color of its skin in a couple of minutes.
Scientists now have discovered how they do it.
Chameleons have two layers of crystal-like skin cells.
They change the structure of the upper layer of cells to alter the way light is reflected.
When a chameleon is relaxed,the cells are close to each other,which reflects light with shortwavelengths,like the color blue.
When a chameleon's skin gets excited,the distance between their cells expands,which reflectslight with long wavelengths like the colors orange or red.
Only adult male chameleons are capable of this color change.
It usually happens when they see a rival male or are courting a mate.
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Midlothian,Virginia is where we're start today.
They're at Bailey Bridge Middle School.
We'll jump to the West Coast town of El Centro.
It's in Southern California,not far from the Mexico border.
Hello to The Spartans of Central Union High School.
And out in the Pacific,on the Hawaiian island of Honolulu,great to hear from The Mustangs.
They're online at Moanalua Middle School.
Cars are not allowed in the Italian city of Venice.
You can take a boat through its 177 canals.
You can walk over its 409 bridges.
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