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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