Biology (Octopus)
Professor:
Ok, now I want to talk about an animal
that has a fascinating set of defense mechanisms. And that‘s the octopus, one
of the unusual creatures that live in the sea. The octopus is prey to many
species, including humans, so how does it escape its predators?
(1) Well, let me back up
here a second. Anyone ever heard of Proteus? Proteus was a God in Greek
mythology who could change form. He could make himself look like a lion or a
stone or a tree, anything you wanted, and he could go through a whole series of
changes very quickly.
Well, the octopus is
the real world version of Proteus. Just like Proteus, the octopus can go
through all kinds of incredible transformations. And it does this in three ways: by
changing color, by changing its texture, and by changing its size and shape.
For me, the most fascinating
transformation is when it changes its color. It‘s a normal skin color, the one
it generally presents, is either red or brown or even grey, and it ‘s speckled
with dark spots. (2) But when it wants to blend in with its environment to hide
from its enemies, it can take on the color of its immediate surroundings: the ocean floor, a rock,
a piece of coral, whatever. Charles?
Student:
Do
we know how that works, I mean, how they change colors?
Professor:
Well, we know that the reaction that
takes place is not chemical in nature. The color changes are executed by two
different kinds of cells in the octopus ‘ skin, mainly by color cells on the
skin‘s surface call chromatophores.
Chromatophores consist of tiny sacks
filled with color dye. There might be a couple hundred of these color sacks per
square millimeter of the octopus ‘ skin, and depending on the species, they can
come in as many as five different colors. Each one of these sacks is controlled
by muscles. If the muscles are relaxed, the sack shrinks, and all you see is a
little white point. But if the muscle‘s contract, then the sack expands, and you can see
the colors. And by expanding different combinations of these color sacks to
different degrees, the octopus can create all sorts of colors. Yes, Elizabeth?
Student:
And just with various combinations of
those five colors, they can recreate any color in their environment?
Professor:
Well, they can no doubt create a lot
with just those five colors, but you are right, maybe they can‘t mimic every
color around them, so that‘s where the second kind of cell comes in.
Just
below the chromatophores is a layer of cells that reflect light from the
environment, and these cells help the octopus
create a precise match with the colors that surround them. The colors from the
color sacks are supplemented with colors that are reflected from the
environment, and that ‘s how they are able to mimic colors with such precision.
So, that‘s how octopus mimic colors.
But
they don‘t just mimic the colors in their environment; they can also mimic the
texture of objects in their environment. They have these little projections on
their skin that allow them to resemble various textures. The projections are
called papillae. (3) If the octopus wants to have a rough texture, it raises the
papillae. If it wants to have a smooth texture, it flattens out the papillae,
so it can acquire a smooth texture to blend in with the sandy bottom of the
sea. So the octopus has the ability to mimic both
the color and the texture of its environment. And it‘s truly amazing how well
it can blend in with its surroundings. You can easily swim within a few feet of
an octopus and never see it.
Student:
I
read that they often hide from predators by squirting out a cloud of ink, or
something like that.
Professor:
Yes.
The octopus can release a cloud of ink if it feels threatened. But it doesn‘t
hide behind it, as is generally believed. Um, the ink cloud is ... it serves to
distract a predator while the octopus makes its escape.
(4) Um, now there‘s a third way that octopus can transform
themselves to blend in with or mimic their environment, and that‘s by changing their shape and size,
well, at least their apparent size. The muscular system of the octopus enables
it to be very flexible to assume all sorts of shapes and postures. So it can contract into the shape of a little round stone,
and sit perfectly still on the seafloor. Or it can nestle up in the middle of a
plant and take the shape of one of the leaves. Even
Proteus would be impressed, I think.
Question 1：
Why does the
professor first mention Proteus?
A. To explain how
the octopus got its scientific name.
B. To introduce
the octopus’ exceptional abilities.
C. To point out that the
octopus played an important role in Greek mythology.
D. To provide an example of a
mythological character that was part animal and part human.
答案：B
解析：
Professor：Well, let me back
up here a second. Anyone ever heard of Proteus? Proteus was a God in Greek
mythology who could change form. He could make himself look like a lion or a stone or a tree, anything you
wanted, and he could go through a whole series of changes very quickly. Well,
the octopus is the real world version of Proteus. Just
like Proteus, the octopus can go through all kinds of incredible
transformations.
由上可知，教授引用Proteus的例子介紹章魚的特性。
關鍵訊號詞：Just like
......
Question 2：
How does an octopus change
color to match the colors in its environment? Click on 2 answers
A. By raising its papillae.
B. By releasing colored ink.
C. By reflecting light from
its environment.
D. By contracting the muscles
around its chromatophores.
答案：CD
解析：
Professor： But when it wants to
blend in with its environment to hide from its enemies, it can take on the
color of its immediate surroundings: the ocean floor, a
rock, a piece of coral, whatever. ............... But if the
muscle’s contract, then the sack expands, and you can see the colors. And by
expanding different combinations of these color sacks to different degrees, the
octopus can create all sorts of colors.
教授提到章魚會從周圍環境中取色。此外，如果肌肉收縮，色素細胞裡的小袋子會膨脹，因此就能看見顏色了。
關鍵訊號詞：But when
...... / But if ......
Question 3：
What does the
professor say about the function of the papillae?
A. They produce
dye in different colors.
B. They propel
the octopus through the water.
C. They change
the texture of the octopus’ skin.
D. They help the
octopus contract into a smaller shape.
答案：C
解析：
Professor：But they don’t
just mimic the colors in their environment; they can also mimic the texture of
objects in their environment. They have these little projections on their skin
that allow them to resemble various textures. The projections are called
papillae. If the octopus wants to have a rough texture, it raises the papillae. If
it wants to have a smooth texture, it flattens out the papillae, so it can
acquire a smooth texture to blend in with the sandy bottom of the sea.
教授提到章魚可藉由調整papillae使皮膚紋理粗糙或光滑。
關鍵訊號詞：They can also
... / If ... so ...
Question 4：
What two examples
does the professor mention to describe the octopus’ ability to change its
shape? Click on 2 answers
A. A small round
stone
B. The leaves of
a plant
C. A cloud of ink.
D. A piece of
coral.
答案：AB
解析：
Professor：Um, now there’s a third way that octopus can transform themselves to
blend in with or mimic their environment, and that’s by changing their shape
and size, well, at least their apparent size. The muscular system of the
octopus enables it to be very flexible to assume all sorts of shapes and
postures. So it can contract into the shape of a little round stone, and sit
perfectly still on the seafloor. Or it can nestle up in the middle of a plant and take the
shape of one of the leaves. Even Proteus would be impressed, I think.
教授舉例章魚可以收縮鑽進小石頭或是依偎在植物中間偽裝成一片葉子。
關鍵訊號詞： a third
way /
So it can ...... Or it can ......
戴爾美語榮獲台灣區托福、GRE、雅思三考場，原地上課考試
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