今回は、第６問 A を終えて
第６問 B に入ります。
それでは、第６問 B の問題を見ていきましょう。
B You are in a student group preparing for an international science
presentation contest. You are using the following passage to create your part
of the presentation on extraordinary creatures.
Ask some to name the world’s toughest animal, and they might say the
Bactrian camel as it can survive in temperatures as high as 50℃, or the Arctic
fox which can survive in temperatures lower than -58℃. However, both
answers would be wrong as it is widely believed that the tardigrade is the
toughest creature on earth.
Tardigrades, also known as water bears, are microscopic creatures. which
are between 0.1 mm to 1.5 mm in length. They live almost everywhere, from
6,000-meter-high mountains to 4,600 meters below the ocean’s surface. They
can even be found under thick ice and in hot springs. Most live in water, but
some tardigrades can be found in some of the driest places on earth. One
researcher reported finding tardigrades living under rocks in a desert without
any recorded rainfall for 25 years. All they need are a few drops r a thin
layer of water to live in. When the water dries up, so do they. The lose all
but three percent of their body’s water and their metabolism slows down to
0.01% of its normal speed. The dried-out tardigrade is now in a state called
“tun,” a kind of deep sleep. It will continue in this state until it is once again
soaked in water. Then, like a sponge, it absorbs the water and springs back to
life again as if nothing had happened. Whether the tardigrade is in tun for 1
week or 10 years does not really matter. The moment it is surrounded by
water, it comes alive again. When tardigrades are in a state of tun, they are
so tough that they can survive in temperatures ad low as -272℃ and as high
as 151℃. Exactly how they achieve this is still not fully understood.
Perhaps even more amazing than their ability to survive on earth – they
have been on earth for some 540 million years – is their ability to survive in
space. In 2007, a team of European researchers sent a number of living
tardigrades into space on the outside of a rocket for 10 days. On their return
to earth, the researchers were surprised to see that 68% were still alive. This
means that for 10 days most were able to survive X-rays and ultraviolet
radiation 1,000 times more intense than here on earth. Later, in 2019, an
Israeli spacecraft crashed onto the moon and thousands of tardigrades in a
state of tun were spilled onto its surface. Whether these are still alive or not
is unknown as no one has gone to collect them – which is a pity.
Tardigrades are shaped like a short cucumber. They have four short legs
on each side of their bodies. Some species have sticky pads at the end of each
leg, while others have claws. There are 16 known claw variations, which help
identify those species with claws. All tardigrades have a place for eyes, but
not all species have eyes. Their eyes are primitive, only having five cells in
total – just one of which is light sensitive.
Basically, tardigrades can be divided into those that eat plant matter, and
those that eat other creatures. Those that eat vegetation have a ventral
mouth – a mouth located in the lower part of the head, like a shark. The type
that eats other creatures has a terminal mouth, which means the mouth is at
the very front of the head, like a tuna. The mouths of tardigrades do not have
teeth. They do, however, have two sharp needles, called stylets, that they use
to pierce plant cells or the bodies of smaller creatures so the contents can be
Both types of tardigrade have rather simple digestive systems. The mouth
leads to the pharynx (throat), whether digestive juices and food are mixed.
Located above the pharynx is a salivary gland. This produces the juices that
flow into the mouth and help with digestion. After the pharynx, there is a tube
which transports food toward the gut. This tube is called the esophagus. The
middle gut, a simple stomach/intestine type of organ, digests the food and
absorbs the nutrients. The leftovers then eventually move through to the anus.
問１ Which of the following should you not include for【 44 】?
① eight short legs
② either blind or sighted
③ plant-eating or creature-eating
④ sixteen different types of feet
⑤ two stylets rather than teeth
問２ For the Secrets to Survival slide, select two features of the tardigrade
which best help it survive. (The order does not matter.) 【 45 】・【 46 】
① In dry conditions, their metabolism drops to less than one percent of normal.
② Tardigrades in a state of tun are able to survive in temperatures exceeding
③ The state of tun will cease when the water in a tardigrade’s body is above
④ Their shark-like mouths allow them to more easily eat other creatures.
⑤ They have an ability to withstand extreme levels of radiation.
問３ Complete the missing labels on the illustration of a tardigrade for
Digestive Systems slide.【 47 】
① (A) Esophagus (B) Pharynx (C) Middle gut (D) Stylets (E) Salivary gland
② (A) Pharynx (B) Stylets (C) Salivary gland (D) Esophagus (E) Middle gut
③ (A) Salivary gland (B) Esophagus (C) Middle gut (D) Stylets (E) Pharynx
④ (A) Salivary gland (B) Middle gut (C) Stylets (D) Esophagus (E) Pharynx
⑤ (A) Stylets (B) Salivary gland (C) Pharynx (D) Middle gut (E) Esophagus
問４ Which is the best statement for the final slide? 【 48 】
① For thousands of years, tardigrades have survived some of the harshest
conditions on earth and in space. They will live longer than humankind.
② Tardigrades are from space and can live in temperatures exceeding the
limits of the Arctic fox and Bactrian camel, so they are surely stronger
waters of hot springs; and they can also thrive on the moon.
③ Tardigrades are, without a doubt, the toughest creatures on earth. They
can survive on the top of mountains; at the bottom of the sea; in the
waters of hot springs; and they can also thrive on the moon.
④ Tardigrades have survived some of the harshest conditions on earth, and
at least one trip into space. This remarkable creature might outlive the
問５ What can be inferred about sending tardigrades into space? 【 49 】
① Finding out whether the tardigrades can survive in space was never
thought to be important.
② Tardigrades, along with other creatures that have been on earth for
millions of years, can withstand X-rays and ultraviolet radiation.
③ The Israeli researchers did not expect so many tardigrades to survive
the harsh environment of space.
④ The reason why no one has been to see if tardigrades can survive on the
moon’s surface attracted the author’s attention.