E
Fish have ears. Really. They’re quite small and have no opening to
the outside world carrying sound through the body. For the past seven years,
Simon Thorrold, a university professor, has been examining fish ears, small
round ear bones called otoliths.
As fish grow, so do their otoliths. Each day, their otoliths gain a
ring of calcium carbonate (碳酸钙). By looking through a microscope (显微镜) and counting these rings, Thorrold can determine the exact age of
a young fish. As a fish gets older, its otoliths no longer get daily rings.
Instead, they get yearly rings, which can also be counted, giving information
about the fish’s age, just like the growth rings of a tree.
Ring counting is nothing new to fish scientists. But Thorold has
turned to a new direction. They’re examining the chemical elements (元素) of each otolith ring.
The daily ring gives us the time, but chemistry tells us about the
environment in which the fish swam on any given day. These elements tell us
about the chemistry of the water that the fish was in. It also says something
about water temperature, which determines how much of these elements will
gather within each otolith ring.
Thorrold can tell, for example, if a fish spent time in the open
ocean before entering the less salty water of coastal areas. He can basically
tell where fish are spending their time at any given stage of history.
In the case of the Atlantic croaker, a popular saltwater food fish,
Thorrold and his assistant have successfully followed the traveling of young
fish from mid-ocean to the coast, a journey of many hundreds of miles.
This is important to managers in the fish industry, who know nearly
nothing about the whereabouts of the young fish for most food fish in the
ocean. Eager to learn about his technology, fish scientists are now lending
Thorrold their ears.
72. What can we
learn about fish ears from the text?
A. They are small soft rings. B.
They are not seen from the outside.
C. They are opening only on food fish. D.
They are not used to receive sound.
73. Why does the
writer compare the fish to trees?
A. Trees gain a growth ring each day. B.
trees also have otoliths.
C. Their growth rings are very small. D.
They both have growth rings.
74. Why is it
important to study the chemistry of otolith rings?
A. The elements of the otoliths can tell the history of the sea.
B. Chemical contents of otoliths can tell how fast fish can swim.
C. We can know more about fish and their living environment.
D. Scientists can know exactly how old a fish is.
75. How would you
understand “fish scientists are now lending their ears”?
A. They are very interested in Thorrold’s research fingings.
B. They want to know where they can find fish.
C. They lend their fish for chemical studies.
D. They wonder if Thorrold can find growth rings from their ears.
第II卷(共35分)