A series of research projects in recent years have looked at the small, spiny, marine invertebrate known as the sea urchin. The sequence of their genetic code has been successfully analysed, revealing a remarkably close resemblance to that of humans. This provides a firmer foundation for the claim that humans and sea urchins share a common ancestor, which must have lived over 540 million years ago.
The red sea urchin, found off the West coast of North America and elsewhere, was considered a pest in the 1960's and attempts were made to eradicate them wherever locals were farming kelp. In the 1970s, though, American sea fisheries discovered a lucrative market in Japan, where certain internal organs of these creatures were considered a delicacy, and by the 1990s they had become one of the most valuable marine resources.
There are implications for these fisheries in the latest findings about the way sea urchins mature. Not only are the invertebrates capable of reaching an age of 200 years or more, but they also show no signs of age-related degeneration. In fact, the more advanced the age of an urchin is, the more enhanced its powers of reproduction seem to be. On the other hand, population growth is limited due to the ease with which juvenile urchins fall prey to a range of environmental threats.
Studies have also looked at growth rates, using measures of carbon-14, which has increased in all living organisms following the atmospheric testing of atomic weapons in the 1950s. These studies confirmed earlier findings, obtained using injections of tetracycline, that the process of enlargement never reaches a ceiling. Growth rates may diminish to only an extra millimeter in circumference per year but they do not cease.
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54. According to the passage, what do red sea urchins eat? a. rotting animal matter
b. tetracylin
c. microscopic animal life
d. kelp
55. What do we learn about the growth rates of the urchins? a. They are generally unreliable.
b. Atmospheric tests affect the growth rates
c. The lastest technique involves using tetracycline.
d. One technique was not possible before the 1950s.
56. Which of the following is NOT true?
a. Human and urchins’ DNAs are identical.
b. Sea urchins first appeared 540 million years ago.
c. Harvesting sea urchins can be a profitable business.
d. The red sea urchin is found only off the West coast of America.
57. According to the passage, there are not more sea urchins in the oceans because... a. of contamination from carbon-14
b. age-related degeneration is widespread.