1 . As a popular subject of study among evolutionary ecologists, the three-spined stickleback (三刺鱼) is known for their different shapes, sizes, and behaviors—they can even live in both sea water and fresh water, and under a wide range of temperatures. But what makes that?
The researchers tracked six populations of the fish before and after seasonal changes to their environment, using genome sequencing (基因组测序) . Seasonal changes result in great changes in habitat structure and balance of salt and freshwater, and only those fish able to tolerate these rapid changes survive into the next season.
“These changes probably resemble the habitat shifts experienced by stickleback populations during the past 10,000 years, says Professor Barrett “We hope to gain insight into the genetic changes that may have resulted from natural selection long in the past.”
Remarkably, the researchers discovered the evidence of genetic changes driven by the seasonal shifts in habitats, which mirrored the differences found between long-established freshwater and saltwater populations. “These genetic changes occurred in independent populations over a single season, highlighting just how quickly the effects of natural selection can be detected,” says Professor Barrett, “the findings suggest that we may be able to use the genetic differences to predict how populations may adapt to the environment.”
The research emphasizes the importance of studying species in dynamic environments to gain a better understanding of how natural selection operates. In the further research, they plan to investigate how repeatable the observed genetic changes are, by testing whether they show up year after year. Doing so would demonstrate their ability to reliably forecast the evolutionary future of these populations.
1. What is paragraph 2 mainly about?| A．The difficulties of the research. | B．The purpose of the research. |
| C．The background of the research. | D．The methods of the research. |
| A．Habitat shifts. | B．Genetic changes. |
| C．Seasonal changes. | D．Independent populations. |
| A．To know what natural selection is. |
| B．To study species in dynamic environments. |
| C．To test the reliability of the present discoveries. |
| D．To forecast the evolutionary future of certain species. |
| A．A science magazine. | B．A science fiction. |
| C．An advertisement. | D．A novel. |
2 . When the leaves begin to change their colors and the birds head south, we know the season is starting to change. On September 7 comes White Dew (白露), the 15th solar term (节气) of the year. It indicates (标志着) the beginning of the cool autumn. As the temperature falls, white dew is often seen on the grass and trees at night.
For w riters and poets, autumn is a difficult season to describe. It ’s the end of the summer, and therefore a little sad. The days seem to get shorter, and when you wake in the morning, t here’s mist(薄雾) and it’s cooler. Winter is just around the corner.
American writer Ernest Hemingway wrote in his book A Moveable Feast (《流动的盛宴》), “You expected to be sad in the fall. Part of you died each year when the leaves fell from the trees and their branches (枝条) were bare (光秃秃的) against the wind and the cold, wintry light. ”
But on the other hand, autumn has its good side. There are so many changes at this time of year, such as the colorful leaves and cooler nights. French w riter Albert Camus even thought autumn was a second spring, “when every leaf is a flower.” This view is also found in the most famous autumn poem in English literature, To Autumn by John Keats. In that poem, Keats says that autumn has its own songs, just like spring.
Another theme of this season is wisdom (智慧). The arrival of autumn is thought to be similar to a person becoming mature (成熟的).
The great Irish poet W.B. Yeats used this idea in his poem The Wild Swans at Coole (《库尔的野 天鹅》), writing about the changing seasons in Coole Park in the west of Ireland. Seeing and counting 59 swans, he remembers first making the count as a young man. Seeing the swans do the same thing for all those years, he’s reminded (提醒) that even though we get older, our hearts always stay the same age.
1. What can be concluded about White Dew ?| A．It is often ignored by w riters and poets. | B．It is the time of year with the most rainfall. |
| C．It is when the temperature begins to drop. | D．It indicates the end of the autumn. |
| A．point out that autumn is very cold | B．present the sad part of autumn |
| C．show that winter w ill soon come | D．express sadness about the end of life |
| A．Autumn is an important season for man. | B．We can always stay young at heart. |
| C．Autumn is related to one’s grow ing old. | D．Nature is full of lessons to be learned. |
| A．The solar term White Dew. | B．Why autumn is a sad season. |
| C．Autumn weather and activities. | D．Famous writers’ description of autumn. |
