In 1872, a 12-year-old Chinese boy
8 . If you’ve ever been bitten by a mosquito, you know how frustrating their bites can be.
Why does a mosquito bite itch?
When a mosquito bites you, it pierces the skin using a special mouthpart to suck up blood and injects saliva (唾液) into your skin. Mosquitoes’ saliva has lots of proteins in it, some of which our body recognizes as foreign, and our immune cells spring into action to try to fight them.
What helps resist the urge to scratch?
“Don’t scratch” is the advice that most experts and health professionals give. As hard and sometimes unrealistic as it can sound, scratching inflames (发炎) the skin, and the inflammation makes the skin itch more. “
Instead, there are dozens of creams and sprays that promise itch relief as well as home remedy (疗法). Choose what’s right for you can often come down to trial and error. In general, all of the various anti-itch creams are very similar. There is no scientific evidence these remedies work, and they can come with their own precautions or side effects.
Some people can have serious allergic reactions to mosquitoes, although in practice it is rare, Vosshall said. If you experience severe symptoms such as breathing trouble, you should seek medical attention immediately.
| A．When to seek medical attention? |
| B．What to do with a mosquito bite? |
| C．It’s not the bite that causes the itch |
| D．The more you scratch, the more they itch |
| E．The little red bumps swell up almost immediately |
| F．Scratching can cause secondary infections and prolong the irritation |
| G．In fact, the best remedy to fight the itch is to prevent a bite in the first place |
9 . The Amazon rainforest is as undisturbed a place as most people can imagine, but even there, the effects of a changing climate are playing out. Now, research suggests that many of the region’s most sensitive bird species are starting to evolve in response to warming.
Birds are often considered sentinel (哨兵) species-meaning that they indicate the overall health of an ecosystem-so scientists are particularly interested in how they’re responding to climate change. In general, the news has not been good. For instance, a 2019 report by the National Audubon Society found that more than two-thirds of North America’s bird species will be in danger of extinction by 2100 if warming trends continue on their current course.
For the new study, researchers collected the biggest dataset so far on the Amazon’s resident birds, representing 77 non-migratory species and lasting the 40 years from 1979 to 2019. During the study period, the average temperature in the region rose, while the amount of rainfall declined, making for a hotter, dryer climate overall. According to the report on November 12 in the journal Science Advances, 36 species have lost substantial weight, as much as 2 percent of their body weight per decade since 1980. Meanwhile, all the species showed some decrease in average body mass, while a third grew longer wings.
Because of the study’s long time series and large sample sizes, the authors were able to show the morphological (形态学的) effects of climate change on resident birds. However, the researchers themselves are unsure and wonder what advantage the wing length changes give the birds, but suppose smaller birds may have an easier time keeping cool. In general, smaller animals have a larger rate of surface area to body size, so they dissipate more heat faster than a bigger animal. Less available food, such as fruit or insects, in dryer weather might lead to smaller body size.
1. Why are scientists fond of doing research on birds?| A．They have small body sizes. | B．They are sensitive to hot weather. |
| C．They live in an undisturbed rainforest. | D．They are ecological balance indicators. |
| A．A third of species have been extinct for a decade. |
| B．36 species lost 2% of their body weight every year. |
| C．Two-thirds of species showed a considerable decrease in weight. |
| D．About 26 species responded to climate change with longer wings. |
| A．Put off. | B．Give off. | C．Put away. | D．Give away. |
| A．That; expose to | B．That; be exposed to | C．It; expose to | D．It; be exposed to |
