If you think about the countless number of animal species on our planet, the giraffe is perhaps one of the most interesting. With its unusual pattern and incredibly long neck, it looks like no other animal on Earth. But how did this mammal come to get its famously huge neck? Well, scientists have been asking themselves this question for centuries.
The most commonly believed answer is that the massive neck — which measures on average 180 centimeters and weighs about 270 kilograms — evolved to allow the animal to reach the leaves of tall trees.
British scientist Charles Darwin was one of the first people to propose this idea in the 1800s.“The giraffe… has its whole frame beautifully adapted for browsing on the higher branches of trees,”he wrote in his famous 1859 book On the Origin of Species. It was Darwin’s belief that the giraffe once had a much shorter neck, but over time, evolution led to longer-necked giraffes being born, which in turn survived as they were able to reach the food that others couldn’t. Yet, there are other theories. According to a paper published in September in the Journal of Arid Environments, the giraffe’s neck evolved to increase its surface-area-to-volume ratio. Because the animal’s neck increases its body’s surface area, it makes it easier for it to keep cool, the paper’s authors wrote. This phenomenon can be seen everywhere in nature, and even in engineering.
For example, this is why elephants have such large ears, and why radiators (暖气片) in homes are flat and thin, as a large surface area allows heat to escape quicker.
Meanwhile, some believe that competition is the answer. A 1996 study by two South African zoologists argued that the male giraffes with the biggest necks are the ones who “win” access to females to reproduce, as they are better at fighting, meaning that their long necks are passed down through the generations. So, it seems like there’s still no definite answer to the question. But until we find the truth, we should at least enjoy this beautiful and interesting creature for what it is today, rather than wonder about where it came from.
1.What idea did Charles Darwin put forward in his book?
A.Giraffe’s necks are 180 cm long and weigh 270 kg on average.
B.Giraffes with a long neck are better at fighting.
C.Giraffes are a species that is born with a long neck.
D.Longer-necked giraffes are able to survive better.
2.What is the article mainly about?
A.Charles Darwin’s theory of evolution.
B.Different functions of the giraffe’s long neck.
C.How the giraffe manages to survive in nature.
D.Theories about why the giraffe has a huge neck.
This article is for all of the teenagers out there. Even though ____ you are years from being fully grown, society regularly expects you to adult. Yes, you are ____ in many ways: many of you drive and do so quite safely, and you handle schedules that would ____ many adults. But you probably cannot process caffeine (咖啡因) as constantly as your parents can because of your still-growing bodies and brains.
I understand it feels grown-up to be drinking a cup of Starbucks. But all of this caffeine may worsen your anxiety, affect tonight’s sleep and tomorrow’s school performance, ____ nutrient absorption and even cause real trouble when mixed with alcohol. The following four aspects may well ____ the theme of this article.
The power of caffeine
Caffeine is widely considered a drug that is socially acceptable, universally used, even cool, but it still causes ____ symptoms such as headaches, fatigue and a lack of attention when removed from coffee-addicts’ diets.
How much is healthy?
Caffeine is by no means a nutrient; you do not need it to be healthy. ____, it is a substance that can leave you lacking nutrients because it has been shown to reduce calcium (钙). Caffeine probably causes the body to release water. And the more caffeinated drinks you consume, the less likely you are to drink water. So experts say that adolescents should consume ____ amounts of caffeine a day (≤100 mg).
Caffeine’s ____
According to the Centers for Disease Control and Prevention, about 65 percent of middle and higher schoolers are ____ to insufficient sleep on school nights. Some of their sleep problems can be mainly attributed to (归因于) caffeine, which can remain in the body for seven hours after ____, thus causing teens’ worse performance the next day. It is widely assumed that adequate sleep ____ proper growth and brain development. During childhood and adolescence, the brain goes through a period called synaptic pruning (突触修剪) when unnecessary connections are promoted.
Caffeine labelling
Caffeine is not listed on the Nutrition Facts column on food labels because it is not a ____. It may be listed as an ingredient, but the amount is not required. Caffeine is now added to foods such as gum, candy and water, along with makeup and beauty products that ____ to reduce swelling (肿块).
Taste preferences and eating habits are often cultivated in childhood and adolescence, so teens, when you consume sweet, caffeinated drinks every time you feel sluggish (无精打采的), you are creating a pattern that may be hard to break as an adult. It is advisable to come up with other ____ ways to boost energy so that you can master adulting better than many adults.
1.A. potentially B. necessarily C. developmentally D. materially
2.A. mature B. experienced C. productive D. disciplined
3.A. delight B. frustrate C. liberate D. exclude
4.A. promote B. assist C. intensify D. discourage
5.A. call for B. account for C. turn to D. appeal to
6.A. withdrawal B. addiction C. nutrition D. infection
7.A. Therefore B. Instead C. Moreover D. Otherwise
8.A. initial B. sufficient C. moderate D. stable
9.A. reputations B. confirmations C. implications D. disadvantages
10.A. subjected B. alerted C. reduced D. opposed
11.A. stimulation B. concentration C. excitement D. consumption
12.A. results from B. contributes to C. benefits from D. attends to
13.A. therapy B. material C. nutrient D. substitute
14.A. fail B. appear C. promise D. happen
15.A. instructive B. comprehensive C. extensive D. alternative
Always the _____ , Franklin believed the practice of moving the time could save on the use of candlelight, as candles were expensive at the time.
A.journalist B.physicist C.chemist D.economist
Heat exhaustion is generally_____ by sweaty skin, tiredness, sickness, dizziness and sometimes fainting, resulting from an inadequate intake of water and the loss of fluids.
A.featured B.characterized C.distinct D.typical
The human body can tolerate only a small range of temperature, _____ when the person is engaged in vigorous activity.
A.essentially B.specially C.generally D.especially
The picture offer the best evidence to date that a planet once _____ dead is actually a lively pot of geological change.
A.assuming B.assumed C.resuming D.resumed
