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1、Toronto is some 475 km in the northwest of New York, while Vancouver, only 200 km from Seattle, is even closer to a major American city.
A、is some 475
B、in the northwest of
C、while Vancouver, only 200
D、even closer to a major American city
E、没有错误
2、The panel of distinguished scientists gathered in Cambridge to discuss the evidences in support of Dr. Thistlethwaite’s revolutionary hypothesis.
A、The panel of distinguished scientists
B、in Cambridge
C、discuss the evidences in
D、support of
E、没有问题
3、Ordinarily the surface of the planet is nearly at the boHing point of water on Earth, 100.2-101 °C according to the data from the orbiting satellite.
A、surface of the planet
B、nearly at the
C、boHing point
D、from the orbiting satellite
E、没有问题
Even though cultures widely assume that boys are stronger and sturdier than girls, basic biological weaknesses are built into the male of our species. First of all, human males seem to be slowly disappearing. Mother Nature has always acknowledged and compensated for the fragility and loss of boys by arranging for more of them: 106 male births to 100 female newborns over the course of human history. But in recent decades, from the United States to Japan, from Canada to northern Europe, wherever researchers have looked, the rate of male newborns has declined. Examining US birth records for the years between 1970 and 1990, they found 1.7 fewer boys per 1,000 than in decades and centuries past; Japan's loss in the same decades was 3.7 boys.
Boys are also more than two-thirds more likely than girls to be bom prematurely before the 37th week of pregnancy. And, despite advances in public health, boys in the 1990s faced a 30 percent higher chance of death by their first birthday than girls; in contrast, back in the 1750s, they were only 10 per cent more likely than girls to die so early in their lives.
Once they make it to childhood, boys face other challenges. They are more prone to a range of neurological disorders. Autism 自闭症 is notoriously higher among boys than girls: now nearly five times more likely, as tallied by the US Centers for Disease Control and Prevention. They are more susceptible than girls to damage from very low-level exposure to lead. Yet another problem: boys suffer from asthma at higher rates. There's also a stronger link between air pollution and autism in boys.
Why do boys face such a burden of physical challenges? The answer is that the male’s problems start in the womb: from his more complicated fetal development, to his genetic makeup, to how his hormones work. The nine-month transformation from a few cells to an infant is a time of great vulnerability. Many chronic illnesses are seeded in the womb. In our species, the female is the default gender, the basic simpler model: Humans start out in the womb with female features (that is why males have nipples). The complicated transformation in the womb from female to male exposes the male to a journey packed with special perils. When the first blast of testosterone 睾酮 from the Y gene comes along at about the eighth week, the unisex brain has to morph into a male brain, killing off some cells in the communication centers and growing more cells in the sex and aggression centers. The simpler female reproductive system has to turn into the more complex male reproductive tract, developing tissues such as the testis and prostate 前列腺.Further, it takes a greater number of cell divisions to make a male; with each comes the greater risk of an error as well as the greater vulnerability to a hit from pollutants.
On top of that challenge, the human male’s XY chromosome 染色体 combination is simply more vulnerable. The two XXs in the female version of our species offer some protection: In disorders where one X chromosome has a genetic defect, the female’s healthy backup chromosome can take over. But with his single X chromosome, the male lacks a healthy copy of the gene to fall back on. The X chromosome, which never shrank, is also a larger chromosome “with far more genetic information than the Y chromosome,’’ finds Irva Hertz-Piciotto, a University of California at Davis autism researcher, “so there may be some inherent loss of key proteins for brain development or repair mechanisms in boys.” This is a clue to the higher autism rate among boys, she asserts.
Females also have a stronger immune system because they are packed with estrogen 雌激素,a hormone that counteracts the antioxidant process. “Estrogen protects the brain,” explains Theodore Slotkin, professor of neurobiology at Duke University's School of Medicine. “It repairs and replaces, even after neural injury,” Low estrogen even leaves boys more sensitive to head injuries. The male brain “is simply a more fragile apparatus, more sensitive to almost all brain insults,” says lead poisoning expert Herbert Needleman.
It is the high levels of testosterone in the womb at critical times in gestation, according to British psychopathologist Simon Baron-Cohen, that are responsible for what he calls “the extreme male brain” -- the kind exhibited by autistic boys - low in empathy, high in systematizing. And in fact US researchers in recent decades have found unusually low estrogen and high testosterone levels among boys with autism.
If the balance of hormones is out of whack in males, what made that happen? Researchers are coming up with some clues. In the New York City neighborhoods near Columbia University's Center for Children’s Environmental Health, families for years routinely sprayed their apartments with a popular insecticide, chlorpyrifos, until it was banned from household use in 2001. The researchers found that prenatal exposure to the chemical seemed to have more of an effect on reducing the IQs of boys than girls. Disruption of their male hormones may be the reason, “One possible explanation for the greater sensitivity of boys to chlorpyrifos is that the insecticide acts as an endocrine disruptor 肉分泌'干扰素 to suppress sex-specific hormones,” said study leader Megan Horton of Columbia.
Similarly, pregnant mothers' exposure to phthalates 邻苯二甲酸酉旨一used in making some vinyl 乙矯基 products and toys as well as some personal care products - has been linked to bigger changes in the behavior, such as aggression and attention problems, of their sons than their daughters. Phthalates also may feminize male genitalia.
Boys also seem to be more vulnerable to bisphenol A, an estrogenic substance used to make polycarbonate plastics as well as the linings of food and beverage cans. Boys, but not girls, exposed to higher bisphenol A levels in the womb or during childhood had more hyperactivity, aggression and anxiety problems, according to a University of California at Berkeley study. In addition, pregnant women exposed to higher levels of the chemical gave birth to baby boys with lower thyroid hormones 甲状腺激素.No such effect was detected in the baby girls. No one knows what these lower levels may mean for the boys’ health because they remained within normal boundaries, but it could have important effects because thyroid hormones guide brain development.
Some of these chemicals act like fake estrogens, others like fake testosterone, but both types seem to disrupt normal development. Animal tests show that a dose of these chemicals inflict the most damage when it hits a fetus. And, because of their biological vulnerabilities, it is boys who may experience the most effects. While not forgoing the push for fairness and equality, it seems wise to accept the scientific reality of male weaknesses. This likely won't mean the end of men, but their vulnerability to environmental contaminants and diseases could have serious ramifications for the future of the entire human race unless we find ways to protect them from harm.
1.If text B is accurate, then the evidence for the assertion that human males are gradually disappearing is( ) .
A、incontrovertible
B、so weak as to call the assertion into question
C、largely from advanced industrial societies and needs to be supplemented with data from other types of societies
D、strong enough to warrant future research into the post-masculine world that lies ahead
2.Compared with girls, boys are( ) .
A、about equally able to survive to their first birthday.
B、still less likely to survive for a year after birth, but the gap is narrowing.
C、less likely to survive till their first birthday, and the gap is wider than in earlier centuries.
D、much likelier to survive to their first birthday, though the gap is not so wide as it was in the 1700s.
3.Nipples in humans are found on the( ) .
A、head.
B、chest.
C、hips.
D、limbs.
4.In paragraph 10 the author asserts that chronic diseases( ) .
A、begin before birth but only become apparent over time.
B、are less characteristic of women than of men.
C、originate, as a rule, before children are bom.
D、are often the eventual result of prenatal conditions and stresses.
5.Backup in paragraph 11 means something that ( ).
A、can step in and take over the function of something that is not working properly.
B、destroys a malfunctioning part, thus benefiting the overall system or organism.
C、prevents a system from continuing along a path that may end in breakdown or destruction.
D、can reverse and change its direction when it encounters a problem, thus enabling a process to continue.
6.The levels of thyroid hormones in new bom males, mentioned in paragraph 16, ( ).
A、are not alarming in themselves, but significant because they are so different for males and females.
B、will definitely lead to more brain-damaged boys than girls,
C、seem certain to produce a marked gap in brain development that will favor girls over boys.
D、lead to more hyperactivity, aggression and anxiety among male children than among females.
7.Imagine that environmental pollution continues at current or higher levels in China. If the information in text B is correct, then Chinese doctors should expect to observe ( ).
A、a decline in the rates of autism, asthma and brain damage from lead poisoning among Chinese children
B、a roughly similar pattern of increasing incidence of autism, asthma and lead-linked brain damage among all mainland children
C、fewer cases of asthma among boys growing up in mainland cities and towns but more cases of autism and lead-linked brain damage among all Chinese children
D、more autism, asthma and lead-linked brain damage among Chinese boys growing up in cities than among other groups of young people in the PRC
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