Eternal（永久的） youth is the first thing many of us might wish for，but there's always a catch.Now，scientists have discovered a version of this story playing out in ant nests，as parasites（寄生蟲） greatly extend the lifespan of worker ants at a terrible cost.
To investigate what's going on，researchers at Johannes Gutenberg University Mainz watched 58 colonies（群體） of the ants for three years，some infected with parasites and some without.By the end of that period，none of the original uninfected worker ants were still alive-- but about 53 percent of the infected insects were.The upper limit for how long they could live remains unknown，but the trend so far seems to be equal to queens，which are known to survive for up to 20 years.
Even at their advanced age，the infected ants still remained their youthful bodies.Young ants start off a yellow color，usually turning brown as they age and hardening their skin，but infected ants stayed yellow.
However，infected ants were far less active than usual，never leaving the nest or helping with any of the usual tasks.Instead，they lazed around the nest while their uninfected colony--mates fed them，cleaned them and even carried them around.In some cases，they were attracting more attention than the queen herself.
It seems like a pretty sweet thing for the individual infected insects，but the colonies as a whole began to suffer.Uninfected ants appeared to be more stressed out and die earlier.
On closer inspection，the team found some metabolic（新陳代謝的） changes in infected ants that drive this biology and behavior.When worker ants are "promoted" to queens，certain genes switch on to boost their lifespan and the parasites also seem to be able to turn these on in their hosts.Infected ants also give off unique chemical signals that drive other ants to want to look after them.
（1）What can .parasites help infected worker ants to do？ BB
A．Behave youthfully.
B．Survive much longer.
C．Develop leadership skills.
D．Gain control over the colony.
（2）How do infected ants differ from uninfected ones？ DD
A．They tend to compete with the queen.
B．They have slower physical development.
C．They experience more metabolic changes.
D．They involve themselves in fewer activities.
（3）What may happen to ant colonies because of parasites？ DD
A．Fewer ant queens.
B．The extinction of colonies.
C．Unfair distribution of food.
D．Early death of uninfected ants.
（4）What does the author intend to do in the last paragraph？ AA
A．To explain the reasons behind the findings.
B．To analyse the problems ant colonies may face.
C．To introduce a new method of studying ant colonies.
D．To assess the consequences of changes in infected ants.
【答案】B；D；D；A
【解答】
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發(fā)布：2024/4/20 14:35:0組卷：1引用：1難度：0.5
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