《考研英语阅读理解100篇 高分版》 Unit 18 - TEXT TWO

Sex is a mystery—and not just to those who indulge in it. By combining her genes with a male's, a female halves her genetic contribution to her offspring, and subsequent generations see it halved again and again. On top of that, the need for each individual to have two parents means the population can grow only half as rapidly as it otherwise might. Why, therefore, bother with the whole messy business in the first place?
Julia Jones of the University of Wales, Bangor, and her colleagues may soon have the answer to that question. They have found a species of crayfish that follows the logic of asexuality and does, indeed, clone itself. Though Dr. Jones did not actually discover this species, she was the person who identified it in the wild—in Madagascar. Her interviews suggest it was imported in about 2003, by people working on a road bypassing Antananarivo, the country's capital. As a result of this accidental import, the stage is set for an unplanned evolutionary experiment. Brute mathematics predict the new species, known as the marbled crayfish, will outcompete the locals. Those who ponder the purpose of sex, though, think the newcomer will eventually face its come-uppance.
The reason, according to those ponderers, is that the genetic diversity promoted by sex is a protection against disease. An asexual female who clones herself ten times is like someone who buys ten raffle tickets, each with the same number. A female who reproduces sexually gets only five tickets for her effort, but they are all different. This, however, is a raffle that the female wants to lose. That is because the prize is premature death for her descendants at the hands of an infection particularly adapted to the winning number—or, rather, the losing combination of genes. If this explanation is right, the marbled crayfish will do very well for an indeterminate period, and will then suddenly vanish.
At the moment, those who work in the paddy fields outside Antananarivo are enjoying the upward part of the trajectory. They are selling marbled crayfish by the condensed-milk-tin load along all the main roads from the city. And the rest of the country is likely to follow suit soon, as the crustacean now appears to be striking out from its bridgehead.
A group of experts has gathered in Antananarivo to draw up a list of questions that need researching. One of their concerns is that the marbled crayfish's sexual cousins have caused havoc elsewhere. The red swamp crayfish, for example, has tucked into the paddy fields of the Iberian peninsula with gusto, eating rice seedlings and burrowing into the banks of drainage channels, causing them to collapse. The enthusiasm that many Malagasies seem to have for spreading their new and fecund friends around the country, to provide an additional “crop”, may thus backfire.
Another worry is that the red swamp invader has helped unleash a deadly fungal disease on native crayfish populations around Europe—a plague to which it is, itself, resistant. That bodes ill for Madagascar's local species. If the theoreticians are correct, a plague will be exactly what gets rid of the newcomer, but it could also spread to the natives, reducing their numbers as well. Until then, however, the researchers can look forward to an experiment involving many a tasty barbecue.
1. The import of the marbled crayfish leads to an unplanned evolutionary experiment because _____.
[A] the reproduction model of the new species is totally different from the other existing species
[B] the new species was originally living in the wild in Madagascar which is different from the new environment
[C] the new species has never been identified before Dr. Jones' research
[D] the new species will threat the existence of the other species
2. Towards the marbled crayfish, those who ponder the purpose of the sex hold the view that _____.
[A] the marbled crayfish will outnumber the locals finally
[B] the marbled crayfish will die out after they exist for a period of time
[C] the marbled crayfish will have a lot of problems in the future
[D] the marbled crayfish will get the upper hand eventually
3. Reproduction is compared to buying raffle tickets in order to illustrate that _____.
[A] the asexual reproduction is of high risk
[B] the sexual reproduction promotes the genetic diversity
[C] the sexual reproduction is of more evolutionary advantage than the asexual reproduction
[D] the asexual reproduction is no better than the sexual reproduction
4. At present, the marbled crayfish in Antananarivo _____.
[A] is living in the upward part of the trajectory outside Antananarivo
[B] is enjoying promising market prospect in the city of Antananarivo
[C] is shrinking in quantity due to the spread of their cousin crayfish
[D] is spreading from Antananarivo to the rest of the country being packed with condensed milk
5. Which one of the following statements is TRUE of the red swamp crayfish?
[A] The red swamp crayfish is a subtype of the marbled crayfish.
[B] The red swamp crayfish carries the virus of a deadly fungal disease.
[C] Malagasy originally planned to grow the red swamp crayfish to increase the crop output.
[D] There is no doubt that the red swamp will get rid of the local species eventually.