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"Hidden" Species May Be Surprisingly Common
Cryptic species animals that appear identical but are genetically quite distant—may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity estimates and wildlife management, to our understanding of infectious diseases and evolution.
Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat, in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographieal regions.
Scientists had previously speculated that cryptic species were predominantly found in insects and reptiles, and were more likely to occur in tropical rather than temperate regions. "Species that are seemingly widespread and abundant could in reality be many different cryptic species that have low populations and are highly endangered. " Says Pfenninger. Until the genetic information of all species in at least one taxon is thoroughly studied, no one will know just how many cryptic species exist. "It could be as high as 30%. " Pfenninger says.
"I'm extremely surprised by their results. " Says Alex Smith of the University of Guelph in Ontario, Canada. "It's a call to arms to keep doing the broad kind of genetic studies that we are doing. "
Sampling as many individuals as possible, scientists hope to complete work on all fish and birds in another 5 to 10 years. Once either of these taxonomic groups is completed, Pfenninger says researchers will be able to decide how many cryptic species exist throughout the animal kingdom.
Examples of cryptic species include the African elephant. A 2001 study found the elephants were actually two genetically distinct, non-interbreeding species, the African bush elephant and the African elephant. The species are currently listed as vulnerable and threatened, respectively, by the World Conservation Union (WCU).
The reclassifications are more than an academic exercise. They define populations that have evolved independently of each other and whose genetic differences can have significant consequences. In the early 1900s misidentification of mosquito species based on morphology confused attempts to control malaria in Europe. Ultimately, what was thought to be a single species was actually made up of six sibling species, only three of which transmitted the disease. "The basic unit in biology is always the species, and you have to know what you are dealing with. " Pfenninger says. Much previous research is now no longer used, he says, because it is not clear what species was being studied.
Which of the following about the significance of the research on cryptic species is NOT true？
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Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
The number of parents teaching their offspring at home will increase if the current public school system continues to be viewed as an irrelevant institution that can hinder a child's ability to learn.
The rise of home-schooling reflects broadening dissatisfaction with formal education in the US. Discontent is high for two reasons. First, public schools are turning out a poor product--illiterate and unprepared graduates. For example, American 13-year-olds have been documented as having math skills that rank below their counterparts in 14 other developed countries. One survey noted that just one-third of high school juniors could place the Civil War in the correct half-century. Equally troubling, public schools have become scenes where drugs are sold, teachers are robbed, and homemade bombs are found in lockers.
Compounding the situation, teachers' unions, school officials, and many politicians adamantly(坚决地) oppose the use of public monies(钱) for innovative solutions, such as vouchers and charter schools. Those alternatives, although not a panacea(万能) for all the present problems, are at least promising vehicles that could help poor and middle-income parents to find better schools for their children and break up the monopoly of a "one-size-fits-all" philosophy of education.
In light of the educational quagmire(沼泽) the US finds itself in, many parents, impatient for reform, are taking matters into their own hands. One alternative that is gaining growing public acceptance is the educational option known as home-schooling. Home-schooling is defined simply as the "education of school-aged children at home rather than at a school". Home-schoolers believe that students who receive instruction simultaneously from the home and the community at large will be more culturally sophisticated than those whose bulk of learning experience is confined to a school. Home-schooling families believe they are using their liberties well and wisely. The American can-do spirit is evident in the home-schools and households parents manage simultaneously. Those families, however, could use some further deregulation, be it through home-school tax credits or a loosening of compulsory attendance school laws, to make their task easier.
According to the text, the number of children being schooled at home has increased because ______.
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