大全(44/63)第5题，百思不得其解，求教

It was once assumedthat all living thingscould be divided into twofundamental and exhaustive categories. Multicellularplants and animals, as well as manyunicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleusand many organelles. On the other hand, the true bacteriaare prokaryoticcell (prokaryoticcell: 原核细胞), which are simple and lack a nucleus. The distinctionbetween eukaryotesand bacteria,initially defined in terms of subcellularstructures(第7题d) visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryoticcells have manyfeatures in common. Forinstance, they translate genetic information into proteins according to the same type of genetic coding(第7题c)(第2题). But even where the molecular processes are thesame, the details in the two forms are different andcharacteristic of the respective forms. For example, the amino acid sequences of various enzymestend to be typically prokaryotic or eukaryotic(第7题e,这里的for example的位置应该是属于不同的，uniform是指统一的…). The differences between the groups andthe similarities within each group made it seem certain to mostbiologists that the tree of life had only two stems. Moreover, argumentspointing out the extent of both structural andfunctional differences between eukaryotes and true bacteria convincedmany biologists that the precursors of the eukaryotes must have diverged fromthe common ancestor before the bacteria arose.

Although much of this picturehas been sustained by more recent research, itseems fundamentally wrong in one respect. Among the bacteria, there are organisms that aresignificantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the treeof life. New techniques fordetermining the molecular sequence of the RNA of organisms(第4题) have produced evolutionaryinformation about the degree to which organisms are related, the time sincethey diverged from a common ancestor, and the reconstruction of ancestral versionsof genes. These techniques have strongly suggested that although thetrue bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria (archaebacteria: [复] n.[微]原始细菌( 一种不同于细菌和动植物细胞且要求完全厌氧条件并能产生甲烷的微生物)), which are also prokaryotes and which resemble true bacteria,(第7题b) represent a distinctevolutionary branch that far antedates the common ancestor of all truebacteria.(第3题)

If the “new techniques” mentioned in line31 were applied in studies of biological classifications other than bacteria,which of the following is most likely?    题干说如果new techniques用在biological classifications就是生物的分类上，那么以下那个最可能发生。定位new techniques:在第2段－－－>New techniques for determining the molecular sequence of the RNA of organisms(第4题) have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria, which are also prokaryotes and which resemble true bacteria,(第7题b) represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria.(第3题)