By what other name is the classification system proposed by Carl Woese known?

Correct answer: Six-kingdom system

Direct answer: B, the six-kingdom system. Carl Woese proposed a three-domain system based largely on molecular differences, especially comparisons involving ribosomal RNA. The three domains are Bacteria, Archaea and Eukarya. In the related six-kingdom arrangement, the earlier broad group Monera is divided into two separate kingdoms: Eubacteria and Archaebacteria. The other four kingdoms are Protista, Fungi, Plantae and Animalia. Thus, the three-domain concept is commonly associated in school biology with a six-kingdom classification. A is incorrect because the five-kingdom system is associated with Robert Whittaker. C and D do not describe Woese’s system. The important distinction is that domains are a higher rank than kingdoms. Memory cue: Woese separates Bacteria from Archaea; remember three domains and, in the corresponding school-level arrangement, six kingdoms.