Categorizing all of the forms of life on the planet has been a persist

Categorizing all of the forms of life on the planet has been a persistent and tricky problem for human thinkers since before the time of Aristotle, but by the mid-twentieth century biologists thought that they had the big picture narrowed down to five kingdoms: animals, plants, fungi, protozoans, and bacteria (also known as prokaryotes or monera). The world of biology was turned upside down in 1977 when the microbiologist Carl Woese declared that there are not five kingdoms but twenty-three, split up between three larger domains: Eucarya, or eukaryotes, which includes animals, plants, fungi, and all other life with complex, nucleated cells; Bacteria, which includes the infinitesimally small, single-celled organisms that lack cell nuclei and that live practically everywhere by the trillions; and Archaea, or archaebacteria, which look like bacteria to the untrained eye but, unlike bacteria, lack peptidoglycan walls and whose cell membranes are composed of glycerol-ether lipids, as opposed to the glycerol-ester lipids that compose cell membranes in bacteria and eukaryotes.

Woese arrived at his new schema by conducting phylogenetic analyses of the ribosomal RNA of bacteria. His research showed that the genetic relationships between certain types of apparently similar bacteria were actually far more distant than anyone had expected; indeed, the genetic difference between any bacterium and any archaean is comparable to or even greater than that between a human and a dragonfly or mushroom. The Bacteria and Archaea, which according to evolutionary theory have been evolving as distinct species for billions more years than have the more complex Eukarya, possess so much genetic diversity within their two domains that they make up the majority of the kingdoms among the three domains. Indeed, the animals, plants, and fungi make up just three kingdoms on the far edge of Woese’s picture of life.

Traditional biologists, predictably, resisted Woese’s new map of life, which in their view relegated the most interesting and complex life forms on earth to the role of odd footnotes at the end of the story. The Harvard zoologist Ernst Mayer never accepted the theory, and in the 1990's proposed a new grouping in which the Eukaryotes form one group and the Bacteria and Archaea form a single group called Prokaryotes, and in which the greater complexity of the eukaryotes is recognized in systematic form. The debate over the categorization of life continues, but the majority of biologists have acknowledged that the increasing body of phylogenetic evidence gives strong support to Woese’s views.

1. According to the information presented in the passage, which of the following is most like the relationship between a bacterium and an archaean?

A. The relationship between an orangutan and a human
B. The relationship between an air conditioner and the color blue
C. The relationship between a mother and her daughter
D. The relationship between an elephant and a fern
E. The relationship between an orangutan and a chimpanzee



2. Based on the material presented in the passage, the biologist Ernst Mayer could be expected to agree most strongly with which of the following statements?

A. Biological categorization should be based not only on phylogenetic relationships, but also upon other factors that more fully take into account the diversity and complexity of life on earth.
B. Of the three domains of life, the Archaea are the most interesting due to their astonishing ability to adapt to the most extreme environments on earth.
C. The category of Prokaryotes should include not only bacteria and archaeans, but protozoans as well.
D. Carl Woese, as a microbiologist, does not know enough about the behavior and life cycles of large animals to make generalized statements about how these animals should be classified.
E. Whether an organism's cell membrane is composed of glycerolester lipids or glycerol-ether lipids should make no significant difference in how an organism is classified.



3. According to the information presented in the passage, which of the following organisms could be expected to have cell membranes composed of glycerol-ether lipids?

A. An oak tree
B. Aslime mold
C. Halobacterium, an archaean that lives in highly saline conditions
D. Cyanobacterium, a photosynthesizing bacterium also known as “blue-green algae”



4. According to the information presented in the passage, a dog would belong to which of the following domains?

A. Animalia
B. Carnivora
C. Monera
D. Eucarya
E. Archaea



5. It can be inferred from the passage that a phylogenetic analysis of ribosomal RNA provides what sort of information?

A. Information concerning the lifecycles of different organisms
B. Information concerning the genetic relationships of different types of organisms
C. Information concerning the cell membranes of microscopic organisms
D. Information concerning the complexity of cellular chemical transfer mechanisms
E. Information concerning the difference between a five-kingdom classification system and a three-domain system