Before biologist Carl Woese’s mid-1970s study of methanogens (microbes, such as Methanomicrobium mobile, that metabolize hydrogen and carbon dioxide in environments without oxygen, producing methane as a by-product), living organisms were categorized as either eukaryotic (having cells with nuclei) or prokaryotic (having no nuclei). However, Woese found that the methanogens he examined had some unique characteristics shared by neither prokaryotes nor eukaryotes, as well as some characteristics in common with both. Perhaps, Woese thought, he had identified a third domain of life.
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Verbal·Craft and Structure·Text Structure and Purpose
easyWhich choice best states the main purpose of the text?
A
To explain how a particular group of life-forms can thrive in an extremely hostile environment
B
To describe what led a researcher to arrive at a particular conclusion about a group of life-forms
C
To identify the differences between three varieties of life-forms
D
To illustrate how a groundbreaking method of categorizing life-forms came to be accepted