“Much of the work of natural selection over the millions of years has been to find ‘decisive’ or ‘single-minded’ molecules whose ‘preference’ for their favoured shape is much stronger than their tendency to coil into any other shape.”
– From Unweaving the Rainbow by Richard Dawkins
Quotation marks are meant to denote something that someone said or wrote. They indicate that these are the exact words used. They do not add meaning. If the quotation marks enclose something that is not a direct quote, then they are out of place and should not be used. Often people enclose a word or words in quotation marks because they don’t quite know what they mean to say and hope that the reader will somehow fill the vacuum and supply the meaning. In other words, quotation marks are a lazy way of avoiding saying what you mean. In this case, Dawkins fails to explain how the molecule in question is selected. In other words, the sentence fails at its one and only job.