Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 6

The "Facts" of Life. Each of these statements was once regarded as a biological fact but is now understood to be untrue. In each case, indicate why the statement was once thought to be true and why it is no longer considered a fact.
(a)Plant and animal tissues are constructed quite differently because animal tissues do not have conspicuous boundaries that divide them into cells.
(b)Living organisms are not governed by the laws of chemistry and physics, as is nonliving matter, but are subject to a "vital force" that is responsible for the formation of organic compounds.
(c)Genes most likely consist of proteins because the only other likely candidate, DNA, is a relatively uninteresting molecule consisting of only four kinds of monomers (nucleotides)arranged in a relatively invariant, repeating tetranucleotide sequence.
(d)The fermentation of sugar to alcohol can take place only if living yeast cells are present.