Answer Key
Chapter 1
1 .D 2 .D 3 .A 4 .B 5 .C 6 .C 7 .D 8 .A 9 .B 10 .D 11 .C 12 .A 13 .D 14 .B 15 .scientific history 16 .Lyme
17 .fermentation 18 .genus, species 19 .Protista and Monera 20 .Prokaryotes 21 .Viruses 22 .pathogen 23 .helminths
24 .virology 25 .nucleus
Chapter 2
1 .C 2 .A 3 .D 4 .B 5 .C 6 .D 7 .B 8 .E 9 .D 10 .D 11 .B 12 .refraction 13 .compound 14 .fluorochromes 15 .atomic
force microscope 16 .400⨯ 17 .acid-fast 18 .Gram stain
Chapter 3
1 .C 2 .D 3 .C 4 .A 5 .C 6 .B 7 .C 8 .C, D 9 .A 10 .D 11 .D 12 .D 13 .B 14 .C 15 .D 16 .B 17 .A 18 .False 19 .False
20 .True 21 .spontaneous generation 22 .epidemiology 23 .miasma 24 .Robert Hooke 25 .bacilli 26 .volutin (or
metachromatic granule) 27 .hydrogen peroxide 28 .actin 29 .Pasteur designed a flask in which media were sterilized
but still exposed to air through the swan neck of the flask. The media remained sterile despite exposure to air
because the airborne bacteria got stuck in the neck and could not get to the media to contaminate it. This refuted the
theory of spontaneous generation because proponents of that theory believed that air contained a “life force” that,
when exposed to the media, chemically produced life from nonlife. 30 .Needham and Spallanzani boiled broths for
different lengths of time. Needham used only brief periods of boiling, whereas Spallanzani boiled his broths for as
long as an hour. Thus, Needham likely did not boil his broths long enough to kill all of the microbes, some of which
may have been heat resistant or survived by forming endospores. Another possibility is that the two scientists may
have used different types of broths, which would have supported the growth of different types and numbers of
microbes. 31 .Schleiden and Schwan believed that cells arose as a result of a crystallization process, whereas
Virchow and Remak believed that cells arose as a result of cell division. 32 .Both mitochondria and chloroplasts
have their own DNA that is genetically and structurally similar to bacterial DNA. Mitochondria and chloroplasts
divide by binary fission independent of the host cell chromosome. We can see examples of endosymbiosis in
modern-day organisms as well, including the photosynthetic bacteria-like organelles of some protists and the
symbiotic bacteria found within the cells of some insects (e.g., cockroaches). 33 .Semmelweis observed a higher
incidence of puerperal fever in the maternity ward staffed by physicians and medical students than in the ward
staffed by midwives. He observed that it was common practice for physicians and medical students to examine
maternity patients after performing autopsies without washing their hands in between these procedures. He
established the practice of having the physicians and medical students wash their hands in chlorinated lime water
before examining maternity patients, and this practice greatly reduced the incidence of puerperal fever in this ward.
34 .In these environments, water flows into cells. Without cell walls, the osmotic pressure would be too great for the
bacterial cell membrane to withstand, and cells would quickly lyse. Cell walls allow bacterial cells living in
hypotonic environments to withstand minor changes in osmotic pressure. 35 .The flagella will rotate in a
counterclockwise direction (run) more frequently and reduce the length of tumbles (rotation of flagella in a
clockwise direction), resulting in an overall movement toward the attractant. 36 .They have 70S (prokaryotic)
ribosomes, a DNA genome most similar to that of prokaryotic cells, and two membranes. Also, mitochondria and
chloroplasts divide in a way similar to binary fission. 37 .Because eukaryotic cells are typically much larger than
prokaryotic cells, they cannot rely exclusively on diffusion and active transport within the cell for the transport of
materials across the cell; they use the endomembrane system to traffic some of these materials. 38 .Possible
answers: Bacterial flagella are composed of thin, stiff protein tubes of flagellin subunits and move in a propeller-like
fashion. Eukaryotic flagella are composed of microtubules arranged in a 9+2 array. These microtubules slide along
each other, allowing each flagellum to bend, producing movement with a whip-like motion. 39 .Results of his
experiment that would have supported the theory of spontaneous generation would have been the growth of
Answer Key 271