Water's density and, consequently, its buoyancy decrease at warmer temperatures. Based on
this consideration and using data from Table 25.1, at which time of year should one expect
diatoms to be storing excess calories mostly as oil?
A) mid-winter
B) early spring
C) late summer
D) late fall

late summer

Judging from Table 25.1 and given that water's density and, consequently, its buoyancy
decrease at warmer temperatures, in which environment should diatoms (and other suspended
particles) sink most slowly?
A) cold fresh water
B) warm fresh water
C) cold seawater
D) warm seawater
E) warm brackish water

cold seawater

Using dead diatoms to "pump" CO2 to the seafloor is feasible only if dead diatoms sink
quickly. Consequently, application of mineral fertilizers, such as iron, should be most effective at
times when diatom valves
A) are thickest, and laminarin is being produced rather than oil.
B) are thickest, and oil is being produced rather than laminarin.
C) are thinnest, and laminarin is being produced rather than oil.
D) are thinnest, and oil is being produced rather than laminarin.

are thickest, and laminarin is being produced rather than oil.

The trophozoites of Giardia were first observed in 1681 in the diarrhea stools of the first
known person to view protists with a microscope, a person named
A) Robert Koch.
B) Robert Hooke.
C) Isaac Newton.
D) van Leeuwenhoek.
E) Louis Pasteur.

van Leeuwenhoek.

Giardia's mitosome can be said to be "doubly degenerate," because it is a degenerate form of
________, an organelle that is itself a degenerate form of ________.
A) nucleus; archaean
B) nucleus; bacterium
C) mitochondrion; proteobacterium
D) mitochondrion; spirochete
E) chloroplast; cyanobacterium

mitochondrion; proteobacterium

The mitosome of Giardia has no DNA within it. If it did contain DNA, then what predictions
should we be able to make about its DNA?
1. It is linear.
2. It is circular.
3. It has many introns.
4. It has few introns.
5. It is not associated with histone proteins.
6. It is complexed with histone proteins.
A) 1, 3, and 5
B) 1, 4, and 5
C) 2, 3, and 6
D) 2, 4, and 5
E) 2, 4, and 6

2, 4, and 5

Given the putative ancestry of Giardia's mitosome, what should we predict is true of the
mitosome?
A) It has electron transport systems that use oxygen as the final electron acceptor.
B) It has a double membrane.
C) It has thylakoids.
D) It contains microtubules, arranged in the 9 + 2 pattern.
E) It contains 80S (eukaryotic) ribosomes.

It has a double membrane.

Given its mode of reproduction and internal structures, which of the following should be
expected to occur in Giardia at some stage of its life cycle?
1. separation (segregation) of daughter chromosomes
2. crossing over
3. meiosis
A) 1 only
B) 3 only
C) 1 and 2
D) 1 and 3
E) 2 and 3

1 only

Unlike most excavates, Giardia trophozoites have no oral groove and are unable to form food
vacuoles. Thus, we should expect its nutrition (mostly glucose) to come from
A) its mitosomes.
B) endosymbiotic cyanobacteria.
C) the ventral disk by which it adheres to the intestinal lining.
D) osmosis involving aquaporins.
E) plasma membrane proteins that are transporters or pumps.

plasma membrane proteins that are transporters or pumps.

During passage through the large intestine, a trophozoite will often secrete a case around
itself, forming a cyst. Cysts contain four haploid nuclei. When cysts "hatch" within a new host,
two trophozoites are released. Thus, which of the following must happen within the cyst, prior to
hatching?
1. meiosis
2. nuclear division
3. S phase
4. binary fission
A) 1 only
B) 1 and 2
C) 2 and 3
D) 2 and 4
E) 2, 3, and 4

2, 3, and 4

The cysts of Giardia are most analogous to the
A) mitochondria of ancestral diplomonads.
B) nuclei of archaeans.
C) endospores of bacteria.
D) capsids of viruses.

endospores of bacteria.

If the mitosomes of Giardia contain no DNA, yet are descendants of what were once free-
living organisms, then where are we likely to find the genes that encode their structures, and
what accounts for their current location there?
A) plasmids; conjugation
B) plasmids; transformation
C) nucleus; horizontal gene transfer
D) nucleus; S phase

nucleus; horizontal gene transfer

The primary treatment for giardiasis (infection with Giardia), as well as for trichomoniasis
(infection with Trichomonas vaginalis) and for amoebic dysentery (infection with Entamoeba
histolytica), is a drug marketed as Flagyl (generic name is metronidazole). The drug also kills
anaerobic gut bacteria. Consequently, which of these are cues that Flagyl's mode of action has
nothing to do with attacking or disabling the parasites' flagella, as the drug's name might imply?
1. It would also harm the flagellated lining of the human intestine.
2. Entamoeba possesses pseudopods, not flagella, yet it is killed by Flagyl.
3. Prokaryotic flagella and eukaryotic flagella are radically different from each other and
unlikely to be harmed by the same chemical.
4. Not all anaerobic gut bacteria possess flagella, yet it kills these bacteria.
A) 1 and 2
B) 1 and 3
C) 2 and 3
D) 1, 2, and 4
E) 2, 3, and 4

2, 3, and 4

What must occur for asexual reproduction to be successful in P. chromatophora?
1. mitosis
2. S phase
3. meiosis
4. equal distribution of cyanelles during cytokinesis
A) 1 only
B) 1 and 2
C) 1, 2, and 3
D) 1, 2, and 4
E) 2, 3, and 4

1, 2, and 4

The closest living relative of P. chromatophora is the heterotroph P. ovalis. What type of
evidence permits biologists to make this claim about relatedness?
A) morphological
B) ecological
C) biochemical
D) genetic
E) fossil

genetic

The closest living relative of P. chromatophora is the heterotroph P. ovalis. P. ovalis uses
threadlike pseudopods to capture its prey, which it digests internally. Which of the following, if
observed, would be the best reason for relabeling P. chromatophora as a mixotroph?
A) a threadlike pseudopod
B) a pigmented central vacuole, surrounded by a tonoplast
C) a vacuole with food inside
D) a secretory vesicle
E) a contractile vacuole

a vacuole with food inside

Which of the following represents the true significance of the finding that the cyanelles of P.
chromatophora stem from a different type of cyanobacterium than gave rise to chloroplasts?
A) This finding indicates that there is a second evolutionary lineage of photosynthetic
eukaryotes.
B) This finding represents the first time that primary endosymbiosis has been directly observed.
C) This finding is the strongest evidence yet for the theory of endosymbiosis.
D) This finding is an example of the phenomenon known as "serial endosymbiosis."
E) This finding is the first evidence that eukaryotic cells do not necessarily digest prokaryotic
cells that manage to gain access to their cytoplasm.

This finding indicates that there is a second evolutionary lineage of photosynthetic
eukaryotes.

The genome of modern chloroplasts is roughly 50% of the size of the genome of the
cyanobacterium from which it is thought to have been derived. In comparison, the genome of P.
chromatophora's cyanelle is only slightly reduced relative to the size of the genome of the
cyanobacterium from which it is thought to have been derived. What is a valid hypothesis that
can be drawn from this comparison?
A) Lytic phage infections have targeted the chloroplast genome more often than the P.
chromatophora genome.
B) P. chromatophora's cyanelle is the result of an evolutionarily recent endosymbiosis.
C) The genome of the chloroplast ancestor contained many more introns that could be lost
without harm, compared to the cyanelle's genome.
D) All three of the hypotheses above are valid.
E) Only A and B are correct.

P. chromatophora's cyanelle is the result of an evolutionarily recent endosymbiosis.

16) If true, which of the following would be most important in determining whether P.
chromatophora's cyanelle is still an endosymbiont, or is an organelle, as the term cyanelle
implies?
A) if P. chromatophora is less fit without its cyanelle than with it
B) if the cyanelle is less fit without the host cercozoan than with it
C) if there is ongoing metabolic cooperation between the cyanelle and the host cercozoan
D) if the magnesium-containing porphyrin ring in the cyanelle's chlorophyll molecules is built by
the cyanelle, whereas the organic portion of the chlorophyll molecules is built by the host
cercozoan
E) if there has been movement of genes from the cyanelle genome to the nuclear genome, such
that these genes are no longer present in the cyanelle genome

if there has been movement of genes from the cyanelle genome to the nuclear genome, such
that these genes are no longer present in the cyanelle genome

If true, which of the following is the best evidence that the cyanelles are providing nutrition
(in other words, calories) to the surrounding cercozoan?
A) if the cyanelle performs aerobic photosynthesis
B) if the vesicle membrane that surrounds each cyanelle possesses glucose-transport proteins
C) if the cyanelle performs aerobic respiration
D) if radiolabeled 14CO2 enters the cyanelle and if, subsequently, radiolabeled glucose is
present in cercozoan cytosol
E) if radiolabeled "heavy" water, 2H2O, enters the cyanelle and if, subsequently, radiolabeled
oxygen appears in cercozoan cytosol

if radiolabeled "heavy" water, 2H2O, enters the cyanelle and if, subsequently, radiolabeled
oxygen appears in cercozoan cytosol

A crucial photosynthetic gene of the cyanobacterium that gave rise to the cyanelle is called
psaE. This gene is present in the nuclear genome of the cercozoan, but is not in the genome of
the cyanelle. This is evidence of
A) reciprocal mutations in the cyanelle and nuclear genomes.
B) horizontal gene transfer from bacterium to eukaryotes.
C) genetic recombination involving a protist and an archaean.
D) the origin of photosynthesis in protists.
E) transduction by a phage that infects both prokaryotes and eukaryotes.

horizontal gene transfer from bacterium to eukaryotes.

Including the membrane of the surrounding vesicle, how many phospholipid (NOT
lipopolysaccharide) bilayers should be found around each cyanelle, and which one of these
bilayers should have photosystems embedded in it?
A) two; innermost
B) two; outermost
C) three; innermost
D) three; middle
E) three; outermost

two; innermost

Which term best describes the symbiotic relationship of well-fed P. bursaria to their
zoochlorellae?
A) mutualistic
B) commensal
C) parasitic
D) predatory
E) pathogenic

mutualistic

The motility that permits P. bursaria to move toward a light source is provided by
A) pseudopods.
B) a single flagellum composed of the protein flagellin.
C) a single flagellum featuring the 9 + 2 pattern.
D) many cilia.
E) contractile vacuoles.

many cilia.

A P. bursaria cell that has lost its zoochlorellae is said to be aposymbiotic. It might be able
to replenish its contingent of zoochlorellae by ingesting them without subsequently digesting
them. Which of the following situations would be most favorable to the reestablishment of
resident zoochlorellae, assuming compatible Chlorella are present in P. bursaria's habitat?
A) abundant light, no bacterial prey
B) abundant light, abundant bacterial prey
C) no light, no bacterial prey
D) no light, abundant bacterial prey

abundant light, abundant bacterial prey

A P. bursaria cell that has lost its zoochlorellae is aposymbiotic. If aposymbiotic cells have
population growth rates the same as those of healthy, zoochlorella-containing P. bursaria in
well-lit environments with plenty of prey items, then such an observation would be consistent
with which type of relationship?
A) parasitic
B) commensalistic
C) toxic
D) predator—prey
E) mutualistic

commensalistic

Theoretically, P.bursaria can obtain zoochlorella either vertically (via the asexual
reproduction of its mother cell) or horizontally (by ingesting free-living Chlorella from its
habitat). Consider a P. bursaria cell containing zoochlorellae, but whose habitat lacks free-living
Chlorella. If this cell subsequently undergoes many generations of asexual reproduction, if all of
its daughter cells contain roughly the same number of zoochlorellae as it had originally
contained, and if the zoochlorellae are all haploid and identical in appearance, then what is true?
A) The zoochlorellae also reproduced asexually, at an increasing rate over time.
B) The zoochlorellae also reproduced asexually, at a decreasing rate over time.
C) The zoochlorellae also reproduced asexually, at a fairly constant rate over time.
D) The zoochlorellae reproduced sexually, undergoing heteromorphic alternation of generations.
E) The zoochlorellae reproduced sexually, undergoing isomorphic alternation of generations.

The zoochlorellae also reproduced asexually, at a fairly constant rate over time.

Which term most accurately describes the nutritional mode of healthy P. bursaria?
A) photoautotroph
B) photoheterotroph
C) chemoheterotroph
D) chemoautotroph
E) mixotroph

mixotroph