42) 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.
Giardia lamblia is an intestinal parasite of humans and other mammals that causes intestinal ailments in
most people who ingest the cysts. Upon ingestion, each cyst releases two motile cells, called
trophozoites. These attach to the small intestine’s lining via a ventral adhesive disk. The trophozoites
anaerobically metabolize glucose from the host’s intestinal contents to produce ATP. Reproduction is
completely asexual, occurring by longitudinal binary fission of trophozoites, with each daughter cell
receiving two, haploid nuclei (n = 5). A trophozoite will often encyst as it passes into the large intestine
by secreting around itself a case that is resistant to cold, heat, and dehydration. Infection usually occurs
by drinking untreated water that contains cysts.
43) 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.
44) Given that Flagyl produces only minor side effects (if any) in humans, and given the set of parasites
that it kills, Flagyl’s mode of action probably involves
A) peptidoglycan.
B) mitochondria or mitosomes.
C) anaerobic metabolic pathways.
D) nuclear envelopes.
E) microtubules.
45) 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
46) 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
47) 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.
48) 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
49) 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.
50) Diplomonads, such as Giardia, contain two haploid nuclei per trophozoite. Thus, during the G1
phase of the cell cycle, there should be a total of how many unreplicated chromosomes per trophozoite,
and during the G2 phase, how many replicated chromosomes per trophozoite?
A) 5; 5
B) 5; 10
C) 10; 10
D) 10; 20
E) 20; 20
51) 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
52) 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.
53) 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
54) 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
Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic
photosynthesis with its two elongated “cyanelles.” The cyanelles are contained within vesicles of the
host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that
gave rise to the chloroplasts of algae and plants.
55) 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
56) 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
57) P. chromatophora secretes around itself a test, or case, of plates made of silica. Which of the
following is another rhizarian that would be in competition with P. chromatophora for the silica needed
to make these plates, assuming limited quantities of silica in the environment?
A) radiolarians
B) foraminiferans
C) all other amoeboid cells
D) all other rhizaria
E) diatoms
58) 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.
59) The genome of modern chloroplasts is roughly 50% 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 conclusion 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 conclusions above are valid.
E) Two of the conclusions above are valid.
60) 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.
61) 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.
62) 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.
63) 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
64) 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
The next few questions refer to the following description.
Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus
Chlorella. When within their hosts, the algae are referred to as zoochlorellae. In aquaria with light
coming from only one side, P. bursaria gathers at the well-lit side, whereas other species of
Paramecium gather at the opposite side. The zoochlorellae provide their hosts with glucose and oxygen,
and P. bursaria provides its zoochlorellae with protection and motility. P. bursaria can lose its
zoochlorellae in two ways: (1) if kept in darkness, the algae will die; and (2) if prey items (mostly
bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae.
65) Which term most accurately describes the nutritional mode of healthy P. bursaria?
A) photoautotroph
B) photoheterotroph
C) chemoheterotroph
D) chemoautotroph
E) mixotroph
66) Which term accurately describes the behavior of Paramecium species that lack zoochlorellae in an
aquarium with light coming from one side only?
A) positive chemotaxis
B) negative chemotaxis
C) positive phototaxis
D) negative phototaxis
67) 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
68) 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.
69) 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
70) 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
71) 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.
End-of-Chapter Questions
The following questions are from the end-of–chapter “Test Your Understanding” section in Chapter 28
of the textbook.
72) Plastids that are surrounded by more than two membranes are evidence of
A) evolution from mitochondria.
B) fusion of plastids.
C) origin of the plastids from archaea.
D) secondary endosymbiosis.
E) budding of the plastids from the nuclear envelope.
73) Biologists suspect that endosymbiosis gave rise to mitochondria before plastids partly because
A) the products of photosynthesis could not be metabolized without mitochondrial enzymes.
B) all eukaryotes have mitochondria (or their remnants), whereas many eukaryotes do not have plastids.
C) mitochondrial DNA is less similar to prokaryotic DNA than is plastid DNA.
D) without mitochondrial CO2 production, photosynthesis could not occur.
E) mitochondrial proteins are synthesized on cytosolic ribosomes, whereas plastids utilize their own
ribosomes.
74) Which group is incorrectly paired with its description?
A) rhizarians morphologically diverse group defined by DNA similarities
B) diatoms important producers in aquatic communities
C) red algae acquired plastids by secondary endosymbiosis
D) apicomplexans parasites with intricate life cycles
E) diplomonads protists with modified mitochondria
75) Which protists are in the same eukaryotic supergroup as land plants?
A) green algae
B) dinoflagellates
C) red algae
D) brown algae
E) both green algae and red algae
76) In life cycles with an alternation of generations, multicellular haploid forms alternate with
A) unicellular haploid forms.
B) unicellular diploid forms.
C) multicellular haploid forms.
D) multicellular diploid forms.
E) multicellular polyploid forms.