Deck 27: Protists

Question 1

Imagine that there are 25 different species of protists living in a tide pool. Some of these species reproduce both sexually and asexually, and some of them can reproduce only asexually. The pool gradually becomes infested with disease-causing viruses and bacteria. Which species are more likely to thrive in the changing environment?

A) the sexually reproducing species
B) the asexually reproducing species
C) Sexually and asexually reproducing species are equally likely to thrive.

Answer 1

A

Question 2

A particular species of protist has obtained a chloroplast via secondary endosymbiosis. You know this because the chloroplasts ________.

A) have nuclear and cyanobacterial genes
B) are exceptionally small
C) have three or four membranes
D) have only a single pigment

Answer 2

C

Question 3

Use the following information to answer the question(s) below.
The mechanism of cell crawling in protist species is not well defined. Pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in vertebrate muscle contraction). However, prior to the study described below, no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists. Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist, but physiological studies had failed to show a functional link between actin, myosin, and cell crawling.
In a study by N. Poulsen et al. (Diatom gliding is the result of an actin-myosin motility system, Cell Motility and the Cytoskeleton 44 (1999):23-22), researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.
Refer to the study by Poulsen et al. and the accompanying figure. The data graphed in the figure could be an artifact if latrunculin A kills this species of diatoms (that is, that may be why the cells are not moving). Which of the following would be the best evidence that latrunculin A is NOT killing the cells?

A) When the toxin was washed off the culture, the cells began to move again.
B) There were still a small percentage of motile cells in the culture treated with the toxin.
C) Most of the cells in the control were moving, indicating that they were alive.
D) When the toxin was applied to another species of diatom, 25 percent of them continued to move.

Answer 3

A

Question 4

Encouraging the growth (via nutrient fertilization) of photosynthetic protists in marine environments may help reduce global warming because ________.

A) photosynthetic protists are primary consumers in many marine food chains
B) photosynthetic protists fix atmospheric carbon dioxide, decreasing atmospheric carbon dioxide levels
C) the increased oxygen consumption by large populations of photosynthetic protists will increase photosynthesis in land plants
D) photosynthetic protists would release a lot of oxygen, and fertilizing them would increase levels of oxygen in the atmosphere

Question 5

Which of the following statements best describes the term synapomorphy?

A) a trait that is shared by more than one monophyletic group
B) a trait common in a single monophyletic group but not generally found outside of that group
C) the state of having several traits in common with different monophyletic groups
D) a trait that evolved in several different monophyletic groups simultaneously

Question 6

Which of the following eukaryotic lineages contains species that all lack functioning mitochondria?

A) Excavata
B) Rhizaria
C) Amoebozoa
D) Stramenopila

Question 7

Protists and bacteria are grouped into different domains because ________.

A) protists eat bacteria
B) bacteria are not made of cells
C) protists have a membrane-bounded nucleus, which bacterial cells lack
D) bacteria decompose protists
E) protists are photosynthetic

Question 8

Consider the following points: (a) All excavates live in environments where oxygen availability is low; (b) all excavates lack mitochondria; and (c) all excavates have some mitochondrial genes. Based on this information, which of the following statements is TRUE of the excavate lineage?

A) Their ancestors were eukaryotes that existed prior to the origin of mitochondria.
B) Their ancestors had mitochondria, but the mitochondria were lost over time.
C) Their ancestors were not able to metabolize glucose.
D) Excavates are in the process of acquiring mitochondria through evolutionary adaptation.

Question 9

All protists are ________.

A) unicellular
B) eukaryotic
C) symbionts
D) monophyletic
E) mixotrophic

Question 10

By examining the phylogenetic tree diagrammed in the accompanying figure, what conclusion can you draw about the species G. microti?

A) It evolved before G. intestinalis.
B) It is more closely related to G. muris than to G. intestinalis.
C) It should not be labeled a species distinct from G. intestinalis.
D) It is part of a monophyletic group that also includes G. intestinalis.

Question 11

Use the following information to answer the question(s) below.
The mechanism of cell crawling in protist species is not well defined. Pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in vertebrate muscle contraction). However, prior to the study described below, no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists. Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist, but physiological studies had failed to show a functional link between actin, myosin, and cell crawling.
In a study by N. Poulsen et al. (Diatom gliding is the result of an actin-myosin motility system, Cell Motility and the Cytoskeleton 44 (1999):23-22), researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.
Refer to the study by Poulsen et al. and the accompanying figure. Latrunculin A is a reversible toxin that disrupts the formation of actin fibers. A culture of a particular species of diatom was treated with this toxin diluted in a buffer, while another culture was treated only with the buffer (no toxin; control). The motility of cells in each culture was assessed by counting the number of cells that were moving during a defined period of time. Which of the following conclusions is reasonable based on the figure?

A) Formation of actin fibers is not necessary for the movement in this species of diatom.
B) The buffer alone largely inhibited movement in this species of diatom.
C) In this species of diatom, fully formed actin fibers are necessary for movement.

Question 12

Protists from which of the following taxonomic groups are most likely to lead to paralytic shellfish poisoning?

A) Dinoflagellata
B) Giardia
C) Plasmodium
D) Toxoplasma
E) Euglena

Question 13

According to the phylogenetic tree in the accompanying figure, G. intestinalis constitutes a ________ group.

A) paraphyletic
B) monophyletic
C) polyphyletic

Question 14

When a mosquito infected with Plasmodium first bites a human, the Plasmodium ________.

A) gametes fuse, forming an oocyst
B) cells infect the human liver cells
C) cells cause lysing of the human red blood cells
D) oocyst undergoes meiosis

Question 15

Which of the following might be a result of adding a secondary consumer to the aquatic ecosystem in the accompanying illustration?

A) a decrease in the number of primary consumers
B) a decrease in the population of decomposers
C) an increase in atmospheric carbon dioxide
D) an increase in the population of scavengers
E) a decrease in the carbon sink

Question 16

Which major eukaryotic lineages form the Bikonta, a monophyletic group characterized by two flagella as a synapomorphy?

A) Rhizaria, Plantae, Amoebozoa, Opisthokonta, Excavata
B) Alveolata, Stramenopila, Rhizaria, Plantae, Excavata
C) Rhizaria, Plantae, Excavata
D) Amoebozoa, Opisthokonta
E) Alveolata, Stramenopila

Question 17

The microsporidian Brachiola gambiae parasitizes the mosquito Anopheles gambiae. Adult female mosquitoes must take blood meals for their eggs to develop, and it is while they take blood that they transmit malarial parasites to humans. Male mosquitoes drink flower nectar. If humans are to safely and effectively use Brachiola gambiae as a biological control to reduce human deaths from malaria, then how many of the following statements should be TRUE?
1) Brachiola should kill the mosquitoes before the malarial parasite they carry reaches maturity.
2) The microsporidian should not be harmful to other insects.
3) Microsporidians should infect mosquito larvae, rather than mosquito adults.
4) The subsequent decline in anopheline mosquitoes should not significantly disrupt human food resources or other food webs.
5) Brachiola must be harmful to male mosquitoes but not to female mosquitoes.

A) 2 and 5
B) 1, 2, 3, and 4
C) 1, 2, and 4
D) 2, 3, 5
E) 3 and 4

Question 18

Alternation of generations occurs in some protists. Which of the following represents the correct sequence of events for this mode of reproduction?

A) gametophyte → gamete → fusion → sporophyte → spore → gametophyte
B) sporophyte → spore fusion → gametophyte → gamete → sporophyte
C) gametophyte → fusion → sporophyte → spore → gamete → gametophyte
D) gamete → fusion → gametophyte →spore → sporophyte → gamete

Question 19

Use the following information to answer the question(s) below.
The mechanism of cell crawling in protist species is not well defined. Pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in vertebrate muscle contraction). However, prior to the study described below, no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists. Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist, but physiological studies had failed to show a functional link between actin, myosin, and cell crawling.
In a study by N. Poulsen et al. (Diatom gliding is the result of an actin-myosin motility system, Cell Motility and the Cytoskeleton 44 (1999):23-22), researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin.
Refer to the study by Poulsen et al. and the accompanying figure. Cultures of a species of diatom were treated with BDM, a reversible inhibitor of myosin function. Which of the following predictions is consistent with the hypothesis that an actin-myosin interaction is necessary for motility?

A) BDM will significantly decrease motility of the cells in culture.
B) BDM will not significantly alter motility of the cells in culture.
C) BDM will significantly increase motility of the cells in culture.

Question 20

Which of the following statements is consistent with the assertion that protists are paraphyletic?

A) There is no common set of synapomorphies that define a protist
B) Protists all share a common set of synapomorphies.
C) Protists are all more primitive than land plants and animals.
D) Protists do not share a single common ancestor.

Question 21

A snail-like, coiled, porous test (shell) of calcium carbonate is characteristic of ________.

A) diatoms
B) foraminiferans
C) ciliates
D) water molds

Question 22

In examining a protist, you notice that it lacks a cell wall, and has movement with cytoplasmic streaming. These data allow you to infer that the species belongs to which of the following protist groups?

A) Excavata
B) Stramenopila
C) Rhizaria
D) Alveolata
E) Amoebozoa

Question 23

Amoeboid movement via long slender pseudopodia is characteristic of ________.

A) foraminiferans
B) water molds
C) dinoflagellates
D) oomycetes

Question 24

Which of the following is NOT a producer?

A) green algae
B) dinoflagellate
C) apicomplexan
D) diatom
E) euglenid

Question 25

You are given an unknown organism to identify. It is unicellular and heterotrophic. It is motile, using many short extensions of the cytoplasm. It has well-developed organelles and two nuclei, one large and one small. This organism is most likely to be a ________.

A) foraminiferan
B) diatom
C) ciliate
D) dinoflagellate
E) slime mold

Question 26

One of the fish in your aquarium dies. Adding which protist to the water would allow you to avoid flushing the dead fish by speeding its decay?

A) an apicomplexan
B) a dinoflagellata
C) a water mold
D) a ciliate
E) a euglenid

Question 27

Dinoflagellates ________.

A) have a glass-like cell wall
B) are all autotrophic
C) have walls that are usually composed of cellulose plates
D) have a feeding groove
E) include species that cause malaria

Question 28

Use the following information to answer the question below.
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 gather 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.
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

Question 29

Diatoms are mostly asexual members of the phytoplankton. They obtain their nutrition from functional chloroplasts, and each diatom is encased within two porous, glass-like valves. Which question would be most important for one interested in the day-to-day survival of individual diatoms?

A) How does carbon dioxide get into these protists with their glass-like valves?
B) How do diatoms get transported from one location on the water's surface layers to another location on the surface?
C) How do diatoms with their glass-like valves keep from sinking into poorly lit waters?
D) How do diatoms with their glass-like valves avoid being shattered by the action of waves?
E) How do diatom sperm cells locate diatom egg cells?

Question 30

Which of the following was derived from an ancestral cyanobacterium?

A) chloroplast
B) mitochondrion
C) flagella
D) mitosome

Question 31

Which of the following protist lineages is appropriately paired with its supportive and/or protective structure?

A) Diatoms have an intricate, chalky, chambered calcium carbonate shell.
B) Parabasalids have an internal support rod, made of cross-linked microtubules, that runs the length of the cell.
C) Alveolates have tough plates in the cell wall that are made up of cellulose.
D) Euglenoids cover themselves with tiny pebbles.
E) Dinoflagellates are surrounded by a glass-like, silicon dioxide cell wall.

Question 32

In the process of alternation of generations, the ________.

A) sporophyte is haploid and produces gametes
B) sporophyte is diploid and produces spores
C) gametophyte is haploid and produces spores
D) gametophyte is diploid and produces gametes
E) spores unite to form a zygote

Question 33

Assume that some members of an aquatic species of motile, photosynthetic protists evolve to become parasitic to fish. They gain the ability to live in the fish gut, absorbing nutrients as the fish digests food. Over time, which of the following phenotypic changes would you expect to observe in this population of protists?

A) loss of motility
B) loss of chloroplasts
C) gain of a rigid cell wall
D) gain of meiosis
E) No changes would be expected.

Question 34

According to the endosymbiotic theory, why was it adaptive for the larger (host) cell to keep the engulfed cell alive, rather than digesting it as food?

A) The engulfed cell provided the host cell with adenosine triphosphate (ATP).
B) The engulfed cell provided the host cell with carbon dioxide.
C) The engulfed cell allowed the host cell to metabolize glucose.
D) The host cell was able to survive anaerobic conditions with the engulfed cell alive.
E) The host cell would have been poisoned if it had digested the engulfed cell.

Question 35

According to the endosymbiosis theory of the origin of eukaryotic cells, how did mitochondria originate?

A) from infoldings of the plasma membrane, coupled with mutations of genes for proteins in energy-transfer reactions
B) from engulfed, originally free-living proteobacteria
C) by secondary endosymbiosis
D) from the nuclear envelope folding outward and forming mitochondrial membranes

Question 36

You discover a new species of protist. Which of the following characteristics would provide the strongest evidence for your hypothesis that your species belongs in Euglenida?

A) It is photosynthetic.
B) It has a pellicle just under the plasma membrane.
C) It reproduces asexually.
D) It is unicellular.
E) It lacks a cell wall.

Question 37

All protists ________.

A) contain a nucleus
B) are smaller than animal cells
C) are unicellular
D) have a cell wall
E) are photosynthetic