Chapter 28 Protists Multiple-Choice Questions 1) Protists are alike in that all are A) unicellular. B) eukaryotic. C) symbionts. D) monophyletic. E) autotrophic. Topic: Concept 28.1 2) Biologists have long been aware that the defunct kingdom Protista is paraphyletic. Which of these statements is both true and consistent with this conclusion? A) Many species within this kingdom were once classified as monerans. B) Animals, plants, and fungi arose from different protist ancestors. C) The eukaryotic condition has evolved only once among the protists, and all eukaryotes are descendants of that first eukaryotic cell. D) Chloroplasts among various protists are similar to those found in prokaryotes. E) Some protists, all animals, and all fungi share a protist common ancestor, but these protists, animals, and fungi are currently assigned to three different kingdoms. Topic: Concept 28.1 3) The strongest evidence for the endosymbiotic origin of eukaryotic organelles is the similarity between extant prokaryotes and which of the following? A) nuclei and chloroplasts B) mitochondria and chloroplasts C) cilia and mitochondria D) mitochondria and nuclei E) mitochondria and cilia Topic: Concept 28.1 4) According to the endosymbiotic 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 prokaryotes C) by secondary endosymbiosis D) from the nuclear envelope folding outward and forming mitochondrial membranes E) when a protoeukaryote engaged in a symbiotic relationship with a protobiont Topic: Concept 28.1 Page 1
5) Which of these statements is false and therefore does not support the hypothesis that certain eukaryotic organelles originated as bacterial endosymbionts? Such organelles A) are roughly the same size as bacteria. B) can be cultured on agar, because they make all their own proteins. C) contain circular DNA molecules. D) have ribosomes that are similar to those of bacteria. E) have internal membranes that contain proteins homologous to those of bacterial plasma membranes. Topic: Concept 28.1 6) Which process allowed the nucleomorphs of chlorarachniophytes to be first reduced, and then (in a few species) lost altogether, without the loss of any genetic information? A) conjugation B) horizontal gene transfer C) binary fission D) phagocytosis E) meiosis Topic: Concept 28.1 7) Which organisms represent the common ancestor of all photosynthetic plastids found in eukaryotes? A) autotrophic euglenids B) diatoms C) dinoflagellates D) red algae E) cyanobacteria Topic: Concept 28.1 8) An individual mixotroph loses its plastids, yet continues to survive. Which of the following most likely accounts for its continued survival? A) It relies on photosystems that float freely in its cytosol. B) It must have gained extra mitochondria when it lost its plastids. C) It engulfs organic material by phagocytosis or by absorption. D) It has an endospore. E) It is protected by a siliceous case. Topic: Concept 28.1 9) Which of these was not derived from an ancestral alpha proteobacterium? A) chloroplast B) mitochondrion C) hydrogenosome D) mitosome E) kinetoplast Topic: Concepts 28.1, 28.2 Page 2
10) A biologist discovers a new unicellullar organism that possesses more than two flagella and two small, but equal-sized, nuclei. The organism has reduced mitochondria (mitosomes), no chloroplasts, and is anaerobic. To which clade does this organism probably belong? A) monera B) the diplomonads C) the ciliates D) protista E) the euglenids Topic: Concept 28.2 11) Which two genera have members that can evade the human immune system by frequently changing their surface proteins? 1. Plasmodium 2. Trichomonas 3. Paramecium 4. Trypanosoma 5. Entamoeba A) 1 and 2 B) 1 and 4 C) 2 and 3 D) 2 and 4 E) 4 and 5 Topic: Concepts 28.2, 28.3 12) Which statement regarding resistance is false? A) Many of the oomycetes that cause potato late blight have become resistant to pesticides. B) Many of the mosquitoes that transmit malaria to humans have become resistant to pesticides. C) Many of the malarial parasites have become resistant to antimalarial drugs. D) Many humans have become resistant to antimalarial drugs. E) Trichomonas vaginalis is resistant to the normal acidity of the human vagina. Topic: Concepts 28.2, 28.3 13) Which of these taxa contains species that produce potent toxins that can cause extensive fish kills, contaminate shellfish, and poison humans? A) red algae B) dinoflagellates C) diplomonads D) euglenids E) golden algae Page 3
14) Which of the following pairs of protists and their characteristics is mismatched? A) apicomplexans : internal parasites B) golden algae : planktonic producers C) euglenozoans : unicellular flagellates D) ciliates : red tide organisms E) entamoebas : ingestive heterotrophs 15) Which of these statements about dinoflagellates is false? A) They possess two flagella. B) Some cause red tides. C) Their walls are composed of cellulose plates. D) Many types contain chlorophyll. E) Their dead cells accumulate on the seafloor, and are mined to serve as a filtering material. 16) Which group includes members that are important primary producers in ocean food webs, causes red tides that kill many fish, and may even be carnivorous? A) ciliates B) apicomplexans C) dinoflagellates D) brown algae E) golden algae 17) You are given an unknown organism to identify. It is unicellular and heterotrophic. It is motile, using many short extensions of the cytoplasm, each featuring the 9+2 filament pattern. It has well-developed organelles and three nuclei, one large and two small. This organism is most likely to be a member of which group? A) foraminiferans B) radiolarians C) ciliates D) kinetoplastids E) slime molds 18) Which of the following is not characteristic of ciliates? A) They use cilia as locomotory structures or as feeding structures. B) They are relatively complex cells. C) They can exchange genetic material with other ciliates by the process of mitosis. D) Most live as solitary cells in fresh water. E) They have two or more nuclei. Page 4
19) Which process results in genetic recombination, but is separate from the process wherein the population size of Paramecium increases? A) budding B) meiotic division C) mitotic division D) conjugation E) binary fission 20) Why is the filamentous morphology of the water molds considered a case of convergent evolution with the hyphae (threads) of fungi? A) Fungi are closely related to the water molds. B) Body shape reflects ancestor-descendant relationships among organisms. C) In both cases, filamentous shape is an adaptation for the absorptive nutritional mode of a decomposer. D) Filamentous body shape is evolutionarily ancestral for all eukaryotes. E) Both A and B are correct. 21) The Irish potato famine was caused by an organism that belongs to which group? A) ciliates B) oomycetes C) diatoms D) apicomplexans E) dinoflagellates 22) If one were to apply the most recent technique used to fight potato late blight to the fight against the malarial infection of humans, then one would A) increase the dosage of the least-expensive antimalarial drug administered to humans. B) increase the dosage of the most common pesticide used to kill Anopheles mosquitoes. C) introduce a predator of the malarial parasite into infected humans. D) use a ʺcocktailʺ of at least three different pesticides against Anopheles mosquitoes. E) insert genes from a Plasmodium-resistant strain of mosquito into Anopheles mosquitoes. Page 5
23) Diatoms are mostly asexual members of the phytoplankton. Diatoms lack any organelles that might have the 9+2 pattern. They obtain their nutrition from functional chloroplasts, and each diatom is encased within two porous, glasslike 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 glasslike valves? B) How do diatoms get transported from one location on the waterʹs surface layers to another location on the surface? C) How do diatoms with their glasslike valves keep from sinking into poorly lit waters? D) How do diatoms with their glasslike valves avoid being shattered by the action of waves? E) How do diatom sperm cells locate diatom egg cells? 24) A large seaweed that floats freely on the surface of deep bodies of water would be expected to lack which of the following? A) thalli B) bladders C) blades D) holdfasts E) gel-forming polysaccharides 25) The following are all characteristic of the water molds (oomycetes) except A) the presence of filamentous feeding structures. B) flagellated zoospores. C) a nutritional mode that can result in the decomposition of dead organic matter. D) a morphological similarity to fungi that is the result of evolutionary convergence. E) a feeding plasmodium. Page 6
The following questions refer to the description and Table 28.1 below. Diatoms are encased in Petri-plate-like cases (valves) made of translucent hydrated silica whose thickness can be varied. The material used to store excess calories can also be varied. At certain times, diatoms store excess calories in the form of the liquid polysaccharide, laminarin, and at other times, as oil. Below are data concerning the density (specific gravity) of various components of diatoms, and of their environment. Table 28.1: Specific Gravities of Materials Relevant to Diatoms Material Specific Gravity (kg/m3) Pure water 1000 Seawater 1026 Hydrated silica 2250 Liquid laminarin 1500 Diatom oil 910 26) Waterʹs density and, consequently, its buoyancy decrease at warmer temperatures. Based on this consideration and using data from Table 28.1, 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 27) Judging from Table 28.1 and given that waterʹs density and, consequently, its buoyancy decrease at warmer temperatures, in which environment should diatoms (and other suspended particles) sink most slowly? A) cold freshwater B) warm freshwater C) cold seawater D) warm seawater E) warm brackish water 28) Using dead diatoms to ʺpumpʺ 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 A) valves are thickest, and laminarin is being produced rather than oil. B) valves are thickest, and oil is being produced rather than laminarin. C) valves are thinnest, and laminarin is being produced rather than oil. D) valves are thinnest, and oil is being produced rather than laminarin. Page 7
29) Theoretically, which two of the following present the richest potential sources of silica? 1. marine sediments consisting of foram tests 2. marine sediments consisting of diatom cases (valves) 3. marine sediments consisting of radiolarian shells 4. marine sediments consisting of dinoflagellate plates A) 1 and 2 B) 1 and 4 C) 2 and 3 D) 2 and 4 E) 3 and 4 Topic: Concepts 28.3, 28.4 30) Thread-like pseudopods that can perform phagocytosis are generally characteristic of which group? A) radiolarians and forams B) gymnamoebas C) entamoebas D) amoeboid stage of cellular slime molds E) oomycetes Topic: Concept 28.4 31) Which of the following produce the dense glassy ooze found in certain areas of the deep -ocean floor? A) forams B) dinoflagellates C) radiolarians D) ciliates E) apicomplexans Topic: Concept 28.4 32) A snail-like, coiled, porous test (shell) of calcium carbonate is characteristic of which group? A) diatoms B) foraminiferans C) radiolarians D) gymnamoebas E) ciliates Topic: Concept 28.4 Page 8
33) Typically as cells grow, their increase in volume outpaces their increase in surface area, and continued survival requires undergoing asexual reproduction to reestablish a healthy surface area to volume ratio. Thus, which of these is least likely to contribute to the ability of a single-celled foraminiferan to grow to a diameter of several centimeters? A) Its threadlike pseudopods dramatically increase its surface area to volume ratio. B) Its symbiotic algae provide oxygen to the cytoplasm. C) Its symbiotic algae absorb metabolic waste products from the cytoplasm. D) Its symbiotic algae provide glucose to the cytoplasm. E) Its calcium carbonate test contributes extra mass. Topic: Concept 28.4 34) What makes certain red algae appear red? A) They live in warm coastal waters. B) They possess pigments that reflect and transmit red light. C) They use red light for photosynthesis. D) They lack chlorophyll. E) They contain the pigment bacteriorhodopsin. Topic: Concept 28.5 35) The largest seaweeds belong to which group? A) red algae B) green algae C) brown algae D) golden algae Topic: Concepts 28.3, 28.5 36) The chloroplasts of land plants are thought to have been derived according to which evolutionary sequence? A) cyanobacteria green algae land plants B) cyanobacteria green algae fungi land plants C) red algae brown algae green algae land plants D) red algae cyanobacteria land plants E) cyanobacteria red algae green algae land plants Topic: Concepts 28.1, 28.5 37) The chloroplasts of all of the following are derived from ancestral red algae, except those of A) golden algae. B) diatoms. C) dinoflagellates. D) green algae. E) brown algae. Topic: Concept 28.5 Page 9
38) A biologist discovers an alga that is marine, multicellular, and lives at a depth reached only by blue light. This alga probably belongs to which group? A) red algae B) brown algae C) green algae D) dinoflagellates E) golden algae Topic: Concept 28.5 39) Green algae often differ from land plants in that some green algae A) are heterotrophs. B) are unicellular. C) have plastids. D) have alternation of generations. E) have cell walls containing cellulose. Topic: Concept 28.5 40) Which taxon of eukaryotic organisms is thought to be directly ancestral to the plant kingdom? A) golden algae B) radiolarians C) foraminiferans D) apicomplexans E) green algae Topic: Concept 28.5 41) If the Archaeplastidae are eventually designated a kingdom, and if the land plants are excluded from this kingdom, then what will be true of this new kingdom? A) It will be monophyletic. B) It will more accurately depict evolutionary relationships than does the current taxonomy. C) It will be paraphyletic. D) It will be a true clade. E) It will be polyphyletic. Topic: Concept 28.5 42) The best evidence for not classifying the slime molds as fungi comes from slime moldsʹ A) DNA sequences. B) nutritional modes. C) choice of habitats. D) physical appearance. E) reproductive methods. Topic: Concept 28.6 Page 10
43) Which pair of alternatives is highlighted by the life cycle of the cellular slime molds, such as Dictyostelium? A) prokaryotic or eukaryotic B) plant or animal C) unicellular or multicellular D) diploid or haploid E) autotroph or heterotroph Topic: Concept 28.6 44) Which of the following correctly pairs a protist with one of its characteristics? A) diplomonads : micronuclei involved in conjugation B) ciliates : pseudopods C) apicomplexans : parasitic D) gymnamoebas : calcium carbonate test E) foraminiferans : abundant in soils Topic: Concepts 28.2-28.6 45) Which of the following statements concerning protists is false? A) All protists are eukaryotic organisms; many are unicellular or colonial. B) The primary organism that transmits malaria to humans by its bite is the tsetse fly. C) All apicomplexans are parasitic. D) Cellular slime molds have an amoeboid stage that may be followed by a stage during which spores are produced. E) Euglenozoans that are mixotrophic contain chloroplasts. Topic: Concepts 28.2-28.6 46) Which of the following is correctly described as a primary producer? A) oomycete B) kinetoplastid C) apicomplexan D) diatom E) radiolarian Topic: Concepts 28.2-28.6 47) A certain unicellular eukaryote has a siliceous (glasslike) shell and autotrophic nutrition. To which group does it belong? A) dinoflagellates B) diatoms C) brown algae D) radiolarians E) oomycetes Topic: Concepts 28.2-28.6 Page 11
48) You are given the task of designing an aerobic, mixotrophic protist that can perform photosynthesis in fairly deep water (e.g., 250 m deep), and can also crawl about and engulf small particles. With which two of these structures would you provide your protist? 1. hydrogenosome 2. apicoplast 3. pseudopods 4. chloroplast from red alga 5. chloroplast from green alga A) 1 and 2 B) 2 and 3 C) 2 and 4 D) 3 and 4 E) 4 and 5 Topic: Concepts 28.2-28.6 49) You are given the task of designing an aquatic protist that is a primary producer. It cannot swim on its own, yet must stay in well-lit surface waters. It must be resistant to physical damage from wave action. It should be most similar to a(n) A) diatom. B) dinoflagellate. C) apicomplexan. D) red alga. E) radiolarian. Topic: Concepts 28.2-28.6 50) Some protists, formerly united as the ʺamitochondriateʺ clade, have recently been shown to be rather diverse. Some of them possess neither mitochondria nor mitochondrial genes (and have been classified as fungi). Others possess no mitochondria, but do have mitochondrial genes in their nuclear genome. Still others have modified mitochondria (viz. mitosomes or hydrogenosomes). Which statement(s) represent(s) consequences of these recent findings? 1. The amitochondriates do not comprise a true clade. 2. The ʺamitochondriate hypothesisʺ concerning the root of the eukaryotic tree has been strengthened. 3. Just as there is a diversity of cyanobacterial descendants among eukaryotes, so too is there a diversity of alpha-proteobacterial descendants among the eukaryotes. 4. If the amitochondriate organisms continued to be recognized as a taxon, this taxon would be polyphyletic. 5. Horizontal gene transfer involving mitochondrial genes has occurred in some amitochondriate organisms. A) 1 only B) 1 and 4 C) 2 and 3 D) 1, 3, and 5 E) all except 2 Topic: Concepts 28.2, 28.6 Page 12
51) Similar to most amoebozoans, the forams and the radiolarians also have pseudopods, as do the white blood cells of animals. If one were to erect a taxon that included all organisms that have cells with pseudpods, what would be true of such a taxon? A) It would be polyphyletic. B) It would be paraphyletic. C) It would be monophyletic. D) It would include all eukaryotes. Topic: Concepts 28.4, 28.6 52) You are designing an artificial drug-delivery ʺcellʺ that can penetrate animal cells. Which of these protist structures should provide the most likely avenue for research along these lines? A) pseudopods B) apical complex C) excavated feeding grooves D) nucleomorphs E) mitosomes Topic: Concepts 28.2-28.6 53) A gelatinous seaweed that grows in shallow, cold water and undergoes heteromorphic alternation of generations is most probably what type of alga? A) red B) green C) brown D) yellow Topic: Concepts 28.2-28.6 Page 13
You are given five test tubes, each containing an unknown protist, and your task is to read the description below and match these five protists to the correct test tube. In test tube 1, you observe an organism feeding. Your sketch of the organism looks very similar to Figure 28.1. When light, especially red and blue light, is shone on the tubes, oxygen bubbles accumulate on the inside of test tubes 2 and 3. Chemical analysis of test tube 3 indicates the presence of substantial amounts of silica. Chemical analysis of test tube 2 indicates the presence of a chemical that is toxic to fish and humans. Microscopic analysis of organisms in tubes 2, 4, and 5 reveals the presence of permanent, membrane-bounded sacs just under the plasma membrane. Microscopic analysis of organisms in tube 4 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in tube 5 reveals the presence of one large nucleus and several small nuclei in each organism. 54) Test tube 2 contains A) Paramecium B) Navicula (diatom) C) Pfiesteria (dinoflagellate) D) Entamoeba E) Plasmodium 55) Test tube 4 contains A) Paramecium B) Navicula (diatom) C) Pfiesteria (dinoflagellate) D) Entamoeba E) Plasmodium 56) Test tube 5 contains A) Paramecium B) Navicula (diatom) C) Pfiesteria (dinoflagellate) D) Entamoeba E) Plasmodium Figure 28.1 Page 14
57) Test tube 3 contains A) Paramecium B) Navicula (diatom) C) Pfiesteria (dinoflagellate) D) Entamoeba E) Plasmodium 58) Test tube 1 contains A) Paramecium B) Navicula (diatom) C) Pfiesteria (dinoflagellate) D) Entamoeba E) Plasmodium Topic: Concept 28.6 59) Which of these are actual mutualistic partnerships that involve a protist and a host organism? A) cellulose-digesting gut protists : wood-eating termites B) dinoflagellates : reef-building coral animals C) Trichomonas : humans D) algae : certain foraminiferans E) all except C Topic: Concept 28.7 60) Which of the following statements concerning living phytoplanktonic organisms are true? 1. They are important members of communities surrounding deep-sea hydrothermal vents. 2. They are important primary producers in most aquatic food webs. 3. They are important in maintaining oxygen in Earthʹs seas and atmosphere. 4. They are most often found growing in the sediments of seas and oceans. 5. They can be so concentrated that they affect the color of seawater. A) 1 and 4 B) 1, 2, and 4 C) 2, 3, and 4 D) 2, 3, and 5 E) 3, 4, and 5 Topic: Concept 28.7 Page 15
The following questions refer to the description 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 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: (1) if kept in darkness, the algae die, and (2) if prey items (mostly bacteria) are absent from its habitat, P. bursaria will digest its zoochlorellae. 61) Which term most accurately describes the nutritional mode of healthy P. bursaria? A) photoautotroph B) photoheterotroph C) chemoheterotroph D) chemoautotroph E) mixotroph 62) 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 63) 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 64) If both host and alga can survive apart from each other, then which of these best accounts for their ability to live together? A) genome fusion B) horizontal gene transfer C) genetic recombination D) conjugation E) metabolic cooperation Page 16
65) 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. 66) If the chloroplasts of the zoochlorellae are very similar to those found in the photosynthetic cells of land plants, then Chlorella is probably what type of alga? A) red B) green C) brown D) golden 67) A P. bursaria cell that has lost its zoochlorellae is said to be ʺaposymbiotic.ʺ It might be able to replenish its contingent of zoochlorellae by ingesting them without subsequently digesting them. Which of these situations would be most favorable to the re-establishment of resident zoochlorellae, assuming compatible Chlorella are present in P. bursariaʹs 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 68) A P. bursaria cell that has lost its zoochlorellae is ʺaposymbiotic.ʺ 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 Page 17
69) 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. 70) Can P. bursaria live in association with any and all strains/species of Chlorella? In an experiment to help answer this question, Chlorella was collected, and cultured separately, from three different sources: (1) P. bursaria cytoplasm, (2) free-living Chlorella, and (3) from cytoplasm of other protist species. A population of P. bursaria was treated with the herbicide, paraquat, which killed all of its zoochlorellae, but otherwise left P. bursaria unharmed. The zoochlorella-free paramecia were then introduced to a 1:1:1 mixture of Chlorella from the three cultures listed above, and subsequently reestablished a contingent of zooclorellae. Two weeks later, zoochlorellae were collected from the P. bursaria cells and tested to determine which Chlorella strain(s) had been maintained within P. bursaria. The different strains of Chlorella are morphologically indistinguishable. Consequently, which of these would be the best test to perform on Chlorella, both before and after re-establishment of zoochlorellae, to determine which Chlorella strains had been maintained within P. bursaria? A) Determine the chemical composition of its cell wall. B) Determine the absorption spectrum of its photosynthetic pigments. C) Determine the sequence of a portion of its mitochondrial DNA. D) Determine the sequence of an exon of a ribosomal RNA gene. E) Determine the endosymbiontʹs diameter. Page 18
The following data were collected two weeks following reintroduction of Chlorella. (NOTE: ʺNativeʺ refers to Chlorella originally taken from P. bursaria cytoplasm.) Figure 28.2: Abundance of zoochlorellae in P. bursaria cytoplasm two weeks after reintroduction 71) Which conclusion is consistent with the data presented in Figure 28.2 above? A) Co-adaptation between P. bursaria and the native strain of Chlorella has occurred. B) All types of Chlorella tested are tolerated equally well by P. bursaria. C) P. bursaria cannot reproduce in the absence of zoochlorellae as well as it can when zoochlorellae are present. D) Zoochlorellae derived from other protists are well adapted to survive within P. bursaria, relative to the native strain. 72) The researchers decided to perform the same experiment over again, only this time, withdrawing P. bursaria samples every other day for testing to get a better picture of the fate of each Chlorella strain over time. Which graph below is most consistent with the results depicted in Figure 28.2, assuming that P. bursaria ingests the various Chlorella strains indiscriminately? Key: A) Page 19
B) C) D) Topic: Concepts 28.1-28.2 73) Which of these precautions would have been most important to insuring the validity of the results? A) Chlorella in the three cultures were genetically identical. B) Roughly equal numbers of each strain of Chlorella were present in the reintroduction mixture. C) The Chlorella cultures were free of bacteria. D) The P. bursaria culture was free of bacteria. E) The Chlorella DNA contained no introns. Page 20
74) Is P. bursariaʹs ability to detect and move toward light an innate ability, or is it due to the presence of zoochlorellae? Arrange the following steps in the proper sequence needed to answer this question. 1. Introduce P. bursaria from both the experimental and control populations to an aquarium that lacks free-living Chlorella, but that contains bacterial prey. 2. Remove equal amounts of water from the well-lit side of the aquarium and the poorly lit side of the aquarium, census the number and kind of P. bursaria present in each sample. 3. Shine light on only one side of the aquarium containing aposymbiotic P. bursaria. 4. Expose one population of P. bursaria (the experimental population) to an herbicide to kill its zoochlorellae. 5. Collect healthy P. bursaria from the well-lit side of an aquarium and divide it into two equal populations: a control population and an experimental population. A) 5 4 1 2 3 B) 5 4 1 3 2 C) 4 1 5 3 2 D) 2 5 4 1 3 E) 2 5 4 3 1 Self-Quiz Questions 1) 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. Topic: Skill: 2) 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. Topic: Skill: 3) 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 Topic: Skill: Page 21
4) Based on the phylogenetic tree in Figure 28.3 in the text, which of the following statements is correct? A) The most recent common ancestor of Excavata is older than that of Chromalveolata. B) The most recent common ancestor of Chromalveolata is older than that of Rhizaria. C) The most recent common ancestor of red algae and land plants is older than that of nucleariids and fungi. D) The most basal (first to diverge) eukaryotic supergroup cannot be determined. E) Excavata is the most basal eukaryotic supergroup. Topic: Skill: 5) Which protists are in the same eukaryotic ʺsupergroupʺ as land plants? A) green algae B) dinoflagellates C) red algae D) brown algae E) A and C are both correct Topic: Skill: 6) 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. Topic: Skill: Page 22