Deck 28: The Origin and Evolution of Eukaryotes

Question 1

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) cyanobacteria → red algae → green algae → land plants

Answer 1

A

Question 2

Which of the following structures in chlorarachniophytes provides evidence that they evolved through the endosymbiosis of a green alga by a heterotrophic eukaryote?

A) food vacuole
B) nucleomorph
C) mitosomes
D) flagella

Answer 2

B

Question 3

Consider the following data:
∙ Most ancient eukaryotes are unicellular.
∙ All eukaryotes alive today have a nucleus and cytoskeleton.
∙ Most ancient eukaryotes lack a cell wall.
Which of the following conclusions about the first eukaryotes is most consistent with the data presented?

A) They were very similar to a plant cell.
B) They were anaerobic.
C) They were capable of phagocytosis.
D) They were photosynthetic.

Answer 3

C

Question 4

Which of the following characteristics do dinoflagellates exhibit?

A) They possess two flagella.
B) They are all autotrophic.
C) They lack mitochondria.
D) They include species that cause malaria.

Question 5

Use the following information to answer the question.
Giardia intestinalis is an intestinal parasite of humans and other mammals that causes intestinal ailments in most people who ingest the cysts. The cysts are dormant forms of this protist that are expelled in the feces of organisms that ingest them.
Which of the following structures to the cysts of Giardia function most like?

A) mitochondria of ancestral diplomonads
B) nuclei of archaeans
C) endospores of bacteria
D) capsids of viruses

Question 6

Which of the following mitigation strategies would be most likely to cause evolution of a drug-resistant strain of Plasmodium?

A) widespread, frequent spraying to kill mosquitoes
B) use of a cocktail of three drugs in patients suffering from malaria
C) widespread, frequent use of a single drug in patients suffering from malaria
D) widespread use of anti-mosquito bed nets

Question 7

Trypanosome infections evade attacks by host immune systems through which of the following mechanisms?

A) production of new cell-surface proteins with a different molecular structure by each new generation
B) production of toxins that kill lymphocytes
C) insertion of its DNA into the nuclear DNA of host cells
D) infection of lymphocytes leading to a decline in the host's ability to fight infection

Question 8

Which of the following statements compares the mitosomes of diplomonads and mitochondria of other types of eukaryotes?

A) The mitosomes in diplomonads and other eukaryotes are identical.
B) Mitosomes in diplomonads have a functional electron transport chain and other eukaryotes do not.
C) Mitosomes in diplomonads lack a functional electron transport chain and other eukaryotes possess one.
D) Mitosomes in diplomonads use oxygen for cellular respiration and other eukaryotes do not.

Question 9

Which of the following statements correctly compares prokaryotic and eukaryotic flagella?

A) They have the same evolutionary origin.
B) They have different structures.
C) They require different sources of energy.
D) They contain their own DNA.

Question 10

Which two genera have members that can evade the human immune system by frequently changing their surface proteins?

A) Plasmodium and Trypanosoma
B) Trichomonas and Paramecium
C) Trichomonas and Trypanosoma
D) Trypanosoma and Entamoeba

Question 11

When a mosquito infected with Plasmodium first bites a human, what is the first process carried out by the Plasmodium?

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

Question 12

Which of the following characteristics is common among all protists?

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

Question 13

Use the following information to answer the question.
Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two specialized structures called "chromatophores." The chromatophores 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.
The closest living relative to P. chromatophora is the heterotroph P. ovalis. P. ovalis uses threadlike pseudopods to capture its prey, which it digests internally. Which of the following characteristics, if observed, would be the best reason for reclassifying P. chromatophora as a mixotroph instead of an autotroph?

A) a pigmented central vacuole, surrounded by a nucleomorph
B) a vacuole with food inside
C) a secretory vesicle
D) a contractile vacuole

Question 14

Which of the following pairs of protists and their ecological roles are correctly matched?

A) apicomplexans-parasites of animals
B) euglenozoans-primarily mixotrophic
C) dinoflagellates-parasites of plants
D) entamoebas-free-living soil organisms

Question 15

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?

A) plasmids
B) mitochondria
C) nucleus
D) chloroplasts

Question 16

After studying a particular species of protist, you suspect that it has obtained a chloroplast via secondary endosymbiosis. Which of the following information would confirm your hypothesis?

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

Question 17

According to the endosymbiotic theory, it was adaptive for the larger host cell to keep the engulfed cell alive, rather than digesting it as food because ________.

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

Question 18

An individual mixotroph loses its plastids, yet continues to survive. Which of the following statements best explains this organism's 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.

Question 19

Which of the following protists have chloroplasts (or structures since evolved from chloroplasts) thought to be derived from ancestral green algae?

A) stramenopiles
B) apicomplexans
C) dinoflagellates
D) chlorarachniophytes

Question 20

Many parasitic members of the excavates lack plastids and have highly reduced mitochondria. Which of the following statements explains these observations?

A) These parasites typically live in low-oxygen conditions, and therefore it was adaptive to move all plastid and mitochondrial genes to the nucleus.
B) The original, eukaryotic ancestors of these parasites did not engulf prokaryotes.
C) These parasites typically live in low-oxygen conditions and therefore loss of genes for plastids and mitochondria did not result in lower fitness.
D) In the future, natural selection will favor descendants that acquire new plastid genes from today's prokaryotes.

Question 21

You have discovered a new species aquatic protist that is a primary producer. It cannot swim on its own. It appears to be resistant to physical damage from wave action due to the presence of a glass-like wall. Which of the following organisms would this organism be most like?

A) diatom
B) dinoflagellate
C) apicomplexan
D) red alga

Question 22

A porous test (shell) of calcium carbonate, through which pseudopodia protrude, is characteristic of which of the following groups of organisms?

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

Question 23

Reinforced, threadlike pseudopods that can perform phagocytosis are generally characteristic of which of the following groups or organisms?

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

Question 24

Use the following information to answer the question.
Healthy individuals of some Paramecium species contain photosynthetic algal endosymbionts of the genus Chlorella. The Chlorella provide their hosts with glucose and oxygen, and Paramecium provides its Chlorella with protection and motility.
A Paramecium cell has lost its Chlorella. It might be able to replenish the Chlorella by ingesting them without subsequently digesting them.
Which of the following situations would be most favorable to the reestablishment of resident Chlorella, assuming compatible Chlorella are present in the Paramecium'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 25

Diatoms are mostly asexual members of the phytoplankton. Diatoms lack any organelles that provide for locomotion. 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 explaining the day-to-day survival of individual diatoms?

A) How do diatoms move from one location on the water's surface layers to another location on the surface?
B) How do diatoms with their glasslike valves keep from sinking into poorly lit waters?
C) How do diatoms with their glasslike valves avoid being shattered by the action of waves?
D) How do diatom sperm cells locate diatom egg cells?

Question 26

Which of the following types of organisms produces algin, a substance used as a thickener in many processed foods?

A) forams
B) dinoflagellates
C) diatoms
D) kelp

Question 27

You are given four test tubes, each containing an unknown protist, and your task is to read the following description and match these four protists to the correct test tube. Use the information in the table to answer the question.

Based on these data, what type of organism is present in tube 1?

A) Paramecium
B) Pfiesteria (dinoflagellate)
C) Entamoeba
D) Plasmodium

Question 28

Which of the following structures provides motility in species of paramecium?

A) pseudopods
B) a single flagellum
C) many cilia
D) contractile vacuoles

Question 29

You are given four test tubes, each containing an unknown protist, and your task is to read the following description and match these four protists to the correct test tube. Use the information in the table to answer the question.

Based on these data, what type of organism is present in tube 3?

A) Paramecium
B) Pfiesteria (dinoflagellate)
C) Entamoeba
D) Plasmodium

Question 30

You are given four test tubes, each containing an unknown protist, and your task is to read the following description and match these four protists to the correct test tube. Use the information in the table to answer the question.

Based on these data, what type of organism is present in tube 4?

A) Paramecium
B) Pfiesteria (dinoflagellate)
C) Entamoeba
D) Plasmodium

Question 31

Which of the following is a characteristic commonly found in ciliates?

A) They use pseudopods as feeding structures.
B) They are often multinucleate.
C) They can exchange genetic material with other ciliates by the process of mitosis.
D) Most live as solitary autotrophs in fresh water.

Question 32

You are given four test tubes, each containing an unknown protist, and your task is to read the following description and match these four protists to the correct test tube. Use the information in the table to answer the question.

Based on these data, what type of organism is present in tube 2?

A) Paramecium
B) Pfiesteria (dinoflagellate)
C) Entamoeba
D) Triceratium (diatom)

Question 33

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 two nuclei, one large and one small. To which of the following groups does this organism likely belong?

A) foraminiferan
B) radiolarian
C) ciliate
D) kinetoplastid

Question 34

Paulinella chromatophora is a cercozoan that secretes a test, or case around itself consisting of plates made of silica. Which of the following is a 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) dinoflagellates
D) diatoms

Question 35

Ciliates like Paramecium typically reproduce asexually. Which process in Paramecium results in genetic recombination but no increase in population size?

A) budding
B) meiotic division
C) conjugation
D) binary fission

Question 36

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "chromatophores." The chromatophores 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.
Including the membrane of the surrounding vesicle, which answer identifies the maximum number of phospholipid bilayers present in the chromatophores of P. chromatophora and the bilayer in which the photosystem is most likely located?

A) two; innermost
B) two; outermost
C) three; innermost
D) three; middle

Question 37

Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "chromatophores." The chromatophores 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.
Which of the following results would be most important in determining whether the chromatophore of P. chromatophora is still an endosymbiont, or is an organelle, as the term chromatophore implies?

A) if P. chromatophora is less fit without its chromatophore than with it
B) if the chromatophore is less fit without the host cercozoan than with it
C) if there is ongoing metabolic cooperation between the chromatophore and the host cercozoan
D) if there has been movement of genes from the chromatophore genome to the nuclear genome, such that these genes are no longer present in the chromatophore genome

Question 38

Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. The Chlorella provide their hosts with glucose and oxygen, and P. bursaria provides its Chlorella with protection and motility.
Which term best describes the symbiotic relationship of well-fed P. bursaria to Chlorella?

A) mutualistic
B) parasitic
C) predatory
D) pathogenic

Question 39

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 the chromatophore of P. chromatophora 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) The chromatophore of P. chromatophora 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 chromatophore's genome.
D) The genome of the cyanobacteria was smaller than the genome of P. chromatophora.

Question 40

A 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

Question 41

In a recent study, researchers found that carbon dioxide was pumped to the ocean floor after adding a small amount of iron to the water. Which of the following organisms was likely responsible for this result?

A) dinoflagellates
B) forams
C) diatoms
D) slime molds

Question 42

Slime molds and fungi were once included in the same taxonomic group due to some specific similarities in morphology and lifestyle. These two groups are now classified in different taxonomic groups. How would you describe these similarities now that the two groups are classified separately?

A) the similarities are homologies
B) the similarities are examples of convergent evolution
C) the similarities are variations of common ancestral traits
D) the similarities are adaptations for much different functions

Question 43

Which of the following results would be most likely if a layer of warm, light water caused by ocean surface warming blocks nutrient upwelling?

A) reduced populations of fish because they avoid warm water
B) increased populations of producers because they have access to more CO₂
C) reduced populations of producers because they have access to fewer nutrients
D) increased populations of producers because fewer fish are produced, and they eat fewer producers

Question 44

Similar to most amoebozoans, the forams and the radiolarians also have pseudopods, as do some of the white blood cells of animals. If one were to construct a taxon that included all organisms that have cells with pseudopods, what type of evolutionary pattern would the tree show?

A) polyphyletic
B) paraphyletic
C) monophyletic
D) it would include all eukaryotes

Question 45

A failure in which of the following processes can result in the formation of a supercell that is characteristic of plasmodial slime molds?

A) mitosis
B) cytokinesis
C) aerobic metabolism
D) endocytosis

Question 46

Green algae and plants are placed in the same phylogenetic group. Which of the following statements presents evidence to support this classification?

A) similarities in mitochondrial structure and enzyme sequences
B) similarities in chloroplast structure and pigment composition
C) similarities in cell wall and membrane structure
D) DNA sequence similarities in genes for ribosome structure

Question 47

Use the following information to answer the question.
Healthy individuals of Paramecium bursaria contain photosynthetic algal endosymbionts of the genus Chlorella. In addition, P. bursaria also ingests bacteria.
Which term most accurately describes the nutritional mode of healthy P. bursaria?

A) photoautotroph
B) photoheterotroph
C) chemoautotroph
D) mixotroph

Question 48

You have discovered a photosynthetic protist that lives in fairly deep water (for example, 250 m deep).To which of the following groups should this organism be classified?

A) diatoms
B) green algae
C) red algae
D) cercozoan

Question 49

Many chlorophytes are unicellular, but others are larger and more complex. What does this indicate regarding the evolutionary history of chlorophytes?

A) the chlorophyte group is not monophyletic
B) the chlorophyte group is monophyletic
C) the chlorophyte group is the protist group most closely related to plants
D) the chlorophyte group contained extensive genetic variability

Question 50

Amoebas are polyphyletic. Based on this fact, which of the following statements regarding their evolution is correct?

A) movement by pseudopodia evolved only once
B) scientists need to continue to investigate the origins and evolutionary history of protists
C) evolutionary history cannot be discovered
D) eukaryotes are also not monophyletic and need to be broken into many groups

Question 51

A biologist discovers an alga that is marine, multicellular, and lives at a depth reached only by blue light. Based on this information, to which of the following groups of algae would this organism be classified?

A) red algae
B) brown algae
C) green algae
D) golden algae

Question 52

SAR is a highly diverse group of protists defined by DNA similarities determined through whole-genome analysis of various organisms in the group. Which of the following conclusions could be drawn from this information?

A) SAR is a paraphyletic group
B) SAR is a monophyletic group
C) SAR includes organisms that have different common ancestors
D) the common ancestor of the members of this group arose relatively recently in evolutionary history

Question 53

What do the multiple branching points at the root of the eukaryotic phylogenetic tree indicate about the evolution of eukaryotes?

A) that unikonts are derived from the SAR clade
B) that Archaeplastids were the first eukaryotes
C) that fungi are more closely related to plants than animals
D) that eukaryotes are all descended from a common ancestor

Question 54

Which of the following statements correctly describes one difference between green algae and land plants?

A) green algae are often unicellular, while land plants are not
B) land plants have plastids and green algae do not
C) algae have alternation of generations but land plants do not
D) land plants have cell walls containing cellulose but green algae do not

Question 55

Living diatoms contain brownish plastids. If global climate change continues to warm surface waters of Earth's oceans, which of the following is the most likely effect on the animals that build coral reefs?

A) The coral animals, which capture planktonic organisms, may be outcompeted by the diatoms.
B) The coral animals' endosymbiotic dinoflagellates may get "shaded out" by the diatoms.
C) The coral animals may die from overeating the plentiful diatoms with their cases of silica.
D) The diatoms' photosynthetic output may over-oxygenate the water.

Question 56

Researchers have shown that "income levels in countries hard hit by malaria are 33% lower than in countries with similar income that are free of the disease." Which of the following statements is correct regarding this observation?

A) This observation suggests that symptoms from malaria cause patients to lose pay because they miss work.
B) This observation is an example of a correlation and therefore causality cannot be inferred as confidently as if we have results from a manipulated experiment.
C) In order to understand the cause of this observation, scientists should eradicate malaria in ten countries but not in ten other comparable countries in order to experimentally test whether malaria caused the low income levels.
D) The observation demonstrates that correlations provide excellent indications of causality.

Question 57

Which of the following types of protists causes the potentially fatal disease dysentery?

A) Entamoeba histolytica
B) Amoeba proteus
C) plasmodial slime molds
D) Dictyostelium discoideum

Question 58

Which of the following organisms is a producer?

A) kinetoplastids
B) apicomplexans
C) diatoms
D) ciliates

Question 59

You have discovered that some members of an aquatic species of motile, photosynthetic protists have evolved 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

Question 60

Which of the following groups is matched with a correct anatomical feature?

A) foraminifera-silicon-rich tests
B) dinoflagellata-holdfast
C) diatoms-tests made of cellulose
D) brown algae-blade

Question 61

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

Question 62

In a life cycle with alternation of generations, multicellular haploid forms alternate with ________.

A) unicellular haploid forms
B) unicellular diploid forms
C) multicellular haploid forms
D) multicellular diploid forms

Question 63

Biologists think 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

Question 64

According to the phylogeny presented in this chapter, which protists are in the same eukaryotic supergroup as plants?

A) green algae
B) dinoflagellates
C) red algae
D) both A and C

Question 65

Which group is correctly paired with its description?

A) diatoms-important consumers in aquatic communities
B) diplomonads-protists with modified mitochondria
C) apicomplexans-producers with intricate life cycles
D) red algae-acquired plastids by secondary endosymbiosis

Question 66

Based on the phylogenetic tree in the figure, which of the following statements is correct?

A) Excavata and SAR form a sister group.
B) The most recent common ancestor of SAR is older than that of Unikonta.
C) The most basal (first to diverge) eukaryotic supergroup cannot be determined.
D) Excavata is the most basal eukaryotic supergroup.