Question 1

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

Accepted Answer

Red algae are known for their ability to thrive in deep ocean waters, where they are able to absorb blue light and perform photosynthesis. They are also multicellular and marine, making them the best fit for the characteristics described in the question. Brown algae are also multicellular and marine, but they typically live in shallower waters and are not restricted to blue light depths. Green algae and golden algae are not typically found in deep ocean waters. Dinoflagellates are unicellular and while they may be found in deep ocean waters, they are not multicellular like the alga described in the question.

Question 2

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

Accepted Answer

Cold seawater is denser than warm seawater or fresh water, providing greater buoyancy, which slows the sinking of diatoms and other suspended particles.

Question 3

The best evidence for not classifying the slime molds as fungi comes from slime molds'
A) DNA sequences.
B) nutritional modes.
C) choice of habitats.
D) physical appearance.
E) reproductive methods.

Accepted Answer

DNA sequences provide the most definitive evidence for determining evolutionary relationships. Slime molds have been found to be more closely related to amoebas and other unicellular protists than to fungi, based on genetic analyses.

Question 4

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.

Accepted Answer

The answer of Using dead diatoms to "pump" CO2 to...

Question 5

Living diatoms contain brownish plastids. If global warming causes blooms of diatoms in the surface waters of Earth's oceans, how might this be harmful to 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.

Accepted Answer

Endosymbiotic dinoflagellates provide a significant contribution to coral growth and survival by producing organic matter via photosynthesis. If diatoms were to "shade out" the dinoflagellates, the corals would potentially lose this important symbiotic relationship and be less resilient to stressors such as warming waters or acidification.

Question 6

If the Archaeplastidae are eventually designated a kingdom, and if 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.

Accepted Answer

If the land plants are excluded from the Archaeplastidae kingdom, then this new kingdom will be paraphyletic because it would not include all descendants of a common ancestor. This is because land plants evolved from within the Archaeplastidae lineage, so excluding them would leave behind a group that is missing some of its descendants.

Question 7

The next few questions refer to the following description and Table 25.1.
Diatoms are encased in Petri-platelike 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. Table 25.1 shows data concerning the density (specific gravity) of various components of diatoms, and of their environment.
  Table 25.1 Specific Gravities of Materials Relevant to Diatoms
-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

Accepted Answer

According to Table 25.1, the density of oil is lower than that of water, so storing excess calories as oil would result in greater buoyancy for the diatoms. As water temperature increases (e.g. in late summer), water density and buoyancy decrease, making it advantageous for diatoms to store excess calories as oil to remain buoyant. Therefore, C) late summer is the best choice for when to expect diatoms to be storing excess calories mostly as oil.

Question 8

Which of the following 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 that involving humans

Accepted Answer

A, B, and D describe mutualistic relationships involving protists. In these partnerships, both the protist and the host organism benefit from the relationship. For example, cellulose-digesting gut protists help wood-eating termites digest wood, dinoflagellates provide reef-building coral animals with nutrients through photosynthesis, and certain algae live in a mutualistic relationship with foraminiferans, providing them with energy through photosynthesis. Trichomonas and humans (C) do not have a mutualistic relationship; Trichomonas vaginalis is a pathogen in humans.

Question 9

You are given five test tubes, each containing an unknown protist, and your task is to read the following description 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 25.1. 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 test tubes 2, 4, and 5 reveals the presence of permanent, membrane-bounded sacs just under the plasma membrane. Microscopic analysis of organisms in test tube 4 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 5 reveals the presence of one large nucleus and several small nuclei in each organism.  Figure 25.1
The next few questions refer to the following description and Figure 25.1.
-Test tube 2 contains
A) Paramecium.
B) Navicula (diatom).
C) Pfiesteria (dinoflagellate).
D) Entamoeba.
E) Plasmodium.

Accepted Answer

Pfiesteria is known to produce potent neurotoxins that are lethal to fish and can cause health problems in humans.

Question 10

You are given the task of designing an aerobic, mixotrophic protist that can perform photosynthesis in fairly deep water (for example, 250 m deep), and can also crawl about and engulf small particles. With which two of the following 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

Accepted Answer

For deep-water photosynthesis, chloroplasts from red algae are ideal because they can absorb light at longer wavelengths, which penetrates deeper into the water. Pseudopods would allow the protist to crawl and engulf particles, fitting the mixotrophic and mobile criteria.

Question 11

Which pair of alternatives is highlighted by the life cycle of the cellular slime molds, such as Dictyostelium?
A) prokaryotic or eukaryotic
B) unicellular or multicellular
C) diploid or haploid
D) autotroph or heterotroph

Accepted Answer

The life cycle of cellular slime molds like Dictyostelium involves a unicellular feeding stage and a multicellular reproductive stage in which individual cells aggregate to form a fruiting body. This highlights the alternative between unicellular and multicellular organisms. The other choices are not relevant to this life cycle.

Question 12

Green algae differ from land plants in that many green algae
A) are heterotrophs.
B) are unicellular.
C) have plastids.
D) have alternation of generations.
E) have cell walls containing cellulose.

Accepted Answer

While some green algae can be multicellular, many are unicellular. Land plants, on the other hand, are almost exclusively multicellular. Therefore, green algae differ from land plants in that many of them are unicellular.

Question 13

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

Accepted Answer

Plasmodium and Trypanosoma both have members that can evade the human immune system by frequently changing their surface proteins. Trichomonas, Paramecium, and Entamoeba do not have this ability.

Question 14

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.

Accepted Answer

Diatoms are photosynthetic protists that are commonly found in the upper layer of aquatic environments. They have a hard outer shell made of silica that provides them with physical protection from wave action. They cannot swim on their own and rely on water currents to move them around. Diatoms are primary producers, meaning they use sunlight to produce their own food through photosynthesis.

Question 15

You are given five test tubes, each containing an unknown protist, and your task is to read the following description 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 25.1. 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 test tubes 2, 4, and 5 reveals the presence of permanent, membrane-bounded sacs just under the plasma membrane. Microscopic analysis of organisms in test tube 4 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 5 reveals the presence of one large nucleus and several small nuclei in each organism.  Figure 25.1
The next few questions refer to the following description and Figure 25.1.
-Test tube 4 contains
A) Paramecium.
B) Navicula (diatom).
C) Pfiesteria (dinoflagellate).
D) Entamoeba.
E) Plasmodium.

Accepted Answer

The presence of an apicoplast is a characteristic feature of Plasmodium, a genus of protists responsible for causing malaria.

Question 16

Similar to most amoebozoans, the forams and the radiolarians also have pseudopods, as do some of the white blood cells of animals (monocytes). If one were to construct a taxon that included all organisms that have cells with pseudopods, 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.

Accepted Answer

A taxon that includes all organisms with pseudopods would be polyphyletic because pseudopods have evolved independently in different lineages, such as amoebozoans, forams, radiolarians, and some animal cells, rather than from a common ancestor.

Question 17

You are given five test tubes, each containing an unknown protist, and your task is to read the following description 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 25.1. 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 test tubes 2, 4, and 5 reveals the presence of permanent, membrane-bounded sacs just under the plasma membrane. Microscopic analysis of organisms in test tube 4 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 5 reveals the presence of one large nucleus and several small nuclei in each organism.  Figure 25.1
The next few questions refer to the following description and Figure 25.1.
-Test tube 3 contains
A) Paramecium.
B) Navicula (diatom).
C) Pfiesteria (dinoflagellate).
D) Entamoeba.
E) Plasmodium.

Accepted Answer

The presence of substantial amounts of silica in test tube 3 indicates the presence of a diatom, such as Navicula.

Question 18

You are given five test tubes, each containing an unknown protist, and your task is to read the following description 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 25.1. 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 test tubes 2, 4, and 5 reveals the presence of permanent, membrane-bounded sacs just under the plasma membrane. Microscopic analysis of organisms in test tube 4 reveals the presence of an apicoplast in each. Microscopic analysis of the contents in test tube 5 reveals the presence of one large nucleus and several small nuclei in each organism.  Figure 25.1
The next few questions refer to the following description and Figure 25.1.
-Test tube 5 contains
A) Paramecium.
B) Navicula (diatom).
C) Pfiesteria (dinoflagellate).
D) Entamoeba.
E) Plasmodium.

Accepted Answer

The answer of You are given five test tubes, each...

Question 19

Which of the following statements concerning protists is true?
A) All protists have mitochondria, although in some species they are much reduced and known by different names.
B) The primary organism that transmits malaria to humans by its bite is the tsetse fly.
C) All apicomplexans are autotrophic.
D) All slime molds have an amoeboid stage that may be followed by a stage during which spores are produced.
E) Euglenozoans that are mixotrophic lack functional chloroplasts.

Accepted Answer

Not all protists are autotrophic or parasitic, but all protists have mitochondria (even if those mitochondria are reduced and called by different names, such as hydrogenosomes or mitosomes).

Answer: B
 The primary organism that transmits malaria to humans by its bite is the Anopheles mosquito, not the tsetse fly.

Answer: E
 Euglenozoans that are mixotrophic have functional chloroplasts, but they can also feed heterotrophically when necessary.

Question 20

Which of the following is correctly described as a primary producer?
A) oomycete
B) kinetoplastid
C) apicomplexan
D) diatom
E) radiolarian

Accepted Answer

Diatoms are unicellular eukaryotic primary producers that are important components of aquatic food chains. They use photosynthesis to convert carbon dioxide into organic matter. Oomycetes, kinetoplastids, apicomplexans, and radiolarians are not primary producers.

Quiz 25: The Origin and Diversification of Eukaryotes

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?

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?

The best evidence for not classifying the slime molds as fungi comes from slime molds'

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

Living diatoms contain brownish plastids. If global warming causes blooms of diatoms in the surface waters of Earth's oceans, how might this be harmful to the animals that build coral reefs?

If the Archaeplastidae are eventually designated a kingdom, and if land plants are excluded from this kingdom, then what will be true of this new kingdom?

Which of the following are actual mutualistic partnerships that involve a protist and a host organism?

Which pair of alternatives is highlighted by the life cycle of the cellular slime molds, such as Dictyostelium?

Green algae differ from land plants in that many green algae

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

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)

Similar to most amoebozoans, the forams and the radiolarians also have pseudopods, as do some of the white blood cells of animals (monocytes) . If one were to construct a taxon that included all organisms that have cells with pseudopods, what would be true of such a taxon?

Which of the following statements concerning protists is true?

Which of the following is correctly described as a primary producer?