Question 1

A particular species of protist has obtained a chloroplast via secondary endosymbiosis.How can you tell?

Accepted Answer

Presence of three or four membranes surrounding the chloroplast indicates secondary endosymbiosis, as the chloroplast has been engulfed by a eukaryotic cell that already had a pre-existing endosymbiotic partner (such as a photosynthetic algae or another photosynthetic protist). The additional membranes are thought to have come from the original host cell's endomembrane system that surrounded the ingested cell. A chloroplast obtained via primary endosymbiosis (the original event that led to the development of all chloroplasts) would only have two membranes.

Question 2

Which of the following observations about flagella is true and is consistent with the scientific conclusion that the flagella from protists and bacteria evolved independently?

Accepted Answer

The observation that the protein structure and mechanism of movement in protist flagella are different from those of bacteria flagella is consistent with the scientific conclusion that they evolved independently. This indicates that the flagella in these two groups of organisms are not homologous and likely evolved through convergent evolution. Option A is incorrect as it suggests that the protein is the same. Option B is not consistent with the idea of independent evolution as it indicates that there are still genetic similarities. Option C is also incorrect as it suggests that the mechanism is the same but the protein is different, which is not consistent with the conclusion of independent evolution.

Question 3

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

Accepted Answer

If protists are paraphyletic, then some of their descendants would have evolved into other eukaryotic groups, meaning that protists are not a monophyletic group that share a common ancestor. Option B is incorrect because if all protists share a common set of synapomorphies, then they would be a monophyletic group. Option C is incorrect because the term "more primitive" is not accurate in describing the evolutionary relationships between groups. Option D is incorrect because even if protists are paraphyletic, they still share a common ancestor (albeit not a single one).

Question 4

Plankton is comprised of photosynthetic protists and bacteria.What is the primary importance of plankton to humans?

Accepted Answer

Plankton serves as the base of the marine food chain and is the primary food source for many marine organisms that humans eat, including fish, shrimp, and shellfish.

Question 5

You discover a new eukaryotic species.It is non-photosynthetic,unicellular,and its motile cells contain a single flagellum.To which group of eukaryotes might this organism belong?

Accepted Answer

The answer of You discover a new eukaryotic species.It is...

Question 6

When a mosquito infected with Plasmodium first bites a human _____.

Accepted Answer

When a mosquito infected with Plasmodium first bites a human, the Plasmodium cells enter the human body and infect the liver cells. The cells then undergo asexual reproduction, forming merozoites, which are then released into the bloodstream, leading to malaria symptoms. The fusion of Plasmodium gametes and formation of oocyst occurs within the mosquito's gut after multiple blood meals. Lysing of red blood cells occurs later in the infection cycle. Meiosis occurs during the formation of Plasmodium gametes.

Question 7

Which of the following statements best describes the term synapomorphy?

Accepted Answer

Synapomorphy is a trait that is unique to a single monophyletic group, meaning that it is not found outside of that group. It is used as a diagnostic feature to indicate a shared evolutionary history within that group.

Question 8

Which of the following is most likely to lead to PSP (paralytic shellfish poisoning)?

Accepted Answer

Paralytic shellfish poisoning is caused by ingestion of shellfish contaminated with saxitoxins produced by certain species of dinoflagellates, including Alexandrium and Dinophysis.

Question 9

Imagine 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?

Accepted Answer

Sexually reproducing species are more likely to thrive because sexual reproduction increases genetic diversity, which can enhance the ability of a population to adapt to changing environments and resist diseases.

Question 10

Figure 29.1
Use the following information to answer the corresponding question(s).
Giardia intestinalis can cause disease in several different mammalian species,including humans.Giardia organisms (G.intestinalis)that infect humans are similar morphologically to those that infect other mammals;thus they have been considered a single species,though other species in the Giardia genus infect other organisms.However,G.intestinalis has been divided into different subgroups based on their host and a few other characteristics.
In 1999,a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species.The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G.intestinalis and a few other morphologically distinct species of Giardia.The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species.
 
-By examining the phylogenetic tree diagrammed in Figure 29.1,what conclusion can you draw about the species G.microti?

Accepted Answer

The phylogenetic tree shows that G.microti is part of a monophyletic group that also includes G.intestinalis, supporting the idea that they are closely related and potentially the same species.

Question 11

Figure 29.5
 
-Which of the following might be a result of adding a secondary consumer (a species that feeds on primary consumers)to the aquatic ecosystem illustrated above?

Accepted Answer

Adding a secondary consumer to the ecosystem will likely result in a decrease in the number of primary consumers, as they will be eaten by the secondary consumer. This will have a cascading effect on the ecosystem, potentially impacting other trophic levels as well. However, the addition of a secondary consumer is unlikely to directly impact decomposers, atmospheric CO₂, scavengers, or the carbon sink.

Question 12

Which of the following monophyletic eukaryotic clades includes photosynthetic species with double-membraned chloroplasts?

Accepted Answer

The answer of Which of the following monophyletic eukaryotic clades...

Question 13

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

Accepted Answer

Excavata includes species such as Giardia, which lack functioning mitochondria and rely on other metabolic pathways for energy production. Rhizaria, Amoebozoa, and Stramenopila all contain species with functioning mitochondria.

Question 14

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

Accepted Answer

Photosynthetic protists fix atmospheric carbon dioxide, decreasing atmospheric CO₂ levels. This would help reduce global warming by reducing the concentration of greenhouse gases in the atmosphere.

Question 15

A particular species of protist lacks the ability to engulf food and does not contain chloroplasts.However,gene sequencing data indicate that this species evolved from a lineage containing many species with the ability to engulf food.What does this information suggest about this species of protist?

Accepted Answer

The fact that this species evolved from a lineage containing many species with the ability to engulf food suggests that it likely lost this ability over time, possibly due to becoming parasitic and no longer needing to ingest food.

Question 16

Figure 29.2
 
-Refer to Figure 29.2 and consider the following data:
Brown algae (protists)include unicellular and multicellular organisms.Red algae (protists)include unicellular and multicellular organisms.Amoebae (protists)include unicellular and multicellular organisms.Which of the following conclusions is consistent with the data presented?

Accepted Answer

The data shows that brown algae, red algae, and amoebae are all protists that include both unicellular and multicellular organisms. Therefore, multicellularity did not evolve only once in the eukaryotic lineage, but instead evolved multiple times as eukaryotes diversified.

Question 17

In an area with a high abundance of algal blooms,the introduction of _____ might alleviate the severity of the blooms.

Accepted Answer

Copepods are small crustaceans that feed on algae and can therefore suppress the growth of algal blooms. By introducing copepods into an area with high algal abundance, they can help control the severity of the blooms. The other choices (A, B, C) are not likely to alleviate the severity of the blooms. Dinoflagellates can actually contribute to harmful algal blooms, plankton are not specific enough to indicate a potential solution, and primary producers (such as algae themselves) would not alleviate the severity of the blooms.

Question 18

Which of the following characteristics is true of all protists?

Accepted Answer

All protists contain a nucleus, as they are eukaryotic organisms. Other characteristics like being unicellular, having a cell wall, or being photosynthetic are not true for all protists.

Question 19

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?

Accepted Answer

The endosymbiotic theory proposes that a larger host cell engulfed a smaller cell, forming a symbiotic relationship that eventually led to organelles such as mitochondria and chloroplasts. These organelles provide the host cell with energy (in the form of ATP) through cellular respiration and photosynthesis, respectively. Therefore, it was adaptive for the host cell to keep the engulfed cell alive because it granted the host cell with a new source of energy.

Question 20

Figure 29.1
Use the following information to answer the corresponding question(s).
Giardia intestinalis can cause disease in several different mammalian species,including humans.Giardia organisms (G.intestinalis)that infect humans are similar morphologically to those that infect other mammals;thus they have been considered a single species,though other species in the Giardia genus infect other organisms.However,G.intestinalis has been divided into different subgroups based on their host and a few other characteristics.
In 1999,a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species.The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G.intestinalis and a few other morphologically distinct species of Giardia.The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species.
 
-According to the phylogenetic tree in Figure 29.1,Giardia intestinalis constitutes a _____ group.

Accepted Answer

Giardia intestinalis is a paraphyletic group because it includes the common ancestor of Giardia intestinalis and Giardia muris, but not Giardia muris itself.

Quiz 29: Protists