27. Protists

Which of the following is one of the main weaknesses of the proposed classification scheme in which all eukaryotes are divided into four supergroups?

Which of the listed examples is a characteristic shared by diplomonads and parabasalids?

Apicomplexans are currently assigned to the SAR clade because __________.

Which of these groups includes photosynthetic unicellular organisms with flagella and contractile vacuoles?

How do trypanosomes withstand the attack of a host's immune system?

What do a carnivorous dinoflagellate, a parasitic apicomplexan, and a ciliate have in common?

Which organisms are capable of producing a "red tide"?

Which of these groups includes parasitic unicellular organisms with a complex of organelles specialized for penetrating host cells and tissues?

Which of these groups is characterized by cells that have more than one nucleus?

What is the purpose of the "floats" in some brown algae?

__________ is a protist that causes late blight of potatoes and was responsible for the Irish potato famine of the 19th century.

In lab class, a plasmodial slime mold is used as a demonstration organism. One of the students does not understand why this organism is not considered multicellular. How would you explain it to her?

Which of the following organisms is commercially harvested to extract algin from their cell walls?

Which of these groups includes unicellular organisms that, due to the structure of their cell walls, can withstand pressures equal to the pressure under each leg of a table supporting an elephant?

What role do diatoms play in the global carbon balance affecting global warming?

Which of the following groups of algae is/are most closely related to land plants?

On some areas of the seafloor, one could observe an "ooze" that is hundreds of meters thick. What creates this ooze?

Many species of red algae are adapted to deeper water due to the fact that __________.

The most important primary producers in marine ecosystems are                .

Which group is incorrectly paired with its description? a. diatoms—important producers in aquatic communities b. red algae—eukaryotes that acquired plastids by secondary endosymbiosis c. apicomplexans—unicellular parasites with intricate life cycles d. diplomonads—unicellular eukaryotes with modified mitochondria

What is the role of PEP carboxylase in C4 and CAM plants? a. It fixes CO2 into an organic acid. b. It produces ATP for the Calvin cycle. c. It replaces rubicso in the Calvin cycle. d. It releases CO2 from organic acids.

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

How can dinoflagellates be harmful to humans? a. They are transmitted by mosquitoes and cause malaria. b. They produce toxins that can be absorbed by clams and other shellfish which, when eaten by people, can lead to paralytic shellfish poisoning. c. They cause amoebic dysentery which leads to severe diarrhea and dehydration. d. They are transmitted by tsetse flies and cause 'sleeping sickness.'

How can dinoflagellates be harmful to humans? a. They are transmitted by mosquitoes and cause malaria. b. They produce toxins that can be absorbed by clams and other shellfish which, when eaten by people, can lead to paralytic shellfish poisoning. c. They cause amoebic dysentery which leads to severe diarrhea and dehydration. d. They are transmitted by tsetse flies and cause 'sleeping sickness.'

Which pair of protists has support structures composed of silica? a. dinoflagellates and diatoms b. diatoms and radiolarians c. radiolarians and forams d. forams and amoebozoans

Which of the following members of the SAR supergroup is incorrectly paired with its clade? a. stramenopiles—brown algae b. alveolates—parasites such as Plasmodium c. alveolates—dinoflagellates d. Rhizaria—diatoms

Based on the phylogenetic tree in Figure 28.2, which of the following statements is correct? a. The most recent common ancestor of Excavata is older than that of SAR. 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.

In step 3 of the citric acid cycle, the enzyme isocitrate dehydrogenase is regulated by NADH. Compare and contrast the regulation of this enzyme with the regulation of phosphofructokinase in glycolysis.

Apply what you know of the relationship between the light-capturing reactions and the Calvin cycle to calculate the number of photons used to produce a new G3P and regenerate RuBP. (Assume 1 ATP is produced for each pair of electrons used to form NADPH.)

The text claims that the evolutionary history of protists can be understood as a series of morphological innovations that established seven distinct lineages, each of which subsequently diversified based on innovative ways of feeding, moving, and reproducing. Explain how the Alveolata support this claim.

Which of the following correctly identify a role of the ATP produced in the light-capturing reactions? Select True or False for each statement. T/F It is used by rubisco to fix CO2 to RuBP. T/F It serves the same role as ATP produced by mitochondria. T/F It is used to regenerate RuBP from G3P molecules. T/F It is used to produce G3P molecules

Draw a chemical equation to represent the redox reaction that occurs when methane (CH4) burns in the presence of oxygen (O2). Identify the reactant that is reduced and the reactant that is oxidized. Of the four molecules that should be in your equation, point out the one that has bonds with the highest potential energy.

Predict how the following conditions would affect the production of O2, ATP, and NADPH and state whether noncyclic or cyclic electron flow would occur in each;(2) blue and red photons hit a chloroplast, but no NADP+ is available

Consider the following: Plasmodium has an unusual organelle called an apicoplast. Recent research has shown that apicoplasts are derived from chloroplasts via secondary endosymbiosis and have a large number of genes related to chloroplast DNA. Glyphosate is one of the most widely used herbicides. It works by poisoning an enzyme located in chloroplasts. Biologists are testing the hypothesis that glyphosate could be used as an antimalarial drug in humans. How are these observations connected?

Early estimates suggested that the oxidation of glucose via aerobic respiration would produce 38 ATP. Based on what you know of the theoretical yields of ATP from cellular respiration, show how this total was determined. Why do biologists now think this amount of ATP per molecule of glucose is not achieved in cells?

Chlamydomonas is a unicellular green alga. How does it differ from a photosynthetic bacterium, which is also single-celled? How does it differ from a protozoan, such as an amoeba? How does it differ from larger green algae, such as sea lettuce (Ulva)?

Suppose a friend says that we don't need to worry about the rising temperatures associated with global climate change. She claims that increased temperatures will make planktonic algae grow faster and that carbon dioxide (CO2) will be removed from the atmosphere faster. According to her, this carbon will be buried at the bottom of the ocean in calcium carbonate shells. As a result, the amount of carbon dioxide in the atmosphere will decrease and global warming will decline. Comment.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Which of the following best describes movement in Physarum? a. Cilia propel the slime mold. b. Flagella propel the slime mold. c. The slime mold moves by amoeboid motion. d. The slime mold moves by gliding motility.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Which of the following best describes movement in Physarum? a. Cilia propel the slime mold. b. Flagella propel the slime mold. c. The slime mold moves by amoeboid motion. d. The slime mold moves by gliding motility.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Physarum is a plasmodial slime mold, whereas Dictyostelum is a cellular slime mold. Compare and contrast movement by the migrating slug stage of Dictyostelium to the plasmodial stage of Physarum.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Does an organism without a brain have the ability to use an externalized 'memory'—a spatial 'slime map' that the organism uses to avoid moving to regions where it has been before? Researchers addressed this question by placing a U-shaped trap between Physarum and its food (see diagram that follows). Twenty-three out of 24 slime molds reached the food when plain agar was used as the growth substrate. However, when the agar was coated with extracellular slime, only 8 of 24 found the food. The mean time in hours that it took the successful slime molds to reach the food when placed on plain agar or agar pre-coated with extracellular slime was compared (P=0.012). Use the P value provided to determine if the difference is significant or not. What conclusion can be drawn from the graph shown here?

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Propose an experiment that would test whether the coating of extracellular slime changed the speed at which the slime mold moved across the substrate.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Develop simple experiments to test whether Physarum prefers (1) brightly lit or dark environments; (2) dry or moist conditions; (3) oats or sugar as a food source.

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Researchers have proposed that slime molds could be used to help to plan the paths of future roadways and railways. Justify this statement.

The buildup of CO2 in the atmosphere resulting from the burning of fossil fuels is regarded as a major contributor to global warming. Diatoms and other microscopic algae in the oceans counter this buildup by using large quantities of atmospheric CO2 in photosynthesis, which requires small quantities of iron. Experts suspect that a shortage of iron may limit algal growth in the oceans. Some scientists have suggested that one way to reduce CO2 buildup might be to fertilize the oceans with iron. The iron would stimulate algal growth and thus the removal of more CO2 from the air. A single supertanker of iron dust, spread over a wide enough area, might reduce the atmospheric CO2 level significantly. Do you think this approach would be worth a try? Why or why not?

When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Researchers have proposed that slime molds could be used to help to plan the paths of future roadways and railways. Justify this statement.