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Exam 29: Protists

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Question 21

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Assume that some members of an aquatic species of motile,photosynthetic protists evolve 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
E) no changes would be expected

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Question 22

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

A) because photosynthetic protists form the base of many marine food chains
B) because photosynthetic protists fix atmospheric carbon dioxide,decreasing atmospheric CO₂ levels
C) because the increased oxygen consumption by large populations of photosynthetic protists will promote land plants to speed up photosynthesis,thus removing CO₂ from the atmosphere
D) because photosynthetic protists would release a lot of oxygen,and fertilizing them would increase levels of oxygen in the atmosphere

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Question 23

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Consider the following points: (a) All excavates live in environments where oxygen availability is low;(b) all excavates lack mitochondria;and (c) all excavates have some mitochondrial genes.Based on this information,which of the following statements is true of the excavate lineage?

You discover a new species of protist.Which of the following characteristics would provide the strongest evidence for your hypothesis that your species belongs in Euglenida?

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

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?

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?

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

Figure 29.3 Use the following information when answering the corresponding question(s) . The mechanism of cell crawling in protist species is not well defined.The textbook states that pseudopodia extension involves interactions between actin and myosin (the same molecules that are involved in mammalian muscle contraction) .However,prior to the study described below,no one had provided convincing data that actin and myosin were actually involved in cell crawling in protists.Anatomical studies had identified the cytoskeletal protein actin just below the surface of the cell membrane in several species of protist;but physiological studies had failed to show a functional link between actin,myosin,and cell crawling. In a study by N.Poulsen et al.(Diatom gliding is the result of an actin-myosin motility system,Cell Motility and the Cytoskeleton 44 (1999) :23-22) ,researchers tested whether motility in a particular species of diatom involves interactions between actin and myosin. -Refer to the study by Poulsen et al.and Figure 29.3.Latrunculin A is a reversible toxin that disrupts the formation of actin fibers.A culture of a particular species of diatom was treated with this toxin diluted in a buffer,while another culture was treated only with the buffer (no toxin;control) .The motility of cells in each culture was assessed by counting the number of cells that were moving during a defined period of time.Which of the following conclusion statements is reasonable based on the above figure?

Alternation of generations occurs in some protists.Which of the following represents the correct sequence of events for this mode of reproduction?

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?

In examining a multicellular protist,you notice that it uses pseudopods to engulf its food,that it reproduces asexually by mitosis,and that it has multiple nuclei.These data allow you to infer that the species belongs to which of the following protist groups?

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

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