PSAT/NMSQT Prep 2022 - Eggert M.D., Strelka A. 2022

How much have you learned?
The method for PSAT reading questions
PSAT Reading

Directions: Take 15 minutes to apply the PSAT Reading passage strategy and question method to the following passage and question set. Assess your work by comparing it to the expert responses at the end of the chapter.

Questions 1—10 refer to the following passage.

The following passage is adapted from a 2016 article about single-celled organisms that was published in a popular science magazine.

¹The vast majority of living things ²are single-celled organisms. Despite ³their great numbers, our understanding ⁴of these life forms on even a basic ⁵biochemical and phylogenetic level is ⁶only a few decades old and continues to ⁷evolve.

⁸For most of the twentieth century, ⁹it was believed that all life forms could ¹⁰be broadly classified into two main ¹¹groups, called domains: eukaryotes, or ¹²organisms possessing a cell nucleus; ¹³and prokaryotes, or organisms lacking ¹⁴such a nucleus. The terms “prokaryotes” ¹⁵and “bacteria” were used more or less ¹⁶interchangeably. Only in the 1970s was ¹⁷it discovered that there are in fact two ¹⁸very distinct groups of prokaryotes, ¹⁹not any more related to each other ²⁰than they are related to the eukaryotes: ²¹bacteria and archaea. This discovery ²²was made by Carl Woese, who in ²³1990 proposed a three-domain system ²⁴based on phylogenetics, or the degree ²⁵of genetic relatedness among species. ²⁶Woese proposed separating bacteria ²⁷and archaea based on analysis of their ²⁸ribosomal RNA, genetic material that ²⁹plays an active role in the formation of ³⁰proteins. The phylogenetic branches of ³¹Bacteria, Archaea, and Eukarya form ³²the basis of the three-domain system of ³³classification still in use today.

³⁴When they were first discovered, ³⁵all archaea were believed to be ³⁶extremophiles—that is, organisms ³⁷living in extreme conditions such as ³⁸very hot, cold, or chemically caustic ³⁹environments. We now know that ⁴⁰these organisms exist in large numbers ⁴¹in virtually all habitats, including in ⁴²the human digestive tract. We also ⁴³know that most prokaryotes that ⁴⁴cause disease are bacteria, not archaea. ⁴⁵And we have an ever-improving ⁴⁶understanding of the biochemical ⁴⁷pathways employed by these two groups ⁴⁸of organisms.

⁴⁹Despite our growing understanding ⁵⁰of prokaryotes, the evolutionary ⁵¹relationships among the Bacteria, ⁵²Archaea, and Eukarya are far from ⁵³clear. A comparison of the genomes of ⁵⁴species in these three domains done ⁵⁵in 1997 showed similarities between ⁵⁶the Bacteria and Archaea in the genes ⁵⁷coding for enzymes, and similarities ⁵⁸between the Archaea and Eukarya in ⁵⁹the genes coding for protein synthesis ⁶⁰machinery. Moreover, although the ⁶¹Archaea are prokaryotes, the proteins ⁶²that give their chromosomes structure ⁶³are similar to those within the nucleus ⁶⁴of the Eukarya. In other words, the ⁶⁵Archaea seem to be related, in different ⁶⁶ways, to both the Bacteria and the ⁶⁷Eukarya. Because the Eukarya are ⁶⁸the most recent domain to evolve, it ⁶⁹has been hypothesized that the first ⁷⁰eukaryotic cell originally arose from a ⁷¹prokaryotic cell within the Archaea.

⁷²If this hypothesis is correct, there ⁷³still remains a tantalizing mystery: the ⁷⁴evolution of the eukaryotic nucleus. The ⁷⁵nucleus is a complex structure within ⁷⁶a eukaryotic cell that is encased in a ⁷⁷membrane and that contains the cell’s ⁷⁸genetic material. There are a number ⁷⁹of competing models for how this ⁸⁰structure might have evolved. Leaving ⁸¹out the most controversial of these, ⁸²which involves viruses, there are three ⁸³that have found significant support ⁸⁴within the scientific community. The ⁸⁵first is the “syntrophic model,” which ⁸⁶states that ancient archaea slipped ⁸⁷inside bacterial cells and eventually ⁸⁸became those cells’ nuclei. The second ⁸⁹model is based on the observation ⁹⁰that certain prokaryotes have recently ⁹¹been discovered to possess a primitive ⁹²nucleus. This model suggests that ⁹³archaea might, by degrees, have ⁹⁴evolved complex chromosomes and ⁹⁵eventually also the nuclear membrane ⁹⁶encasing those chromosomes. Finally, ⁹⁷the most recent model proposes that ⁹⁸ancient archaea could have developed ⁹⁹a second external cell membrane, with ¹⁰⁰the internal cell membrane eventually ¹⁰¹becoming the nucleus. Whether any of ¹⁰²these models turns out to be correct, ¹⁰³the discovery of the Archaea as a ¹⁰⁴separate prokaryotic domain has given ¹⁰⁵rise to a fascinating field of research ¹⁰⁶into evolutionary relationships.

1. The main purpose of the passage is to

A. describe the discovery of the Archaea domain and its implications.

B.suggest that the three-domain system of classification should be more widely adopted.

C.refute the idea that bacteria are the most ancient life forms.

D. argue for the inclusion of eukaryotes in the Archaea domain.

2. Based on information in the passage, it can be reasonably inferred that ribosomal RNA

A. has improved our biochemical understanding of single-celled organisms.

B.determines whether or not a single-celled organism has a nucleus.

C.serves as a marker of how closely different species are related to one another.

D. exists only in archaea that prefer extreme environments.

3. Which choice provides the best evidence for the answer to the previous question?

A. Lines 2—7 (“Despite... evolve”)

B.Lines 8—14 (“For most... a nucleus”)

C.Lines 21—25 (“This discovery... species”)

D. Lines 34—39 (“When... environments”)

4. In line 30, “branches” most nearly means

A. boughs.

B.offices.

C.chapters.

D. groupings.

5. The author presents the idea that the Eukarya evolved from the Archaea as

A. conclusively proven.

B.plausible but not definitively established.

C.unlikely at best.

D. convincingly disproved.

6. Which choice provides the best evidence for the answer to the previous question?

A. Lines 30—33 (“The phylogenetic... today”)

B.Lines 45—48 (“And we... organisms”)

C.Lines 49—53 (“Despite... clear”)

D. Lines 92—96 (“This model... chromosomes”)

7. The third paragraph serves mainly to

A. note a common misconception about the Archaea.

B.present new information about extremophiles.

C.draw a contrast between the Bacteria and the Archaea.

D. provide examples of the improved understanding of prokaryotes.

8. According to the passage, the genetic similarities between the Archaea and the Eukarya are significant primarily because

A. they imply extremophilic origins for the Archaea.

B.they suggest an evolutionary origin for the Eukarya.

C.they undermine the belief that the Bacteria are of more ancient origin than the Archaea.

D. they make it impossible to consider more than three phylogenetic domains.

9. In line 79, “models” most nearly means

A. ideals.

B.hypotheses.

C.examples.

D. figurines.

10. According to the passage, the syntrophic model of the evolution of the eukaryotic nucleus posits that

A. the first eukaryotes arose from a fusion of archaea and bacteria.

B.viruses played a role in producing the first eukaryotic cells.

C.the first eukaryotes developed directly from archaea.

D. a second cell membrane was involved in its development.