PrepTest 110

Topic: Science

Paragraph 1

• Paragraph note
  • Initial dismissal of and subsequent evidence for Lamarck's claim (animal's use/disuse of organ gets passed down)
• Views, minor Meta-Structures, and the author's attitude
  • Lamarck's belief:
    • An animal's use or disuse of an organ gets passed down to its offspring (first sentence)
  • Example of an animal that's organ was affected by ancestors use, according to Lamarck:
    • The giraffe's long neck came from their ancestors' stretching their necks (second sentence)
  • Biologists' rebuttal:
    • They couldn't figure out how an animal's use/disuse would get passed down genetically, so they argued that Lamarck's theory doesn't occur (third sentence)
  • Author's defense:
    • New research has found many examples of Lamarck's theory (last sentence)
  • Author's attitude: "has uncovered numerous examples" (last sentence)

Paragraph 2

• Paragraph note
  • First example of Lamarck's view (if bacterial walls are removed, bacteria multiply without walls)
• Views, minor Meta-Structures, and the author's attitude
  • First example of Lamarck's view, according to the author:
    • If an experimenter removes the cell wall from a bacterium, the bacterium will continue to grow and multiply without walls (first and second sentences)
  • Cause-and-effect relationship, according to the author:
    • Changes in how the genes interact cause later bacteria to lack cell walls (last sentence)

Paragraph 3

• Paragraph note
  • Second and third examples of Lamarck's view (new genes: fruit flies infected with virus; E.coli passing along "plasmid")
• Views, minor Meta-Structures, and the author's attitude
  • Examples where genes are added or eliminated and passed on to offspring, according to the author:
    • Fruit flies infected with a virus that makes them vulnerable to CO2 will pass on that gene to offspring — but infected flies' offspring can also be resistant to CO2 if the eggs are kept warm (second and third sentences)
    • An E.coli bacterium carrying a "plasmid" can pass it on to another E.coli bacterium, which will then be passed on to offspring (fourth sentence)
  • Definition of "plasmid": small ring of genetic material (fourth sentence)
  • Author's view on E.coli example:
    • It's noteworthy because it may suggest a way that evolution was sped up (last sentence)
  • Example of how evolution could have been sped up, according to the author
    • Cells may have acquired the ability to carry out photosynthesis through a bacterium with that trait (last sentence)
  • Author's attitude: "fundamentally different" (first sentence); "especially noteworthy" (last sentence); "may have" (last sentence); "would have taken" (last sentence)

Paragraph 4

• Paragraph note
  • Implications of evidence (two genes: vertical and horizontal, which can be transferred among different species)
• Views, minor Meta-Structures, and the author's attitude
  • List of two types of genes, according to the author:
    • Vertical genes: inherited from ancestors (second sentence)
    • Horizontal genes: inherited from environment and even unrelated organisms (third and fourth sentences)
  • Examples of ways genes can be transmitted horizontally from unrelated organisms, according to the author:
    • From bacteria to plants or yeast (fourth sentence)
  • Author's view:
    • Horizontal transmission may show how Lamarck's theory works (last sentence)
  • Author's attitude: "suggests" (first sentence); "appears to show" (fourth sentence); "may well be" (last sentence); "may eventually prove" (last sentence)

Main Point: The discovery of numerous examples of bacteria passing down acquired traits suggests the existence of "horizontally transmitted" genes, which may eventually vindicate Lamark's formerly discredited hypothesis of the inheritance of acquired characteristics.

Rebutting Critics: This Rebutting Critics Meta-Structure best fits this passage's argument.* In this Meta-Structure, the author presents criticisms of the subject matter before mounting a defense against those criticisms. In this case, the author describes why biologists discredited Larmack's hypothesis in the first paragraph. In later paragraphs, the author shows how recent research shows numerous examples of bacteria passing down acquired traits to their offspring, which may vindicate Lamarck's hypothesis.

In a Rebutting Critics passage, the main point is generally the author's central defense. To help us anticipate the main point, we can often find a conclusion where the author summarizes their defense. But in this passage, the author provides no such conclusion. So, we summarized the author's defense for them: "The discovery of numerous examples of bacteria passing down acquired traits suggests the existence of horizontally transmitted' genes, which may eventually vindicate Lamark's formerly discredited hypothesis of the inheritance of acquired characteristics."

*You could also argue that this passage uses a Correcting the Record Meta-Struture. After all, there is considerable overlap between the Rebutting Critics and Correcting the Record Meta-Structures. Typically, when passages frame the view the author corrects/rebuts as a criticism, it's best to consider the passage a Rebutting Critics passage. If the passage frames the view the author corrects/rebuts as a misunderstanding, it's best to consider the passage a Correcting the Record passage. Since the biologists from the first paragraph are framed as critics of Lamarck's hypothesis, we went with Rebutting Critics. But Correcting the Record would likely lead you to the same main point and understanding of the passage's structure.

Example: The most prominent minor Meta-Structure is the example. The author provides three examples of bacteria that can pass down acquired traits: wall-less bacteria (P2, S2), CO2-vulnerable bacteria (P3, S2), and E.coli with a plasmid (P3, S4). These examples will likely figure into one or two questions — probably either a Minor Point or Argument Structure question.

Just because the author is defending Lamarck’s hypothesis in light of new evidence doesn’t mean the author believes Lamarck’s hypothesis has been confirmed. The author says we don’t have enough evidence to confirm Lamarck’s hypothesis in the last paragraph (P4, S5). Moreover, Lamarck’s hypothesis concerns animals, while all the new evidence concerns bacteria. Just because bacteria can pass on acquired characteristics doesn’t mean an animal can. Several questions will likely prey on test-takers who misinterpret the relationship between the author’s argument and Lamarck’s hypothesis, so we need to make sure we understand the distinction between the two.