While researching a topic, a student has taken the following notes:Crown shyness is a phenomenon in which the tops (crowns)...
GMAT Expression of Ideas : (Expression) Questions
While researching a topic, a student has taken the following notes:
- Crown shyness is a phenomenon in which the tops (crowns) of neighboring trees grow close together but don't overlap.
- To explain how this happens, Australian forester M.R. Jacobs proposes the mutual abrasion theory.
- According to Jacobs's theory, when trees brush against one another, branches break off.
- Malaysian scholar Francis S.P. Ng posits the mutual shade avoidance theory.
- According to Ng's theory, when tree branches detect shade from nearby trees' branches, they stop growing.
The student wants to compare the causes of crown shyness proposed in the two theories. Which choice most effectively uses relevant information from the notes to accomplish this goal?
While Jacobs proposes that crown shyness is caused by neighboring tree branches brushing against one another, Ng posits that it occurs when branches detect shade from nearby trees' branches.
Both Jacobs and Ng have proposed theories to explain what causes crown shyness.
Ng posits the mutual shade avoidance theory, whereas Jacobs proposes an alternative theory.
Jacobs's mutual abrasion theory proposes that when neighboring trees brush against one another, branches break off, resulting in a phenomenon in which the tops of trees grow close together but don't overlap.
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Crown shyness is a phenomenon in which the tops (crowns) of neighboring trees grow close together but don't overlap." |
|
| "To explain how this happens, Australian forester M.R. Jacobs proposes the mutual abrasion theory." |
|
| "According to Jacobs's theory, when trees brush against one another, branches break off." |
|
| "Malaysian scholar Francis S.P. Ng posits the mutual shade avoidance theory." |
|
| "According to Ng's theory, when tree branches detect shade from nearby trees' branches, they stop growing." |
|
Provide Passage Architecture & Core Elements
Main Point: Two experts propose different theories to explain crown shyness: Jacobs attributes it to physical damage from branches brushing together, while Ng attributes it to trees' response to shade detection.
Step 2: Interpret the Question Precisely
What's being asked? The student wants to compare the causes of crown shyness proposed in the two theories.
What type of answer do we need? A statement that directly contrasts the specific causal mechanisms proposed by Jacobs versus Ng.
Any limiting keywords? None specified.
Step 3: Prethink the Answer
The right answer should:
- Mention both theories and their proposed causes
- Clearly contrast Jacobs's physical mechanism (brushing/breaking) with Ng's biological mechanism (shade detection/growth stopping)
- Focus specifically on the causes, not just mention that theories exist
While Jacobs proposes that crown shyness is caused by neighboring tree branches brushing against one another, Ng posits that it occurs when branches detect shade from nearby trees' branches.
✓ Correct
- Directly contrasts both causal mechanisms: Jacobs says brushing causes it, Ng says shade detection causes it
- Matches our prethinking perfectly
Both Jacobs and Ng have proposed theories to explain what causes crown shyness.
✗ Incorrect
- Simply states that both proposed theories without comparing their causes
- Doesn't fulfill the goal of comparing what each theory says causes crown shyness
Ng posits the mutual shade avoidance theory, whereas Jacobs proposes an alternative theory.
✗ Incorrect
- Names Ng's theory but only calls Jacobs's an "alternative theory" without specifying causes
- Fails to compare the actual mechanisms
Jacobs's mutual abrasion theory proposes that when neighboring trees brush against one another, branches break off, resulting in a phenomenon in which the tops of trees grow close together but don't overlap.
✗ Incorrect
- Only explains Jacobs's theory without mentioning Ng's proposed cause
- Completely fails to compare the two theories as requested