A major focus of modern evolutionary ecology is the study of coevolution: investigating interactions between organisms in nature and analyzing...
GMAT Reading Comprehension : (RC) Questions
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A major focus of modern evolutionary ecology is the study of coevolution: investigating interactions between organisms in nature and analyzing how interacting pairs of organisms influence one another as they evolve. One of the most remarkable coevolutionary interactions is between various species of Heliconius butterflies and various species of Passiflora vines. Heliconius butterflies lay their eggs only on Passiflora vines and select only the newest, most tender shoots for the newly hatched Heliconius caterpillars to feed on. The effect of this parasitism is that caterpillars, either by defoliating a juvenile vine or devouring new shoots on a mature vine, prevent the vine from reproducing. In response, Passiflora vines have developed defenses against Heliconius butterflies.
One of the factors Heliconius butterflies take into account when deciding where to lay eggs is the shape of the leaves of the potential host plant. However, the leaves of some Passiflora species have gradually come to resemble the leaves of several nonhost plants closely, and from seedling to maturity, the shape of Passiflora leaves undergoes dramatic changes. A butterfly's ability to recognize the shape of Passiflora leaves reduces the reproductive potential of the plant, and scientists have hypothesized that varying their leaf shapes is a mechanism that has evolved in Passiflora vines under the pressure of Heliconius parasitism. This has not been an entirely successful strategy for the plants, however, since Heliconius butterflies have developed the ability to recognize other Passiflora characteristics, including leaf chemistry, in locating Passiflora vines, and variations in leaf shape have not been sufficient to deter the butterflies from laying eggs.
Because the caterpillars of some Heliconius species eat the eggs of other Heliconius species, the presence of an egg on a leaf can cause a female to reject a plant as a potential egg-laying site. Recent field studies have discovered further evidence of a possible coevolutionary relationship: some species of Passiflora vines have developed yellow spots identical in color and shape to Heliconius eggs. Subsequent studies of "egg-mimicry" reveal that it has been found in only some two percent of the 500 known Passiflora species, indicating that it probably evolved relatively recently, but where it does occur, it has been a successful deterrent to Heliconius egg-laying.
Ques. 1/4
With which of the following statements about the coevolutionary relationship between Passiflora vines and Heliconius butterflies would the author of the passage be most likely to agree?
Solution
1. Passage Analysis:
Progressive Passage Analysis
| Text from Passage | Analysis |
|---|---|
| A major focus of modern evolutionary ecology is the study of coevolution: investigating interactions between organisms in nature and analyzing how interacting pairs of organisms influence one another as they evolve. | What it says: Scientists study how two different living things affect each other's evolution over time. What it does: Introduces the main scientific concept and defines it clearly. Source/Type: Factual statement about scientific field. Connection to Previous Sentences: Opening sentence - establishes the framework for everything that follows. Visualization: Think of two dance partners who gradually change their moves based on what their partner does - each influences how the other evolves their dancing style. Reading Strategy Insight: Notice how the author immediately defines "coevolution" - this is your foundation. Everything else will be examples of this concept. |
| One of the most remarkable coevolutionary interactions is between various species of Heliconius butterflies and various species of Passiflora vines. | What it says: Here's a specific example of coevolution: certain butterflies and certain vines. What it does: Provides the concrete example that will illustrate the abstract concept from sentence 1. Source/Type: Factual example. Connection to Previous Sentences: This directly applies sentence 1's definition - we're moving from "organisms influence each other as they evolve" to "HERE are the specific organisms." Visualization: Picture two specific characters: Heliconius butterflies vs. Passiflora vines - they're the main actors in our coevolution story. Reading Strategy Insight: Feel confident here - you're not learning something new, you're getting a concrete example of what you already understand. |
| Heliconius butterflies lay their eggs only on Passiflora vines and select only the newest, most tender shoots for the newly hatched Heliconius caterpillars to feed on. | What it says: The butterflies are very picky - they only use these specific vines, and only the youngest, softest parts. What it does: Explains the butterfly's behavior in detail. Source/Type: Factual description of animal behavior. Connection to Previous Sentences: This builds on sentence 2 by explaining HOW the butterflies interact with the vines. We now understand the butterfly's side of the "interaction between organisms." Visualization: Imagine a very selective restaurant customer who only eats at one specific restaurant and only orders the daily special made from the freshest ingredients. What We Know So Far: Coevolution = mutual influence; our example = butterflies & vines; butterflies are completely dependent on vines. What We Don't Know Yet: How this affects the vines, how the vines respond. |
| The effect of this parasitism is that caterpillars, either by defoliating a juvenile vine or devouring new shoots on a mature vine, prevent the vine from reproducing. | What it says: The butterfly babies damage the vines so badly that the vines can't make new baby vines. What it does: Explains the negative impact on the vines and introduces the term "parasitism." Source/Type: Factual cause-and-effect relationship. Connection to Previous Sentences: This completes the interaction picture from sentence 3. Now we see both sides: butterflies depend on vines (sentence 3) AND butterflies harm vines (sentence 4). Visualization: If 100 vines could normally reproduce, after butterfly damage maybe only 60 can reproduce successfully. Reading Strategy Insight: This is still building the same basic relationship - you're learning the consequences of what sentence 3 described. |
| In response, Passiflora vines have developed defenses against Heliconius butterflies. | What it says: The vines fought back by evolving protective measures. What it does: Introduces the vine's counter-response and signals we'll learn about their defenses. Source/Type: Factual statement about evolutionary response. Connection to Previous Sentences: This is the coevolution payoff! Sentence 1 said organisms "influence one another as they evolve" - sentences 2-4 showed butterflies influencing vines, and NOW sentence 5 shows vines evolving in response. Visualization: Like a prey animal developing better camouflage after being hunted - the vines are evolving defenses because of butterfly pressure. Reading Strategy Insight: This is the "mutual influence" promised in sentence 1 - you're seeing coevolution in action, not learning a new concept. |
| One of the factors Heliconius butterflies take into account when deciding where to lay eggs is the shape of the leaves of the potential host plant. | What it says: Butterflies choose egg-laying spots based partly on what the leaves look like. What it does: Provides specific detail about how butterflies select vines. Source/Type: Factual detail about butterfly behavior. Connection to Previous Sentences: This builds on sentences 3-5 by explaining HOW butterflies find their target vines. It sets up for learning what vine defenses might target this selection process. Visualization: Picture a butterfly hovering over plants, looking at leaf shapes like a person comparing house styles before choosing where to move. Reading Strategy Insight: This narrows focus to one specific aspect (leaf shape) - expect this detail to connect to the "defenses" mentioned in sentence 5. |
| However, the leaves of some Passiflora species have gradually come to resemble the leaves of several nonhost plants closely, and from seedling to maturity, the shape of Passiflora leaves undergoes dramatic changes. | What it says: Some vines evolved leaves that look like other plants (that butterflies don't use), and their leaf shapes change dramatically as they grow. What it does: Provides the first specific example of vine defense. Source/Type: Factual description of evolutionary adaptation. Connection to Previous Sentences: Perfect connection! Sentence 6 said butterflies use "leaf shape" to choose vines, so sentence 7 shows vines responding by changing their "leaf shapes." This is sentence 5's "defenses" in action. Visualization: Imagine 20 Passiflora vines disguising themselves - 15 evolve to look like oak leaves, 5 look like maple leaves, and all of them keep changing their appearance as they age. Reading Strategy Insight: This is coevolution in action - you're seeing the back-and-forth adaptation promised in the opening. |
| A butterfly's ability to recognize the shape of Passiflora leaves reduces the reproductive potential of the plant, and scientists have hypothesized that varying their leaf shapes is a mechanism that has evolved in Passiflora vines under the pressure of Heliconius parasitism. | What it says: When butterflies can identify vine leaves, it hurts the vine's reproduction. Scientists think leaf-shape-changing evolved specifically because of butterfly pressure. What it does: Restates and clarifies the cause-and-effect relationship we've been building. Source/Type: Scientific hypothesis/interpretation. Connection to Previous Sentences: This is NOT new information! It's confirming what we could already infer from sentences 6-7: butterflies use leaf shape (sentence 6) → vines change leaf shape (sentence 7) → scientists conclude this is an evolutionary response. Visualization: Before leaf disguises: 40% of vines reproduce successfully. After leaf disguises: 70% of vines reproduce successfully. Reading Strategy Insight: Feel relieved here - this is clarification, not new complexity. The author is helping you understand the logic behind what you just read. |
| This has not been an entirely successful strategy for the plants, however, since Heliconius butterflies have developed the ability to recognize other Passiflora characteristics, including leaf chemistry, in locating Passiflora vines, and variations in leaf shape have not been sufficient to deter the butterflies from laying eggs. | What it says: BUT the leaf disguise trick didn't work perfectly because butterflies evolved to recognize other clues like chemical smell, not just appearance. What it does: Shows the ongoing coevolutionary arms race - butterflies evolved a counter-response. Source/Type: Factual outcome of the evolutionary interaction. Connection to Previous Sentences: This continues the coevolution story: vines adapted (sentence 7) → but butterflies adapted back by using different recognition methods → the mutual influence continues. Visualization: Round 1: Vines disguise appearance. Round 2: Butterflies learn to "smell" the right plants instead of just looking at them. Score: Butterflies still winning. Reading Strategy Insight: This shows coevolution is ongoing - it's not one adaptation, but a continuing back-and-forth process. |
| Because the caterpillars of some Heliconius species eat the eggs of other Heliconius species, the presence of an egg on a leaf can cause a female to reject a plant as a potential egg-laying site. | What it says: Some butterfly babies eat other butterfly babies, so if a butterfly sees an egg already on a leaf, she won't lay her egg there. What it does: Introduces a new butterfly behavior that will be relevant to the next vine defense strategy. Source/Type: Factual description of butterfly behavior. Connection to Previous Sentences: This introduces new information about butterfly behavior, but note what we DON'T know yet: how this connects to vine defenses. This appears to be setting up for another example. Visualization: Mother butterfly approaches leaf with existing egg: "Someone else's baby is here, and my baby might get eaten - I'll find a different leaf." What We Don't Know Yet: How this butterfly behavior relates to vine evolution - but expect this to connect to vine defenses soon. |
| Recent field studies have discovered further evidence of a possible coevolutionary relationship: some species of Passiflora vines have developed yellow spots identical in color and shape to Heliconius eggs. | What it says: Scientists found some vines that evolved fake eggs - they look exactly like real butterfly eggs. What it does: Reveals the second vine defense strategy and connects it to the butterfly behavior from the previous sentence. Source/Type: Recent research findings. Connection to Previous Sentences: Brilliant connection! Sentence 10 explained that butterflies avoid leaves with eggs → sentence 11 shows vines evolved fake eggs to exploit this behavior. This is another example of sentence 5's "defenses." Visualization: Imagine 30 vine leaves: 10 have real butterfly eggs, 20 have convincing fake eggs that fool butterflies into thinking "this spot is taken." Reading Strategy Insight: This follows the same pattern as the leaf-shape example - observe butterfly behavior → vines evolve to exploit that behavior. |
| Subsequent studies of "egg-mimicry" reveal that it has been found in only some two percent of the 500 known Passiflora species, indicating that it probably evolved relatively recently, but where it does occur, it has been a successful deterrent to Heliconius egg-laying. | What it says: Only 10 out of 500 vine species have this fake-egg trick, suggesting it's a new evolution, but where it exists, it works well against butterflies. What it does: Provides the outcome and effectiveness of the second defense strategy. Source/Type: Research findings and conclusions. Connection to Previous Sentences: This completes the second defense example just like sentence 9 completed the first defense example. Compare: leaf disguises "not entirely successful" vs. egg mimicry "successful deterrent." Visualization: Defense Strategy Report Card: Leaf shape changes = C grade (partial success), Egg mimicry = A grade (works where present), but egg mimicry only in 10 out of 500 species. Reading Strategy Insight: You've now seen the complete coevolution cycle twice - this reinforces rather than complicates the central concept from sentence 1. |
2. Passage Summary:
Author's Purpose:
To explain how coevolution works by showing a detailed example of two species that have influenced each other's development over time
Summary of Passage Structure:
In this passage, the author builds their explanation in clear steps:
- First, they define coevolution as the scientific study of how different organisms influence each other's evolution
- Next, they introduce a specific example of butterflies and vines, explaining how the butterflies depend on and damage the vines
- Then, they describe how the vines have fought back by developing two different defense strategies: disguising their leaves and creating fake eggs
- Finally, they evaluate how well each defense strategy has worked, showing that this evolutionary battle is ongoing
Main Point:
Coevolution is a back-and-forth process where species continuously adapt to each other's changes, as shown by butterflies and vines that keep developing new strategies to outsmart each other
Question Analysis:
This question asks us to identify which statement about the coevolutionary relationship the author would most likely agree with. We need to find an answer that aligns with how the author presents and characterizes the butterfly-vine relationship throughout the passage.
Connecting to Our Passage Analysis:
From our passage analysis, several key insights emerge:
- The author establishes coevolution as organisms that "influence one another as they evolve" - emphasizing ongoing mutual influence
- The passage demonstrates a back-and-forth pattern: butterflies harm vines → vines develop defenses → butterflies adapt to overcome defenses
- The author presents two complete cycles of this adaptation process (leaf shape changes and egg mimicry)
- Sentence 9 shows the first defense "has not been an entirely successful strategy" because "butterflies have developed the ability to recognize other characteristics"
- Sentence 12 shows the second defense has been "a successful deterrent" but exists in only 2% of species, indicating it "probably evolved relatively recently"
- The overall structure shows this as an ongoing process rather than something with a definitive endpoint
Prethinking:
The author presents coevolution as a dynamic, continuing process. The passage shows multiple rounds of adaptation and counter-adaptation, with some strategies failing and new ones emerging. The phrase "relatively recently" for egg mimicry and the ongoing nature of butterfly counter-adaptations suggest this relationship will continue evolving. The author would likely agree with a statement that captures this ongoing, dynamic nature rather than one that suggests a static outcome or endpoint.
Answer Choices Explained
A
It will eventually result in a decrease in the number of Passiflora species.
Why It's Wrong:
• The passage shows vines successfully developing new defenses (egg mimicry works as "successful deterrent")
• There's no evidence suggesting species reduction - the author presents this as an ongoing relationship
• The passage focuses on adaptation strategies, not species extinction
Common Student Mistakes:
1. Does the fact that butterflies overcome some vine defenses mean vines are losing the evolutionary battle?
→ Remember that the passage shows vines developing new, more successful strategies over time
2. Since butterflies can overcome leaf-shape defenses, are vines doomed?
→ Note that egg mimicry is described as "successful" and "relatively recent" - vines are still evolving
B
It has ensured that Passiflora species will survive longer than Heliconius species.
Why It's Wrong:
• The passage presents an ongoing relationship where both species continue adapting
• There's no evidence about which species will survive longer
• The author shows both species successfully evolving counter-strategies
Common Student Mistakes:
1. Since vines are developing defenses, does this mean they're winning?
→ The passage shows both species successfully adapting - it's not about one "winning"
2. Do successful vine defenses guarantee their survival advantage?
→ Coevolution involves ongoing adaptation by both species, not permanent advantages
C
It will probably end because the development of egg-mimicry by Passiflora vines will force Heliconius butterflies to find other host plants.
Why It's Wrong:
• The passage shows egg mimicry exists in only 2% of species, so it's not universal
• Previous defenses (leaf shape) didn't force butterflies to leave - they adapted instead
• The pattern suggests continuing adaptation rather than relationship termination
Common Student Mistakes:
1. Since egg mimicry is "successful," will this solve the problem permanently?
→ Notice it only exists in 2% of species and butterflies have previously adapted to overcome defenses
2. Will one really effective defense end the coevolutionary relationship?
→ The passage pattern shows butterflies developing counter-adaptations, not abandoning their host
D
It has been more thoroughly studied than any other coevolutionary relationship in nature.
Why It's Wrong:
• The passage makes no comparative claims about research thoroughness
• The author presents this as "one of the most remarkable" examples, not the most studied
• No evidence is given about the extent of research on other coevolutionary relationships
Common Student Mistakes:
1. Does "remarkable" mean "most studied"?
→ "Remarkable" refers to the quality of the interaction, not the amount of research
2. Do detailed examples indicate more extensive study?
→ The author provides detail to illustrate coevolution principles, not to claim research superiority
E
It is a dynamic, continuing process that may produce further variations in the plants and butterflies.
Why It's Right:
• Directly aligns with the passage's demonstration of ongoing back-and-forth adaptation
• Matches the author's presentation of coevolution as continuous mutual influence
• Consistent with evidence of recent evolution (egg mimicry) and ongoing adaptation
• Captures the essential nature of coevolution as defined in the opening
Key Evidence: The passage shows "organisms influence one another as they evolve" and demonstrates this through multiple cycles of adaptation and counter-adaptation, with egg mimicry described as evolving "relatively recently," indicating the process continues.
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