Certain genetically modified strains of maize produce a powerful natural insecticide. The insecticide occurs throughout the plant, including its polle...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Evaluate

MEDIUM

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Certain genetically modified strains of maize produce a powerful natural insecticide. The insecticide occurs throughout the plant, including its pollen. Maize pollen is dispersed by the wind and frequently blows onto milkweed plants that grow near maize fields. Caterpillars of monarch butterflies feed exclusively on milkweed leaves. When these caterpillars are fed milkweed leaves dusted with pollen from modified maize plants, they die. Therefore, by using genetically modified maize, farmers put monarch butterflies at risk.

Which of the following would it be most useful to determine in order to evaluate the argument?

Whether the natural insecticide is as effective against maize-eating insects as commercial insecticides typically used on maize are

Whether the pollen of genetically modified maize contains as much insecticide as other parts of these plants

Whether monarch butterfly caterpillars are actively feeding during the part of the growing season when maize is releasing pollen

Whether insects that feed on genetically modified maize plants are likely to be killed by insecticide from the plant's pollen

Whether any maize-eating insects compete with monarch caterpillars for the leaves of milkweed plants growing near maize fields

Solution

Passage Analysis:

Text from Passage	Analysis
Certain genetically modified strains of maize produce a powerful natural insecticide.	What it says: Modified maize plants make their own bug killer What it does: Sets up the basic fact about GM maize having insecticide properties What it is: Author's factual claim
The insecticide occurs throughout the plant, including its pollen.	What it says: The bug killer is everywhere in the plant, even in the pollen What it does: Expands on the previous fact by showing the insecticide spreads to pollen specifically What it is: Author's clarification
Maize pollen is dispersed by the wind and frequently blows onto milkweed plants that grow near maize fields.	What it says: Wind carries maize pollen to nearby milkweed plants What it does: Connects the pollen fact to a new element - shows how pollen reaches milkweed What it is: Author's factual claim Visualization: Wind → Maize pollen (with insecticide) → Milkweed plants
Caterpillars of monarch butterflies feed exclusively on milkweed leaves.	What it says: Monarch caterpillars only eat milkweed leaves What it does: Introduces monarchs and connects them to milkweed from the previous statement What it is: Author's biological fact
When these caterpillars are fed milkweed leaves dusted with pollen from modified maize plants, they die.	What it says: Monarch caterpillars die when they eat milkweed with GM maize pollen on it What it does: Combines all previous facts to show a deadly outcome for monarchs What it is: Author's experimental finding Visualization: Milkweed + GM pollen → Monarch caterpillars eat → Death
Therefore, by using genetically modified maize, farmers put monarch butterflies at risk.	What it says: Farmers using GM maize endanger monarch butterflies What it does: Draws the main conclusion from all the evidence presented What it is: Author's conclusion

Argument Flow:

The argument builds step by step: GM maize has insecticide → insecticide is in pollen → wind spreads pollen to milkweed → monarchs eat milkweed → pollen kills monarchs → therefore GM maize threatens monarchs

Main Conclusion:

Farmers who use genetically modified maize put monarch butterflies at risk

Logical Structure:

This is a causal chain argument where each premise links to the next, creating a pathway from GM maize use to monarch butterfly danger. The evidence shows how insecticide moves from maize to pollen to milkweed to caterpillars, with each step supported by the previous facts

Prethinking:

Question type:

Evaluate - We need to find what information would help us determine whether the conclusion (that GM maize puts monarch butterflies at risk) is actually valid based on the evidence given.

Precision of Claims

The argument makes specific claims about quantity (how much pollen reaches milkweed), activity (whether lab conditions match real-world conditions), and frequency (how often monarchs actually encounter this pollen in nature).

Strategy

For evaluate questions, we need to think about the key assumptions the argument makes and create scenarios that would either strengthen or weaken the conclusion when we get more information. We should look for gaps between the evidence presented and the conclusion drawn - what's missing that we'd need to know to properly judge this argument?

Answer Choices Explained

Whether the natural insecticide is as effective against maize-eating insects as commercial insecticides typically used on maize are

This asks about comparing the effectiveness of natural vs. commercial insecticides against maize-eating insects. However, this doesn't help us evaluate whether monarchs are at risk. The argument isn't about how well the insecticide works on crop pests - it's about whether monarchs encounter deadly pollen in real-world conditions. Even if the natural insecticide is less effective on crop pests, it could still kill monarchs if they encounter it.

Whether the pollen of genetically modified maize contains as much insecticide as other parts of these plants

This compares insecticide concentration in pollen versus other plant parts. While this might seem relevant, we already know from the argument that caterpillars die when fed milkweed with the pollen, so the pollen clearly contains enough insecticide to be lethal. Whether other parts have more or less doesn't change the risk to monarchs from pollen exposure.

Whether monarch butterfly caterpillars are actively feeding during the part of the growing season when maize is releasing pollen

This addresses the crucial timing question - whether monarch caterpillars are actively feeding when maize plants release pollen. This directly tests a key assumption in the argument's causal chain. If caterpillars aren't feeding during pollen season, the entire threat disappears regardless of how toxic the pollen is. If they are feeding during this time, it confirms the risk is real. This information would definitively help evaluate the argument's conclusion.

Whether insects that feed on genetically modified maize plants are likely to be killed by insecticide from the plant's pollen

This asks about whether insects that actually eat maize plants are killed by the pollen. This is irrelevant to monarch safety since monarchs don't eat maize - they only eat milkweed that gets contaminated with pollen. The fate of maize-eating insects doesn't tell us anything about the risk to monarchs.

Whether any maize-eating insects compete with monarch caterpillars for the leaves of milkweed plants growing near maize fields

This asks about competition between maize insects and monarch caterpillars for milkweed leaves. This is completely off-topic since monarchs don't compete with maize-eating insects for food - monarchs eat milkweed, not maize. This information wouldn't help evaluate whether GM maize threatens monarchs.

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