Arthropods—brine shrimp, hawk moths, and many other invertebrate animals—have a nervous system made up of a brain, nerve cord, and...
GMAT Information and Ideas : (Ideas) Questions
Arthropods—brine shrimp, hawk moths, and many other invertebrate animals—have a nervous system made up of a brain, nerve cord, and other nerves. Researchers have gained insights about this system in ancient arthropods from traces found in various fossils. For example, in a study of two fossils of the extinct arthropod species Mollisonia symmetrica, Javier Ortega-Hernández, James Weaver, and team observed clear signs of a nerve cord. They also saw possible indications of a synganglion, a brain-like mass of nerves. Researchers hope to identify more features of the nervous systems of prehistoric arthropods as additional fossils are found.
Which choice best states the main idea of the text?
There are several similarities between the brains of hawk moths and the brains of brine shrimp.
Fossil evidence can contribute to the understanding of the nervous system in ancient arthropods.
Newly discovered fossils suggest that ancient hawk moths and ancient brine shrimp had spines.
Researchers need to focus on finding more fossils of ancient arthropods.
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| Arthropods—brine shrimp, hawk moths, and many other invertebrate animals—have a nervous system made up of a brain, nerve cord, and other nerves. |
|
| Researchers have gained insights about this system in ancient arthropods from traces found in various fossils. |
|
| For example, in a study of two fossils of the extinct arthropod species Mollisonia symmetrica, Javier Ortega-Hernández, James Weaver, and team observed clear signs of a nerve cord. |
|
| They also saw possible indications of a synganglion, a brain-like mass of nerves. |
|
| Researchers hope to identify more features of the nervous systems of prehistoric arthropods as additional fossils are found. |
|
Provide Passage Architecture & Core Elements
Visual Structure Map:
[CONTEXT: Modern arthropod nervous systems]
↓
[MAIN CLAIM: Fossils reveal ancient arthropod nervous systems]
├── Specific Example: M. symmetrica study
│ ├── Evidence 1: Nerve cord traces
│ └── Evidence 2: Possible synganglion
└── Future Direction: More fossils = more discoveries
Main Point: Fossil evidence provides valuable insights into the nervous systems of ancient arthropods.
Argument Flow: The passage establishes what we know about modern arthropod nervous systems, then explains how researchers use fossil evidence to understand ancient versions. It supports this with a specific study example and concludes by noting the potential for future discoveries through additional fossil findings.
Step 2: Interpret the Question Precisely
What's being asked? The main idea of the entire text
What type of answer do we need? A statement that captures the central message or primary focus
Any limiting keywords? 'main idea' tells us we need the overarching point, not a detail
Step 3: Prethink the Answer
- The passage is fundamentally about how fossil evidence helps scientists understand ancient arthropod nervous systems
- The right answer should capture this connection between fossils and learning about prehistoric creatures' biology
- It should reflect that this is an ongoing area of research where fossils provide valuable information about ancient life forms
- So the right answer should emphasize how fossil evidence contributes to our understanding of ancient arthropods' nervous systems
There are several similarities between the brains of hawk moths and the brains of brine shrimp.
✗ Incorrect
- Claims the text discusses similarities between hawk moth and brine shrimp brains
- The passage mentions these creatures only as examples of modern arthropods, not to compare their brains
- Completely misses the main focus on fossils and ancient creatures
Fossil evidence can contribute to the understanding of the nervous system in ancient arthropods.
✓ Correct
- States that fossil evidence contributes to understanding ancient arthropod nervous systems
- Perfectly matches our passage analysis - this is exactly what the text demonstrates
- Aligns with our prethinking about the connection between fossils and scientific understanding
Newly discovered fossils suggest that ancient hawk moths and ancient brine shrimp had spines.
✗ Incorrect
- Claims fossils suggest ancient creatures had spines
- The passage discusses nerve cords and synganglions, not spines
- Fundamental misreading of the scientific content
Researchers need to focus on finding more fossils of ancient arthropods.
✗ Incorrect
- Focuses on researchers needing to find more fossils
- While the passage mentions hopes for future discoveries, this misses the main point about what fossils already contribute
- What trap this represents: Students might focus on the final sentence about future research rather than the passage's primary message