Conflicting viewpoints and evidence-based models
Compare assumptions and predictions, then choose evidence that actually discriminates between competing explanations.
What you will tackle
- Identify assumptions and predictions of scientific arguments/models
- Compare conflicting viewpoints accurately
- Determine supporting, contradicting and inconclusive evidence
- Use observations to improve or limit a model
Write each model's prediction explicitly
In the original lake example, Model A attributes a low oxygen measurement chiefly to warmer water, predicting lower oxygen at warmer sites regardless of depth. Model B chiefly attributes it to limited mixing, predicting lower oxygen in poorly mixed deeper water even at a comparable temperature. Both can agree on an observation while proposing different mechanisms.
Prefer a comparison with different predicted outcomes
A useful discriminating test keeps other relevant conditions comparable. A result both models predict cannot decide between them. A contradicting observation can reject an overly strong version of a model without proving every detail of its competitor. New evidence may require a combined or qualified explanation.
| Dose (mg) | Height (cm) |
|---|---|
| 0 | 8 |
| 5 | 12 |
| 10 | 15 |
| 15 | 13 |
Build your notes, then practise
Work on paper before opening an explanation. Guided tasks provide a starting point; independent tasks remove the scaffolding; application tasks ask you to justify a method or interpretation in context.
Guided practice
Guided 1
For the two lake models, compare equally warm water with good mixing and poor mixing. Which model predicts a difference most directly, and what would lower oxygen only in the poorly mixed sample support?
Show a starting hint
Hold one proposed cause constant while testing the other.
Compare with the explained answer
- Temperature is held comparable.
- Model B predicts a mixing-related difference more directly.
- The result supports a mixing contribution; it does not prove temperature never matters.
Answer / response criteria: Model B; evidence for a mixing contribution, with a bounded conclusion.
Independent practice
Independent 1
Model C says every additional 5 mg of fertiliser increases height. The displayed means are 8,12,15,13 cm at doses 0,5,10,15 mg. Identify a contradiction. Does it prove that 10 mg is optimal for all plants?
Compare with the explained answer
- The 10-to-15 mg step decreases the mean from 15 to 13 cm.
- That contradicts every-step increase.
- Only the tested plants and doses are represented; an all-plants optimum is not established.
Answer / response criteria: The final step contradicts Model C; a universal optimum is not established.
Application practice
Application 1
A student argues that two rock layers with similar fossils must have formed at exactly the same time. Another argues that similar environments could support similar organisms over an interval. Propose additional evidence and describe a suitably qualified conclusion.
Compare with the explained answer
- Compare multiple fossil types, layer sequences and independent dating evidence if available.
- Distinguish approximate correlation from an exact date inferred from a single shared fossil.
- A conclusion can support a likely overlapping age range while recording uncertainty and alternative explanations.
Answer / response criteria: Use several independent correlations/dating lines; infer a supported age relationship rather than exact simultaneity from one fossil similarity.
What can you explain now?
A student argues that two rock layers with similar fossils must have formed at exactly the same time. Another argues that similar environments could support similar organisms over an interval. Propose additional evidence and describe a suitably qualified conclusion.
Compare with the explanation
Use several independent correlations/dating lines; infer a supported age relationship rather than exact simultaneity from one fossil similarity.
Explain the reasoning before comparing. This review records your self-assessment rather than an official score or mastery decision.
After trying it yourself, choose your next review. This is your self-assessment.
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Source and review status
Coverage follows the named requirements and examples in the 2026–2027 ACT test guide and subject descriptions. That guide explicitly does not list every possible topic. The broader coded College and Career Readiness Standards are also mapped to conceptual teaching and practice; this does not calibrate a learner to a score band. The separate scientific-background context list and reading-complexity rubric have their own stated limits.
Original teaching and explained self-check practice are available. Specialist review and difficulty calibration remain pending. Essays require self-check or teacher review and are not automatically marked or awarded official scores.
Official source specification / guide