Reading Comprehension: science passages

A typical science passage introduces a phenomenon, explains a hypothesis, describes evidence, and discusses implications or limitations. The author may present competing hypotheses or show how a new finding changes an earlier view. Some passages focus on a single study. Others compare several studies or explain a mechanism.

For example, a passage might describe how a certain bird species navigates using magnetic fields. It presents a hypothesis, describes an experiment with magnets, reports the results, and notes that the findings may not apply to other species. The questions ask about the hypothesis, the evidence, and the author's qualifications.

A hypothesis is a proposed explanation. Evidence is the data that supports or challenges it. The passage may use words such as "suggests," "indicates," "consistent with," and "supports" to describe the relationship. These words matter. A finding that is consistent with a hypothesis does not prove it.

Distinguish between the hypothesis and the observation. If a passage says that a drug reduces symptoms in mice, the observation is the reduction. The hypothesis may be that the drug affects a specific pathway. The passage may then describe an experiment designed to test that mechanism.

Science passages often describe an experimental group and a control group. The control group provides a baseline. If the experimental group improves and the control group does not, the treatment may be responsible. If both groups improve, the treatment may not be the cause.

Look for alternative explanations. A study may find that students who eat breakfast perform better on tests. The passage may note that the students who eat breakfast also sleep more. The alternative explanation weakens the claim that breakfast is the cause.

Data can be accurate while the interpretation is uncertain. A passage may report a correlation and then caution that correlation does not prove causation. The author may say that the results are "suggestive" or that further research is needed. These qualifications are often the target of inference questions.

Pay attention to sample size, duration, and context. A study of 20 people over two weeks may not support a broad claim about the general population. A laboratory result may not transfer to real-world conditions. The author may mention these limits explicitly.

Some passages present two or more explanations for the same phenomenon. The author may favor one, reject another, or remain neutral. Track the evidence for each explanation. A question may ask why the author mentions a particular finding, and the answer may be that it undermines one explanation and supports another.

The main idea of a science passage is often a claim about what the evidence shows, not a description of every experiment. If the passage presents a new hypothesis and evaluates it, the main idea may be that the hypothesis is promising but not fully confirmed.

Purpose questions ask why the author wrote the passage. The answer may be to explain a phenomenon, to evaluate a study, to reconcile conflicting findings, or to caution against an overgeneralization. Choose the answer that covers the whole passage, not one paragraph.

Inference questions in science passages often ask what would happen if a certain condition changed, or what the findings imply for another case. The answer must follow from the passage's logic. If the passage says a plant grows best in acidic soil, an inference is that adding an alkaline substance may reduce growth. It is not an inference that the plant cannot grow anywhere else.

Application questions ask you to apply a principle from the passage to a new situation. Identify the principle, then choose the case that matches its structure. The topic may change, but the logical relationship stays the same.

Some science passages describe a mechanism rather than an experiment. A mechanism explains how a process works, step by step. For example, a passage might explain how a protein binds to a receptor and triggers a response. Questions about mechanisms ask you to follow the sequence or identify what would happen if one step were blocked.

Model questions ask what a simplified representation implies. A model may omit details that are not relevant to the question. Do not treat the model as a complete description of reality. If the passage says a model assumes a constant temperature, that assumption is part of the model, not necessarily a fact about the real world.

Science passages often end with a call for further research or a statement that the findings are preliminary. These qualifications are not filler. They tell you how strongly the author believes the conclusion. A question may ask what additional evidence would support the hypothesis, or what the passage suggests about the limits of the study.

If the passage says the results are consistent with a hypothesis, the author is not claiming proof. The correct inference is that the hypothesis remains plausible, not that it is confirmed. Distinguish between "supports" and "proves," and between "suggests" and "demonstrates."

1. Identify the phenomenon and the hypothesis.
2. Track the experiment, the data, and the conclusion.
3. Note any alternative explanations or limitations.
4. For main idea questions, choose the claim that covers the whole passage.
5. For inference questions, stay within the study's logic.
6. For application questions, match the structure of the principle.

• Using outside scientific knowledge.
• Treating a correlation as proof of causation.
• Assuming a study applies to all populations.
• Confusing the hypothesis with the conclusion.
• Ignoring a limitation the author mentions.
• Choosing an answer that is true but not supported by the passage.