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A biological or physical science passage is straightforward, giving you the scoop on something. It may be how stellar dust is affected by gravity, how to build a suspension bridge, or how molecular theory applies. The passage may be difficult to get through (because it goes into depth on an unfamiliar subject), so read it quickly for the gist and go back later for the details.

When approaching biological and physical science passages, don’t get hung up on the scientific terminology. Just accept these terms as part of the story and keep reading. The terms may function as key words to help you locate the answers within the passage even if you don’t know what the terms mean.

Here’s a science passage for you to practice on. Don’t forget to check the introduction paragraph for the overall gist of the passage and to look for the high-level contribution of each paragraph. If you know each paragraph’s purpose, you can quickly find the details when you need them.

 Microbiological activity clearly affects the mechanical strength of leaves. Although it cannot be denied that with most species the loss of mechanical strength is the result of both invertebrate feeding and microbiological breakdown, the example of Fagus sylvatica illustrates loss without any sign of invertebrate attack being evident. Fagus shows little sign of invertebrate attack even after being exposed for eight months in either a lake or stream environment, but results of the rolling fragmentation experiment show that loss of mechanical strength, even in this apparently resistant species, is considerable.

 Most species appear to exhibit a higher rate of degradation in the stream environment than in the lake. This is perhaps most clearly shown in the case of Alnus. Examination of the type of destruction suggests that the cause for the greater loss of material in the stream-processed leaves is a combination of both biological and mechanical degradation. The leaves exhibit an angular fragmentation, which is characteristic of mechanical damage, rather than the rounded holes typical of the attack by large particle feeders or the skeletal vein pattern produced by microbial degradation and small particle feeders. As the leaves become less strong, the fluid forces acting on the stream nylon cages cause successively greater fragmentation.

 Mechanical fragmentation, like biological breakdown, is to some extent influenced by leaf structure and form. In some leaves with a strong midrib, the lamina breaks up, but the pieces remain attached by means of the midrib. One type of leaf may break cleanly, whereas another tears off and is easily destroyed after the tissues are weakened by microbial attack.

 In most species, the mechanical breakdown will take the form of gradual attrition at the margins. If the energy of the environment is sufficiently high, brittle species may be broken across the midrib, something that rarely happens with more pliable leaves. The result of attrition is that where the areas of the whole leaves follow a normal distribution, a bimodal distribution is produced, one peak composed mainly of the fragmented pieces, the other of the larger remains.

 To test the theory that a thin leaf has only half the chance of a thick one for entering the fossil record, all other things being equal, Ferguson (1971) cut discs of fresh leaves from 11 species of leaves, each with a different thickness, and rotated them with sand and water in a revolving drum. Each run lasted 100 hours and was repeated three times, but even after this treatment, all species showed little sign of wear. It therefore seems unlikely that leaf thickness alone, without substantial microbial preconditioning, contributes much to the probability that a leaf will enter a depositional environment in a recognizable form. The results of experiments with whole fresh leaves show that they are more resistant to fragmentation than leaves exposed to microbiological attack. Unless the leaf is exceptionally large or small, leaf size and thickness are not likely to be as critical in determining the preservation potential of a leaf type as the rate of microbiological degradation.

1. The passage is primarily concerned with

Why leaves disintegrate

An analysis of leaf structure and composition

Comparing lakes and streams

The purpose of particle feeders

How leaves’ mechanical strength is affected by microbiological activity

The passage reads primarily about leaves, making that its primary concern, so eliminate Choices (C) and (D) right off. Choice (A) is too broad, as other causes of disintegration may exist that the passage doesn’t mention. Choice (B) is too specific: The passage mentions leaf structure, but not as its primary focus. Correct answer: Choice (E).

2. Which of the following is mentioned as a reason for leaf degradation in streams? Consider each of the three choices separately and select all that apply.

Mechanical damage

Biological degradation

Large particle feeders

The second paragraph of the passage tells you that “loss of material in stream-processed leaves is a combination of biological and mechanical degradation.” Choice (C) is incorrect because the passage specifically states that the pattern of holes is contrary to that of large particle feeders. The correct answers are Choices (A) and (B).

3. The conclusion that the author reached from Ferguson’s revolving drum experiment was that

Leaf thickness is only a contributing factor to leaf fragmentation.

Leaves submerged in water degrade more rapidly than leaves deposited in mud or silt.

Leaves with a strong midrib deteriorate less than leaves without such a midrib.

Microbial attack is made worse by high temperatures.

Bimodal distribution reduces leaf attrition.

The middle of the last paragraph tells you that leaf thickness alone is unlikely to affect the final form of the leaf. You probably need to reread that sentence a few times to get past the jargon, but a detail or fact question is the type of question you should be sure to answer correctly. Choice (B) introduces facts not discussed in the passage; the passage doesn’t talk of leaves in mud or silt. Choice (C) is mentioned in the passage but not in Ferguson’s experiments.

Nothing about high temperatures appears in the passage, which eliminates Choice (D). Choice (E) sounds pretentious and pompous — and nice and scientific — but has nothing to do with Ferguson. To answer this question correctly, you need to return to the passage to look up Ferguson specifically, not merely rely on your memory of the passage as a whole. Correct answer: Choice (A).

Be careful to answer only what the question is asking. Answer-choice traps include statements that are true but don’t answer the question.

4. The tone of the passage is

Persuasive

Biased

Objective

Argumentative

Disparaging

The passage is hardly persuasive; it isn’t really trying to change your opinion on an issue. It objectively presents scientific facts and experimental evidence. Because you know the gist of the passage and the context of each paragraph, the answer is obvious. Correct answer: Choice (C).

5. Select the sentence in the fourth paragraph that explains the form of mechanical breakdown of most species of leaves.

Key words come in handy in answering this question. The first and only place mechanical breakdown is mentioned is in the first sentence of the fourth paragraph. Correct answer: “In most species, the mechanical breakdown will take the form of gradual attrition at the margins.”

6. Which would be an example of “energy of the environment” (fourth paragraph, second sentence)?

Wind and rain

Sunlight

Animals that eat leaves

Lumberjacks

Fuel that may be harvested

The passage is about the degradation of leaves, which you already know. The fourth paragraph discusses factors that may break a brittle leaf across its center, or midrib. Sunlight may do this, but it wouldn’t necessarily target the midrib, so out with Choice (B). Animals would digest the leaves such that the leaves wouldn’t degrade, so no more Choice (C). Lumberjacks may leave leaves behind (so to speak), but the passage is all about natural factors, so down with Choice (D). Finally, there’s nothing about harvesting fuel, so Choice (E) is out. This leaves Choice (A), wind and rain, which makes sense. The wind and rain physically affect the leaf and both cause degradation and breaking along its weak point, the midrib. Correct answer: Choice (A).