Table 1 shows the results of measuring dissolved oxygen (DO) levels at different depths in a lake.
Depth (m) DO (mg/L) 0 8.2 5 7.8 10 6.1 15 4.3 20 2.9
Question: According to Table 1, as depth increases, the dissolved oxygen level:
A. increases only. B. decreases only. C. increases then decreases. D. remains constant.
Answer: B. Read the DO column top to bottom: 8.2 → 7.8 → 6.1 → 4.3 → 2.9. It consistently decreases. No extra knowledge needed — just read the numbers.
Using the same table, what would the DO level most likely be at a depth of 12 meters?
Solution: 12 m is between 10 m (DO = 6.1) and 15 m (DO = 4.3). The drop over that 5 m interval is mg/L, or mg/L per meter. At 12 m (2 m past 10 m): mg/L. The answer would be approximately 5.4 mg/L.
Experiment: Students tested how the mass of a pendulum bob affects its period (time for one complete swing). They used bobs of 50g, 100g, 150g, and 200g, keeping the string length at 1.0 m and the release angle at 15° for all trials.
Question: In this experiment, the independent variable is:
A. the period of the pendulum. B. the mass of the bob. C. the length of the string. D. the release angle.
Answer: B. The independent variable is what the experimenter intentionally changed — the mass of the bob (50g, 100g, 150g, 200g). The period (A) is the dependent variable (what they measured). String length (C) and release angle (D) are controls (held constant).
The same pendulum experiment found that the period was approximately 2.01 seconds for all four bob masses. A student hypothesizes that "the period of a pendulum depends on the mass of the bob."
Question: Do the experimental results support the student's hypothesis?
A. Yes, because the period increased as mass increased. B. Yes, because a heavier bob has more gravitational force acting on it. C. No, because the period remained approximately constant despite changes in mass. D. No, because the string length was not varied in the experiment.
Answer: C. The data shows the period was about 2.01 s regardless of mass — no change in the dependent variable when the independent variable changed. This means mass does not affect period, which contradicts the hypothesis. Choice A is factually wrong (period did not increase). Choice B uses outside physics reasoning, not the data. Choice D addresses a limitation but does not directly evaluate the hypothesis about mass.
Scientist 1: The extinction of large ice-age mammals (megafauna) was caused primarily by climate change. As glaciers retreated, habitats shifted faster than large animals could adapt. Fossil pollen records show rapid vegetation changes during this period.
Scientist 2: The extinction was caused primarily by human hunting. Megafauna had survived previous interglacial periods with similar climate shifts. The extinctions coincide with human arrival on each continent, not with any specific climate event.
Question: Scientist 2 would most likely argue that fossil pollen evidence showing rapid vegetation changes:
A. proves that climate change was the primary cause of megafauna extinction. B. is irrelevant because megafauna did not eat plants. C. does not explain the extinctions because similar vegetation changes occurred in earlier periods that megafauna survived. D. supports the human hunting hypothesis because vegetation changes attracted human hunters.
Answer: C. Scientist 2's core argument is that megafauna survived previous interglacial periods — so climate change alone cannot explain why they went extinct this time. The pollen evidence shows vegetation changed, but Scientist 2 would say that happened before too without causing mass extinction. Choice A is Scientist 1's position. Choice B is absurd (megafauna were herbivores or omnivores). Choice D creates an unsupported connection.