ACT Science Practice Test: Life Science and Earth Science Passages
- Life Science and Earth Science Passages
- 10 questions
- 11 minutes
This test has two original passages, one on yeast and one on soil, each followed by five questions. ACT Science does not expect you to know biology or geology facts in detail; the answers come from the tables and the descriptions. Use outside knowledge only to explain a pattern the data already show.
Tap an option to mark your answer. You can change your mind, or tap the same option again to leave the question blank. The correct answers and explanations appear when you finish the test.Tap an option to answer; tap it again to leave the question blank.
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Question 1
Passage I
Yeast cells break down sugar and release carbon dioxide gas (CO2). This process is controlled by enzymes, proteins that work best within a certain temperature range.
Students mixed 5 g of dry yeast and 10 g of sugar into 100 mL of water in each of five flasks. Each flask was placed in a water bath at a different temperature and connected to a gas syringe. After 20 minutes, the students recorded the volume of CO2 collected in each syringe.
Table 1 Temperature (°C) CO2 collected in 20 min (mL) 10 3 20 11 30 26 40 21 50 2 At which of the tested temperatures did the yeast produce the most CO2?
Correct answer: B
Table 1 shows the largest volume, 26 mL, at 30°C. At 40°C the volume is lower (21 mL), and at 50°C it is almost zero.
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Question 2
Passage I (see above):
In this experiment, the dependent variable was the:
Correct answer: D
The students measured the CO2 volume to see how it responded to temperature, so it is the dependent variable. Temperature was the factor they changed, and the sugar mass and time were kept the same.
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Question 3
Passage I (see above):
If the students had also tested a flask at 25°C, the volume of CO2 collected in 20 minutes would most likely have been:
Correct answer: A
25°C lies between 20°C (11 mL) and 30°C (26 mL), and the volume rises steadily over that range, so the result should fall between those two values.
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Question 4
Passage I (see above):
Which explanation is most consistent with the passage for the small volume of CO2 at 50°C?
Correct answer: C
The passage says the process depends on enzymes that work best in a certain range; above that range they stop working well, so production drops. Every flask had the same amounts of yeast and sugar, and nothing suggests a problem with the syringes.
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Question 5
Passage I (see above):
A student predicted that CO2 production would increase with every rise in temperature from 10°C to 50°C. Do the results support this prediction?
Correct answer: D
Production rose from 10°C to 30°C but then fell to 21 mL at 40°C and 2 mL at 50°C, so it did not increase at every step. The rise up to 30°C is only part of the pattern.
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Question 6
Passage II
Soils differ in the size of their particles. Sand grains are 0.05-2 mm across, clay particles are smaller than 0.002 mm, and loam is a mixture of sand, silt and clay particles.
A student filled three identical tubes with 10 cm of dry sand, loam or clay. Each tube had a screen at the bottom and stood over a beaker. The student poured 500 mL of water onto each soil, recorded the time until water stopped dripping from the tube, and measured the volume of water collected in the beaker. Water that was not collected was retained (held) by the soil.
Table 1 Soil Time until dripping stopped (s) Water collected (mL) Water retained (mL) Sand 35 440 60 Loam 140 345 155 Clay 610 260 240 According to Table 1, which soil retained the most water?
Correct answer: A
Clay retained 240 mL, compared with 155 mL for loam and 60 mL for sand. Clay also let the least water through, 260 mL.
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Question 7
Passage II (see above):
What percent of the 500 mL of water poured onto the loam was retained by the loam?
Correct answer: C
The loam retained 500 − 345 = 155 mL, and 155 ÷ 500 = 0.31, or 31%. The choice 69% is the share that drained through (345 ÷ 500).
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Question 8
Passage II (see above):
Based on the passage, as the average particle size of the soil decreased, the time until dripping stopped:
Correct answer: B
Sand has the largest particles and drained in 35 s; loam, a mixture, took 140 s; clay, with the smallest particles, took 610 s. Smaller particles leave smaller spaces for water to move through.
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Question 9
Passage II (see above):
Which statement best describes the relationship shown in Table 1?
Correct answer: D
Sand drained fastest (35 s) and retained the least (60 mL); clay drained slowest (610 s) and retained the most (240 mL). Loam lies between them on both measures.
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Question 10
Passage II (see above):
After a heavy rain, on which of the three soils would water most likely stay on the surface the longest?
Correct answer: C
Water moved through clay most slowly, taking 610 s to drain through the tube, so rain would soak in slowly and puddles would last longest on clay. Sand let water through in about a twentieth of that time.
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