ACT Science Practice Test 106

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


In nature, different types of organisms often form symbiotic (mutually beneficial) relationships with each other. One such example of this is between certain types of fungi and plants; this relationship is known as a mycorrhiza. The association provides the fungus with food through access to sugars from photosynthesis in the plant. In return, the plant gains the use of the fungi's surface area to absorb mineral nutrients from the soil. It is believed that without the assistance of fungi, these plants would not be able to absorb crucial nutrients, including phosphates, from the soil. Two experiments were performed to study the effect that the plant-fungi relationship has on plant growth.

Experiment 1

For 6 weeks, several specimens of three different types of plants, selected from among four different types of plants, were grown in a greenhouse. The average growth in inches of each type of plant was recorded every two weeks. The soil used for the plants was treated to remove any trace of fungi to establish expected growth without the plant-fungi association. The results are shown in Table 1.

Experiment 2

In this experiment, several specimens of four different types of plants were grown in a greenhouse for six weeks, and the average growth in inches of each type of plant was recorded every two weeks. This time, however, untreated soil that contained fungi was used. The results are shown in Table 2.

Information on the plant types used is given in Table 3.

1. The results of Experiment 1 indicate that during what time frame did all of the plant types studied experience the greatest increase in growth rate?

F. 0-2 weeks
G. 2-4 weeks
H. 4-6 weeks
J. Cannot be determined from the given information.

2. A plant from which climate type was NOT studied in Experiment 1?

A. Prairie
B. Tropical forest
C. Northern forest
D. All climate types were studied in Experiment 1.

3. Based on the results of Experiment 1, which plant type experienced the most total growth between Week 2 and Week 6?

F. Plant Type 1
G. Plant Type 3
H. Plant Type 4
J. Each plant type experienced the same total growth.

4. Based on the experiments, on the growth of which plant type did the presence of fungi in the soil have the greatest effect?

A. Plant Type 1
B. Plant Type 3
C. Plant Type 4
D. The fungi had the exact same effect on all plant types

5. Based on the results of Experiments 1 and 2, which of the following statements is most accurate?

F. The presence of fungi has little or no impact on plant growth.
G. Removing fungi from soil can help to increase growth in some plants.
H. The presence of certain fungi in the soil increases plant growth.
J. Fungi cannot survive in local greenhouses.