ACT Science Practice Test 105

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.


The common grackle is one of the most abundant species of bird in North America. When two male grackles encounter each other, there is often a threat display (a loud, abrasive call). The dominant male usually forces the submissive male to cower and eventually fly away. A biologist conducted two experiments to determine the rank in aggression in male grackles. In the experiments described below, five adult male birds were placed together in a cage and their interactions were observed and recorded.

Experiment 1

To determine what factors might affect aggressiveness, the biologists recorded the sequence in which the birds were placed in the cage, their weight, their ages, and the number of calls each grackle made during the experiment. In addition, the birds were ranked according to their aggressiveness toward each other, from most aggressive (1) to least aggressive (5). The results are shown in Table 1.

Experiment 2

The male grackles were placed back into the cage in the same sequence as in Experiment 1. The results of all aggressive encounters (number of calls) between pairs of birds were recorded. A bird was declared a "winner" if it forced the other bird, the "loser," to flee from the encounter. Table 2 shows the results of the interactions between the birds. There were no draws (ties) observed.

Table 3 summarizes the results of all the encounters for each bird.

1. Which of the following generalizations about the relationship between body weight and rank is consistent with the experimental results?

F. The heaviest bird will be the most dominant.
G. The heaviest bird will be the most submissive.
H. Body weight has no effect on rank.
J. The lightest bird will be the most dominant.

2. It was suggested that the more dominant a male grackle is, the more likely it is to mate. Accordingly, one would predict, based on win-loss records, that the grackle with the highest likelihood of mating would be:

A. Grackle B.
B. Grackle D.
C. Grackle C.
D. Grackle A.

3. A sixth grackle, whose body weight was 330 grams and whose age was 24 months, was added to the experimental cage. It was observed that the bird called a total of 10 times during the experiment. Based on the results of Experiment 1, what would be the rank of the sixth grackle in terms of its aggressiveness?

F. 3
G. 4
H. 5
J. 6

4. According to the results of Experiments 1 and 2, which of the following factors is (are) related to the dominance of one male grackle over other males?

I. Age

II. Body weight

III. Number of calls

A. I and II only
B. I and III only
C. II only
D. III only

5. One can conclude from the results of Experiment 2 that Grackle C and Grackle A had a total of how many encounters with each other?

F. 5
G. 20
H. 25
J. 30

6. A criticism of this study is that the order that the grackles were placed in the cage may have affected the aggressiveness of each bird. The best way to refute this criticism would be to:

A. randomize the order before starting the experiments.
B. repeat the experiments several times with different orders each time.
C. place the birds in the cage in order of their age.
D. place the birds in the cage in order of their weight.