ACT Science Practice Test 53

PASSAGE VI

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.

PASSAGE VII

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.