Passage I

Two experiments examined how pH and temperature affect the activity of Amoeba limax (a single-celled eukaryote).

Experiment 1

Twenty identical glass slides were equally divided into 5 groups (Groups 1−5). Each slide was then prepared as follows: First, a drop of water containing a single 1-day-old A. limax was placed on the slide. Next, the water (but not the A. limax) was removed and replaced with a drop of an aqueous solution having a pH of 8.2. Then, a glass cover slip was placed over the drop, and paraffin (a type of wax) was used to seal the edges of the cover slip.

Each of the Group 1 slides was incubated at a temperature of 0°C. During incubation, the movement of the A. limax on each slide was observed for 30 min, and the total distance traveled (TDT) by the A. limax over the 30 min was recorded. The average TDT for Group 1 was then determined.

The procedure for Group 1 was repeated for each ofGroups 2−5, except that each group was kept at a different

incubation temperature.

The results are shown in Table 1.

Table 1 adapted from C. F. A. Pantin, “On the Physiology of Amoeboid Movement II.—The Effect of Temperature.” ©1924 by The Company of Biologists Ltd.

Experiment 2

Twenty more of the slides were equally divided into 5 groups (Groups 6−10). Each slide was prepared as in Experiment 1, except that for each group, the aqueous solution had a different pH (see Table 2).

Each of the Group 6 slides was incubated at a temperature of 10°C. During incubation, the movement of the A. limax on each slide was observed for 30 min, and the TDT by the A. limax over the 30 min was recorded. The average TDT for Group 6 was then determined. The procedure for Group 6 was repeated for each of Groups 7−10.

The results are shown in Table 2.

Table 2 adapted from C. F. A. Pantin, “On the Physiology of Amoeboid Movement III.—The Action of Calcium.” ©1926 by The Company of Biologists Ltd.