ACT Reading Practice Test 98: NATURAL SCIENCE

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.


NATURAL SCIENCE: This passage is adapted from the article "Swarm Savvy" by Susan Milius (©2009 by Society for Science & the Public).

Only a few millimeters long, rock ants (Temnotho-
?rax albipennis) prove difficult to track in the wild but
excellent for the tabletop world of the laboratory.

When something terrible happens to a rock ant
5home, such as a researcher lifting off the roof, the
majority of ants cluster in the ruins. A quarter to a third
of the colony scurries out looking for new possibilities.

"I think of the ants as a sort of search engine," ant
biologist Nigel Franks says. In one set of tests, he and
10his students disrupted a nest and watched to see what
the ants would make of a series of new possibilities that
improved with distance. The best nest was almost three
meters distant, nine times as far from the original home
as a nearby but less appealing choice. "It was just such
15fun doing this experiment because the ants won,"
Franks says.

In spite of the epic distances, the ants typically
found and agreed to move into the best nest. "They're
fantastic at it," Franks says.

20Franks and Elva Robinson, both of the University
of Bristol, monitored rock ants by fitting them with
radio-frequency identification tags. The data suggest
that each scout follows a simpler rule than previously
thought, Robinson, Franks and their colleagues
25reported online in Proceedings of the Royal society B.

Instead of making direct comparisons between
sites, a scout follows a threshold rule. If she finds a
poor site, she keeps searching. When she finds a site
that exceeds her "good enough" threshold, she returns
30to the original nest

Next, previous work shows, the scout recruits a
new scout to join her on a trek to the good site. She
dashes around tapping her antennae on other ants and
releasing a pheromone from her sting gland, explains
35Stephen Pratt of Arizona State University in Tempe.
Usually she finds a volunteer within a minute or so, and
the two set off tandem running.

Scout A, who knows the way, runs back toward the
nest while her follower, B, jogs closely enough to tap
40antennae against the leader. Should A sprint a little too
fast and dash beyond antennae range, she slows until
her partner catches up. Periodically the two ants stop,
and the newbie looks around as if learning landmarks.
It's a slow way to get to the site, and Franks argues that
45it qualifies as animal teaching.

When the ants do reach the possible site, the
recruit explores it and, depending on her assessment,
returns to recruit yet another scout.

As with bees, it's the quorum of scouts at the sites
50that matters. When enough of them gather at a particu-
lar place to encounter each other at a sufficiently high
rate, they've got a decision.

Once scouts reach that decision, their behavior
changes. Each scout dashes back to the nest, but instead
55of coaxing a nest mate for a tour, she just grabs some-
body. She uses a mouthpart hook, an over-the-shoulder
throw, and off she goes with the passive nest mate
curled on her back in an ant version of the fetal posi-
tion. Carrying takes about a third as long as leading
60would, and scouts can haul the rest of the colony to a
new home within hours. The ants shift from the inde-
pendent info gathering of scouts to group implementa-
tion of the quorum's decision.

Rock ants' willingness to thrive in the lab allows
65experiments on finer points of collective decisions
making, Pratt says. For example, forcing a crisis among
the ants demonstrates that they will, in a pinch, trade
accuracy for speed. When researchers destroy an old
nest so that ants are completely exposed, the ants scope
70and relocate within hours. Other experiments that just
offer the ants a better nest but don't ruin their current
one can result in days of deliberation. Speed has its
costs, and ants in a hurry now and then make mistakes,
such as splitting the colony between two nests. Slower
75moves prove more accurate.

The quorum system could be widespread in group
behavior in nature, Pratt says. Overall it's a beautiful
tool, allowing for carefully balanced independence plus
some shortcut speed. Yet the system "has a dark side,"
80he acknowledges. Once individuals have made their
independent assessments and then a quorum has
reached agreement, fellows copy the quorum behavior.
The chances are low that the whole quorum will reach
the same wrong decision. But flukes can happen. In
85most uses of a quorum, "it's going to make a decision
more accurate," he says, "but it also slightly increases
the incidence of these rare events when you get it really
spectacularly wrong."

1. The passage makes clear that a main objective of the research of Franks and Robinson was to:

A. determine the properties of rock ant scouts' pheromones.
B. destroy rock ant habitats in the laboratory.
C. observe the behavior of rock ant scouts in the wild.
D. study the decision making of rock ant scouts.

2. In the passage, Franks reacts to his findings regarding the behavior of rock ants with what could best be described as:

F. frustration and impatience.
G. surprise and confusion.
H. concern and empathy.
J. amusement and admiration.

3. Based on the passage, an example of rock ants working as "a sort of search engine" (line 8) would be:

A. a colony selecting one scout ant to find the best site for a new nest.
B. a third of a colony deciding to nest at a nearby but somewhat deficient site.
C. several ants bypassing a poor nest site for the pur-pose of finding a better site.
D. individual ants leading nest mates one by one to a new nest.

4. The passage suggests that which action of Scout A most strongly influences Scout B to follow Scout A to a new nest site?

F. Scout A tapping its head against the ground
G. Scout A dashing to and from the new site
H. Scout A releasing a pheromone
J. Scout A rejecting a poor site

5. In the passage, Pratt suggests that the dark side of the quorum system is that the remainder of the colony:

A. follows the quorum decision even when the quorum is wrong.
B. is often left behind in the old nest after a quorum decision.
C. sometimes challenges the quorum, leading to a split in the colony.
D. is in danger of not knowing how to reach the new nest.

6. As it is used in line 43, the word newbie most nearly refers to:

F. Scout A.
G. Scout B.
H. either Scout A or Scout B.
J. any ant at the original nest.

7. Based on the passage, if Scout B believes that a site Scout A found is acceptable, what does Scout B do next?

A. Returns to the original nest
B. Taps its antennae on Scout A
C. Begins building at the new site
D. Examines the area surrounding the new site

8. The passage state that the final decision to move a colony to a new site is made by rock ant scouts when:

F. the first scout to approve a new site brings a second ant to the site.
G. there are enough scouts at the site that they encounter each other at a sufficiently high rate
H. at least half of the colony has already relocated to the new site
J. two scouts set off tandem running to a new site and other ants follow

9. The passage suggests that the shortest length of time in which rock ant scouts can move a colony to a new home is:

A. minutes.
B. hours.
C. days.
D. weeks.

10. Compared to their behavior when their current nest is disrupted by researchers, how does the behavior of rock ants differ when their current nest is left intact but they're offered a better nest?

F. They make a decision about where to move collec-tively as opposed to individually.
G. They're not as concerned with the accuracy of their decision to move.
H. They take more time deciding whether to move the colony to the new nest.
J. They split the colony between the current nest and the new nest instead of moving the entire colony