Biology Now, 2e

Caves of Death ■ 11

fungus through the air, 18 were put into close

contact with naturally infected bats, and 29

had the fungus applied directly to their wings

(Figure 1.6).

As noted earlier, when scientists test a

prediction of a hypothesis and find it upheld,

the hypothesis is said to be supported. Scien-

tists can be relatively confident in a supported

hypothesis, but they cannot say that the

hypothesis has been proved true. Even well-

established scientific ideas can be overturned if

new evidence against the prevailing view comes

to light. Albert Einstein is famously reported to

have said, “No amount of experimentation can

ever prove me right; a single experiment can

prove me wrong.”

After watching both the control group and

the treatment group, Blehert saw what he had

hypothesized: physical exposure to the fungus

or not exposed. Typically, a researcher obtains

a sufficiently large sample of study subjects and

assigns them randomly to two groups. Random-

ization helps ensure that the two groups are

comparable to start with.

One group, the control group, is main-

tained under a standard set of conditions with

no change in the independent variable. Blehert

had 34 healthy bats in his control group; he

kept these bats in the laboratory, under the

same conditions as the other bats, except for one

difference: he did not expose them to Geomyces

destructans.

The other group, known as the experimen-

tal or treatment group, is maintained under

the same standard set of conditions as the

control group, but the independent variable is

manipulated. Blehert exposed 83 healthy bats

to the fungus. Of these, 36 were exposed to the

34 bats were housed;

none developed WNS.

36 bats were housed in a

separate aviary but the same

laboratory room as WNS-infected

bats, so they shared the same

air; none developed WNS.

29 bats had the

white-nose fungus

applied to their wings;

all 29 developed WNS.

18 bats were housed in

the same aviary as

WNS-infected bats; 16 of

the 18 developed WNS.

Group 1: Group 2:

Contact exposure

Group 3:

Fungus applied to wings

Group 4:

Control group Airborne exposure

Figure 1.6

Blehert’s experimental design

Blehert and his colleagues captured 117 healthy bats and brought them into the laboratory. They divided the bats into control

and treatment groups and observed them for 102 days.

Q1: Which is the control group in this experiment, and what are the three treatment groups?

Q2: What is the hypothesis being tested in this experiment?

Q3: In one or two sentences, state the conclusions you can draw from the experiment. Was the hypothesis supported?

Why or why not?