Biology Now, 2e

Caves of Death ■ 13

Scientific fact should not be confused with

scientific theory. Outside of science, people often

use the word “theory” to mean an unproven expla-

nation. In science, a theory is a hypothesis, or a

group of related hypotheses, that has received

substantial confirmation through diverse lines of

investigation by independent researchers. Scien-

tific theories have such a high level of certainty

that we base our everyday actions on them. For

example, the germ theory of disease, formally

verified by Robert Koch in 1890, is the basis for

treating infections and maintaining hygiene in

the modern world (Figure 1.8).

Fact: Bats

with white

noses have

been observed

in the wild.

Pseudogymnoascus

destructans is the

fungus responsible for

white-nose syndrome in

bats.

Tomato blight is caused

by the fungus

Phytophthora infestans.

Frog populations

worldwide have been

decimated by the fungus

Batrachochytrium

dendrobatidis, or Bd.

Hypothesis: A

fungal infection

is responsible

for the spread

of white-nose

syndrome and

is associated

with higher

mortality across

bat populations

and species.

1

2

Theory:

Specific

pathogens

(“germs”)

are directly

responsible

for specific

diseases

and

conditions

(germ

theory of

disease).

3

Figure 1.8

Facts, hypotheses, and theories

It is important to distinguish among facts, hypotheses, and theories when thinking and talking about science.

Q1: Give one fact about bats that you learned from this chapter.

Q2: What is another example of evidence for the germ theory of disease? (Hint: Think about human diseases.)

Q3: Explain in your own words the difference between a fact and a hypothesis, and between a hypothesis and a theory.

No End in Sight

According to the U.S. Fish and Wildlife Service,

white-nose syndrome has killed more than

6 million bats across the United States since

2007 and shows no signs of slowing. As of

this writing, the disease has spread to 29 U.S.

states and 5 Canadian provinces. In March

2016, hikers found a bat in Washington State

with WNS, and Rhode Island’s first case was

confirmed two months later. Almost all species

of bats that hibernate in these regions have

been affected, including little brown bats and