1. 1.4 What Is Science?
Science is the systematic inquiry – through observation and experiment – into the origins, structure, and behavior of living and nonliving environments

2. 1.4 What Is Science?
Science is based on the principle that all events have natural causes
The belief that some events happen through supernatural forces (e.g., the actions of Greek gods)
The belief that all events can be traced to natural causes that we can comprehend (natural causality)
Corollary: Evidence gathered from nature has not been deliberately distorted to fool us

3. 1.4 What Is Science?
The scientific method is an important tool of scientific inquiry
The scientific method consists of six interrelated elements
Observation
Question
Hypothesis
Prediction
Experiment
Conclusion

4. 1.4 What Is Science?
The scientific method is an important tool of scientific inquiry (continued)
Scientific inquiry is a rigorous method for making observations
The scientific method for inquiry follows six steps

5. 1.4 What Is Science? The six steps of scientific inquiry
1. Observation of a specific phenomenon
2. The observation, in turn, leads to a question
3. The question leads to formulation of a hypothesis, based on previous observations, which is offered as an answer to the question

6. 1.4 What Is Science? The six steps of scientific inquiry (continued)
The hypothesis leads to a prediction, which is the expected outcome of testing if the hypothesis is correct
The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments
The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion

7. 1.4 What Is Science?
Biologists test hypotheses using controlled experiments
Two types of situations are established
A baseline or control situation in which all possible variables are held at a constant
An experimental situation in which one factor, variable, is manipulated to test the hypothesis to determine that this variable is the cause of an observation
Science is useless unless communicated
The scientific method is illustrated by experiments by Francesco Redi and Malte Andersson

8. Obtain identical pieces of meat and two identical jars
Figure E1-1 The experiment of Francesco Redi illustrates the scientific method
Observation:
Flies swarm around meat left in the open; maggots appear on the meat.
Question:
Where do maggots on the meat come from?
Hypothesis:
Flies produce the maggots.
Prediction:
IF the hypothesis is correct, THEN keeping the flies away from the meat
will prevent the appearance of maggots.
Experiment:
Obtain identical pieces of
meat and two identical jars
Place meat
in each jar
Experimental variable:
Leave the jar
uncovered
Cover the jar
with gauze
gauze prevents the
entry of flies
Leave exposed
for several days
Controlled variables:
Leave covered
for several days
time, temperature,
place
Flies swarm around
and maggots appear
Results
Flies are kept from
the meat;
no maggots appear
Control situation
Experimental situation
Conclusion:
The experiment supports the hypothesis that flies are the source of
maggots and that spontaneous generation of maggots does not occur. 8

9. Figure E1-2 The experiment of Malte Andersson
Observation:
Male widowbirds have extremely long tails.
Question:
Why do males, but not females, have such long tails?
Hypothesis:
Males have long tails because females prefer to mate with long-tailed males.
Prediction:
IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates.
Experiment:
Divide male birds
into four groups
Manipulate the
tails of the males
Do not
change the tail
Cut the tail and
re-glue in place
Experimental
variable:
Cut the tail to half of
the original length
Add feathers to
double the tail length
length of tail
Release the males,
wait a week,
count the nests
Release the males,
wait a week,
count the nests
Controlled
variables:
Release the males,
wait a week,
count the nests
Release the males,
wait a week,
count the nests
location, season,
time, weather
Average of
about one nest
per male
Average of
about one nest
per male
Results
Average of less
than half a nest
per male
Average of
About two nests
per male
Control groups
Experimental groups
Conclusion:
The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to mate
with short-tailed males) is supported. 9

10. 1.4 What Is Science? Scientific theories have been thoroughly tested
A scientific theory is a general and reliable explanation of important natural phenomena that has been developed through extensive and reproducible observations and experiments
A scientific theory is best described as a natural law, a basic principle derived from the study of nature, which has never been disproven by scientific inquiry

11. 1.4 What Is Science?
Scientific theories have been thoroughly tested (continued)
The cell theory (that all living organisms are composed of cells) and the theory of evolution are fundamental to the study of biology
Natural causality is the principle that all events can be traced to natural causes
Natural laws apply to every time and place
Scientific inquiry is based on the assumption that people perceive natural events in similar ways

12. 1.4 What Is Science?
Scientific theories have been thoroughly tested (continued)
New scientific evidence may prompt radical revision of existing theory
For example, the discovery of prions

13. 1.4 What Is Science?
Scientific theories have been thoroughly tested (continued)
Before 1980, all known infectious diseases contained DNA or RNA
In 1982, Stanley Prusiner showed that the infectious sheep disease scrapie is caused by a protein (a “protein infectious particle,” or prion)
Prions have since been shown to cause “mad cow disease” and diseases in humans
The willingness of scientists to revise accepted belief in light of new data was critical to understanding and expanding the study of prions

14. 1.4 What Is Science?
Scientific theories involve both inductive and deductive reasoning
Inductive reasoning is used in the development of scientific theories
A generalization is created from many observations that support it and none that contradict it
For example, the theory that Earth exerts gravitational forces on objects began from repeated observations of objects falling downward toward Earth and from no observations of objects falling upward away from Earth

15. 1.4 What Is Science?
Scientific theories involve both inductive and deductive reasoning (continued)
Deductive reasoning is the process of generating hypotheses based on a well-supported generalization (such as a theory)
For example, based on the cell theory, any newly discovered organism would be expected to be composed of cells

16. 1.4 What Is Science?
Scientific theories are formulated in ways that can potentially be disproved
Basic principles of science are referred to as theories because theories can be disproved or falsified
Falsifying theories is distinctly different between scientific theories and faith-based beliefs
“Each creature on Earth was separately created” cannot be subjected to scientific inquiry because it is a belief rooted in faith

17. 1.4 What Is Science? Science is a human endeavor
Human personality traits are part of “real science”
Scientists, like other people, may be driven by pride, ambition, or fear
Scientists sometimes make mistakes
Accidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances

18. 1.4 What Is Science? Science is a human endeavor (continued)
In the 1920s, bacteriologist Alexander Fleming grew bacteria in cultures
One of the bacterial cultures became contaminated with a mold
Fleming was about to destroy the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture

19. 1.4 What Is Science? Science is a human endeavor (continued)
Fleming hypothesized that the mold produced an antibacterial substance
Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin