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
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
1.4 What Is Science?
The scientific method is an important tool of scientific inquiry The scientific method consists of six interrelated elements
ObservationQuestionHypothesisPredictionExperimentConclusion
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
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
1.4 What Is Science?
The six steps of scientific inquiry (continued)
4. The hypothesis leads to a prediction, which isthe expected outcome of testing if the hypothesis is correct
5. The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments
6. The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion
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
Figure E1-1 The experiment of Francesco Redi illustrates the scientific method
Observation:
Question:
Hypothesis:
Prediction:
Experiment:
Conclusion:
Experimental variable:
Controlled variables:
Experimental situationControl situation
Results
Leave the jaruncovered
Leave exposedfor several days
Flies swarm aroundand maggots appear
Cover the jarwith gauze
Leave coveredfor several days
Flies are kept fromthe meat;
no maggots appear
gauze prevents theentry of flies
time, temperature,place
Obtain identical pieces of meat and two identical jars
Place meat in each jar
IF the hypothesis is correct, THEN keeping the flies away from the meatwill prevent the appearance of maggots.
The experiment supports the hypothesis that flies are the source ofmaggots and that spontaneous generation of maggots does not occur.
Flies swarm around meat left in the open; maggots appear on the meat.
Where do maggots on the meat come from?
Flies produce the maggots.
Figure E1-2 The experiment of Malte AnderssonObservation:
Question:
Hypothesis:
Prediction:
Experiment:
Conclusion:
Experimentalvariable:
Controlledvariables:
Experimental groupsControl groups
Results
Do notchange the tail
Release the males,wait a week,
count the nests
Average ofabout one nest
per male
Male widowbirds have extremely long tails.
Why do males, but not females, have such long tails?
Males have long tails because females prefer to mate with long-tailed males.
IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates.
Divide male birdsinto four groups
Manipulate thetails of the males
length of tail
location, season,time, weather
Cut the tail andre-glue in place
Release the males,wait a week,
count the nests
Average ofabout one nest
per male
Cut the tail to half ofthe original length
Release the males,wait a week,
count the nests
Average of lessthan half a nest
per male
Add feathers todouble the tail length
Release the males,wait a week,
count the nests
Average ofAbout two nests
per male
The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to matewith short-tailed males) is supported.
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
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
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
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
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
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
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
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
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