Adapted from Holt Biology 2008
Observation
The process of obtaining information by using the senses; the information obtained by using the
senses.
Adapted from Holt Biology 2008
Hypothesis
A testable idea or explanation that leads to scientific investigation.
A possible explanation that can be tested by
observation or experimentation.
Hypotheses are not guesses.
Adapted from Holt Biology 2008
Theory
A system of ideas that explains many related
observations and is supported by a large
body of evidence acquired through
scientific investigation.
Hypothesis or Theory?
In everyday language, there is little difference between a hypothesis and a theory. But in science, the meanings
of these words are more distinct. A hypothesis is a specific, testable prediction for a limited set of
conditions. A theory is a general explanation for a broad range of data. A theory can include hypotheses
that have been tested and can also be used to generate new hypotheses. The strongest scientific theories
explain the broadest range of data and incorporate many well-tested hypotheses.
Adapted from Holt Biology 2008
Experiment
A procedure that is carried out under
controlled conditions to discover,
demonstrate, or test a fact, hypothesis,
theory, or general truth.
Adapted from Holt Biology 2008
Control Group
In an experiment, a group that serves as a
standard of comparison with another group to which the control group is identical
except for one fact.
Adapted from Holt Biology 2008
Variable
An element, feature, or factor that is liable
to vary or change.
Adapted from Holt Biology 2008
Controlled Experiments
A procedure that tests one factor at a time
and that uses a control group and an experimental group.
Adapted from Holt Biology 2008
Experimental Group
Identical to the control group except for one
factor, or variable.
Adapted from Holt Biology 2008
Independent Variable
The single factor that scientists change in an
experiment.
Adapted from Holt Biology 2008
Dependent Variable
Factors that may change in response to
the independent variable.
Beginning a Scientific Investigation
Most scientific investigations begin with observations
that lead to questions.
Adapted from Holt Biology 2008
Beginning a Scientific Investigation
Observation is the act of noting or
perceiving objects or events using the
senses.
Adapted from Holt Biology 2008
Adapted from Holt Biology 2008
YOUR TURN
With a partner, read the Chapter 1 Section 2 Active Reading – Scientific Methods
1st - Take turns reading the questions aloud to each other, alternating questions.
2nd - Take turns reading the selection aloud to each other, alternating sentences or paragraphs.
Adapted from Holt Biology 2008 Adapted from Holt Biology 2008
YOUR TURN
As you read discuss the content.
Reread and discuss each question. Write down the best answer to the question using full descriptive sentences.
• Be prepared to share your ideas with the class.
Adapted from Holt Biology 2008
2
Beginning a Scientific Investigation
To answer a question, scientists
first formulate a hypothesis that
leads to scientific investigation.
Adapted from Holt Biology 2008
Beginning a Scientific Investigation
A hypothesis is a possible explanation
that can be tested by observation or experimentation.
Adapted from Holt Biology 2008
Scientific Experiments
An experiment is a procedure that is carried out under
controlled conditions to test a
hypothesis.
Adapted from Holt Biology 2008
Scientific Experiments
A controlled experiment tests
one factor at a time and uses a control
group and an experimental group.
Adapted from Holt Biology 2008
Control Group
A control group is a group that serves as
a standard for comparison in an
experiment.
Adapted from Holt Biology 2008
Experimental Groups
The experimental groups are identical to the control group
except for one factor, called a
variable.
Adapted from Holt Biology 2008
Independent Variable
The single factor that scientists change in an
experiment is called the independent
variable.
Adapted from Holt Biology 2008
Scientific Experiments
Factors that may change in response to the independent variable are called
dependent variables.
Adapted from Holt Biology 2008
Scientific Experiments
Scientists analyze changes to the
dependent variables in order to
understand how the independent
variable affects the system that they are
studying.
Adapted from Holt Biology 2008
Scientific Experiments
There are often cases in which
experiments are not possible or not
ethical.
Adapted from Holt Biology 2008
Scientific Experiments
In a study, researchers gather
data about a system by making
observations rather than by
manipulating independent
variables. Adapted from Holt Biology 2008
Scientific Experiments
After conducting an experiment,
researchers analyze their results to learn whether the results
support their hypothesis or not.
Adapted from Holt Biology 2008
Scientific Experiments
Scientists draw conclusions that
explain the results of their
experiments.
Adapted from Holt Biology 2008
Scientific Experiments
Scientists verify their conclusions by
conducting their experiments many
times and by checking to see if
other scientists have found similar
results. Adapted from Holt Biology 2008
Bias
Every person has his or her own point of view. A particular
point of view is called a bias.
Adapted from Holt Biology 2008
Bias
Scientists try to prevent bias from
affecting their work, but bias can still
influence an experiment.
Adapted from Holt Biology 2008
Bias
Sources of funding, personal
involvement in a product, and other conflicts of interest
can affect an experiment.
Adapted from Holt Biology 2008
Scientific Experiments
It is wise to view all scientific claims in their context and think critically about
them.
Adapted from Holt Biology 2008
Scientific Theories
In science, a theory is a system that explains many
related observations and is
supported by a large body of
evidence.
Adapted from Holt Biology 2008
Scientific Theories
The main difference between a theory and a hypothesis is that a
hypothesis is a specific, testable prediction for
a limited set of conditions and a
theory is a general explanation for a
broad range of data. Adapted from Holt Biology 2008
Scientific Theories
Constructing a theory often
involves considering contrasting ideas
and conflicting hypotheses.
Adapted from Holt Biology 2008
Scientific Theories
If the results of a scientific
experiment can be reproduced many
times, the research may help
develop a new theory.
Adapted from Holt Biology 2008
Scientific Theories
Future research may cause a theory to be
revised or even rejected.
Adapted from Holt Biology 2008
Scientific Theories
By investigating and challenging
theories, scientific understanding
grows.
Adapted from Holt Biology 2008
Hypothesis or Theory?
In everyday language, there is little difference between a hypothesis and a theory. But in science, the meanings
of these words are more distinct. A hypothesis is a specific, testable prediction for a limited set of
conditions. A theory is a general explanation for a broad range of data. A theory can include hypotheses
that have been tested and can also be used to generate new hypotheses. The strongest scientific theories
explain the broadest range of data and incorporate many well-tested hypotheses.
Think, Share, Write #2
How does the scientific use of the word theory differ from how it is
used by the general public?
Think, Share, Write #2
How does the scientific use of the word theory differ from how it is
used by the general public?
Answer
Summary
Most scientific investigations begin
with observations that lead to questions.
Adapted from Holt Biology 2008
Summary
Scientists can conduct controlled experiments and perform studies in
order to test a hypothesis.
Adapted from Holt Biology 2008
Summary
The main difference between a theory and a hypothesis is that a
hypothesis is a specific, testable prediction for a
limited set of conditions, while a theory is a general explanation for a
broad range of data. Adapted from Holt Biology 2008
Section Review
1. Summarize the processes that scientists often use when beginning scientific investigations.
Section Review Critical Thinking
4. Analyzing Methods Provide one example of a case in which an experiment would not be possible and one example in which an experiment would not be ethical.
Section Review Critical Thinking
5. Forming Hypotheses - A friend notices that her dog is getting thinner even though she has not changed how much she feeds him. Propose three testable hypotheses to explain the dog’s weight loss.