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Biology Chapter 1 Section 2 How Science Works

Miller Levine Dragonfly Book
by

Mark Meredith

on 25 August 2013

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Transcript of Biology Chapter 1 Section 2 How Science Works

END OF SECTION
A well-tested explanation that unifies a broad range of observations is a
hypothesis.
variable.
control.
theory.
1–2
The mistaken belief that living organisms can arise from nonliving matter is called
biogenesis.
Pasteur's theory.
spontaneous generation.
Spallanzani’s hypothesis.
1–2
In an experiment, the variable that is deliberately changed is called the
control.
independent variable.
dependent variable.
constant.
1–2
Major Theories in Biology

Germ Theory of Disease
Evolutionary Theory
Cell Theory
Gene Theory of Inheritence
Scientific Theory
How a Theory Develops

As
evidence
from numerous investigations builds up, a hypothesis may become so well supported that scientists consider it a theory.

In science, the word theory applies to a well-tested explanation that unifies a broad range of observations.
The Impact of Pasteur’s Work

Pasteur saved the French wine industry, which was troubled by unexplained souring of wine.

He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms.
Repeating Investigations
Pasteur's Test of Spontaneous Generation

Louis Pasteur conclusively disproved the hypothesis of spontaneous generation.
Pasteur showed that all living things come from other living things.
Repeating Investigations
Setting Up a Controlled Experiment

Independent Variable
(manipulated variable)

Dependent Variable
(responding variable)

One early hypothesis was
spontaneous generation
.

For example, maggots on meat
In 1668, Redi proposed a different hypothesis: that maggots came from eggs that flies laid on meat.

The process of testing a hypothesis includes:
Asking a question
Forming a hypothesis
Setting up a controlled experiment
Recording and analyzing results
Drawing a conclusion
Designing an Experiment

How do scientists test hypotheses?

A hypothesis should be tested by an experiment in which only one variable is changed at a time.
Designing an Experiment
1-2 How Science Works
A scientific explanation does not become a theory until
a majority of scientists agree with it.
it has been supported by evidence from numerous investigations and observations.
it is first proposed as an explanation.
it is published in a textbook.
1–2
Which of the following was the manipulated variable in Redi’s experiment?
the kind of meat used
the temperature the jars were kept at
the gauze covering on some jars
the kind of fly that visited the jars
1–2
Pasteur’s Experiment
Repeating Investigations
Gravy is free of microorganisms.
Gravy is teeming with microorganisms.
Spallanzani's Test of Redi's Findings 
Repeating Investigations
Gravy is boiled.
Gravy is boiled.
Spallanzani's Test of Redi's Findings 
Repeating Investigations
Drawing a
Conclusion

Scientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion.
Uncovered jars
Covered jars
Controlled Variables:
jars, type of meat,
Location, temperature,
time
Redi’s Experiment
Asking a Question

Many years ago, people wanted to know how living things came into existence. They asked:

How do organisms come into being?
How does a scientific theory develop?
Flask is sealed.
Flask is open.
Full transcript