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Biology

Chapter 1: Section 2

What is maggot therapy?

Where did people think life came from?

How do scientists test hypotheses?

Whenever possible, a hypothesis should be tested by an experiment in which only ______

variable is changed at a time. All other variables should be kept ___________, or controlled.

Designing an Experiment

The process of testing a hypothesis includes:

Asking a _________________ Forming a _____________________

Setting up a _____________________ experiment

________________ and _________________ results

Drawing a _______________________

Asking a Question

Many years ago, people wanted to know how living things came into existence. They asked:How do organisms come into being?

Forming a Hypothesis Redis experiments

One early hypothesis was_________________________________, or the idea that life could come

from _________________________ matter. For example, most people thought that maggots

_______________________ appeared on meat.In 1668, __________ proposed a different _______________: that maggots came from eggs that

flies laid on meat.

Setting Up a Controlled ExperimentThe variable that is deliberately changed is called the_____________________variable.

(Independent Variable) This is the _________.

The variable that is observed and that changes in _________________ to the manipulated variableis called the______________________variable. (Dependent Variable) This is the __________

Recording and Analyzing Results

Scientists keep written ________________ of their observations, or ___________.

Sometimes _____________________ are used to record certain kinds of observations.

Drawing a Conclusion

Scientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion.

Redis results supported the hypothesis that maggots were produced by _________, not

_____________________ ________________________

Repeating Investigations

Scientists repeat experiments to be sure that the results match those already obtained.

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Needham's Test of Redi's Findings

Needham challenged Redis _______________ by claiming that spontaneous generation________________ occur under the right conditions.

Needhams Test of Redis Findings

Needham _____________ a bottle of gravy and ____________ it.

After several days, the gravy was swarming with _____________________

Needham concluded that these organisms came from the gravy by

______________________ _______________________

Spallanzani's Test of Redi's Findings

.

Spallanzanits was questioning whether microorganisms did come from boiled gray. He thoughtthat Needham didnt ______________ the gravy long enough.

Pasteur's Test of Spontaneous Generation

Louis Pasteur conclusively _______________ the hypothesis of

______________________ ____________________.

Pasteur showed that _______ living things come from other_________________ things.

The Impact of Pasteurs Work

Pasteur saved the French _______________ industry, which was troubled by unexplained souringof wine.

He saved the ____________ industry, which was endangered by a silkworm disease.

He began to uncover the nature of infectious diseases, showing that they were the result ofmicroorganisms.

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When Experiments Are Not Possible

It is not always possible to do an ______________ to test a hypothesis. For example: Wild animals must be _____________ without disturbing them.

__________________ considerations prevent some experiments.

By carefully planning alternative investigations, scientists can discover reliable _______________that add to scientific understanding.

How a Theory DevelopsAs ___________________ from numerous investigations builds up, a hypothesis may become sowell supported that scientists consider it a theory.

In science, the word theory applies to a _______________________ explanation that unifies a

broad range of observations.

No theory is considered absolute truth.

As new evidence is uncovered, a theory may be __________________ or __________________

by a more useful explanation.

Scientific QUIZ

1. In an experiment, the variable that is deliberately changed is called the

a. control.

b. manipulated variable.c. responding variable.

d. constant control.

2. The mistaken belief that living organisms can arise from nonliving matter is called

a. biogenesis.

b. Pasteur's theory.c. spontaneous generation.

d. Spallanzanis hypothesis.

3. Which of the following was the manipulated variable in Redis experiment?a. the kind of meat used

b. the temperature the jars were kept at

c. the gauze covering on some jarsd. the kind of fly that visited the jars

4. A well-tested explanation that unifies a broad range of observations is a

a. hypothesis.b. variable.

c. control.

d. theory.

5. A scientific explanation does not become a theory untila. a majority of scientists agree with it.

b. it has been supported by evidence from numerous investigations and

observations.c. it is first proposed as an explanation.

d. it is published in a textbook.

END OF SECTION