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Unit 1 Chapter 1 & 2. What is Science??. What is the goal of science?. Investigate. explain. predictions. understand. Science: an organized method Uses evidence to explain event Collects and organizes information Deals only with natural world

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Unit 1

Chapter 1 & 2

What is Science??

What is the goal of science?





  • Science:

  • an organized method

  • Uses evidence to explain event

  • Collects and organizes information

  • Deals only with natural world

  • Looks for patterns and connections

  • Scientists:

  • Propose explanations that can be tested

  • by examining evidence

  • Because of new tools, techniques and

  • discoveries, our (scientists) understanding

  • of science is always changing

It is essential that we have an understanding

of science to make intelligent decisions about

a wide variety of issues that affect our lives.




Stem cell research

Heart disease


  • Thinking like a scientist:

  • During this course you will be developing

  • your skills to think like a scientist.

  • Using the scientific method

  • 1. Identify a problem or question

  • 2. Set up observations

  • 3. Develop a hypothesis

  • 4. Conduct experiments

  • 5. Coming to a conclusion

There are several vocabulary words that must be

understood before we can begin as scientists--


information gathered from observations

Quantitative: Numbers



logical interpretation based on prior

knowledge or experience

  • Observation:

  • Using the senses to study the world

  • Using tools to collect measurements

  • Examining previous research results

  • Hypothesis:

  • proposed scientific explanation for a set of observations.

  • Using prior knowledge


is an ongoing process!!!!!!!

How do scientists work?

How do scientists test hypothesis?

How does a scientific theory develop?


  • Greek philosopher Aristotle

  • extensive observations of the natural world.

  • Explained observations through reasoning

  • After Aristotle:

  • Living things = different rules = nonliving things

  • Forces = living things from nonliving things

About 400 years ago these established ideas began

being challenged

Have you ever wondered where the maggots came

from that are lurking in your trash can?

The maggots seem to suddenly appear out of nowhere!!

To find out you will need to

conduct a scientific investigation--

  • ask questions

  • form a hypothesis

  • set up a controlled experiment

  • record and analyze results

  • draw a conclusion

  • Ask 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

    • Spontaneous generationwas one early hypothesis or the idea that life could come from nonliving matter.

    • For example, most people thought that maggots spontaneously appeared on meat.

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

Setting Up a Controlled experiment

An hypothesis should be tested by an experiment in which

only one variable is changed at a time.

All other variables should be kept unchanged or controlled.

Factors in an experiment that can change are called



equipment used, type of material, amount of

material, temperature, light and time

The variable that is deliberately changed is called the manipulated variable.

The variable that is observed

and changes in response

to the manipulated variable

is called the

responding variable.

Redi’s Experiment

Redi’s Experiment

Redi’s Experiment

  • Recording and Analyzing Results

    • Scientists keep written records of their observations, or data.

    • Sometimes drawings are used to record certain kinds of observations.

Today, researchers use computers to record their work.

Online storage makes it easier for researchers to review the data.

  • Drawing a Conclusion

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

    • Redi’s results supported the hypothesis that maggots were produced by flies, not spontaneous generation.

Repeating Investigations

Scientists repeat experiments to be

sure that the results match those already obtained.

  • Needham challenged Redi’s results by claiming that spontaneous generation could occur under the right conditions.

Needham’s Test of Redi’s Findings

  • Needham sealed a bottle of gravy and heated it.

  • After several days, the gravy was swarming with microorganisms.

  • Needham concluded that these organisms came from the gravy by spontaneous generation.


Gravy was not hot enough

Designed a flask

Spallanzani's Test of Redi's Findings

Gravy is boiled.

Gravy is boiled.

Spallanzani's Test of Redi's Findings

Flask is open.

Flask is sealed.

Spallanzani's Test of Redi's Findings

Gravy is teemingwith microorganisms.

Gravy is free ofmicroorganisms.

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.

The Impact of Pasteur’s Work

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

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

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

When Experiments Are Not Possible

  • It is not always possible to do an experiment to test a hypothesis.

  • Example:

    • Wild animals must be observed without disturbing them.

    • Ethical considerations prevent some experiments.

  • By carefully planning alternative investigations, scientists can discover reliable patterns that add to scientific understanding.

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.

No theory is considered absolute truth.

As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation.