1. Biology 112 Chapter 1 Overview (Accompanies GR Chap1)
Holyoke Walsh

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The goal of science is to:
investigate and understand the natural world.
explain events in the natural world.
use those explanations to make useful predictions.
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1-2 How Scientists Work
Scientists make educated guesses about how things work the way they do. These are called HYPOTHESIS.
How do scientists test hypotheses?
A hypothesis should be tested by an experiment in which only one variable is changed at a time.
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Asking a Question
Many years ago, people wanted to know how living things came into existence. They asked:
How do organisms come into being?
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Forming a Hypothesis
One early hypothesis was spontaneous generation aka: abiogenesis.
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.
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Setting Up a Controlled Experiment
manipulated variable (independent)
responding variable (dependent)
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Redi’s Experiment
Uncovered jars
Covered jars
Controlled Variables:
jars, type of meat,
Location, temperature,
time
In a controlled experiment, only one variable is tested at a time. Redi designed an experiment to determine what caused the sudden appearance of maggots. In his experiment, the manipulated variable was the presence or absence of the gauze covering. The results of this experiment helped disprove the hypothesis of spontaneous generation.
What do you think are the manipulated and responding variables in this experiment??
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Redi’s Experiment
Manipulated Variable:
Gauze covering that keeps flies away from meat
Several days pass.
Responding Variable:
whether maggots appear
Maggots appear.
No maggots appear.
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Drawing a Conclusion
Scientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion.
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10. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Gravy is boiled.
Gravy is boiled.
Spallanzani’s experiment showed that microorganisms will not grow in boiled gravy that has been sealed but will grow in boiled gravy that is left open to the air. Interpreting Graphics What variable was controlled in this experiment?
Which variables are controlled??
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11. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Flask is open.
Flask is sealed.
Is the flask the manipulated or responding variable??
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12. Repeating Investigations
Spallanzani's Test of Redi's Findings 
Gravy is teeming with microorganisms.
Gravy is free of microorganisms.
Helped prove the theory of BIOGENESIS!!!! Living things come from other living things!
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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.
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Pasteur’s Experiment
Broth is free of microorganisms for a year.
Curved neck is removed.
Broth is teeming with microorganisms.
Pasteur’s experiment showed that boiled broth would remain free of microorganisms even if air was allowed in, as long as dust and other particles were kept out.
Broth is boiled
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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.
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16. Scientific Method Summary
Ask questions, make observations
Gather information
Form a hypothesis (educated guess)
Set up a controlled experiment
Manipulated variable - the variable that is deliberately changed (aka independent variable) Responding variable is variable that is observed (aka dependent variable)
5)Record and analyze results
6)Draw a conclusion
7)Repeat & share findings

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1-3 Studying Life
Photo Credit: © Andrew Syred/Science Photo Library/Photo Researchers, Inc.
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18. What are some characteristics of living things?
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Living things share the following characteristics:
*REFERENCE PAGE – pages 16/17 of student text!!
1. made up of units called cells – smallest unit of life considered to be “alive”
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20. Characteristics of Living Things
Reproduction

21. Characteristics of Living Things
3. Universal genetic code
Genetic code is common, with minor variations, to every organism on Earth.
That information, carried in DNA, is copied and passed from parents to offspring

22. Characteristics of Living Things
4. Grow & Develop

23. Characteristics of Living Things
5. obtain and use materials and energy

24. Characteristics of Living Things
6. respond to their environment

25. Characteristics of Living Things
7. Maintain a stable internal environment (called homeostasis)

26. Characteristics of Living Things
8. change over time