UNIT 1: THE NATURE OF LIFE

CHAPTER 1: THE SCIENCE OF BIOLOGY

Ms. PetrucciBiology

Chapter 1: The Science of Biology

Vocabulary

Section 1-2: How Scientists Work

• Spontaneous generation• Controlled experiment• Manipulated (Independent) Variable• Responding (Dependant) Variable• Theory

1-2 How Scientists Work• Systematically

Designing an Experiment

1. Make Observations/Ask a Question

2. Research/Form a Hypothesis

3. Set up a Controlled Experiment

4. Record and Analyze Results

5. Draw a conclusion• Communicate Results• Repeat

Set up a Controlled Experiment

• Use only one variable• Control (keep unchanged) all others• Manipulated variable is changed• Responding variable is observed

• Francesco Redi (1668)• Needham (1748)• Lazzaro Spallanzini (1765)• Louis Pasteur (1800's)

Variables• Dependent Variable

• Independent Variable

Redi’s Experiment• Spontaneous Generation

Needham’s Experiment• Spontaneous generation can occur under the right

conditions. Was Redi wrong!?

• 1765

• Nonliving Gravy does not produce living things.

• New organisms are produced only by existing organisms

• 1861

• Fixed the “no air” claim of Needham.

• Some flasks still sterile today.

Disproved Spontaneous Generation!

Life can only come from other life.

Three Experiments

Practice the Scientific Method

• Think about how you would test how the amount of a certain fertilizer determines if the fertilizer would grow taller plants.

Brainstorm• Decide how you would go about conducting an

experiment or investigation to study this.

• Identify the Dependant Variable and the Independent Variable

• I will provide you results

Data

Does more fertilizer = better growth?

Analyze these results.

What if you Cannot Experiment?• When might an experiment not be possible?• How can we answer scientific questions without

experimentation?Human Studies

Field Studies

Obs

erva

tiona

l Stu

dies

Models

What is a Theory??