Chapter 1: The Science of Biology

Science

• What is science?– An organized way of using evidence to learn

about the natural world

• What is the goal of science?– To investigate and understand the natural world,

to explain events in the natural world, and to use those explanations to make useful predictions

Science• Science is an ongoing

process and is ever changing

• New techniques, technology, and discoveries are constantly being developed and allow us to bring more understanding to our natural world

• What are some ways that science has changed?

The Scientific Method

Steps1. Observation (form question)2. Hypothesis3. Make a prediction4. Controlled Experiment (Repeat,

Repeat, Repeat)5. Analyze Data6. Conclusion7. Share Data

The Scientific Method

• Observation: The first step in the scientific method

• What is an observation?– Use of one or more of the senses to

gather information

• Look around the classroom and make an observation

• The information that you gather in your observations is data

The Scientific Method

• 2 Types of Data– Quantitative Data- expressed in numbers

by counting or measuring– Qualitative Data- are descriptive and

involve characteristics and cannot be counted

• Quantitative Data is easier to analyze because it is less objective

The Scientific Method

• After observations a question is formed• That question leads to the formation of

a hypothesis – A hypothesis is a proposed scientific

explanation for a set of observations

• Scenario: You are at the grocery store and the woman in front of you is buying diapers and baby food– Observation?– Hypothesis?

The Scientific Method• People used to think things arose by

Spontaneous Generation (life came from nonliving things).

• Forming a Hypothesis– Use prior knowledge– Use logical inference– Use informed, creative imagination

• There can be several hypotheses for a set of observations

• Written as an “If… then…” statement• A hypothesis is not valid if it cannot be tested

somehow– Controlled experiments– Gathering more data

1.2 How Scientists Work

• The Scientific Method (cont.)– After the hypothesis, you need

to test it with an experiment– Experiment

•A procedure that tests the hypothesis

The Scientific Method

• A good VALID experiment will have ONE variable

• A variable – factor in the experiment that is factor in the experiment that is

being testedbeing tested

Scientific Method - Controls Scientific Method - Controls and Variablesand Variables

Scientific Experiments Scientific Experiments Follow RulesFollow Rules..

• An experimenter changes one factor and observes or measures what happens.

The Control VariableThe Control Variable

• The experimenter makes a The experimenter makes a special effort to keep special effort to keep other other factors constantfactors constant so that so that they will not effect the they will not effect the outcome.outcome.

• Those factors are called Those factors are called control variables.control variables.

What is the Purpose What is the Purpose of a Control?of a Control?

• Controls are NOT being tested• Controls are used for

COMPARISON

Other Variables

• The factor that is changed is known as the independent variable.

• The factor that is measured or observed is called the dependent variable.

Example of Controls Example of Controls & Variables& Variables• For example, suppose you want to figure

out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one.

• Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the What are the Variables in Your Variables in Your Experiment?Experiment?

• Varying the route is the Varying the route is the independent variableindependent variable

• The time it takes is the The time it takes is the dependent variabledependent variable

• Keeping the same walker Keeping the same walker throughout makes the walker throughout makes the walker a a control variable.control variable.

One more thing… it is

best to make several trials with each independent variable.

The Scientific Method

• After the experiment, data is analyzed, then a conclusion is drawn, and findings are reported

The Scientific Method

• Summary• Observation --> Hypothesis -->Making

predictions --> Designing a controlled experiment (repeat, repeat, repeat) --> Analyze data --> Draw conclusions Report Findings

The Scientific Method

• What if a controlled experiment cannot be done?

• What kinds of situations?• Researchers then have to come up with

alternatives: observations, surveys• There are cons to this however

– Bias– Many variables

• They try to eliminate some of these problems by using greater numbers, and factoring in different variables

The Scientific Method

• What is a theory?– A well-tested explanation that unifies a

broad range of observations

• A theory develops only through investigations (not always the same experiments) being tested over and over again

Questions?

• "Time is a great teacher, but unfortunately it kills all its pupils." -- (Louis) Hector Berlioz