Unit 1 NotesIntro to Biology,

Experimental Design & The Scientific Method

Scientific Investigation vs Technological Design

• Scientific Investigation – process followed to determine the relationship between the independent and dependent variable described by the hypothesis– Goal is to answer a question, perhaps advance the

knowledge of science• Did using this new fuel help lower pollution?

• Technological Design – process followed to design products or processes to meet specific needs– Goal is to create a specific outcome, perhaps

advance the standard of living in societies• We have created a lower pollution emitting car

Scientific Investigation Technological Design

Identifies a problem – asks a question

Identifies a problem or need

Researches related information

Researches related information

Designs an investigation or experiment

Designs a process or a product

Conducts the investigation or experiment – repeated trials

Implements the design or the process – repeated testing

Analyzes the results Analyzes the results

Evaluates the conclusion – did the results refute or verify the hypothesis

Evaluates the process or product – did it meet the criteria

Communicates the findings Communicates the product or process

Scientific Investigation vs Technological Design

Science and Society

• Ethics – moral principles and values held by humans– What role do ethics play in scientific

research and results?

• Can science answer all questions?• Technology – application of

scientific research to address society’s needs– Can technology solve all problems?

Types of Research

• Two main types– Quantitative (Quantity)

• Uses controlled experiments• Results are numerical data

– Qualitative (Quality)•Descriptive• Relies on observations of situations out of

scientist’s control• Results are descriptions of observations• Often an important tool for wildlife studies

Methods of Biology

• The series of steps used by scientists to gather information and answer questions is called the Scientific Method.

• If you had a question or a problem to solve, what steps would you go through to resolve it?

Scientific Method

•State the Problem– Take note of something no one has seen

before or has yet to explain

Scientific Method

• Gather Information– Observation - Gathering information using your

senses– Information gathered should be:

• Credible - trustworthy• Accurate - correct – based on supported data • Relevant - applicable, related to the topic of the

investigation

– These sources could be • Previous scientific investigations• Science journals• Textbooks• Other credible sources, such as scientifically reliable

internet sites.

Observation vs. Inference

• Inference – making a judgment based upon an observation and past experience

•Make at least 3 observations about this picture.

•Make at least 3 inferences about this picture.

• Make three observations and inferences with this new information

• Does the new information change your responses?

What does this final picture do to your previous inferences?

Scientific Method

•Form a Hypothesis– Create a testable explanation for the

situation that you observed

Scientific Method

•Test the Hypothesis - Experiment– Design an experiment

• An organized procedure for collecting information under controlled conditions

– The experiment will have two groups•Control – all conditions

are kept the same•Experimental – conditions

match that of the control except for the one factor being tested

Scientific Method• Testing…• An important part in the experiment design is

the sample size – the number of test subjects– A large sample size increases the reliability of

results– A large sample size decreases the effect of errors

on the outcome• How could having a larger sample size help

the following experiments?– Tim tested the effect of fertilizer on two plants.

The one with fertilizer grew taller than the one without it.

– Suzy developed a drug to lower cholesterol. She gave it to two patients who later died.

Scientific Method

• Testing…– The condition that is changed in the

experiment is the independent variable – it will be the only thing that can affect the outcome

– The outcome observed is the dependent variable – it depends upon the changes made to the independent variable

– Note: Some experiments cannot be controlled so other observation methods have to be used• Example: wildlife study

Independent vs. Dependent Variables

• Mark the independent (cause) and dependent (effect) variable in each situation

• Suzy wanted to test how changing her diet affected her weight.

• The track team members that ran extra laps at practice ran better times at the next meet.

• Jack planted half of his roses in the shade and the other half in the direct sunlight and measured the differences in plant height and bloom production.

Scientific Method•Record and Analyze Data

– Record Data• Data – information obtained from experiments

– Observations– Results

• Data should be precise and accurate– Precision – the degree to which measurements made in the same way agree with

each other » If you and I measure it, do we get the same thing?

– Accuracy – the degree to which the value measured agrees with the true or accepted value

»Even if we both got the same thing, did we measure it correctly?– Data must then be analyzed or interpreted

• Graphs • Tables• Charts

Tables

• All tables must include the following– Title– Clearly labeled

columns and rows– Labeled units

• Data should show relationship between independent and dependent variable

Effects of Fertilizer on Plant Height

Amount of Plant Fertilizer

(g)Independent

Height of Plant (cm)

Dependent

2 12

6 20

10 4

Graphs• All graphs must include the following

– Title– A label for each axis– Labeled units– Legend– Data properly depicted

* Independent on x-axis* Dependant on y-axis

x-axis

y- axis

Graphs• What type of graph should I use?• Line

– For continuous quantitative data•Height of plant over time •Stock market prices over

time– Line graph relationships

•Direct variation – one variable increases as the other increases (or decreases as the other decreases)

•Inverse variation – one variable decreases as the other increases

Graphs• Bar

– For non-continuous data (usually in categories)•Number of people who

watch each TV show surveyed

• Pie– For data that are parts of

a whole•Percentage of those

polled that chose each TV show

0

5

10

15

20

25

30

# o

f Peo

ple

CSI Tyra Lost Survivor

TV Shows

Favorite TV Show

Percent of People Chose Each Show as Their Favorite

25%25%

30% 20%

CSI

Tyra

Lost

Survivor

International System of Measurement (SI)

• Basic units of measurement– Length – meter (m)

•Tool – ruler or meter stick– Volume – liter (L)

•Tool – graduated cylinder– Mass – gram (g)

•Tool – triple-beam balance– Time – second (s)

•Tool - stopwatch– Temperature – Kelvin (K) [We will most

often use Celsius (°C)]•Tool - thermometer

Units of Measurement• Metric system – based on 10kilo (k) – kilometers (km) 1000 metershecto (h) – hectometers (hm) 100 metersdeca (da) – decameters (dam) 10 metersBasic unit (m, L, g) – meter (m) 1 meterdeci (d) – decimeter (dm) 0.1 metercenti (c) – centimeter (cm) 0.01 metermilli (m) – millimeter (mm) 0.001 meter

King Henry Died By Drinking Chocolate Milk

Converting one metric unit to another

k h da Basic unit d c m(m, L, g)

• To convert from one unit to another, move the decimal same direction and number of places the units are from each other– 12 kilometers is ?? centimeters

• centimeters are 5 places to the right• 1,200,000 cm

– 134 decigrams is ?? hectograms• hectograms are 3 places to the left• 0.134 hg

Accuracy vs. PrecisionCorrect vs. Consistent

Scientific Method

• State a Conclusion– Did the data support the hypothesis?

•If yes…–Verify results

»Can the experiment be repeated?»Do other scientists support the findings?

•If no…–Repeat the experiment–Revise the experiment–Develop a new hypothesis

Scientific Method

•Repeat– No matter what happened!– Fact – Observable phenomenon that

can be confirmed by scientists many times

– Form a Theory – a hypothesis tested over a long period of time, supported by separate experiments

Fact vs. Theory• Which is Fact…Which is Theory?

–Dinosaurs were cold blooded.–The caterpillar is 3.5 cm long.

Identifying Study ComponentsA student noticed that when a dog is cut, the dog periodically licks its wounds. Usually after a few days, the wound begins to heal without ever

showing signs of infection. The following steps outline the student's line of reasoning:

A. I wonder why the dog's wound doesn't become infected.B. The dog's saliva must prevent the growth of infection-causing bacteria.C. I'll obtain a bacterial culture and grow the same kind of bacteria in two identical

culture dishes. Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other alone. I'll cover both dishes. Then I'll observe what happens each day for a week.

D. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both dishes over the course of the week. However, the bacteria in the treated dish grew more slowly than the bacteria in the untreated dish.

E. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the bacteria. I'll observe what happens each day for a week.

• What was the student’s hypothesis?• Which step described the experimental set up?• Identify the control• What is the independent variable?• What is the dependent variable?• What data did the student collect?• What is a possible conclusion from this experiment? • Is that conclusion a fact or an inference?

Identifying Study ComponentsA student noticed that when a dog is cut, the dog periodically licks its wounds.

Usually after a few days, the wound begins to heal without ever showing signs of infection. The following steps outline the student's line of reasoning:

A. I wonder why the dog's wound doesn't become infected.B. The dog's saliva must prevent the growth of infection-causing bacteria.C. I'll obtain a bacterial culture and grow the same kind of bacteria in two

identical culture dishes. Once the bacteria start growing, I'll add dog saliva to only one of the dishes and leave the other alone. I'll cover both dishes. Then I'll observe what happens each day for a week.

D. Even after adding the dog saliva to one of the dishes, the bacteria continued to grow in both dishes over the course of the week. However, the bacteria in the treated dish grew more slowly than the bacteria in the untreated dish.

E. I think I'll try something else. I'll start with two identical culture dishes, as before, and use the same kind of bacteria in each dish, but this time I'll treat one dish with dog saliva before I add the bacteria. I'll observe what happens each day for a week.

• What was the student’s hypothesis?• Which step described the experimentalexperimental set up?• Identify the control• What is the independent variable?• What is the dependent variable?• What data did the student collect?• What is a possible conclusion from this experiment? • Is that conclusion a fact or an inference?