Introduction & Scientific Method

Biology 101ASpring 2008

• Introduction• Safety• Notebooks• Scientific method• Protocol writing experiment• Review protocol experiment• Preview Tuesday’s lab

Safety- Appendix A

• Fire and earthquake• Eye protection• No food or drinks• Wash your hands when leaving• Dispose of hazardous/biohazardous materials

appropriately

How to be successful in Bio 101A

• Come to class• Be prepared• Be punctual• Complete all assignments in a timely manner• Reflect on your learning• Apply lecture concepts to lab (and vice versa)• Get help, help others (cooperate)

Notebooks

• Hardbound• Name edges & cover; number pages• Pages 1-4: TOC• Blue or black ink• No wite-out• Completely chronological order• Date & 2 signatures for each page- before

leaving lab

Scientific Method

• Not formulaic• Inquiry based• Discovery Science vs. Hypothesis testing

Charles Darwin became curious about how species came about

• Dropped out of med school

• Didn’t much like Divinity school, either

• Became a naturalist aboard the HMS Beagle

The Voyage of the Beagle

Darwin’s critical observations were comparisons between island species and

mainland species

Marine Iguana and South American Iguana

Flightless cormorants live only on the Galapagos

A Variety of Finches are found in the Galapagos

Finches each have adaptations for different small island environments

Darwin’s inference: The finches have a common ancestor, which adapted to different niches

Likewise, the marine iguanas must have come from the mainland

Hypothesis testing

LE 1-25a

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Observations

Question

LE 1-25b

Hypothesis #1:Dead batteries

Hypothesis #2:Burnt-out bulb

Test prediction

Test falsifies hypothesis

Prediction:Replacing batterieswill fix problem

Prediction:Replacing bulbwill fix problem

Test prediction

Test does not falsify hypothesis

Does excess iron decrease growth in laboratory rats?

• How can we test this?• How many groups should we

use?• What size are the groups?• How shall we create the

groups?• What is our independent

variable?• What is our dependent

variable?• What are the control variables?

Is evolution testable?

Adaptive radiation in the lab

• In variable environments, varying strains of P. fluorescens are generated

• Strains are genetically distinct

• When environments are homogeneous, no such variants are generated

ANALYSIS OF eyeless FUNCTION

ey2 and eyR = spontaneous mutationsmutant phenotype = small/no eyesrecessive to wild-type allele

Halder et al.

eyeless (ey)

NECESSARY!

NotNecessary

Expressionof phenotype

Knock the gene outLOSS-OF-FUNCTION

NECESSARY?

NotSufficient

NOExpression

of phenotype

SUFFICIENT!

Ectopically express geneGAIN-OF-FUNCTION

SUFFICIENT?

eyeless

NOExpression

of phenotype

Expressionof phenotype

A Closer Look at Hypotheses in Scientific Inquiry

• A scientific hypothesis must have two important qualities:– It must be testable– It must be falsifiable

The Myth of the Scientific Method

• The scientific method is an idealized process of inquiry• Very few scientific inquiries adhere rigidly to the

“textbook” scientific method

• In mimicry, a harmless species resembles a harmful species

• An example of Batesian mimicry is a stinging honeybee and a nonstinging mimic, a flower fly

A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations

LE 1-26

Flower fly (nonstinging)

Honeybee (stinging)

LE 1-27

Scarlet king snake

Eastern coralsnake

Scarlet king snake

Key

Range of scarlet king snake

NorthCarolina

Range of easterncoral snake

SouthCarolina

LE 1-28

(a) Artificial king snake

(b) Artificial brown snake that has been attacked

In areas where coral snakes were present, most attacks were on brown artificial snakes.

In areas where coral snakeswere absent, most attackswere on artificial king snakes.

LE 1-29

% of attacks onartificial king snakes

% of attacks onbrown artificial snakes

Field site withartificial snakes

83%

NorthCarolina

SouthCarolina

17%

16%

84%

Key

Designing Controlled Experiments

• What variables were controlled in this experiment? How were they controlled?

• Researchers usually “control” unwanted variables by using control groups to cancel their effects

An alternative experimental design