Introduction & Scientific Method Biology 101A Spring 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 batteries will fix problem Prediction: Replacing bulb will 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

ey 2 and ey R = spontaneous mutations mutant phenotype = small/no eyes recessive to wild-type allele Halder et al. eyeless (ey)

NECESSARY! Not Necessary Expression of phenotype Knock the gene out LOSS-OF-FUNCTION NECESSARY? Not Sufficient NO Expression of phenotype SUFFICIENT! Ectopically express gene GAIN-OF-FUNCTION SUFFICIENT? eyeless NO Expression of phenotype Expression of 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 coral snake Scarlet king snake Key Range of scarlet king snake North Carolina Range of eastern coral snake South Carolina

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 snakes were absent, most attacks were on artificial king snakes. LE 1-29 % of attacks on artificial king snakes % of attacks on brown artificial snakes Field site with artificial snakes 83% North Carolina South Carolina 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