Introduction to the Biology Lab The Scientific Method

LABORATORY SAFETY

Student Conduct Do NOT smoke, eat, drink, or bring food or drinks into the laboratory room Do NOT apply cosmetics or handle contact lenses Wash your hands thoroughly with soap and water before leaving the laboratory room each day Do NOT remove organisms or chemicals from the laboratory Work carefully and methodically COME PREPARED TO LAB FOR THAT DAY’S WORK

Basic Laboratory Safety NO OPEN-TOED SHOES Secure loose hair and clothing to avoid accidents Place non-essential books, etc. out of the way of your experiments Never pipette by mouth

Safety Equipment Know the location of the First Aid Kit Know the location and proper way to use the Shower Know the location and proper way to use the Eye Wash Basin NOTIFY YOUR INSTRUCTOR OF ANY EVENT THAT NECESSITATES THE USE OF THESE

Disposing of Materials Common paper and uncontaminated towels can be placed into the normal trash Cotton swabs, coverslips, and other used lab material MUST be placed into the red, plastic trash receptacle Broken glassware MUST be placed in the cardboard “sharps” container for glassware

Care of Microscopes Microscopes are located at each lab station Following their use, miscroscope: 1.Scanning (4X) lens should be in place 2.Stage should be at lowest setting 3.Rheostat should be adjusted to its lowest setting 4.Cord should be wrapped carefully around the base and not “flopping” around 5.Ocular lenses should face back of cabinet YOUR INSTRUCTOR WILL INSPECT THEM BEFORE YOU ARE PERMITTED TO LEAVE

Care of the Lab Place seats back under benches before you leave Wipe down the sink-tops with paper towel if you are among the last students in the lab – Remove any paper towels left behind by less conscientious students THE LAB SHOULD LOOK AS NICE AFTER YOU ARE DONE AS IT DID BEFORE YOU STARTED

Check Your Understanding What is the last thing you should do each day before leaving the lab? What is the only mandatory piece of “clothing” required for you to be able to work within the lab? Differentiate between where you should dispose of paper towels and other paper items, cotton swabs and other used lab items, and broken glassware. How should you clean up a piece of broken glassware? Discuss the proper way your microscope should be put away after each use. Following completion of any lab session, describe how your: – lab bench should look (including chair). – lab sink should look.

SCIENTIFIC METHOD Scientists Make Observations and Then Form and Test Hypotheses

Scientific Inquiry Science is a “way of knowing” – Understanding of the natural world Inquiry is the methodical approach for deriving answers to questions posed by observations of the world around us

Making Observations Recorded observations are data 1.Qualitative – descriptions rather than measurements 2.Quantitative – recorded measurements (tables/graphs) Leads to Inductive Reasoning – Generalizations are derived from numerous specific observations – e.g. “Goldfish and roses and mushrooms are made of cells, therefore all organisms are made of cells”

Forming and Testing Hypotheses Seeks to explain the cause of behind an observation – Hypotheses provide tentative answers based on available data and inductive reasoning Deductive Reasoning is used to validate hypotheses – Uses general premises to extrapolate what the results should be if the premises are true – “if…then” logic (e.g. “if humans are organisms, then humans are made of cells”)

Types of Hypotheses Null is stated as a negative – e.g. “Humans are not made of cells” Alternative is stated as a positive – e.g. “Humans are made of cells” The null and alternative hypotheses are mutually exclusive and both cannot be true

Hallmarks of a GOOD Hypothesis It must be testable – Hypotheses must have a way of being validated It must be falsifiable – Hypotheses can NEVER be proven true beyond a shadow of a doubt – New experimental techniques may invalidate (falsify) it

Experimental Controls and Repeatability Controlled Experiments compare an experimental group with a control group – Should differ in only one factor (Independent Variable) – The control group is used to cancel out all effects that the scientists is NOT interested in examining Observations in science are only convincing if the results are repeatable

Theories in Science 1.Scientific theories are much broader in scope than simple hypotheses 2.Scientific theories typically give rise to many new hypotheses that can be tested 3.Scientific theories are supported by a wider range of experimental evidence than single hypotheses 4.Theories, like hypotheses, are falsifiable given new experimental data

Check Your Understanding Discuss the implication of the fact that lab work performed by scientists uses scientific inquiry. Differentiate between quantitative and qualitative data (observations). Differentiate between deductive and inductive reasoning. How does each contribute to our understanding of the natural world around us? Define hypothesis. Differentiate between a null and an alternative hypothesis. What are the hallmarks of a “good” hypothesis? Explain what a controlled experiment is. Why is important to always strive to perform a controlled experiment? Differentiate between a dependent and an independent variable. Compare and contrast a theory and a hypothesis.