1. HONORS BIOLOGY LABORATORY SKILLS The Scientific Method

2. Making Observations Asking Questions Forming a Hypothesis (Generating a Null Hypothesis) Making Predictions Designing an Investigation Testing the Predictions (Collecting, processing data) Conclusion

3. Hypotheses and Predictions  A scientific hypothesis is a possible explanation for an observation or a scientific problem that is given to you. Features of a sound hypothesis:  It offers an explanation for an observation  It refers to only one independent variable  It is written as a statement  It is testable by experimentation  It is based on further research, observations or prior knowledge  It leads to predictions about the system (or the topic of your experiment)

4. Hypotheses…let’s give it a try! Example 1: During an experiment on bacterial growth, the girls noticed that bacteria in cultures grew at different rates when the dishes were left overnight in different parts of the laboratory. (This is an observation) Hypothesis:

5. Hypotheses…one more try! Example 2: Observation – During an experiment on plant cloning, a scientist noticed that the root length of plant clones varied depending on the concentration of a hormon added to the agar. Hypothesis:

6. Variables You must identify the variables that you are testing and the ones that you keep constant. A variable is any characteristic or property that is measurable or observable. You must use units with your variables Types of variables:  Independent variable  Dependent variable  Controlled variable

7. Independent Variable Set by the person carrying out the investigation (ex. Temperature, light intensity, pH) Recorded on the x axis of the graph during data presentation There is always only one in an investigation Must record proper unit

8. Dependent Variable Measured during the investigation (ex. Plant growth, heart rate etc) Recorded on the y axis of the graph during data presentation There is always only one in an investigation Must record proper unit

9. Controlled Variables Factors that are kept the same or controlled. List these in the method as appropriate to your own investigation

10. Let’s play with variables! (don’t need to write this down) Look at the picture and explanation on the board on catalase activity and answer the following questions: 1. Write a suitable hypothesis for this experiment: 2. Name the independent variable with the proper unit: ___________________________ 3. List the equipment needed to set the independent variable, describe how it was used: 4. Name the dependent variable with the proper unit: ___________________________ 5. List the equipment needed to set the dependent variable, describe how it was used: 6. List three variables that might have been controlled in this experiment:

11. Data Collection Design a data table to record your results. Your data table should clearly show the units and values of the independent and dependent variables. When you design your data table, leave some room for data processing.

12. Data Presentation -- Types of Graphs Choosing the wrong graph can obscure information and make data more difficult to interpret. Some examples…  Scatter Graph  Line Graph  Bar Graph  Pie Graph

13. Scatter Graph In scatter graphs, there is no manipulated (independent) variable but the variables are usually correlated. The points on the graph do not need to be connected, but a line of best fit is often drawn through the points  The data for this graph must be continuous for both variables.  Useful for determining the relationship between two variables.

15. Line Graph Line graphs are used when one variable (called the independent variable), affects another, the dependent variable. The independent variable is the experimental treatment or time. The dependent variable is usually the biological response.  The data for line graphs must be continuous for both variables.  Include proper labels with units, title, a key and connect the dots at all times when using line graphs.

17. Bar Graph The data for this graph are non-numerical and discrete for at least one variable, in other words, they are grouped into separate categories. There are no independent or dependent variables.  The data are discontinuous, so the bars do not touch  Multiple data sets can be displayed using different colored bars placed side by side within the same category.

19. What Is a Scientific Model? A scientific model is a representation of an object or system. An example of a scientific model would be a diagram of a cell or a map.. Even a model rocket! Any model is based on a certain set of observations. A good model must be able to explain as many characteristics of these observations as possible, but also be as simple as possible.

21. And as a review, watch: http://www.youtube.com/watch?v=jPaGOH wv7mQ http://www.youtube.com/watch?v=jPaGOH wv7mQ