Biology-Unit I-Part A The Scientific Method

Skills for the Biologist A. Lab Safety: A laboratory must be a safe place. It is the responsibility of each student to avoid accidents. Here are a few general laboratory safety rules. 1. Read and follow all directions exactly. 2. Work quietly and carefully. 3. Do not fool around. 4. Work only when the teacher tells you to. 5. Be sure you know what you are doing. 6. Follow all safety procedures and wear safety equipment.

Skills for the Biologist B. Measurement in the lab The most common system of measurement used by scientists is the metric system. The Metric system is used worldwide & based on multiples of ten. 1. Metric units: a) Distance (length): meters (m) Use a Meter stick or Ruler b) Mass (amount of matter): grams (g) Use a Triple Beam Balance

Skills for the Biologist d) Temperature: Celsius (C) Use a Thermometer e) Time: Hours (hr) or Seconds (s) Use a Stopwatch C. Organization and Interpretation of Data A scientist’s observations need to be recorded in an orderly manner. Two common methods used to record observations are the data table and graph.

Skills for the Biologist 1. Data table: The data table is used to record numerical data. The information is organized by arranging observations into columns with appropriate headings.

Skills for the Biologist 2. Bar Graph(Histogram): A bar graph allows a scientist to compare data.

Skills for the Biologist 3. Line Graph: A line graph is used to show relationships between two or more variables.

Skills for the Biologist a) Independent variable: is placed on the horizontal (bottom) or X axis Independent variables are usually the variables that the scientist controls. Ex. Temperature, amount of light, etc. b) Dependent variable: is placed on the vertical (side) or Y-axis. Dependent variables depend on the changes in the independent variable.

The Scientific Method The Scientific Method The technique used by scientists to solve problems and gain scientific information. The Scientific Method is a process of logical thinking. Steps of the scientific method: 1. Problem 2. Hypothesis 3. Experimentation 4. Observations 5. Conclusions

The Scientific Method (cont.) Steps of the scientific method in detail: 1. Problem: A problem must be stated. It is a question for which a scientist is trying to find an answer. Ex. Will a plant grow in complete darkness? 2. Hypothesis: is an educated guess about the answer to the problem. The hypothesis is based on information which has been learned about the problem. Always written in if…then format. Ex. If….then….

The Scientific Method (cont.) 3. Experimentation: set up a controlled experiment that will test the hypothesis. a) Controlled experiment: an experiment which tests only one factor. Ex. 2 of the same species plant, one grown in complete darkness, and the other grown in regular light b) Variable: is the factor to be tested Ex. amount of light Independent variable: Controlled by the scientist Dependent variable: Changes because of the expt c) Control: A exact duplicate experiment without the variable. Ex. Plant grown in regular light

The Scientific Method (cont.) 4. Observations: measurements, notes, records of things seen, heard, felt, during the experiment. Usually, observations are made using units of measure. 5. Conclusions: explanations of the problem based on the observations. True conclusions must be backed up by observations and data from the experiments. Ex. I conclude that ………….. Because my data showed that….

The Scientific Method (last slide!) Scientific law: scientific facts based on experiments which have been done repeatedly. Ex: Law of Gravity Theories however are possible explanations of complex problems. Theories can change. Ex: Theory of Evolution