Scientific Method Chapter 1

What is Science? “The goal of science is to investigate and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions.” (Biology Text Book)

How do we do this? Scientific Method Series of logical steps used to find answers or new questions PHEOCR (Prancing Horses Elated On Candy Rocks) Refer to handout Problem – The question you’re trying to answer Hypothesis – must be a testable idea MUST be in the form of a statement Experiment (or collect/analyze data) Observations – 2 types of data to collect Quantitative – number/measurement data Qualitative – non number observations Conclusion – Support or refute your hypothesis…you can NEVER prove your hypothesis correct!!!!!!!!!!!!!!!!! Repeat (PS: A theory is a well tested and supported hypothesis, generaly accepted to be true)

Variables Variables come in three main types: Manipulated (Independent) Responding (Dependent) Constant (Sometimes called controlled) Manipulated variable (Only 1 per experiment) The scientist has direct control of this variable This variable is the only variable that is changed between experiment groups Responding variable The scientist has NO direct control of this variable This variable changes in response to the experiment Normally the responding variable is a result of the experiment and depends on what the manipulated variable is Constant variables These variables stay the same through the entire experiment, no matter what There are many constant variables in every experiment

Variable Example You hear drinking only carrot juice for a long period of time will turn you orange. To test this, you have 5 people drink nothing but carrot juice for 1 week, and 5 people drink nothing but water for 1 week. Of the 5 drinking carrot juice, 5 turned orange Of the 5 drinking water, 5 stayed normal Identify the Manipulated, Responding and 2 constant variables

Experiment Design: Setting up the Groups Control GroupExperimental Group(s) This group will have a known or expected outcome Used as a basis for comparison to the experimental group Ex: The people drinking water This is the “Guinea Pig” group There may be more than one per experiment The hypothesis is tested on this group Compare this group to the control to see if the hypothesis is supported or refuted Ex: People drinking Carrot Juice

Mythbusters: Bull in China Shop Mythbusters are the Masters of experimental design! Create a hypothesis: What do you think will happen if bulls are let loose in a china shop? Watch the “Bull in China Shop” clip YouTube - Mythbusters: Bull In A China Shop and make notes of the YouTube - Mythbusters: Bull In A China Shop Manipulated Variable Responding Variable Constant Variables

Graphs There are two main types of graphs used in this class: Bar Graphs Line Graphs Bar graphs are used for comparisons between variables (usually groups or categories) Line graphs are used for change over time X-Axis = Manipulated (Independent) Variable Y-Axis = Responding (Dependent) Variable

Rules of Graphing ALWAYS use PENCIL (0,0) is always the origin Please DON’T use Graph breaks The numbers should go up by the same increment at every line EX: by 2’s, 5’s, 10’s, 100’s etc The x-axis scale and y-axis scale CAN be different If you don’t have a point for (0,0) in the data table, don’t start your line at (0,0) Bars must be the same width in a bar graph Make sure to label the title, x and y axis and include UNITS

The Metric System Scientists use a common system of measurement called the Metric System Also known as: International System (SI) Based on units of 10 Three basic Units Meter Liter Gram Basic Prefixes: Kilo, deca, deci, centi, milli, micro

Compare English to SI

Metric System Conversion Chart

Microscopes There are a few different types of microscopes Some small: Compound Light Microscope (We will use this a lot this year) Some Huge: Scanning Electron Microscopes (SEM) or Transmission Electron Microscopes (TEM) Both of these are about the size of a large refrigerator and can take pictures of objects at 10,000’s time magnification! These shoot beams of electrons on an object and an image is displayed on a computer

Other Lab Techniques Cell Cultures Growing groups of cells in a laboratory, usually all identical to each other Cell Fractionization Using chemicals and blenders to break cells into pieces in order to examine one tiny part

Something to think about