Biology As A Science The Scientific Method Why

Biology As A Science

The Scientific Method: Why have it?

Scientific Method 1. Define Problem 2. Formulate Hypothesis 3. Test Hypothesis • • -Write out the materials and methods needed Need Positive and Negative Controls

What is a Control Group?

Beginning of Experiment Positive Control Group: Experimental Group: Negative Control Group: Known fertilizer and water Experimental fertilizer and water Water only

150 ft End of Experiment 90 ft 50 ft

What is a Variable? What was the variable in the example?

Independent vs. Dependent Variables

New Experiment Positive Control Group: 1 ounce known fertilizer and water Experimental Group 1: 1 ounce experimental fertilizer and water Experimental Group 2: Negative Control Group: 2 ounces of water experimental fertilizer and water

150 ft 130 ft 100 ft

How many variables were in the experiment?

• Independent Variables: – Number varies but you control it – Ex. Amount of fertilizer you added • Dependent Variables: – Number varies but nature controls it – Ex. Height reached by the tree

More Scientific Method 4. Collect Data: – Display in form of graph or table or photo in a “Results” section of a scientific paper 5. Analyze data and make conclusions about data in a “Conclusions” section of a scientific paper

How do we decide in an objective way if measured differences are significant? • Ex. Avg Control Group Plant Height=12 in • Avg Experimental Group Plant Height= 12. 7 in • 0. 7 inches: Was this because of my fertilizer or just by chance?

Statistics Step 1: Null Hypothesis=premise that no difference exists. Step 2: Collect Data Step 3: Use statistics to determine the probability that any differences are due to chance Step 4: If there is a probability of error or chance below 5% then Null Hypothesis correct

More Scientific Method 6. Report your paper to the world for examination and duplication

Theory vs. Law?

Theory “Sick people have Bacteria A” “Sick People have Parasite Q” Germ Theory= Germs cause us to be sick “Sick people have Fungus P” “Sick people have Virus X”

• Theory= Established explanation given for many different observations seen by researchers = Explanation for many proven hypothesizes

Law of Gravity= • Things always fall towards the center of Earth • This event is always seen over and over • Accepted at face value, no proof needed • Law doesn’t go into How? and Why? • Law based on 1000 s of observations

The Metric System • Length=Meter • Volume=Liter • Mass=Gram

Metric System • • 1 Meter= 1000000 micrometers or Microns 1 Meter= 1000 mm 1 Meter= 100 cm 1 Kilometer= 1000 meters

Question • 2 cm= ___ Microns? • 50 micrometers= ____ mm?

Tools of a Biologist • Light Microscopes: – Simple Microscope (Single Lens-Magnifying Glass (1600 s) – “Inventor”: really improved on existing technology

Microscopes • Really 1590 invented by: • Hans and Zaccharias Janssen (father and son)

Tools of a Biologist – Compound Microscope (2 lenses) – Robert Hooke (1600 s)

Modern Compound Light Microscope PARTS

Tissue Prep for Microscopy 2. Embed in wax 3. Slice with Microtome, Mount on slide, Stain 1. Fixation

Stains • Help visualize details of specimen – Vital Stains=Don’t harm living specimens (ex. Methyl Blue) – Lethal Stains=Kills Specimen (ex. Iodine)

Tissue Prep Center Microtome Water bath with sliced wax/tissue Embedding Area

Tissue prep-Mount onto slides

Dissecting Scope/Zoom Scope 3 D Image More working space Can view “large” objects

Cheek Cells using Phase-Contrast Microscope No Stains Needed Can view live specimens

Scanning Electron Microscope 100, 000 X Magnification Can’t view live organisms 3 D Image Blast electrons at object

Red Blood Cells using a SEM

Transmission Electron Microscope 2 D Image Can’t View live organisms 250, 000 X Mag Blast electrons at object

Blood Cells using a TEM

Confocal Laser Microscope

Ever been in a centrifuge?

Centrifuge • Separate mixtures based on density • Most dense at bottom of tube • Least dense at top

Chromatography Separation into components based on solubility in solvent Sample Solvent

Spectrophotometry • Use light absorbance to determine the concentration of substances Detect amount of light that made it through

Spectrophotometry Known Absorbance # Concentration Unknown Concentration Absorbance #

Spectrophotometry • Spectrophotometry Demo

Electrophoresis Separate mixtures based upon size and charge

Electrophoresis

Tissue Culture

Microdissection

Recombinant DNA

Transgenic Organisms • Fluorescent “Reporter” Genes