1. The Scientific Method
PHEOC

2. Problem Identify the question - a problem to solve
Do background research to prepare

3. Hypothesis An educated guess that can be tested
Independent Variable: the one change that is made
Dependent Variable: result that occurs due to the IV.
Written: If Independent Variable, then Dependent Variable.
Ex: If music is played to plants, then they will grow taller.

4. Experiment
Procedure that tests a hypothesis by collecting info under controlled conditions.
Control: the group with conditions that are kept the same or “normal”
Experimental: The part of the experiment where one factor or variable is changed.
Constants: Parts of the experiment that stay the same in the control & experimental groups.

5. Observation
Collecting and organizing data/information from the experiment.

6. Conclusion Reporting results (graphs, reports)
True scientific studies do repeated trials
Form a theory when repeated trials give the same results
If results are not what was expected, scientists still report results and may try again or adjust their hypothesis first

7. Law vs Theory Law: fact of nature known to be true
Law of gravity
Theory: explanation of a phenomenon or behavior that is supported by a large body of evidence
Theories can be changed based on new evidence
They are never proven to be 100% true

8. Germ Theory - timeline
7000 b.c. – drilling holes in people’s heads to release evil spirits “causing disease”
377 bc – Hippocrates – body fluids cause disease
1300s - incense tried to cure the Black Death
1800s - people still believe illness is due to supernatural causes.
Louis Pasteur proposed that microorganisms cause disease

9. Germ Theory (cont.)
antiseptic technique reduces surgery infections
1883 – Koch’s postulates prove pathogens cause disease
1900s – drinking water treated with chlorine to reduce cases of cholera
Penicillin was used to treat infections
Vaccine against polio is made
New diseases are springing up, SARS

10. Cell Theory 1665 - Hooke identifies cells through use of a microscope.
Leeuwenhoek made a better lens to observe cells in greater detail.
Schleiden studies plant structures- finds they are made of cells

11. Cell Theory (cont.)
Schwann studied animal structures -concluded from Schleiden’s work and his - all living things are made of cells. (although Schwann thought cells spontaneously formed)
1855 Virchow proposed that all cells come from other pre-existing cells
Cell Theory Principles:
All organisms are made of cells
cells are produced by other existing living cells
The cell is the most basic unit of life

12. Theory of Natural Selection
Buffon – recognizing there are variations among species
1794 – E. Darwin (Charles Darwin’s grandfather) begins considering how organisms could evolve through mechanisms such as competition.
Lamarck - evolution due to environmental changes over time.

13. Theory of N.Selection (cont.)
1830s - Charles Darwin - influenced by Lamarck’s ideas and his species variation studies; continues his research on evolution
Theory of Natural Selection now states:
Individuals with inherited beneficial adaptations will produce more offspring.

14. Quantitative vs. Qualitative
Research
Quantitative vs. Qualitative

15. Quantitative
Results in numerical data
Involves counts or measurements

16. Qualitative Descriptive Results purely observational data
Useful because in some cases descriptions are more important than measurements.

17. Resources:
- Holt McDougal, “Biology” 2010