Download Scientific Method

The Scientific Method
PHEOC
Problem
Identify the question
- a problem to solve
– Do background research to prepare
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.
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.
Observation
Collecting and organizing
data/information from the experiment.
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
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
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.
1857 - Louis Pasteur proposed that
microorganisms cause disease
Germ Theory (cont.)
1865 - antiseptic technique reduces surgery
infections
1883 – Koch’s postulates prove pathogens
cause disease
1900s – drinking water treated with chlorine
to reduce cases of cholera
1928 - Penicillin was used to treat infections
1955 - Vaccine against polio is made
2002 - New diseases are springing up, SARS
Cell Theory
1665 - Hooke identifies cells through
use of a microscope.
1674 - Leeuwenhoek made a better
lens to observe cells in greater detail.
1838 - Schleiden studies plant
structures- finds they are made of cells
Cell Theory (cont.)
1839 - 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
Theory of Natural Selection
1749 - 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.
1809 - Lamarck - evolution due to
environmental changes over time.
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.
Research
Quantitative vs. Qualitative
Quantitative
Results in numerical data
Involves counts or measurements
Qualitative
Descriptive
Results purely observational data
Useful because in some cases
descriptions are more important than
measurements.
Resources:
- Holt McDougal, “Biology” 2010