1. a Proposed Explanation Whose Validity Can Be Tested

THE SCIENTIFIC METHOD

I.  hYPOTHESES

A.  Definition

1.  A proposed explanation whose validity can be tested

B.  Characteristics

1.  Must be consistent with all available data

2.  Must make predictions

3.  Must be testable

4.  Tentative

C.  Inductive and Deductive reasoning

1.  Inductive reasoning is used in hypothesis making

a)  Use available data to formulate a possible explanation of a phenomenon

b)  Goes from the specific to general

2.  Deductive reasoning is used in hypothesis testing

a)  Often takes the form of "If . . . . then . . . " statements

b)  Goes from general to specific

3.  Example

a)  Available data: trees, dogs, cats, and fungi are composed of cells

b)  Inductive reasoning

(1)  Since all these life forms are composed of cells (specific data), I hypothesize that all living things are composed of cells (general statement)

c)  Deductive reasoning

(1)  If all living things are composed of cells (general), then fungi (which are living) should be composed of cells (specific)

D.  Avoid common fallacies in hypothesis construction

1.  Cause and effect

2.  Anecdotal evidence

a)  Information based on personal experience or testimonials

II.  Hypothesis testing (experimental design)

A.  Experiments should utilize an experimental group and a control group

1.  The two groups should be treated exactly the same, except for one variable

a)  Experimental group is exposed to the variable being tested

b)  The control group treated with a placebo

(1)  A placebo is a substitute for the variable and is known to have no effect

(2)  Without the placebo, there would be two differences between the experimental group and control group: (1) the experimental variable, and (2) the knowledge of not being exposed to the experimental variable

B.  Variables

1.  Experimental variable

a)  Component of the experiment being tested

2.  Dependent variable

a)  Result or change that occurs due to the experimental variable

C.  Quantify data

1.  Express data with numbers

D.  Interpret data

1.  Apply statistics to your data to help understand their significance

E.  Present the data

1.  Purpose

a)  Let others evaluate, confirm, and repeat your experiments

b)  If data is not presented, your research will be wasted, as others will have to perform the same experiments

III.  biological theories

A.  Background

1.  After making a hypothesis and testing it you have several options

a)  Discard or modify the hypothesis

(1)  If the data does not support a hypothesis, the hypothesis must be discarded or modified

(2)  In this case, the data falsifies the data

b)  Tentatively accept your hypothesis

(1)  Data can only support a hypothesis, not prove it

(2)  Future data might falsify a hypothesis, therefore, scientist do not say " the data proves the hypothesis"

(a)  They often use the term "the data supports the hypothesis"

2.  Theories

a)  Definition

(1)  A hypothesis that is overwhelmingly supported by a large body of evidence can become a theory

b)  Characteristics

(1)  Usually a unifying theme, rather than a collection of facts

(2)  Is NOT a fuzzy or weak guess

B.  The Cell Theory

1.  (i) All living organisms are composed of cells, and (ii) cells come from cells

2.  Contributors

a)  Robert Hooke

(1)  Coined the term "cell" to represent cells seen from the cork of an Oak Tree

b)  Antonie van Leeuwenhoek

(1)  First to describe unicellular organisms

c)  Mathias Schleiden and Theodor Schwann

(1)  Theorized that all living organisms are composed of cells

C.  The Biogenesis Theory

1.  Life comes from preexisting life

2.  Spontaneous generation, or abiogenesis, was a disproved concept of life arising from inanimate objects

D.  The Evolution Theory

1.  Populations change over time

2.  Contributor

a)  Charles Darwin

b)  Explains the unity and diversity of life forms

3.  Components

a)  Descent with modification

(1)  There is a large diversity in a species, some more fit to survive than others

b)  Natural selection

(1)  Ones able to leave more offspring will pass more of its traits to the next generation

E.  The Gene Theory

1.  Organisms contain coded information that dictates, their form, function, and behavior

2.  This explains the resemblance of offspring towards their parents and the UNITY or similarities among life forms, since we all have a common ancestor