Chapter 1 – Nature of
Biology
Sections 1.1, 1.3, 1.5, 1,6, 1.7, 1.8
1.1 Levels of organization define scope of
biology
1.3 Cells are the structural and functional
units of life
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Cell – Lowest level of structure the can
perform all activities required for life. Basic
unit of life. All cells are membrane bound and
contain DNA.
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Prokaryotic Cell – Cells lacking a nucleus. Lacks
organization. No organelles?? Bacteria
Eukaryotic Cell – Cells containing a nucleus and
organelles. Plants, Animals, Fungi.
Cells give rise to other cells. Basis for all
reproduction
1.3 Prokaryotic Cell and Eukaryotic Cell
1.5 The diversity of life can be arranged
into three domains
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Taxonomy – Branch of biology responsible for
classifying and naming species.
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Species – term used for a particular type of organism.
Binomial naming system
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Homo sapiens (genus and species)
Kingdoms – classification scheme under which all
organisms were organized (Animal, Plant, Fungi, Protista,
Monera)
Domains – new scheme based on DNA sequencing.
Based on the fact that there are two very distinct types of
prokaryotes
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Includes Bacteria, Archaea, Eukarya
1.5 Taxonomy (Domain Scheme)
Bacteria and Archaea (all prokaryotes)
Split from each other in ancient times
and have distinct differences in DNA
sequences and genes
Common Ancestor
3.5 bya
What properties do you think this species had?
Includes Eukaryotes
Plants
Animals
Fungi
Protists
Live in extreme conditions,
reminiscent of ancient times.
Use of sulfuric acid for energy
1.6 Evolution explains the unity and
diversity of life
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Charles Darwin (1859 On Origin of Species
by Means of Natural Selection)
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Diversity of life can be explained by natural
selection – occurs when heritable variations are
acted on by environmental factors that favor the
reproductive success of some individuals over
others.
1.6 Natural Selection (Darwin)
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Observations (involves using one or more of
the senses to gather information – data)
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#1 Individual variation – Not all individuals are th
same
#2 Overproduction and competition
Inference (logical interpretation of the data)
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Unequal reproductive success. Those with the
best heritable variations will have the best chance
to reproduce and pass genes on to next
generation.
Natural variation gives advantage
Natural Variation
1.6 Observations lead to Inferences
Observation #1 –
Variation
Inference –
Natural Selection
Observation #2 –
Overproduction and
Competition
1.6 Theory
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Darwin’s idea has become so well supported
that it is now considered a theory.
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Theory – well tested explanation that unifies a
broad range of observations.
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Similarity in DNA
Diversity of life
Fossil Record
Antibiotic Resistance
Bacterial Evolution
1.7 Discovery Science vs. Hypothesis
Based Science
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Science - Way of knowing. Seeks natural causes
for natural phenomena. i.e. study of what we can
observe, measure.
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Discovery – Describing nature. Uses data gathered from
observations (technology) to describe.
 All living things are made of cells
 All living things are based on the universal code of DNA.
Hypothesis Based – Explaining nature. Involves making
and testing a hypothesis.
 If all living things are made of cells, then plants are
made of cells
 If all living things contain DNA, then bacteria would
contain DNA.
Hypothesis-based science uses and tests
hypotheses
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A scientific method of investigation involves the
following steps:
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Observe & identify a problem (make an inference)
State a hypothesis
Design & perform an experiment
Form conclusions
Replicate the work
Concept Map – Rough draft due
tomorrow
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Main Concept – Scientific Method
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Sub Concepts
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Observation
Inference
Hypothesis
Theory
Controlled Experiment
Control Group
Experimental Group
Manipulated Variable
Responding Variable
Independent Variable
Dependent Variable
Key Terms
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Experimental group—group that is exposed to the experimental
(independent/manipulated) variable.
Control group—group that is not exposed to the experimental
variable.
Independent/manipulated variable—experimental variable,
what you test on the experimental group to see if it makes a
difference. What is new and novel. What is to be studied.
Dependent variable/responding variable—some factor you
measure in both groups to see if it changes.
Hypothesis—a reasonable explanation supported by
observation and/or research.
Criteria for Evaluating Hypotheses
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A hypothesis should be a clear, concise
statement that focuses on a specific welldefined problem.
It should be testable.
It should contain the independent and
dependent variable and state a cause and
effect relationship.
Formal Hypothesis Writing
Step 1
 Form a question based on observations. For
instance, if you notice your pet mice have more
babies when you feed them corn rather than pellets,
this is an observation. Your question, therefore, may
be: Do mice produce more babies when fed corn?
You can test this, but first you must form a
hypothesis.
Step 2
 Write down what you predict will happen in your
experiment. For instance, you can predict that if you
feed some of your mice corn, they will produce more
babies than mice to which you feed pellets.
Formal Hypothesis Writing
Step 3
 Determine your manipulated and responding
variables. Both the manipulated and responding
variables must be measurable and testable.
Step 4
 State as If manipulated variable, is related to
responding variable, then prediction (what you
expect will happen in lab.
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Example: If a corn fed diet increases mice offspring
production, then those mice fed corn will produce more
offspring than those fed pellets.
Example #1
Problem

Spontaneous Generation?
Independent variable (manipulated)
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Preventing flies from getting to meat
Dependent Variable (Responding)
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Maggots
Hypothesis
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If the absence of flies on meat (prevents)
maggots, then the meat in the covered jars will
lack maggots.
Redi’s Experiment
PROCEDURE
Uncovered jars
Controlled Variables:
jars, type of meat,
location, temperature,
time
Covered jars
Several
days pass
Manipulated Variables:
gauze covering that
keeps flies away from
meat
Responding Variable:
whether maggots
Maggots appear
No maggots appear
appear
CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous
generation of maggots did not occur.