THE SCIENCE OF BIOLOGY
Section 1–1 What Is Science?
What Science Is and Is Not
• The goal of science is to investigate and
understand nature, to explain events in
nature, and to use those explanations to
make useful predictions.
• Science is an organized way of using
evidence to learn about the natural world.
Evidence Based on Observation
What does observation involve?
• Observation involves using one or more
of the senses
– sight, hearing, touch, smell, and sometimes
taste—to gather information.
– The information gathered from observation is
called evidence or data
Complete the table about types of observations
Types of
Observations
Observations
Involve
Example
Quantitative
Numbers
There are seven
birds at the
feeder.
Qualitative
Characteristics
One of the birds
that cannot be
has a red head.
easily measured or
counted
Interpreting the Evidence
Inference - is a logical interpretation
based on prior knowledge and
experience.
Explaining the Evidence
Hypothesis -is a possible explanation for
a set of observations or an answer to a
scientific question.
In science, a hypothesis is useful only if it
can be tested.
Three ways from which hypotheses
may arise are:
• From prior knowledge
• From logical inferences
• From imaginative guesses
What do scientists assume can be
discovered through scientific inquiry?
• They assume that the basic rules that
apply to all events in the universe can be
discovered.
What are some qualities that are desirable in
a scientist?
Qualities include curiosity, honesty,
openness, skepticism, and a recognition
that science has limits.
Section 1–2 How Scientists Work
• The idea that life can arise from nonliving
matter is called Spontaneous
Generation.
• Francesco Redi’s hypothesis about the
appearance of maggots was that flies
produce maggots.
Designing an Experiment
• What are variables in an experiment?
They are factors that can change.
• Ideally, how many variables should an
experiment test?
It should test only one variable at a time.
•When a variable is kept unchanged in an
experiment, it is said to be a control.
What is a controlled experiment?
• A controlled experiment is an experiment in
which one variable is changed while the other
variables are controlled.
TYPE OF VARIABLE
DEFINITION
Independent
The variable that is
(Manipulated) Variable
deliberately changed in an
experiment
Dependent
(Responding) Variable
The variable that is
observed and changes in
response to the
independent variable.
What is measured.
Redi’s Experiment on
Spontaneous Generation
Several
Days
Pass
Maggots Appeared
No Maggots Appear
In Redi’s experiment, what were the
independent variable and the dependent
variable?
• The independent (manipulated) variable
was the presence or absence of the
gauze covering
• The dependent (responding) variable was
whether maggots appear.
Scientists use the data from a controlled
experiment to evaluate the hypothesis
and draw a conclusion.
• Anton van Leeuwenhoek - discovered a world
of tiny moving objects in rainwater, pond water,
and dust that he called “animalcules.”
• John Needham - claimed spontaneous
generation could occur under the right
conditions. He repeated Redi’s experiment
using gravy which he put in a bottle, sealed and
heated it. Microorganisms were found in it when
he examined the contents.
Lazzaro Spallanzani - One of the first to
disprove spontaneous generation. An
Italian scientist who proved microorganisms
could be killed by boiling. (Italian 1767)
In the late 1700's, Lazzaro Spallanzani tried to
disprove this by performing a controlled
experiment with broth:
• He put broth into two flasks (glass
containers) and sterlized them both by
boiling the broth.
• One of the flasks was left open to the air.
• The other flask was sealed up to keep out
any organisms that might be floating in the
air.
• Microrganisms developed only in the
uncovered flask.
From this, Spallanzani concluded:
• That the microorganisms did NOT come
from the broth, but were in the air that
entered the flask.
• Therefore, not even microorganisms came
from nonliving things.
Louis Pasteur - a French scientist settled the
spontaneous generation argument by designing a
special flask that showed as long as broth was
protected from microorganisms, it remained free
of living things.
Louis Pasteur’s Experiment
Boil broth
No
Growth
Neck
breaks
Microbes grow
Controlled experiments are not
always possible because
•
•
Ethics prevent most experiments with
humans
In field studies researchers try not to
disturb systems they observe
Theory is a well-tested explanation
that unifies a broad range of
observations.
Section 1–3 Studying Life
What is biology?
• Biology is the science that seeks to
understand the living world.
Characteristics of Living Things
• Living things are made up of cells.
• Living things reproduce and produce new
offspring.
• Living things are based on a universal
genetic code.
• Living things grow and develop.
• Living things obtain and use materials and
energy.
• Living things respond to their environment.
• Living things maintain a stable internal
environment.
• Taken as a group, living things change over
time.
Living things or organisms are made up of
small self-contained units called cells.
•
•
Unicellular- single celled organisms
Multicellular- contain many cells
All organisms produce new organisms
through reproduction.
2 types of reproduction:
•Sexual
•Asexual
Growth & Development - each type of
organism has a distinctive life cycle a pattern of
growth & change.
Example:
Fly eggs  Larva (maggots) 
Adult fly
All organisms use energy and a constant
supply of materials to grow, develop &
reproduce.
The amount of energy determines the
organism’s metabolism.
Organisms respond to their environment.
Example:
• Amount of light
• Change in temperature
• Combinations such as the amount of water
& temperature
Internal Balance – Living things maintain an
internal stability “Homeostasis”
If homeostasis is disrupted in a major way an
organism cannot survive.
Example: bird’s feathers maintain its body temp.
during both cold & warm weather
Evolution-Organisms as a group must be
able to change over time to insure
survival.
• The study of biology is divided into
levels of organization.
BIOSPHERE
ECOSYSTEM
COMMUNITY
POPULATION
ORGANISM
GROUP OF CELLS
CELLS
MOLECULES
Chapter 1 Section 1-4 Tools & Procedures
• What measurement system do most
scientists use?
• Most scientists use the metric system
when collecting data & performing
experiments
• The metric system is based on
multiples of 10
Common Metric Units
Length (meter)
Mass (gram)
1 m = 100 cm
1 m = 1000 mm
1000 m = 1 km
1kg = 1000 g
1 g = 1000 mg
1000 kg = 1 t
(metric ton)
Volume (liter)
Temperature ( ̊ C)
1 L = 1000 mL
1 L = 1000 cm3
0 ̊ C freezing point of
water
100 ̊ C boiling point of
water
Terms:
– Observation: What is seen or measured.
– Inference: A conclusion based on
observation or evidence.
– Hypothesis: A prediction based on
available evidence. A good hypothesis
states both cause and effect.
– A correct hypothesis can be tested
and falsified (proven incorrect) using
an experiment.
– The easiest way to write a correct
hypothesis is as an “if-then”
statement. (ex: If I give patients this
pill, then they will not get sick.)
– Theory: An explanation of natural
events that is supported by strong
evidence.
• Misconception: “Theories are things
that are opinions, or are not proven.”
This is an incorrect use of the word
“theory” in a scientific context. A
scientific theory is not a simple guess
or conjecture, and is strongly
supported by evidence.
• Theories tie together many scientific
facts, hypotheses and laws.
•
Controlled Experiment:
Compares the results of an
experiment between two (or
more) groups.
– Experimental group: Group being
tested or receiving treatment.
– Control group: “Normal” group.
Should be identical to experimental
group in every way except one: it
does not receive the new
treatment.
– Placebo: A sugar pill or other “fake”
treatment given to the control group.
– Independent Variable: Variable that
is being tested (ex: new drug, new
fertilizer).
• The “If” part of an “If-then”
hypothesis.
• The independent variable is
always plotted on the X axis.
– Dependent Variable: Variable
that is measured at the end of an
experiment; the results.
• The “then” part of an “If-then”
hypothesis.
• The dependent variable is
always plotted on the Y axis.
Characteristics of a good
experiment:
– Can be repeated the same way
and get the same results.
– Have large sample size/many test
subjects.
– Are performed for longer periods of
time.
– Test only one independent
variable. All other
characteristics of the tested
groups should be the same.
– Are peer reviewed – examined
by several scientists to
determine its accuracy.
– Must test the hypothesis and
show whether it is wrong or
right.
– Is objective – the experiment
and conclusion are fair and
unbiased. Fact and opinion are
not mixed.
– The experiment follows
established ethical and legal
standards
D. Graphs and Data Tables
– Data tables are used to organize data
which will be plotted in a graph.
• First column in the table is for the
independent variable.
• Second column is another for the
dependent variable.
• Each column
should be titled,
and include
units of
measurement.
• Data in the
table must be
arranged in
ascending or
descending
order.
Making a Line Graph
• Line graphs can be used to show how
something changes over time. They have an
x-axis (horizontal) and a y-axis (vertical).
1. Always refer to your ‘Guide to Good Graphs’
2. Always give your graph a title
3. The x-axis (horizontal line) of a graph is
always your independent variable and the
y-axis (vertical line) is the dependent
variable. Usually, the x-axis has numbers
for the time period, and the y-axis has
numbers for what is being measured.
4. Always label the x and y axes and give the
units.
For example- Time in seconds
5. Make sure your data is graphed as large as
possible in the space you've been given.
Title of the Graph
0
1
2
3
4
X-axis (independent variable)
5
Both the x and y axis of the graph
must be labeled or titled. These
labels are typically the same
ones used in the data table.
Once again units of
measurement must be written
with the title.
The independent variable is
always plotted on the x-axis.
The dependent variable is always
plotted on the y-axis.
The x and y axis must be numbered.
• These numbers must increase by a
uniform increment (that is you must
count by 1’s, 2’s, 5’s, 10’s, etc).
• Your numerical scales should take
up most of the axes. Squeezing it
all into the bottom corner makes
the graph impossible to read and
no credit will be given.
• The numbers must line up with
the grid lines of the graph, not
with spaces between them.
• You do not need to start
numbering your axis with 0.
 All points plotted on
your graph must be
surrounded by a
circle (or sometimes
a square or triangle,
depending on the
directions)
Microscopes
• comes from greek words
– micro means small
– skop means see
• Most commonly used microscope is the
Compound Light Microscope
-allows light to pass through specimen &
uses two lenses to form an image
-can be used for both dead or living tiny
organisms
-chemical stains or dyes may be used to
help see structures better
Electron microscope
-used to study very small objects
-can visualize objects 1000x smaller than what
is seen with a light microscope
-Can not be used with living organisms
2 types:
1.) Transmission electron microscope
(TEMs)
-shines a beam of electrons through a thin
specimen
2.) Scanning electron microscope (SEMs)
-runs a pencil like beam of electrons back
& forth across the specimen’s surface
-good for 3D surface images
Laboratory Techniques
How biologists study cells
• Cell Cultures
• a single cell is put into a nutrient solution
• the cell reproduces to produce a group of
cells
• the cells are than used to test
– cell responses
– cell interactions
– specific cells
• Cell Fractionation
-separates one part of a cell from the rest of
the cell using a centrifuge so it may be
studied