The Nature of Science
Unit I
Measurement
 What kind of data can be collected?
 qualitative data
 quantitative data
 What system is used for quantitative data?
 the SI system (metric mostly) uses powers of 10
and certain prefixes; used by scientists
throughout world to avoid confusion
Measurement
 Value (unit)
 Length (meter, m) 
 Mass (gram, g)

 Volume (liter, L) 
 Time (second, s) 
 Temperature

(degree Celsius, C)
 Standard Equipment
 Meter stick, ruler
 Triple-beam balance
 Graduated cylinder,
syringe, micropipette
 Stopwatch
 Thermometer
Metric Prefixes & Values
 the SI system is based on powers of 10
 kilo - hecto - deca - base unit - deci - centi – milli
 k
h
D
***
d
c
m
 1000 - 100 - 10 -
***
- 1/10 - 1/100 - 1/1000
 Example: a kilometer = 1000 meters
 How long is a millimeter?
 Is a decaliter larger or smaller than a deciliter?
 How many centigrams are in a gram?
Metric Conversions
 Because the SI system is based on powers of
10 it is easy to convert between units
 kilo – hecto – deca – base unit – deci – centi – milli
 “King Henry died by drinking chocolate milk”
 K -- H -- D -- B -- D -- C -- M
 See demonstration on board…
Science…
 …tries to disprove rather than prove
 Difficult to do enough experiments to truly prove
 …can be done well, or poorly
 Must examine with a critical eye
 …is not democratic
 Based on confirmed observations
 …does not follow neat little steps (lab
packet)
 Though basic steps always followed…
Scientific
investigations
start with an
observation
and a
question!
Scientific
Method
Scientific Method
 The following steps will be followed when
conducting labs in this class…






I. Problem/Purpose
II. Background/Research
III. Hypothesis
IV. Experiment
V. Data Analysis
VI. Conclusions
~ see Lab Report Format for more specifics!
Steps of the
Scientific Method
1. Problem/Question: Develop a
question or problem that can
be solved through
experimentation.
Steps of the
Scientific Method
2. Observation/Research: Make
observations and research
your topic of interest.
Do you remember the
next step?
Steps of the
Scientific Method
3. Formulate a Hypothesis:
Predict a possible answer to
the problem or question.
Example: If soil temperatures
rise, then plant growth will
increase.
Steps of the
Scientific Method
4. Experiment: Develop and
follow a procedure.
Include a detailed materials list.
The outcome must be
measurable (quantifiable).
Steps of the
Scientific Method
5. Collect and Analyze Results:
Modify the procedure if
needed.
Confirm the results by retesting.
Include tables, graphs, and
photographs.
Steps of the
Scientific Method
6. Conclusion: Include a
statement that accepts or
rejects the hypothesis.
Make recommendations for
further study and possible
improvements to the
procedure.
Steps of the
Scientific Method
7. Communicate the Results: Be
prepared to present the project
to an audience.
Expect questions from the
audience.
Think you can name all
seven steps?
Experimental Design
 Large sample size
 Replicated many times
 Control Group
 The “baseline”…what results compared against
 Controlled Variables
 Remain the same between all groups, so that
they are NOT factors in the experiment
Experimental Design - Variables
 Independent Variable  Dependent Variable
(“I” set up beforehand)
(“Data” collected
“During” experiment)
~ is the only variable that ~ is the effect of the
independent variable
is changed between
experimental groups
~ it is what you measure
as you experiment
~ example: color of light
on plants
~ ex: height plants grow
Data Tables
Independent Variable
(unit)
Dependent Variable
(unit)
Data Tables
Table 1. Height of Sunflowers when Grown in Varying Colors of Light
Color of Light
White (daylight)
Red
Blue
Green
Sunflower Height (cm)
7
6
8
3
Graphing Data Tables
9
8
Graph 1. Height of Sunflowers when Grown in
Different Colors of Light
7
6
Dependent
Column
5
4
Responds
3
2
Y axis
1
0
white
red
blue
Manipulated
Independent
X axis
green
Graph
Graph 1. Height of Sunflowers when Grown in
Different Colors of Light
9
8
7
Height of
Sunflowers
(cm)
6
5
4
3
2
1
0
white
red
Color of Light
blue
green
Characteristics of Life
What processes or traits must all
living organisms exhibit be
considered a live?
Characteristics of Life…
 How do you know something is alive???
(With a group of 4 students…)
-Identify the characteristics that are
common to all living organisms.
 Put your ideas on chart paper…
 Be prepared to share your findings with the
class…
Characteristics of Living Things
Organisms are living things. All living
things:
1.
2.
3.
4.
5.
6.
are composed of one or more cells
contain similar chemicals
Take in and expend energy
Grow and develop
Respond to their surroundings
Reproduce – on the cellular & organismal level
All Living Things Are Made Of Cells
 A cell is the basic unit of structure and
function in an organism.
 Unicellular organisms are single-celled
organisms. Bacteria, the most numerous
organisms on Earth, are unicellular.
 Multicellular organisms are composed of
many cells. The cells of organisms use
energy to grow and repair injured parts.
Cells Are Composed Of Similar
Chemicals.
 The most abundant chemical in cells is
water.
 Another chemical called carbohydrate is a
cell’s energy source.
 Proteins and lipids are the building
materials of cells.
 Nucleic acids are the genetic materials
that direct the cell’s activities.
All Organisms Need Energy
Some make their own food (energy)…
Some don’t make their own food…
 Organisms that can make their own food
are called autotrophs.
 Organisms that cannot make their own
food are called heterotrophs.
Living Things Grow and Develop
You weren’t born being the size you are now…
Zygote…Embryo…Fetus…Newborn…
Infant…Toddler…and so on…
 Growth is the process of becoming larger.
 Development is the process of change that
occurs during an organism’s life to produce a
more complex organism.
All Organisms React to their
Surroundings
The alternative to “responding” to your
surroundings….EXTINCTION!!!
 A change in an organism’s surroundings
that causes the organism to react is called
a stimulus. An organism reacts to a
stimulus with a response—an action or
change in behavior.
All Organisms Can Reproduce
 Another characteristic of organisms is the ability
to reproduce, or produce offspring that are
similar to the parents.
Pre-AP Bio Exam Review
 Define the independent variable
 Define the dependent variable
 Define experimental group
 Define control group
 Define constants
 Review Safety Symbols Handout
 Identify parts of the scientific method
 Interpret data tables and graphs
 Be able to identify and know function of
lab equipment
 Be able to read lab equipment
 Metric Measurements/Conversions
 Characteristics of Life
The Chemistry of Water
Why is water essential for life?
 Makes up most content of cells
 Required for chemical reactions
 Required to grow food
 Provides shelter/protection
 Aids in transport of materials
Why Water?
 Water is neutral, but its electrons are a little
off-set
 The oxygen side is slightly negative
 The hydrogen side is slightly positive
 This is called POLARITY…it is the key to almost
all of water’s special traits!
Properties of water:
Polarity
 Water’s polarity allows
for “hydrogen bonds”
 These H-bonds make
water “stick” to itself
and many other
things…resulting in its
special properties
 What?
Properties of water:
Cohesion & Adhesion
Attraction between water and itself (or
another molecule)
 Why?
Polar ends grab each other
 Ex:
Water moving up a stem
 What?
Properties of water:
High Surface Tension
Difficult to break surface of water
 Why?
H-bonds make water stick to itself
 Ex:
Insects walking on water
Properties of water:
High Specific Heat
 What?
Water holds its temp; is hard to change it
 Why?
Must break H-bonds for water to change temp
 Ex:
Bodies of water maintain stable envir. temps; temps
within organisms remain stable
Properties of water:
High Heat of
Vaporization
 What?
Must remove lots of heat before water
vaporizes
 Why?
Must break all H-bonds holding molecules first
 Ex:
Cooling systems in animals
Properties of water:
Ice Less Dense Than Liquid Water
 What?
Ice will float in water
 Why?
H-bonds hold water molecules farther
apart (more volume)
 Ex:
Ponds insulated in
winter
Properties of water:
Ice Less Dense than Liquid Water
Properties of water:
Universal Solvent
 What?
Water dissolves many
substances
 Why?
Charged ends pull on
other charged particles
 Ex:
Most rxns require
chemicals in solution
Water is neutral…so why does it
“have charges”?
 Water dissociates into ions
(ions are particles with charges)
 Not very many ions actually form, but it is
enough to matter
Dissociation of Water
 In pure water [H+] = [OH-]…which means
pH is 7, or neutral
 When acids dissolve in water
…there are more H’s than OH’s
 When bases dissolve in water
…there are fewer H’s than OH’s
How do we know how acidic or
basic something is?
 pH scale measures how acidic/basic
 Scale is 0-14
Neutral = 7
 Acid < 7
Base > 7
 Each # is 10X greater than next #
 Ex: pH 3 is 10X more acidic than pH 4
…how much more acidic is pH 2 than pH 5?
pH Scale
Why does pH matter to life?
 Most cells are at pH of about 7
 Even slightest change in pH can be
harmful/deadly because chemical rxns can
be altered/inhibited
 Acid rain harmful because organisms
forced to take in acidic water…formed
when fossil-fuels react with water in air
Acid Rain
The End