A Tour Of The Science Practices
SP1. USING REPRESENTATIONS AND
MODELS
What’s a Model?
Models are representations of thoughts.
Models can be physical, computational,
mathematical, or literally any other way that a
thought can be represented (though in science,
they tend to be one of the first three, or maybe
verbal).
You are expected to be able to create, describe,
refine, use, and re-express representations and
models in the work that you do in this course.
Be Careful!
Do not make the mistake of confusing a
model for the reality that it represents.
Models are always simplifications of
reality.
3 Ways to Work On SP1
1. When you are shown models or representations,
take a moment and acknowledge that is what is
happening.
1. Create alternate models and representations of
the concepts that you are investigating from the
ones that you are being shown by your teacher.
1. Take models and representations that you are
using in class, and identify the simplifications in
them. Refine the model to show this additional
complexity.
Activity
Working in groups of three or four, analyze a
model:
• Graphically represent the model.
• Explain what it being modeled.
• Describe the simplifications in the model.
A Tour Of The Science Practices
SP2. USING APPROPRIATE MATHEMATICS
Math!
Math is the most objective way we have to
describe and model scientific phenomena.
You are expected to be able to justify the
selection of a mathematical routine, apply a
mathematical routine, and estimate
numerical quantities.
Biologists have an unfair reputation for not
liking math. This is not acceptable. Math
must be embraced, and loved.
3 Ways to Work On SP2
1. Practice, practice, practice.
2. Try to come up with estimates of
ridiculously big numbers.
3. When you see math being used in class,
try to justify why the math is appropriate
for the task it is being used for.
Activity
Estimate each of the following:
• The number of students in the school.
• The number of people in deer park.
• The number of hairs on your arm.
How is the process that you use similar for
each of these activities?
How is it different?
A Tour Of The Science Practices
SP2. USING APPROPRIATE MATHEMATICS
MATH SKILLS- METRIC SYSTEM
What You Have To Do
The metric system is the measurement system of
science. It is based on powers of 10, which modify a
base quantity of the major dimensions of matter, energy,
and time in the universe.
Prefixes are used to denote every power of 10 from 10-3
through 103, and then every three powers of ten larger
and smaller.
Biology ranges all over the metric system.
Selected prefixes and their quantities are provided on the
formula sheet that you will have during the AP exam.
Selected Metric Prefixes
Factor
Prefix
Symbol
109
giga
G
106
mega
M
103
kilo
k
10-2
centi
c
10-3
milli
m
10-6
micro
μ
10-9
nano
n
10-12
pico
p
The Metric System Rules!
There are a lot of benefits to using the metric
system.
1. The common powers of 10 structure makes
arithmetic with widely different numbers very
easy.
2. It is universal among all scientists on the
planet. A kilometer always signifies the same
distance in all cultures.
You need to use the metric system in all data
recording and data calculations that you engage in
during this course.
A Tour Of The Science Practices
SP2. USING APPROPRIATE MATHEMATICS
MATH SKILLS- DILUTIONS
What You Have To Do
The dilution equation is provided on the
formula sheet that you will have during the
AP exam.
It is useful in lab. You may use it or not, but
you need to be able to use it (for the exam,
and in your life as a competent laboratory
scientist
C=
concentration
V = Volume
i = initial
f = final
You will know (or be able to figure out) three
of these variables. You will use the equation
to figure out the fourth.
Sample Problem
How much of a solution of 2M sucrose
must be diluted to make 3L of a 1M
sucrose solution?
A Tour Of The Science Practices
SP3. SCIENTIFIC QUESTIONING
What makes a question scientific?
Not all questions can be addressed scientifically.
There are limitations on the kinds of questions that
science can answer.
Example: What happens to us when we die?
Inherently limited in what science can tell us
Scientific answer: Our bodies are decomposed
back in to simpler compounds, which are
reincorporated by the ecosystems of the planet.
You need to be able to pose, refine, and evaluate
scientific questions.
3 Ways to Work On SP3
1. Question how the knowledge that you are
learning in this course was determined.
2. Work on asking scientifically
useful/interesting questions…and then
refining them into even better questions.
3. Try to recognize when a question is not
going to be appropriate for scientific
investigation.
Activity
Working in groups of three or four, ask some
questions:
• Pick an area of biology that interests you.
• Write two examples of scientifically valid
questions.
• Write two examples of scientifically invalid
questions
What makes a particular question more or less
valid for scientific inquiry?
Revise your scientifically invalid questions to
make them valid.
A Tour Of The Science Practices
SP4. DATA COLLECTION
Data is Important
Science relies on data to answer questions.
Data is generated in many different circumstances,
including field investigations and experimentation.
The circumstances in which data is collected will
influence how useful that data is for answering
questions.
You need to be able to justify the selection of data,
design a plan to collect data, collect data, and
evaluate sources of data.
3 Ways to Work On SP4
1. Identify which data sources will be most
useful for answering particular scientific
questions.
2. Determine what sorts of equipment and
procedures are used to collect specific
types of data.
3. Use the data sets generated by other
scientists to develop your answers to
scientific questions.
Activity
You are interested in investigating the
feeding preferences of slugs.
• Determine how you are going to collect
data.
• Determine what data you will collect.
• Explain how your data will help you
address your question.
A Tour Of The Science Practices
SP5. DATA ANALYSIS
Once You Have It, Analyze It
The analysis of data is how science develops
explanations.
Analysis and evaluation of data include
statistical, graphical, and computational
manipulation of a data source.
You need to be able to analyze data, refine
observations and measurements based on the
analysis of data, and evaluate the evidence
provided by a data set.
3 Ways to Work On SP5
1. When investigating a particular scientific
explanation, evaluate the data that supports
(and refutes) the explanation.
2. In experimental settings, use the data that is
being generated to determine if the data is
appropriate for the experiment.
3. Determine the statistical aspects of a
particular data set, and consider how they
support or refute a particular explanation for
the data set.
A Tour Of The Science Practices
SP5. DATA ANALYSIS
MATH SKILLS- DESCRIPTIVE STATISTICS
How do we describe data?
Descriptive statistics are used to tell us
about the characteristics of a particular data
set.
Each descriptive statistic tells us something
different, and may be more or less useful
depending on the data set, and the concepts
it is supporting or refuting.
Mean, median, mode, range
Let’s try a sample
Sample data set A:
5cm, 5 cm, 10 cm, 20 cm
Mean: The sum of all of the data points in a
data set, divided by the number of items in the
data set.
_
x = mean
n = size of the
sample
(number of items)
Let’s try a sample
Sample data set A:
5cm, 5 cm, 10 cm, 20 cm
Mode: The most common value among the
items in the data set.
Median: The middle value of the data set, or
the mean of the middle two values in the data
set.
Range: The difference between the highest
value and lowest value in the data set.
A Tour Of The Science Practices
SP5. DATA ANALYSIS
MATH SKILLS- STANDARD DEVIATION
Standard Deviation
A measurement of the variance of the items
in the data set
The higher the standard deviation, the
further away most data points are from the
mean of the data set. The equation is on
the formula sheet in sigma notation.
s = standard
deviation
Sample Problem
Determine the mean and standard
deviation of these data sets:
Sample data set A:
5 cm, 5 cm, 10 cm, 20 cm
Sample data set B:
8 cm, 9 cm, 11 cm, 12 cm
A Tour Of The Science Practices
SP5. DATA ANALYSIS
MATH SKILLS- STANDARD ERROR
Standard Error
A measurement of the variance in the means of data
sets taken from the same population.
Different samples will usually have different means.
Standard error tells us how varied those means will
be.
Useful because if two data sets have means that are
more than 2 standard errors away from each other
(actually 1.96) have a 95% confidence that they are
statistically significant.
deviation
SEx = standard
Sample Problem
Determine the standard error of these two
data sets:
Sample set 1: 6.2 g, 6.4 g, 6.6 g, 7.0 g
Mean:
~6.6g
s= +/- ~0.34g
Sample set 2: 12.2 g, 12.3 g, 12.6 g, 13.0 g
Mean = ~12.5g
s= +/- ~0.359g
A Tour Of The Science Practices
SP5. DATA ANALYSIS
MATH SKILLS- HYPOTHESIS TESTING
A Statistical Hypothesis
Our statistical expectation is NOT the same
thing as our experimental expectation. The
hypothesis of the experiment governs how
we frame our statistical expectation, but our
statistical hypothesis is ALWAYS the null
hypothesis (that the variation between
expectation and observation is due to
chance)
Chi-Square Testing
A way to determine if the variance between what we
observe and what we expect in a set of categorical
data is statistically significant or not.
X2= chi-square value
o = observed values
e = expected values
When do we use this?
The major areas where categorical data will
be encountered in this course will be in
ecology (ex. distribution of organisms in an
environment) and mendelian genetics (ex.
Number of progeny that have certain
inherited characteristics).
Sample Problem
An ecologist is habitat preferences of periwinkles on the rocky
coast line of the New England coast. She hypothesizes that more
periwinkles will be found closer to the tide line. To test her
hypothesis, she collects data by counting the number of
periwinkles within a .5 m2 quadrat sample that she observes on a
rocky coast line location at low tide:
Distance from low tide:
periwinkles:
At low tide line:
36
1 meter above low tide:
2 meters above low tide:
3 meters above low tide:
4 meters above low tide:
Total:
75
Number of
24
10
3
2
Determine if the difference in the number of periwinkles observed
in each location is statistically significant.
Chi-Square Table
Degrees of Freedom
p
1
2
3
4
5
6
7
8
0.05
3.84
5.99
7.82
9.49
11.07
12.59
14.07
15.51
0.01
6.64
9.32
11.34
13.28
15.09
16.81
18.48
20.09
If we don’t reject the null, it DOES NOT
mean that the null is accepted. It just means
that it has “failed to be rejected.”
A Tour Of The Science Practices
SP6. SCIENTIFIC EXPLANATIONS
What is a “scientific” explanation?
Scientific explanations are always tentative, and supported
by evidence.
A scientific explanation must be testable. If an explanation
cannot be tested, science can not support or refute it.
Scientific explanations that support a broad range of
observable phenomena are called “theories”.
You need to be able to justify claims with evidence,
construct explanations based on evidence, articulate the
reasons an explanation or theory is refined or replaced,
and evaluate alternative scientific explanations.
3 Ways to Work On SP6
1. Never make a claim without evidence to
support it.
2. Consider the evidence that supports the
explanations and theories that you will be
exposed to in this course. Explain how and
why they have had to be revised over time.
3. Consider alternative explanations for the
phenomena that you investigate in this
course. Analyze how the available evidence
supports or refutes these alternatives.
Activity
Briefly compose a response as to what you
feel the parts of a scientific explanation are.
Describe the function of each part.
Activity
Introducing the Explanation Tool (Yay!)
A Tour Of The Science Practices
SP7. MAKING CONNECTIONS
Everything is Connected
Science connects concepts that span several
scales of space and time.
Science depends on many different kinds of
information from a variety of domains to make
explanations. Biological explanations use
physical, chemical, and mathematical information.
You need to be able to connect phenomena and
models across spatial and temporal scales, and
connect concepts across domains to generalize
and extrapolate ideas.
3 Ways to Work On SP7
1. Actively consider how the concepts of this
course rely on knowledge from a variety
of domains.
2. Spend time relating temporal scales and
spatial scales to the ones that you are
most familiar with.
3. Consider how biological explanations
agree or conflict with explanations from
other sciences.
Activity
Choose one of the following statements of
biological knowledge:
• Living systems must acquire energy from
the environment.
• The cell is the fundamental unit of
organization in living systems.
• All living systems share a common
ancestor billions of years ago.
List the knowledge from other scientific
fields that will inform and support your
chosen statement
Image Credits
All images taken from AP Biology materials
published by the College Board.