Transcript Document

Internal assessment
"The gift of fantasy
has meant more to
me than my talent
for absorbing
positive knowledge."
"The secret to
creativity is knowing
how to hide your
sources."
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IA in Biology has 3 (5) components
1.
2.
3.
4.
5.
Design (D) – marked twice
Data Collection and processing (DCP) -marked
twice
Conclusion and Evaluation (CE) - marked twice
(Manipulative Skills – assessed over the course of the year)
Personal Skills – assessed in the Group 4 project)
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Design has 3 ‘Aspects’
Aspect 1: Defining the problem and selecting
variables
Aspect 2: Controlling the Variables
Aspect 3: Developing a method for collection
of data
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Look at Page 23 of your IB Introduction
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Aspect 1: Defining the problem
(research question) and selecting
variables
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Design involves
1.
2.
3.
4.
5.
6.
A Research Question (RQ): focussed, with
observations and limits
Variables: relevant independent and
dependent
Recognition of uncertainties and sources of
error
Effective methods to control variables
Effective methods to measure variables
Sufficient measurements/ data for analysis
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Important ‘Regulations’ imposed by IB
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The teacher is only allowed to provide an ‘openended problem’ to investigate
The teacher is only allowed to suggest a ‘general’
research question’
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Students can NOT be
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Given a focused research question
Told the likely outcome of the experiment
Told which independent variable to select
Told which variables to hold constant
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We will work over the next 2 weeks on the
following ‘General’ research questions:
1.How do different concentrations of a specific
solution affect osmosis in plant or vegetable
tissue
1.How
do different concentrations of a specific
solution diffuse across a semi-permeable
membrane?
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Simple Design ‘tips’
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It is easier to adapt a ‘known and used
method’, than to invent a whole new method!
It is NOT appropriate to derive a known or
existing law or constant
Be original, but try to keep your method
simple!
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Your Design is YOUR design
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If a school sends in two identical design IA’s then
the whole class will be marked down for IB
grading
All design projects MUST BE YOUR OWN
WORK
You must think of your own research question
Your description of variables must be
comprehensive
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There are 6 sections to your design IA
1.
2.
3.
4.
5.
6.
7.
Research question
Background information
Accurately defined variables (independent,
dependent, controlled)
Apparatus
Risk assessment
Assessment of potential errors and uncertainties
Materials and Method used
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…so how do you come up with an
‘original’ Research Question?
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Remember your Scientific Method, and essential
components of experimental Design
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Observation (Inference)
Research Question/ Hypothesis/Null Hypothesis
Data – quantitative and qualitative
Variables
Controlled experiment
Control group
Research Question
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Your research question must be PRECISE and
it must be MEASURABLE
The simplest methods:
What is the effect of x (independent variable)
on x (dependent variable)?
Is x correlated with y?
We must have a principle (hypothesis)/ question
that we can objectively test using quantitative
methods
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Referenced background Information is
essential
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The RQ must be based on
background knowledge and
observation
The RQ can be presented as
a hypothesis, based on
biological reasoning
A brief referenced
introduction will
provide background
information and
justification for your
Research Question
An example!
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You have been asked to design an experiment
investigating factors that affect biological enzyme
activity
Some preliminary research (Google) has explained
that lead may impede plant growth through acting on
catalase: http://oas.uco.edu/03/paper/fenska.htm
You decide to investigate this…
What would an appropriate Research Question be?
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Research Question
Does lead nitrate inhibit the activity of
catalase?
Is this sufficiently precise?
No! we don’t know how much lead nitrate is
being used, nor how we will measure catalase
activity…
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Precise RQ:
Do concentrations ranging from 0.01 M – 0.25
M lead nitrate in the reaction mixture inhibit
the rate of production of oxygen from
hydrogen peroxide by potato catalase at room
temperature?
Better, but we still don’t know how rate of
oxygen production is being measured…
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Precise RQ:
Is the production of a head of bubbles of
oxygen from hydrogen peroxide inhibited by
concentrations of 0.01 M – 0.25 M lead nitrate
in the reaction mixture?
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ASPECT 2 OF DESIGN:
CONTROLLING THE
VARIABLES
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Dependent Variable
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What you will measure
Must be specified clearly
Include units
Will form the Y-axis of your graph
Do NOT use ‘rate’ unless you have actually
measured rate in xxs-1
Do not use ‘amount’ – use ‘volume’ or ‘mass’…
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Independent Variable
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What you will manipulate
Forms the X-axis of your graph
The range must be chosen carefully..aim for
several integers
You may wish to include ‘negative controls’
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Controlled variables
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Variables which could potentially affect the
dependent variable and thus affect the data
You must detail these and keep as many as possible
constant
Examples include: temperature, total volume of
reaction mixture, pH, concentration of solutions,
surface area, time, light intensity, source of
biological material used
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Uncontrolled variables?
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Ideally, you should have none!
If you cannot eliminate certain
environmental conditions, you must monitor
and record them
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Identify the experimental
VARIABLES
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Dependent – what you
measure (Y-Axis)
Independent – what you
change (X- axis)
Controlled – what remains
constant
(Uncontrolled – variables
which may be hard to control)
Ideally you should have all
variables controlled,
excepting one dependent and
one independent variable
Example: Effect of Lead Nitrate on
catalase activity
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Independent variable: presence or absence of lead
nitrate in the reaction mixture
Dependent variable: rate of production of oxygen
Does this delineate the variables adequately?
Is ‘rate of oxygen production’ truly the dependent
variable?
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Example: Effect of Lead Nitrate on
catalase activity
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Independent variable: presence of lead nitrate at
concentrations of 0.01 M – 0.25 M in the reaction
mixture
Dependent variable: change in % oxygen in closed
chamber, measured using Vernier® probe
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ASPECT 3: DEVELOPING A
METHOD FOR COLLECTION
OF DATA
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How much data is enough?
How much data is enough?
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That all depends on the experiment!
The IB love 5 X 5 experiments!
The teacher cannot tell you:
• HOW to collect the data
• How much data to collect…
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The classical five by five model
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5 different test groups
Repeat the procedure
for each group 5 times
Not all experimental
procedures need a 5 X
5 model!
Apparatus and materials
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The appropriate apparatus must be selected and stated
Quantity (SI units, volume/mass), size of
measurement equipment must be stated
You must use the most precise means of measuring
your specific materials
Uncertainty of apparatus and materials must be
discussed
A picture or photo of your apparatus is always
GREAT!
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Risk Assessment!
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Scientific experiments shouldn’t be
dangerous!
You must point out potential dangers – sharp
scalpels, Bunsen burners, boiling water,
potentially caustic chemicals
You must detail how you will avoid potential
dangers
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Materials and Methods
1.
2.
Write in the passive voice, in the future tense
Use paragraphs or bullet points
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What are Standard International (SI) ?
Measurement
SI Units/accepted non-SI units
Distance
m, cm, mm
Mass
Kg, g, mg
Volume
dm3, cm3
Concentration
Moles, millimoles
Time
Seconds, minutes
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Design exemplar: Investigation into the effects
of milk on growth rate of young rats
A classic experiment on
young laboratory rats,
carried out 100 years
ago
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Group A were fed a baked
dry diet only
Group B were fed with the
same diet plus 5cm3 milk
each day
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Research Question: How will milk affect the
rats’ growth?
Milk
No
milk
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Independent and Dependent variable
Independent – the presence of milk in the
diet
Dependent – the growth rate
Was this
measured?
Accurate?
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Independent and Dependent variable
I - The presence or absence of 5 cm3 of milk as
a daily supplement to a dry diet
D – the mass of each rat measured every 5 days
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Controlled variables
1.
2.
Gender
Age
Precise?
Shows control?
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Method to control variables
1.
2.
The rats will be fed daily
The cages will not be moved
Controlled?
Repeatable?
Make a list of other controlled variables
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Method to control variables
1.
2.
Every day, each rat will be given 20g of
dried food, the food remaining from the
previous day will be removed and weighed
to record the amount of food consumed
each day
The room will be air-conditioned at a steady
temperature of 20 oC ± 1oC
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Controlled variables
1.
2.
3.
30 male rats will be tested in each
group
The testing will begin when the rats are
20 days old, after weaning has finished
The groups will be kept on the diet for
20 days and then the diets will be
switched for a further 20 days
(crossover study)
Sufficient
results
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