Transcript Practical Investigation

Practical Investigation
Students are to carry out a guided
investigation on an organism
Practical Investigation
• Students are to investigate an aspect of the
ecological niche of the organism.
• It is essential that they develop an
understanding of the ecological niche of the
organism before the investigation is carried
out
Practical Investigation
• The investigation is to be done individually
• The investigation and report writing must be
at a NCEA level 3
• This standard is worth 4 credits
Planning an Investigation
• There is great information in your “Continuing
Biology” text book by Meg Bayley.
Log books - 1B5
• Ideas such as rough notes, brainstorming,
possible investigations, collection of data and
observations, research and planning, failures,
successes and tentative conclusions.
• Is a working document - neatness is not
important.
• Purpose is to show investigative skills, and to
record checking of milestones for Task 2.
Planning an Investigation
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Step 1) Knowing the Organism.
• Investigate the ecological niche.
– An understanding of the normal way of life so an
experiment can be designed to yield meaningful results.
• The introduction must briefly refer to relevant
aspects of the ecological niche.
• And in detail when discussing the significance of he
results in the discussion section of the report
What is an Ecological Niche?
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• “The opportunities provided by the habitat and the
adaptations of the organism to make the most of
those opportunities”
• Aspects that should be focused on are:
– The usual habitat of the organism and what the organism
gains from this habitat.
– Adaptations of the organism that allow it to exploit its
ecological niche
– Important relationships the organism has with others in
the habitat, such as feeding, predation, competition.
What is an Ecological Niche?
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1) For the habitat use quantitative or
qualitative data for the factors (abiotic and
biotic)
2) For adaptations consider structural,
physiological, behaviour and life cycle as
factors
Planning an Investigation
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Step 2: The Statement of Purpose
• Needs to be very specific
• Both independent and dependent variables
should be clearly identifiable
• Enable a quality method to be written that
tests it
• Must be related to an aspect of the ecological
niche
• Must not be a guess
Planning an Investigation
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Step 3: The Method
• The independent variable must be clearly
specified and it must have a range of values
– At least 4 for Achieved.
– No more than 6.
– Light and dark do not constitute as a range - a
range of at least four different specific
intensities I.e. 0% light, 25% light, 50% light,
75% light, 100% light
Planning an Investigation
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• The dependent variable must be clearly
specified
– Activity/Growth is not specific enough
– Measurement of the dependent variable must
also be described.
– I.e. ‘the time taken for 10 slaters to clump
together’
Planning an Investigation
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• How other key variables were controlled must
be described.
– These can affect the investigation if not controlled
– Think abiotic!
• Describing how the data will be collected
– Use units where appropriate.
– Try to write it for someone who has no
background in biology. Clear and specific
Planning an Investigation
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• Ensure that when planning your method:
– The range for the independent variable doesn’t
go beyond the tolerance limits of the organism.
– Its appropriate to the organism’s niche
– The increments between the values of the range
have been established in a valid way (trialing
maybe done.
Planning an Investigation
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– The measurement of the dependent variable has
been done in a valid way
– How the data will be collected.
– How the other variables or factors that may affect
the investigation are controlled
Planning an Investigation
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Step 4: The Data
The data collected can either be quantitative or
qualitative…..
What is the difference?
• Quantitative:
o Numerical data obtained through some type
of measurement.
oIt is relatively straightforward to analyse for
reliability using some method of processing.
oE.g. the water temperature is 25C
Planning an Investigation
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• Quantitative:
• Descriptive rather than numerical.
• Can be more variable as they are difficult to
• measure objectively and can be difficult to
establish the reliability
• E.g. the water in the beaker is warmer than the water
in the sink
Planning an Investigation
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• Collecting and recording data
– Raw data measured and/or collected must be recorded
and sufficient data must be collected so a trend or pattern
can be seen (requirement for M or E)
– The method should include ways in which sufficient data
can be collected.
– Several measurements for each independent value
(repeats) and/or having a suitable range for the
independent variable allows for a fair test.
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– Data must be relevant.
– Ensure your data is recorded clearly and
accurately, flow on errors from mistakes can
effect your grade.
Planning an Investigation
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• Data is normally recorded in tables or charts;
features that allow any trends or patterns in the data
to be clearly seen include:
– A full title that includes descriptions of the independent
and dependent variables
– Full headings and appropriate units for each column
and/or row.
– Ruled lines around the sets of data
– The data are ordered in a logical way
– Raw and processed data are clearly identifiable from
each other
The effect of temperature on the heart rate of Daphnia
magna (n=20)
Full,
descriptive
title
Independent
variable
Temperature(C)
Avearge heart
rate(beats min-1)
5
10
15
22
27
49
20
25
30
35
80
152
200
50
No units in body of
table
Full,
descriptive
headings
Dependent
variable
Values
vertically
aligned
and to
same
number of
significant
figures
and/or
decimal
points.
Planning an Investigation
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• Transforming raw data in someway so that they can
be used to show a pattern or trend.
• Data should initially be processed (where
appropriate) into the form that is stated in the
hypothesis (e.g. rate, speed, density, percentage,
frequency).
• Correct number of significant figures needs to be
used.
Planning an Investigation
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• Mean - the average of a set of data, calculated by
adding the individual data values and dividing by
the number of values.
A consideration when calculating the mean is that
outliers (values very different to other data points)
skew the mean. Repeating an investigation several
times can lead to outliers being rejected or ignored
• Median - the middle value the same number of
values are above the median as below.
COPY the missing notes
• Standard deviation – (S) represents the spread or variability
of the data.
A high standard deviation means that the data are widely
scattered around the mean; the best way to reduce the
standard deviation is for more data to be collected by
repeating the investigation.
•The standard
deviation is usually
calculated at the
same time as the
mean using the
formula:
S=
QuickTime™ and a
decompressor
are needed to see this picture.
Planning an Investigation
• Standard Error - is a measure of how close your
calculated sample mean is to the true population
mean, i.e. the reliability of your sample mean.
Standard error is calculated using the formula:
– Confidence intervals shows the range in which a
parameter such as the true mean is estimated to lie. They
are usually shown on graphs as a line equidistant above
and below each plotted parameter – 95% confidence
range represents 2 standard deviations above and below,
99% represents 3 standard deviations above and below
Planning an Investigation
• Data can be processed into a graph (See
Meg Bayley).
– Line graphs – continuous data that have been
obtained from an investigation into how the
manipulation of one factor affects another
– Histograms – continuous data recorded in
categories or ranges, but the dependent variable
is frequency rather than a measurement.
– Bar graphs – used when data are discontinuous
or cannot be quantified
– Kite diagrams – used to show abundance of
organisms, usually along a transect line in a field
of study
– Scatter graphs – drawn to show trends between
two variables that correlate, but there is no
manipulation of one of the variables.
Your Data
Is it grouped in
separate divisions or
in class size intervals
Is it in a group
Was one variable
altered during the
experiment
Use a line
graph
Use a
scatter graph
Separate
divisions
Use a bar graph, kite
graph or pie graph
Class size
intervals
Use a
histogram
• Step 6: Statistical Analysis
– Refer to Handout.
• Step 7: Conclusion
– Refer to Handout.
• Step 8: The Report
– Refer to Handout.