A good, basic framework; try to add much more
detail/explanation to show your biological knowledge and
understanding. Perhaps preserve a more formal, impersonal
style? What follows are only suggestions – I take no responsibility
for their inclusion – you were there, I wasn’t!
Biology Coursework
An investigation into the abundance of freshwater shrimp in St. Johns Beck
– where is this? Can you give a map reference?- in relation to the
concentration of dissolved oxygen levels in the water – when was this
done? The time of year is important – see later!
Aim
To investigate how the abundance of shrimp is affected by different oxygen
concentrations in a fresh water stream.
Background information
Shrimp classification:
Phylum Arthropoda
Clan Crustacea
Order Amphipoda
Family Gammaridae
Freshwater shrimp have 10 jointed legs and well-developed swimming legs under
their tail called swimmerets.
They live under rocks, close to the freshwater riverbanks and on aquatic plants.
Freshwater shrimp eat decomposing vegetation, bacteria and algae particles,
by using their first two pairs of legs to grab the food and put it in their mouth.
How do shrimp get oxygen?
<<<DIAGRAM>> >
Give information on other factors affecting species abundance. E.g. Many
abiotic/biotic factors influenced by man, climate, topography or soil and
vegetation such as pollution, temperature, water exchange/mixing, pH, light,
abundance of plants, nutrient status presence of competitors/predators…
However, oxygen is a fundamental requirement for all living organisms. In order
to fulfil this crucial need in all organisms whatever their surface/area to volume
ratio, many adaptations have arisen (gills, trachea, lungs, respiratory pigments,
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circulatory systems etc. ). These help ensure that all organisms obtain sufficient
oxygen to…(explain the need in terms of respiration/energy/movement etc.refer to the fact that shrimps live in water – a dense medium with currents and
less oxygen than air- so need to be able to maintain their position/move in
search of food/circulate water through their gills etc.)
The importance of oxygen to life seems likely to be reflected by variation in
population numbers with oxygen concentration giving rise to this investigation.
(This explains why you chose to investigate the factor you did and how you
arrived at your hypothesis.)
Hypothesis
“There will be a greater abundance of freshwater shrimp in areas of higher
dissolved oxygen concentration in the stream.”
Dependent Variable
I will be measuring the variation in abundance of the freshwater shrimp
population (explain how e.g.) as shown by the absolute numbers obtained in
samples
Independent Variable
 The concentration of dissolved oxygen levels in the water at sample points.
The independent variable is likely to be affected by other factors, both
biotic and abiotic e.g.
Depth of stream and temperature (explain why-affects solubility of
oxygen, density and mixing)
Velocity of water (affects aeration, turbidity, could wash organisms away)
Plant population size (produce oxygen in photosynthesis)
Light (less light less photosynthesis)
Season (activity slower in cold weather)
Also, as mentioned before, the concentration of dissolved oxygen may
not be the only factor affecting shrimp numbers. A large number of
controlled variables need to be established to make the investigation as
fair as possible and to reach a valid conclusion (all this explains the need
for controlled and measured variables)
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Controlled Variables
 Due a pilot test that I previously carried out, I found that the temperature of
the water, the pH levels in the water and the TDS(total dissolved solids) were
constant through the majority of the investigation so I will not be measuring
these three variables in my coursework investigation.
 I will only take samples from one stream (St. John’s Beck). This is because
there may be different environmental conditions, such as amount of
<<food>>, affecting the lifecycle of the freshwater shrimp.
 All samples will be taken at approximately the same time of day/season
 I will be alert to any large changes in oxygen concentration that might
indicate an increased Biological Oxygen Demand (BOD) due to pollution.
Measured Variables
There are certain abiotic factors cannot be controlled when carrying out my
investigation so I will measure them systematically, along with the independent
variable. These factors are:
 Depth of the freshwater stream
 Velocity of the water
It is important to measure these abiotic factors because they all directly affect
the lifecycle of freshwater shrimp so they may have a part in affecting my final
result in proving my hypothesis correct or incorrect.
Equipment (listing it here introduces the items before you mention them in
what follows – I have changed the order slightly, too)
 Two tape measure reels – I will place one of these tape measures across the
length of the river to measure 16 meters for each of my 16 sites. I will place
the other across the width of the river to define the middle of the 16 sites (so
there are 8 sites on each side of the tape measure). (give precision)
 D-shaped net – This is used to catch organisms in the water. I have chosen to
use this net because it has holes small enough to entrap the freshwater
shrimp but large enough to let debris pass through.
 Flat tray – This is used to hold the contents of my sample. This will be my basis
for the collection and counting of the freshwater shrimp contained in my
sample.
 Magnijar – if I am not confident of the organism’s classification, I will place it
in the Magnijar to get a more accurate view of it.
 ID key - I will use this in conjunction with the magnijar to identify the specific
features of the organism I have isolated from the flat tray to see if it is, in fact
a freshwater shrimp.
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 Pipette – I will use this in my investigation to isolate small freshwater shrimp
from my sample, to place in my palette.
 Spoon – I will use this to isolate larger shrimp that I deem would be unkind to
fit into a pipette.
 Palette - Once I have isolated one shrimp from the flat tray, I will place it in a
palette filled slightly with water. In my pilot study I discovered that if the
palette is filled to the top with water, the shrimp might float or swim away.
Using a palette will help me to tally the numbers of shrimp that I collect
effectively.
 What did you use to measure depth? How precise was it? (m/cm/mm?)
 What did you use to measure oxygen levels? (?precision)
 What did you use to measure velocity? (Precision)
 What did you use to measure the time? (?precision)
 Anything else? Pad? Pencil? Boots? Safety/first aid equipment?...
Sampling Strategy
When sampling my data I will use a specific method all the way through to
maintain a fair, non-bias investigation. I will work along a line transect,
systematically, taking a reading of oxygen levels, depth of water, and impellor
readings (that I will later convert into velocity readings) at every one metre. Eight
meters will be measured in the riffle, and eight in the pool. Can you include a
map/diagram showing the exact position of your transect and sample sites
together with an explanation of “riffle” and “pool”?
In my pilot test I did kick samples lasting one minute each but I found that there
were far too many shrimp to reliably count so I will take 16 kick samples for 30
seconds at each site (every one metre).
When taking my kick samples, I will hold the D-shaped net downstream from me
while I disturb the riverbed with my foot in front of the net. I will aim to make each
stroke of my foot to have similar pressure. Once I have done this once, I will move
the net horizontally one place to the left. I will ensure that it is one place by
flipping the net round to measure the distance with the flat bottom of the net.
To improve accuracy and reliability I shall carry out a statistical test on my results.
Statistical Technique (mention it here because you talk about it below)
I have chosen to use Spearman’s Rank as my statistical test due to the nature of
my investigation. It is the most suited for my investigation because I am looking
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for a correlation between two variables (number of freshwater shrimp and
concentration of oxygen).
Null Hypothesis
“There will be no difference in the abundance of freshwater shrimp due to
dissolved oxygen concentration in the stream.”
I am going to take 16 kick samples because, due to the nature of the statistical
technique I have chosen, to test for a significant correlation between my two
variables, I need a minimum of 12-15 pairs of measurements to be taken.
Did you take any measurements to indicate overall species diversity or total
population numbers at each site? If not, consider commenting on that in your
evaluation – numbers of other organisms might have had an effect on shrimp
numbers.
Did you take just one reading of everything at each site? (It‘s not clear from your
Method.) If not, say how many you took and how you would average the
readings to improve reliability and reduce the effect of random errors. If not,
comment on the possible advantages of doing so in your evaluation.
Method
What health/safety precautions did you take?
 When arriving at the river, set up two tape measure reels in the river; one
across the width of the river, and one across the length. The two tape
measures should cross in the middle of the pool and riffle, leaving 8 meters on
each side.
 Measure all the abiotic factors that may affect the results of your
investigation at each site. Detail the factors (oxygen conc., depth, velocity)
and HOW you measured them.
 Now, do a kick sample for 30 seconds each at each site. Keep the D-shaped
net as close to the riverbed as possible so no organisms evade the net.
 Empty the sample into the flat tray, on the riverside, and gently wash the
organisms off the net into the tray.
 Do a 10mintue count of the freshwater shrimp using the pipette or the spoon
to place them one by one into the palette and tally the results. Explain this
more – what exactly is a 10 minute count? Why did you do it
(?fairness/accuracy/chance to get a reasonably sized sample because of
time to ID?)
 Place any organism that is hard to identify in the magnijar and use the ID key
to help identify them. Return them carefully to the tray or palette as
appropriate.
 When counting time has expired, empty all the organisms back into the river,
downstream of your next sample to minimise any harmful effects due to
stress, change of environment etc. and to reduce the risk of recounting
released shrimps. (another point for your evaluation – how likely is it that some
were counted more than once?)
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 Repeat all points from point 3. (So did you do more than one reading at each
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site? If so, your next move would be to calculate averages.)
Tabulate results.
Illustrate finding with scatter diagram/s to highlight any trend/pattern
together with any anomalous results
Check any trends using
Spearman’s Rank statistical test to observe any correlation between the two
variables.
Draw a conclusion from the results and use it to accept/reject the hypothesis.
Establish how much confidence can be placed in your hypothesis by
comparing Spearman’s Rank Coefficient (as calculated) with the critical
value for the appropriate number of pairs as found in tables.
Evaluate the validity of your findings, suggesting ways of improving fairness,
reliability, accuracy and precision where possible.
Suggest a use/extension for the investigation.
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