Ethical Issues:
Brine shrimps are very delicate, they are living organisms and therefore must take care not to harm them when it is being handled. For this reason, the egg cysts that hasn't hatched and the hatched larvae that had survived in the experiment will immediately be placed at the recovery aquarium for future survival possibilities.
Independent and Dependent Variables:
The independent variable for this investigation is the variation in the temperature where the eggs are going to be incubated and dependent variable is the amount of egg cyst of the brine shrimps that are going to hatch.
*Safety and risk assessments will be mentioned at the methods.
You need
• Brine shrimp egg cysts
• 2 g sea salt for each treatment
• 100 cm3 de-chlorinated water for each treatment
• 40 cm3 beaker of salt water
• 100 cm3 beakers (one for each temperature to be tested)
• Water baths or incubators (one for each temperature to be investigated)
• Stirring rod
• Magnifying glass
• Pair of forceps
• Fine glass pipette
• Bright light
• Access to refrigerator
• Sheet of graph paper 3 cm × 4 cm
Methods:
1. Label four 100 cm3 beakers and weigh (or measure) out into each of them 2 g of
sea salt.
2. Now add 100 cm3 of water to each and stir it until the salt dissolves.
3. Find out the temperatures of the four places you will investigate; they should
range from cold to very warm. *for this experiment, the group I was in decided to look at 5°C,20°C,25°C , and 30°C.
4. Label the containers with the appropriate temperature.
5. The containers should be kept as follows:
6. Next, when all the students are ready, you need to add the egg-cysts.
Here are the following extra precautions and methods that are needed to be followed:
Wet the square of graph paper using a few drops of salt water. Dab the paper onto the white sheet to pick up approximately 40 eggs. This looked like a tiny shake of pepper.
Used a magnifying glass to count the eggs and cut the graph paper so that there are exactly 40 eggs.
Put the paper with the 40 eggs into the beaker (eggs-side down). After 3 minutes, use a pair of forceps to gently remove the paper, made sure that all the egg cysts have washed off into the water.
If you have time, repeat this test series. Incubate the beakers at the appropriate temperatures.
The next day count the number of hatched larvae in each of the beakers. To do this:
Place a bright light next to your beaker, or place it so that the light is only coming from one side. If any brine shrimps have hatched they will swim to the light.
Using the fine pipette, count the hatched brine shrimps by catching them and put them in another small beaker.(HAZARD WARNING - the
glass pipette is sharp and dangerous if broken - be careful)
Add the totals carefully and write down your results.
If your results are reliable you will expect to achieve similar results each time.
Results:
Table 1. to show the number of brine shrimps hatched after 2 days of incubation
Bar Chart 1: A bar chart to show how many number of eggs hatched at each temperature tested.
Analysis:
From the bar chart results, we can see that most of the brine shrimps' eggs cyst hatched at 25°C where as I have predicted was going to be somewhere in this temperature to be most responsive, primarily because this is the optimum temperature where the brine shrimps survives the most especially during hatching and grow best when kept as close as possible to optimum keeping requirements. Obviously, even though the result of survival rate were small it is undeniable that at 20°C, there were at least 3 brine shrimps that survived which can be considered as part of the optimum estimation temperature and therefore shows possibility of survival rates for the hatched egg cyst.
At 5°C, there were no results obtained, therefore this says that the development of the egg cyst at this temperature might not be the best condition because it is too low for metabolic processes that the egg will go through Amazingly enough even though the results were taken form the “mean”/ average number of eggs hatched after two days within the 4 groups of students who did the experiment in the class, there were obvious results that it did not worked not only once but throughout this temperature chosen, therefore this means that certainly no overall results will be gained. During the investigation, at 30°C, there was only one sea monkey that had survived showing that again, it might not be the best condition to be.
One another aspect from which the temperature might have affected the number of egg hatched was the enzymes that works within the brine shrimps. I have said this because, from previous biological knowledge that I have learnt, I know that the temperature affects the rate of enzyme- catalysed reaction. It was known that at low temperatures, the reaction is slow, this sort of have supported the results because at 5°C, there were actually no eggs hatched, therefore can possibly one of the reason.
Through out the experiment “optimum” condition was often mentioned, however, what it exactly means is much complex than what it sounds like, for an instance, because the pattern that results have shown used an increasing temperature, this means that , as the temperature increases if we are talking about the responsiveness of the enzymes during the hatching of the egg cyst, there are more collisions so the substrate binds with the enzyme's active site more frequently, thus increasing the rate of reaction of the hatching processes.
For this investigation we can see that the “optimum” temperature is 25°C, this means that this is the temperature at which the rate of reaction is at its highest peak..
Overall, the investigation that have been carried out so far provides a valid results especially when we know that it was taken from the mean results of the class. However, for sure, some errors definitely have occurred because the amount of survival rates were really low,. This will be then discussed at the evaluation.
Evaluation:
Throughout the experiment, the results obtained from the methods are relatively fair because we have tried to carried out the experiment's replication as fair as possible and that the given results were enough to be analysed. However, even if in turns this have produced valid results, it was reliable but not as accurate as it was expected because errors cannot be avoided which might have contributed into the outcome results of these experiments in this way.
There were few points why this experiment can be considered as valid and reliable. For an instance, the when the eggs are being counted before the experiment into at least 40, there is a possibility that there were mistakes in counting it because there were very small and cannot be clearly seen even if magnifying glasses were used. This difficulty wasn't only experienced by one student but as a whole class, therefore this might have affected the over all results.
Another obvious inaccuracies that have occurred happened even before the eggs were places at test tubes was the miscalculation of the 40 eggs to be hatched. At some groups, they have exceeded to 3-8 eggs which already have gone over 40 eggs and already indicates that the results are inaccurate, in which this can be considered as a systematic error.
Another problem which might have affected the results was that it was hard to see and count the sea monkeys that had survived as they were very small which means there is a possibility that we could have counted or accidentally missed out some hatched brine shrimps, the fact that it is also possible that we were counting a dead brine shrimp just floating around. So it can be deduced that it can possibly because of human error.
Because at some point the results can be not reliable as it was expected, there is not a very distinct further observation that I can comment on as they all look spread out. If I was to draw a straight line graph for this I would see that there would be little if any correlation.
When doing this experiment in particular we have to look at some issues that are ethical and by this I mean when testing shrimps for the use of science which I briefly mentioned in the beginning o the investigation.. I had decided that it was OK that we used these eggs for the sake of science as it may help us in the future. We will also release these back into the water once we have finished with them. The ethical issues will be mainly brought up when we start carelessly using a higher number of shrimps than we needed.
In every experiment, only the reliable and accurate results are useful. The more of these we do and taking an average we will be able to get a fairly good result and because we used the class results I believe that normally this is going to be a highly reliable experiment even though possibilities errors occurred. This may not be the case when we get errors from places and so to get an even better result we should look at the results and take out some of the anomalous results. An example of an anomalous result is that I had got a result that is very different from the others, such as egg hatched at 30°C. For example if we got a high number of shrimps that had hatched and then in one of the trials we see that there is not any that had hatched, then this will be anomalous. We could blame this on systematic errors. As I have mentioned before we may only have 40 shrimps. If we exceed this number then we might find that there are errors due to that the space occupied by each shrimp egg is too small. Another error is that we do not know that the room temperature is constant and if we left it over a couple of days we may have found that the temperature at night may not necessarily be the same as it was in the day before.
However, there is always room fro improvements. For an example:
Repeat the investigation ate last 3 times more for each group to gain a wider results ensuring that is replicated with same method used at same standard conditions.
Consider the following:
Whether that the temperature water baths that will be used for the experiment is enough for the brine shrimp to hatch as it is known to be a sub-topical species,therefore considerations might be needed, also the salinity of the water may varied that the hatching success may not possibly adapt to it compared with natural hatching in the sea water, so changes in mass of salt can be considered too.
References:
- http://www.saseahorse.com/brine_shrimps.htm
- http://www.msc.ucla.edu/oceanglobe/pdf/SandyBeachesEstuary/Sandy_BrineShrimp.pdf
-
- Salters-Nuffield Advanced Biology AS Heinemann page 186.Edition published in 2002.