I completed an online future learn course on biochemistry which was both interesting and useful as it gave me more of an idea about what biochemistry entails and the different jobs that involve this area of science. Over the first week, I watched a number of videos and read articles about biochemistry in general. These videos involved listening to a number of experienced professors who have a background in biochemistry after having studied it at university and now putting their knowledge into practice in their careers. Out of the topics covered, I learnt more about basic biochemistry skills and had a go at the random quizzes that were set by the course. To round up the first week I took part in an online discussion about what I felt biochemistry meant to me, in which I discussed how different aspects of biology and chemistry overlap. In week 2 I was introduced to metabolism and energetics again looking at the timeline of significant discoveries in this area. The articles I read and the videos I watched interested me as they involved learning more about enzymes and proteins and how they are involved in both the lab and in the body. This was also directly linked to solving energy problems through the use of enzymes in biochemistry as many of the professors talked about the use of bioenergy and the potential for the future. Finally, in week 3 there was more of a focus around synthetic biology and the production of natural products and drugs for the use of the medical industry. This involved various articles around vitamin C as well as an experiment involving measuring the vitamin C content of aqueous solutions. Many of the videos delivered by the different professors were focused on the future of biochemistry for the future such as its importance in the creation of antibiotics, as well as its relation to plant biochemistry. To finish off this course I was informed about different career paths involving biochemistry which helped me gain a clearer picture of its application to real life problems. To add to this, the ‘breadth of biochemistry’ article gave me an idea of the skills required to enter this area of work, such as advanced analytical skills, problem solving and good communicative skills.
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Investigate the effect of different sampling methods on estimates of the size of a population7/1/2016 When calculating the abundance or distribution of an organism, there are numerous different methods that are used. These methods include quadrats, both square and point, transects and mark release and recapture involving the Lincoln index. All of these methods have their advantages and disadvantages and affect the accuracy of the population size estimate.
Quadrats This involves a frame, usually square, acting as the area in which the sample of the population will be taken. The quadrat is laid on the ground at a random point. This random point may be chosen by a random number generator and the quadrat placed on a coordinate grid. Once the quadrat is on the ground, a value for the estimated population can be obtained through either individual counts or percentage cover. Both of these are examples of quantitive sampling techniques as the results are quantifiable. A number of quadrats are laid down at different points and a mean of the population size is calculated. This number is then multiplied by total area to gain an estimation for the whole area. Quadrats are advantageous because they are simple and easy to use and because of the random nature of their position, they provide an objective result. There are however limitations including the problems with the sample area that can be analysed and deciding whether or not to include those organisms on the edges of the quadrat. Another major issue is that they cannot be used to examine fast-moving animals as they are not present in the quadrat for long enough to be taken into account. A final issue would be with the randomness of the sample site as there is often bias as to where the quadrat is placed, especially if they are thrown on the ground to determine the area to measure. Another type of quadrat is the point quadrat which is essentially a horizontal bar consisting of pins which stick in the ground. The organisms that these pins come into contact with are measured to achieve a population estimate. These are quick and efficient and don’t squash any vegetation meaning they are more ethical to use. Additionally, they create a clearer picture as the organisms are easier to see. The drawbacks to this method is that it is limited to habitats with soil as the pins are unable to stay upright in any other material. As well as this, they are unsuitable for animals as the pins cannot touch them. The final limitation would be that it is easy to miss out the rarer, smaller species using pins. ACFOR scale This scale is used for measuring the abundance of species and is very subjective as it involves the scientist using the ranking scale to determine a value for the population size. The scale ranges from A meaning abundant to R meaning rare and either is calculated by the percentage cover or the number of organisms to work out how common the organism is in that particular area. The major issue with this is that it is subjective, meaning the same result may not be achieved upon repeats. As well as this it is hard to say exactly the point at which the value goes from abundant to common or occasional to rare. This ties in with the limitation of the scale being subjective. To add to this, different species may be more easily recognised which has a downside as it causes bias and may result in the scientist identifying that particular species as more abundant due to it being more clear and easier to see. Transects Transects are used to systematically sample a site meaning it is not a random method. This method involves stretching a tape between 2 points and recording very individual organism, whether that is a plant or an animal, that touches the tape. Transects are positioned so that as you move along the tape, there is environmental change, meaning the measurements taken are not replicates but in fact completely different readings. An alternative method would be the belt transect involving 2 tapes aligned and the ground between them is surveyed. Quadrats can also be used along these tape measures to achieve systematic samples of the population at different stages along the tape. This is great for measuring the distribution of organisms dependent on changes in abiotic factors because these factors will change as you move along the tape. To look at these correlations between population size and abiotic factors such as soil pH, samples must be taken at regular intervals along the tape measure. Mark, release and recapture This method is used to estimate the population size of a certain species in a particular area. To do this you collect a sample of the population by using, for example, netting or a pitfall trap, and recording the number of individual organisms caught. Before releasing these organisms, they must be marked. After a suitable time period, repeat this process in the same area and capture some more organisms. Record those organisms which are marked and count those which are unmarked. The Lincoln index is then used to estimate the population size. The total population size equals the number of animals captured first multiplied by the number of animals recaptured the second time all divided by the number of marked organisms recaptured. This method is beneficial for calculating population sizes when you cannot see the organisms in their habitat, for example crabs. However there are numerous limitations with the method because it assumes there have been no births, deaths or migrations over the sampling period. As well as this, there is a possibility that marking the organism reduces the individual’s chance of survival, for example by inhibiting their visibility, or decreasing their ability to move, both of which can affect the estimate for the population size. Another assumption made is that the individual organisms redistribute themselves evenly, whereas in fact they may be more concentrated in the place of release which can affect results. A final limitation is that the method assumes all organisms are equally likely to get caught, when in fact some organisms are trap-happy and some are trap-shy. This affects the population estimate using the Lincoln index because those organisms that were caught in the first place and then marked, are either the ones likely to get caught again (trap-happy) or have learnt from their mistakes and will avoid being caught again (trap-shy). Overall each method has its advantages which makes them suitable for estimating populations of certain types of organisms, for example, the mark, release and recapture method involves moving organisms whereas quadrats are for organisms that do not move. We can see that, however, each method has its own limitations whether that can affect the accuracy of the population size value. Moreover, the style of sampling, whether it is random, systematic or stratified can affect the reliability of the results as it may lead to bias and the results might not be an accurate representation of the population size. I will be investigating the effect of temperature on the abundance of rabbits in a given area. The organism I will be investigating will be the rabbit and I must ensure it is the same species of rabbit to ensure valid results as different species of rabbit may prefer different temperatures. My independent variable is temperature and to carry this out I will measure the population of the rabbits in a given area at different times of the year and therefore at different temperatures. I will take readings on days where the temperature is roughly 0°C, 5°C, 10°C, 15°C, 20°C, 25°C and 30°C and will use various thermometers in the area to obtain an average value for the temperature. I will repeat my readings at least three times at each temperature to improve my reliability. The dependent variable will be the population size of the rabbits in the given area. To measure this I will use the mark, release and recapture method whereby the rabbits are safely caught using a rabbit trap are marked with a band and then recaptured. These rabbit traps will be randomly distributed within the marked out area using a random number generator and the traps are placed on a coordinate grid. Those of which are marked and unmarked are noted and counted again. The time period over between release and recapture will be 120 minutes and this will be one of my control variables. Using the Lincoln index I will put together these values to obtain an estimate of the population in that area. My control variables will be the availability of food meaning there should be no lack of food in the area otherwise this may put off rabbits and affect the results. This may mean that when there is significantly less vegetation, putting in place food substitutes to maintain a constant food supply. As well as this, I will control predation in the area, preventing animals such as foxes from affecting the rabbit abundance.
There are issues associated with this experiment as it assumes there are no deaths, births of migrations. Therefore to take these into account I will make a note of the time of year the readings were taken to work out if they were taken before, during or after breeding season so I know of any external influences on the results. As well as this, when carrying out the mark, release and recapture sampling method, I will ensure that the way in which the rabbit is marked is safe, ethical and will not affect their chance of survival by reducing their movement which would therefore affect the results. Another issue with this would be that assumptions are made with how effectively the rabbits will be distributed after being released. I will take into account that they will not be evenly distributed which means they are likely to be more abundant in certain areas. To overcome this problem, I will leave them for 120 minutes (2 hours) to allow more time for them to spread out. |
Ciara Branagan
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October 2016
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