KEGS Biology Blog


Monday 1st October Section 2
September 29, 2012, 6:31 pm
Filed under: Uncategorized

Daws Hall Follow up 1

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10 Comments so far
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Limitations of Random Sampling (in relation to Daws Hall work):

1) Time: The process of random sampling may be too time consuming and therefore limitations may arise when identifying a sample. Although it is the most reliable form of sampling, other methods could have perhaps been quicker. (There may be practical constraints in terms of time available and access to certain parts of the study area)

2) Representation: Randdom sampling could result in a poor representation of the whole population since we are sampling a relatively small proportion of the overall population.This is made worse if the study area is very large.

Comment by Deelan Vadher

http://newsinfo.inquirer.net/279802/weird-sea-creature-new-species-found-in-ph

New species allegedly discovered nickmaned the “bubble fish”

Comment by Deelan Vadher

Simpson’s biodiversity index—Indicates how biodiverse an area is, the greater the figure, the greater the biodiversity.

To gain top marks for graphs—-Always use a ruler and pencil, label the axes, include units, line of best fit if necessary, title.

Influences on biodiversity- Amount of sunlight available, nutrients in the soil, competition, water levels, pH of soil, human actions.

Potential limitations of Simple random sampling
1)Sample representation: Simple random sampling has often resulted in an inaccurate portrayal of the population as we sampled a comparatively small percentage of the whole population.This effect is magnified if the area to be studied is of a great area.

2)Time needed: Carrying out random sampling is often too time consuming and as a result limitations are common when attempting to take a sample. Although it is the most reliable sampling method, other techniques could be carried out at a faster and more efficient rate.There are often practical constraints, especially the time available and access to some parts of the area of study.

Comment by yuansun

Limitations of random sampling:

Chance: You could get a rare species by random and this is not representative of the whole population but just one area

Sample size: A small random sample may not be representative

Comment by nisithadissanayake

useful website stating advantages and disadvantages of random sampling- http://www.experiment-resources.com/simple-random-sampling.html

Comment by roobennithi

Limitations of using quadrats:
– individuals in a species may be too small to see and therefore are missed out and not counted which affects results as true value isn’t recorded.
– sample isn’t exactly representative of the whole area. it’s really just an estimation
– some species may be too big to fit the quadrat over but a bit of it does go into the quadrat so the question arises as to whether it should be counted or not ? Which leads to samples being subjective

Comment by halima95

Limitations of counting species richness
-Subjective (often 2 plants of the same species are mistaken for separate species)
-This is an issue because: could potentially lead to misrepresentative data
-Solution: use a identification chart, note down key characteristics for each species, or use a dichotomous key

Comment by bensubhani

Limitations of using Quadrats:
-The same plant may overlap more than one square, which may lead to a miscalculation of the number of species. This will affect the results as the number of species would be slightly higher.
-Solution: Count the plant in the square it occupies most space in, or count it in the square where its roots are.

Comment by candicetam

Limitations of Random Sampling
Random sampling is unlikely to be completely representative of an entire population within any large area, as unless an entire area is covered, you cannot be totally sure whether or not your findings will be accurate for the whole area, regardless of how similar the habitat under investigation may be throughout.

Consequences
If you happen to pick a small area within which you find the only members of a species within a habitat, but expand your results to fit the whole habitat, this could lead to a huge overshot of the true number of that species in the area. Conversely, if a species is abundant in an area which you do not sample, you will again be unfairly sampling the entire area, as you may record that it is scarce within the habitat.

Improvement
Although it is not easy due to time and cost, the only real solution is to simply sample a greater proportion of the habitat. The easiest way to do this is to collate results, however if you do this, it is likely that you will lose the randomness of your sample, unless you can be completely sure that the data you use was collected in the same fashion as your own

Comment by jakepalmer1

1) Representation: A small random sample may not be representative of the whole area, for example we may encounter a species of plant that is abundant in only the area we sampled, and therefore would not be representative of the whole area.

2) Subjective: One person may identify a plant different to another person, leading to a misrepresentation of data. To solve this use a identification chart, note down key characteristics for each species, or use a dichotomous key.

Improvement
Although it is not easy due to time and cost, the best way to improve our data is to simply sample a greater proportion of the habitat. The fastest and simplest way to do this is to collate results with other students.

Comment by spencerfinch




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