# Measuring growth ?

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#1
Hello ! Here's a link to the question paper , my question is 7(b )https://qualifications.pearson.com/c...e_20170111.pdf
my approach to this was to grow several plants at different distances and then to use a transect to meausre the abundance , find out where the highest abundance was closest to the bush and to plant the plants there. Here's a link to the mark scheme
https://qualifications.pearson.com/c...s_20170301.pdf
I was wondering if abundace was an acceptable point for MP 5 or in other words,if measuring abundance was okay to represent growth . My exam is just around the corner and I could use all the help I get , thanks
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1 year ago
#2
(Original post by Leah.J)
Hello ! Here's a link to the question paper , my question is 7(b )https://qualifications.pearson.com/c...e_20170111.pdf
my approach to this was to grow several plants at different distances and then to use a transect to meausre the abundance , find out where the highest abundance was closest to the bush and to plant the plants there. Here's a link to the mark scheme
https://qualifications.pearson.com/c...s_20170301.pdf
I was wondering if abundace was an acceptable point for MP 5 or in other words,if measuring abundance was okay to represent growth . My exam is just around the corner and I could use all the help I get , thanks
Before answering, I must stress that I have no idea of what your syllabus requires.
The problem with "abundance" might be that it suggests number of plants. IOf you are starting off with just one individual plant at each location on the transect, this implies that you would need to experiment to run for several seasons for the original plants to reproduce. Even then, you would have the problem that you plants growing in a given spot might have arrived there from somewhere else - so it's not a well controlled test.
The mark scheme idea, based on measuring the growth of single experimental plantsm is better because you don't have these variables to worry about.
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#3
(Original post by OxFossil)
Before answering, I must stress that I have no idea of what your syllabus requires.
The problem with "abundance" might be that it suggests number of plants. IOf you are starting off with just one individual plant at each location on the transect, this implies that you would need to experiment to run for several seasons for the original plants to reproduce. Even then, you would have the problem that you plants growing in a given spot might have arrived there from somewhere else - so it's not a well controlled test.
The mark scheme idea, based on measuring the growth of single experimental plantsm is better because you don't have these variables to worry about.
Ok thanks . Can I ask one more thing ? What is kick sampling ? And may I ask , are you a bio teacher ? Because I have 1 quick question on phagocytosis
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1 year ago
#4
(Original post by Leah.J)
Ok thanks . Can I ask one more thing ? What is kick sampling ? And may I ask , are you a bio teacher ? Because I have 1 quick question on phagocytosis
I'm not a bio teacher, so my knowledge isn't particularly relevant to teaching syllabuses (I have postgrad qualifications in zoology). Phagocytosis is not one of my things, but feel free to ask!
The only time Ive heard of "kick sampling" is when you do a survey of a stream. You stick a net at a point on the bed of the stream and then kick the stream-bed just upstream of the net to catch (and sample) the creatures that live in it.
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#5
(Original post by OxFossil)
I'm not a bio teacher, so my knowledge isn't particularly relevant to teaching syllabuses (I have postgrad qualifications in zoology). Phagocytosis is not one of my things, but feel free to ask!
The only time Ive heard of "kick sampling" is when you do a survey of a stream. You stick a net at a point on the bed of the stream and then kick the stream-bed just upstream of the net to catch (and sample) the creatures that live in it.
Ohh , wow . Thank you I just have a few miscinceptions .Um about kick sampling , I saw it in the mark scheme answer of one question .
https://qualifications.pearson.com/c...e_20150112.pdf

https://qualifications.pearson.com/c...c_20150305.pdf
Q8bi Just to make sure I understand , I'm going to throw a net at regular intervals and count the number of each species and then note it down , is that it ? Does the mp 5 mean that I need to take the sample from the same depth everytime ? What do they mean by measuring abiotic factors ? How is that gonna help me in any way ? Also, isn't this method unethical ? Isn't this just killing organisms just to know how theyre distributed ? One final question , to measure distribution , is the sampling always systematic ? If not , how do I know when to carry out systematic sampling and when to carry out random sampling ?
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1 year ago
#6
(Original post by Leah.J)
Q8bi Just to make sure I understand , I'm going to throw a net at regular intervals and count the number of each species and then note it down , is that it ? Does the mp 5 mean that I need to take the sample from the same depth everytime ? What do they mean by measuring abiotic factors ? How is that gonna help me in any way ? Also, isn't this method unethical ? Isn't this just killing organisms just to know how theyre distributed ? One final question , to measure distribution , is the sampling always systematic ? If not , how do I know when to carry out systematic sampling and when to carry out random sampling ?
Net sampling? Yes, basically. You kick the streambed because the creatures you are looking for are generally not swimming free in the open water, but holding onto stones (typically, that's what freshwater shrimps do). or in the top layer of the gravel/mud of the streambed (bloodworms).

The whole point is that you are trying to measure just one variable - oxygen content - using the occurence of the indicator animals as a proxy. So you need to eliminate all other posssible sources of variation in the indicator animal numbers, So the sample sizes need to be the same, the sample should be taken from the same depth in the water column, from portions of the stream flowing at the same speed and at the same temperature (the abiotic factors). Otherwise, these things may be the cause of changes in the numbers of your indicator animals rather than oxygen level (for example, it might be that shrimps cannot tolerate high water speeds, so even if you have lots of oxygen in a fast flowing bit, you won't get many shrimps there). If you cannot do a systematic sample and avoid variation in the abiotic factors like this, recording the things most likely to affect animal numbers, then you may be able to take that into account when calculating your results.

Ethics - kick sampling generally doesn't kill much (stream living creatures are usually adapted to cope with things like sudden surges of water and disturbances like animals walking through the stream), but you are right to be concerned about what is a sampling method that will inevitably disturb the habitat and cause a degree of harm

Use systematic sampling when you are examining a gradient of species or features in a habitat and you want to see how species composition varies along the gradient. Random sampling would not work in this example because your random quadrats might all end up at one end of the oxygen gradient/distance from pollutant - then you would never find out how the O2 content changed with distance. Its also useful where you want to avoid the risk of clustered selection - if you uise random samples, there is sometimes a danger that if you are sampling something that is very common in certain spots and absent in others, you will miss them altogether - or else think that they are everywhere! Random sampling is good when the important factor is avoiding biased sampling, but here it's more importantt o make sure you sample from every part of the gradient.

In practice, a mixture of random and sytematic sampling is often used in fieldwork. eg random selection of sample quadrats and then systematic sampling within the quadrats (eg "count the number of aphids on every tenth flower in your random qquadrat square")
Hope that helps
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