Biology edexcel unit 6

[Bebololz]

Hi there ,
anyone got anything about unit 6 ? notes or tips on how to write the answers ? also an explanation of the statistical analysis needed for question 2 will be very helpful
thanks

 

[Dr Bob]

Did you get any help yet? Are there specific things you have problems with?

 

[Bebololz]

I got some help with the statistical analysis thingy but I still have trouble with question 3 part C ... I don't know how to write it and I can't find a sample answer to write like it

 

[Dr Bob]

The easiest way to write the answer is to stick to a logical order -
- write what the independent variable is (what you are changing in the experiment)
- how many values of the independent variable will you have (pick at least five and give an example of the range you will use)
- what is the dependent variable and how will you measure it (be specific)
- name two control variables
- name how you will control them
- mention that you will do repeats for each experiment
That should give you at least 8 marks and then two for writing it all out in a logical order, not using bullet points and making sure you use the correct spelling and scientific vocabulary.

Hope this makes sense?

 

[Bebololz]

ummm can you send me a sample answer that follows this way because I dont get it yet

 

[Paras]

The easiest way to write the answer is to stick to a logical order -
- write what the independent variable is (what you are changing in the experiment)
- how many values of the independent variable will you have (pick at least five and give an example of the range you will use)
- what is the dependent variable and how will you measure it (be specific)
- name two control variables
- name how you will control them
- mention that you will do repeats for each experiment
That should give you at least 8 marks and then two for writing it all out in a logical order, not using bullet points and making sure you use the correct spelling and scientific vocabulary.

Hope this makes sense?

are you a teacher? you seem to be very knowledgeable. Thanks for all your help man!

 

[Dr Bob]

ummm can you send me a sample answer that follows this way because I dont get it yet

Have a look at this - it is an example of the experiment design question and the mark scheme - I have added in some notes to let you see the pattern in these answers. If you look through other questions like this and their mark schemes you will hopefully see these common features.
Let me know if it doesn't make sense!!

 

[Bebololz]

It was really helpful thx a bunch Dr. Bob

 

[Dr Bob]

It was really helpful thx a bunch Dr. Bob

Very welcome!

 

[Bebololz]

Dr. Bob do you have anything about the preliminary work ?

 

[Bebololz]

I compiled this file myself can you check if it's accurate or not ?

 

[iram arif]

Can anyone expect which experiment will come in 2015 june in question 1 of unit 6???

 

[iram arif]

The easiest way to write the answer is to stick to a logical order -
- write what the independent variable is (what you are changing in the experiment)
- how many values of the independent variable will you have (pick at least five and give an example of the range you will use)
- what is the dependent variable and how will you measure it (be specific)
- name two control variables
- name how you will control them
- mention that you will do repeats for each experiment
That should give you at least 8 marks and then two for writing it all out in a logical order, not using bullet points and making sure you use the correct spelling and scientific vocabulary.

Hope this makes sense?

Can you tell me that in belt transect methode , can we place quadrat randomly? ?what is the difference between line transect n belt transect? ?

 

[iram arif]

I m not understanding the question no 3 of jan 2011.....the ms says that students have to do random sampling by referring to transect methode? ??? Transect methode comes in systematic sampling r8?????
plz help someone need uurgent help

 

[iram arif]

Dr. Bob do you have anything about the preliminary work ?

0lz help me out with the questions I asked above

 

[Dr Bob]

Dr. Bob do you have anything about the preliminary work ?

Sorry for the delay.

You usually get marks for:
- practising the method, or checking that the method actually works (!)
- deciding on a range for the independent variable
- deciding how exactly youare going to measure the dependent variable e.g. measure plants from the tip of the shoot to the end of the root, or measure the dry mass of a plant etc
- deciding how long you will run the experiment for e.g. expts involving plant growth tend to need longer - 10days/2 weeks minimum
- deciding what are the best conditions for e.g. growing bacteria or plants (this is obviously different to the independent variable)
The idea is that you are doing a trial/pilot experiment to get a rough idea of the conditions to use before you go ahead and do your big Nobel Prize-winning experiment where you will gather much more data.

 

[Dr Bob]

Can you tell me that in belt transect methode , can we place quadrat randomly? ?what is the difference between line transect n belt transect? ?

No, if you are using a transect it means you are following a straight line along which the abiotic conditions will be changing - you are looking to see if these changes affect the number/distribution of organisms. So you count the number of organisms in the quadrat at the start of the transect, then move along the transect e.g. 1metre and then count again, move on, count etc - this is sometimes called systematic sampling.
Line transect/belt transect? - I think the belt one uses quadrats - the line one can use things like point quadrats etc, but I have never been 100% sure? The belt transect alows you to measure the number of organisms more accurately - line transect is more useful for just saying if the organism is there or not.

Random sampling tends to happen when you are comparing the numbers of organisms between two sites e.g. one shady site and one in bright sunshine. You would set out a grid and then using random numbers, generate coordinates for placing the quadrat on the grid, then count the organisms. Generate more random numbers, place the quadrat, count etc.

With systematic sampling you are looking for a relationship between an abiotic factor and the number/distrubution of organisms (this helps with your null hypothesis and the statistical test to use when analysiing) - with random sampling you are looking to see if there is a difference.

Let em know if none of this makes sense!!

 

[Dr Bob]

I m not understanding the question no 3 of jan 2011.....the ms says that students have to do random sampling by referring to transect methode? ??? Transect methode comes in systematic sampling r8?????
plz help someone need uurgent help

I think wht they mean in that you can do the experiment two ways - one by comparing two areas (one with high light, one with low) - then you would do random sampling in a grid in the low light area and compare these results to random sampling in a grid in a high light area. The second way to do the experiment is to set a transect along where the light intensity changes e.g. one end of the transect in a high light area and the other end in a low light area. You can then sample as you work along the transect. I thnk it's just two different methods for investigating the same question?
If you used the first method, you would be comparing between two sites and so use either t-test or Mann-W U test. If you used the second method, you are looking to see if the is a correlation between light intensity and plant numbers/cover etc as you go along the transect, so would use the Spearman rank correlation test.

Make sense?

 

[Dr Bob]

The number of means is used to calculate the critical value . if the calculated positive or negative value of P is higher than the critical value then the null hypothesis is rejected and there is no positive or negative correlation.

I compiled this file myself can you check if it's accurate or not ?

For the Spearman Rank Correlation - if the calculated value is higher, then the null hyp. is rejected, yes - but then the conclusion is that there is a significant correlation and you can tell is it is a positive or negative correlation from the +/- sign on the calculated value.

Also for the Mann-Whitney U test - if the null hyp. is rejected, then there is a significant difference between the two medians.

 

[iram arif]

No, if you are using a transect it means you are following a straight line along which the abiotic conditions will be changing - you are looking to see if these changes affect the number/distribution of organisms. So you count the number of organisms in the quadrat at the start of the transect, then move along the transect e.g. 1metre and then count again, move on, count etc - this is sometimes called systematic sampling.
Line transect/belt transect? - I think the belt one uses quadrats - the line one can use things like point quadrats etc, but I have never been 100% sure? The belt transect alows you to measure the number of organisms more accurately - line transect is more useful for just saying if the organism i

Random sampling tends to happen when you are comparing the numbers of organisms between two sites e.g. one shady site and one in bright sunshine. You would set out a grid and then using random numbers, generate coordinates for placing the quadrat on the grid, then count the organisms. Generate more random numbers, place the quadrat, count etc.

With systematic sampling you are looking for a relationship between an abiotic factor and the number/distrubution of organisms (this helps with your null hypothesis and the statistical test to use when analysiing) - with random sampling you are looking to see if there is a difference.

Let em know if none of this makes sense!!

Thanks alot..do have any stuff which can guide us in unit 6...???
Do u have any idea that which experiment will come in our paper??