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Edexcel GCE Biology Unit 4 6BI04 June 2013

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Oh also how much are we meant to know about estimating the time of death etc? The specification point on it is very vague and suggests you only need to know the ways it can be determined?!
does anyone have any predictions on whats coming up? especially the big questions
Original post by Lastminutepanic
Oh also how much are we meant to know about estimating the time of death etc? The specification point on it is very vague and suggests you only need to know the ways it can be determined?!


i think your expected to know it to quite a bit of detail as in the jan 2013 paper there was a 5 mark question on it, saying that , its less likely to come up then
Does anybody have any ideas of what might come up???
Reply 64
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SKK94
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Original post by ADAOBI123
mark scheme for 2013 paper please ?

Here it is...
6BI04_01_rms_20130307.pdf162.1KB
Original post by SKK94
Here it is...



thank you xxxxxx
Reply 66
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SKK94
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What is the difference between allele frequency and gene pool?? :s-smilie:
This is what I think:
- Allele frequency is the number of different alleles in a population
- Gene pool is the total number of different genes in a population
Someone please correct me if I am wrong :rolleyes:
Original post by SKK94
What is the difference between allele frequency and gene pool?? :s-smilie:
This is what I think:
- Allele frequency is the number of different alleles in a population
- Gene pool is the total number of different genes in a population
Someone please correct me if I am wrong :rolleyes:


I learnt them as:

Allele frequency: the number of times (as a percentage or decimal) the same allele appears in a gene pool

Gene Pool: the number of alleles present in a population at one time
Original post by SKK94
What is the difference between allele frequency and gene pool?? :s-smilie:
This is what I think:
- Allele frequency is the number of different alleles in a population
- Gene pool is the total number of different genes in a population
Someone please correct me if I am wrong :rolleyes:



Total number of alleles in a population - Gene pool

The proportion of one allele in a population - Allele frequency
Explain how does vaccination bring about the increase in the level of antibodies?
Reply 70
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SKK94
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Original post by amberee
I learnt them as:

Allele frequency: the number of times (as a percentage or decimal) the same allele appears in a gene pool

Gene Pool: the number of alleles present in a population at one time



Original post by yarshad
Total number of alleles in a population - Gene pool

The proportion of one allele in a population - Allele frequency


Thanks a lot! I think I get it now.

So when they say allele frequency increases (due to selection pressure), does it mean the proportion of the advantageous allele in the population has increased?
Reply 71
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SKK94
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Original post by bubblegummer
Explain how does vaccination bring about the increase in the level of antibodies?


Vaccinations are a form of artificial active immunity, where the weakened form of a pathogen is injected into the body (the antigens still function though).
Cells of the immune system can bind to the antigens (provided they have the specific shape on their receptors) and specific antibodies can be made.
I think in this case, the humoral response occurs( eventually resulting in B memory cells and B effector cells):
- The B memory cells are able to 'remember' the pathogen - in case of secondary infection
- The B effector cells become Plasma cells, which then produce the required antibodies.
(edited 10 years ago)
Original post by SKK94
Thanks a lot! I think I get it now.

So when they say allele frequency increases (due to selection pressure), does it mean the proportion of the advantageous allele in the population has increased?


yeah only those with the beneficial allele survive and are able to pass on their genes (which have the beneficial allele) and those that don't can't adapt to the environment so they die out because they are outcompeted

I hope that's right anyway. One of the topics I need more work on ^__^
Reply 73
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Obtas
12
Original post by Lastminutepanic


-Describe the role of micro-organisms in the decomposition of organic matter and the recycling of carbon.

Thanksss

-Decomposition by microorganisms
-These microorganisms respire
-Releasing carbon dioxide for photosynthesis
-Methane released in anaerobic condition
-Methane available as fuel

Another mark scheme:
-Carbon/organic compounds digested
-Digestion provides respiratory substrates
-Carbon dioxide released from respiration
-This carbon dioxide is available for photosynthesis
Reply 74
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Obtas
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Original post by Lastminutepanic
Oh also how much are we meant to know about estimating the time of death etc? The specification point on it is very vague and suggests you only need to know the ways it can be determined?!


Just the ways TOD can be determined, i.e, stage of succession, decomposition, body temp, rigor mortis and forensic entomology.
Reply 75
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Obtas
12
I've seen a question on the Jan 2011 paper, "Describe how the organisms that cause TB are taken up by macrophages", on the mark scheme is mentions the point of 'labelling of bacteria by B lymphocytes/cells', what does this mean?
Reply 76
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Volltorb
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Original post by SKK94
Vaccinations are a form of artificial passive immunity, where the weakened form of a pathogen is injected into the body (the antigens still function though).
Cells of the immune system can bind to the antigens (provided they have the specific shape on their receptors) and specific antibodies can be made.
I think in this case, the humoral response occurs( eventually resulting in B memory cells and B effector cells):
- The B memory cells are able to 'remember' the pathogen - in case of secondary infection
- The B effector cells become Plasma cells, which then produce the required antibodies.

Its actually active artificial immunity, the vaccine can involve either: weakened virus/bacteria (so its harmless); toxin that's been altered into an harmless form; or an actual part of the pathogen containing the antigen (non self) that leads to specific immunity.
Reply 77
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Volltorb
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Original post by Satta101
I've seen a question on the Jan 2011 paper, "Describe how the organisms that cause TB are taken up by macrophages", on the mark scheme is mentions the point of 'labelling of bacteria by B lymphocytes/cells', what does this mean?

Stimulated B cells> B effector cells> Plasma cells> antibodies.
The B cells (indirectly) lead to antibodies being produced, these antibodies bind to specific antigens on the bacteria (labelling them). this labeling, therefore allows macrophages and other phagocytes to identity them more quickly.
Reply 78
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SKK94
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Original post by amberee
yeah only those with the beneficial allele survive and are able to pass on their genes (which have the beneficial allele) and those that don't can't adapt to the environment so they die out because they are outcompeted

I hope that's right anyway. One of the topics I need more work on ^__^


Thanks :smile:
Original post by Satta101
I've seen a question on the Jan 2011 paper, "Describe how the organisms that cause TB are taken up by macrophages", on the mark scheme is mentions the point of 'labelling of bacteria by B lymphocytes/cells', what does this mean?


B cells label the bacteria as foreign objects and this allows phagocytes to engulf the bacteria. Basically they can recognise the bacteria they need to kill a lot easier.
I hated that question :unimpressed:

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