A level Biology: Post your doubts here!

[Farhad221]

why not C for question 11?

coiling forms teritary structure wheras quatenary is due to multiple polypeptides combing togther.

 

[Tasneem_m98]

someone please help..
why is the answer to question number 39 in M/J 2013 paper 13, D, and not B, when in another year (O/N 2013 paper 12 number 40) the answer is D??
link to M/J 2013: http://www.studentbounty.com/pastpa...el/Biology (9700)/2013 Jun/9700_s13_qp_13.pdf
link to O/N 2013: http://www.studentbounty.com/pastpa...el/Biology (9700)/2013 Nov/9700_w13_qp_12.pdf

 

[Farhad221]

someone please help..
why is the answer to question number 39 in M/J 2013 paper 13, D, and not B, when in another year (O/N 2013 paper 12 number 40) the answer is D??
link to M/J 2013: http://www.studentbounty.com/pastpapers/Cambridge International Examinations (CIE)/International AS and A Level/Biology (9700)/2013 Jun/9700_s13_qp_13.pdf
link to O/N 2013: http://www.studentbounty.com/pastpapers/Cambridge International Examinations (CIE)/International AS and A Level/Biology (9700)/2013 Nov/9700_w13_qp_12.pdf

 

[Tasneem_m98]

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the statements in each question are exactly the same, yet in one question, ALL of them, including statement 4 of course, are considered valid, whereas in another question, statement 4 is considered invalid.
how come???!

 

[Farhad221]

the statements in each question are exactly the same, yet in one question, ALL of them, including statement 4 of course, are considered valid, whereas in another question, statement 4 is considered invalid.
how come???!

D is not valid while 123 are valid

 

[Tasneem_m98]

D is not valid while 123 are valid

i agree, but the markscheme says 1,2,3, and 4 are valid (option D) in m/j 2013 and that's what i dont understand.

 

[qwertypoiu]

Guys don't take screenshot of your whole desktop the images are too large and take long time to load. Just crop the question, paste it, and preferably tell what the answer is and others will try explain.

 

[princess Anu]

can somebody write ans to this
Explain why sickle cell anemia is common in areas where malaria is endemic.(3)

 

[Tasneem_m98]

Guys don't take screenshot of your whole desktop the images are too large and take long time to load. Just crop the question, paste it, and preferably tell what the answer is and others will try explain.

i have posted links to papers and their answers, m/j 2013 paper 13 number 39 answer is D, o/n 2013 paper 12 number 40 answer is D

 

[Farhad221]

can somebody write ans to this
Explain why sickle cell anemia is common in areas where malaria is endemic.(3)

is it paper 2 or 3

 

[qwertypoiu]

i have posted links to papers and their answers, m/j 2013 paper 13 number 39 answer is D, o/n 2013 paper 12 number 40 answer is D

I don't help anyone with question 38-40, these are ecological stuff with nitrogen cycle and bla bla confusing stuff so yeah sorry can't help you

 

[princess Anu]

can somebody help with Q5b NO7 / P2

 

[princess Anu]

is it paper 2 or 3

2 obv

 

[qwertypoiu]

can somebody write ans to this
Explain why sickle cell anemia is common in areas where malaria is endemic.(3)

Where malaria is endemic, it is an advantage to have sickle cell anaemia. It gives you advantages over others, whereas others may die of malaria, you are unlikely to, because your blood cells are sickle shaped and so are not suitable for Plasmodium to survive in.
Having said that, sickle cell anaemia does increase the risk of death as well. Therefore, in areas where malaria is endemic, it is best to be a carrier of sickle cell anaemia.
Half your blood cells are sickle shaped, but the other half are fine. Therefore, you're protected from malaria, and at the same time don't suffer from the severe symptoms of sickle cell anaemia.
If natural selection favours sickle cell carriers due to the existence of malaria in certain regions of the world, it is not surprising that sickle cell anaemia is common there.
For example, if two sickle-cell carriers have a child, there is 25% chance that he will have sickle cell anaemia.

 

[Farhad221]

paper 2 obv

Thats unusual becuase the relation in sicke cell anaemia and malaria is part of natural selection which is A2 anyways here is the explaination,
People with sickle cell anaemia can not acquire malaria as the sickle plasmodium cannot live in sickle red blood cells hence, people with siclkle cell anaemia have a selective advantage against those who dont therefore it is comon in areas where malaria in an endemic
Can you tell me which year is the question from.

 

[qwertypoiu]

can somebody help with Q5b NO7 / P2

In order to compare countries and see which populations are more susceptible to Tuberculosis, we must compare cases per 100,000.
This is because different countries have different population.
If we say, for example, that one million people died of TB in switzerland, and the same number in China, would it mean that the population of these countries are equally susceptible to the disease? No!
1 million represents around 13% of Switzerland population, whereas it's probably less than 0.1% of Chinese population.

So citing cases per 100,000 makes fair comparison, since population of different regions around the world differ.

 

[princess Anu]

its from n01
but I donot understand the fact that why is malaria even endemic in those regions? shouldn't it be non existent :/

 

[qwertypoiu]

its from n01
but I donot understand the fact that why is malaria even endemic in those regions? shouldn't it be non existent :/

Not everyone is sickle cell anaemic, so not everyone is protected from malaria.
Tropical areas have higher temperatures, which is suitable for Plasmodium to live inside mosquito (at least 20 degrees celsius).
Tropical areas tend to have rainy season, so places there tend to have stagnant water such as puddles, which is essential for mosquito to lay eggs in.

 

[Farhad221]

its from n01
but I donot understand the fact that why is malaria even endemic in those regions? shouldn't it be non existent :/

qwertypoiu has explained it in detail , so as you can see not everyone has sickle cell anemia and there are people that die due to sickle cell anemia. Plus being a carrier or having sickle cell anemia counts too. Its a kind of compilcated if you want to know more read the chapter on natural selection.

 

[Farhad221]

Not everyone is sickle cell anaemic, so not everyone is protected from malaria.
Tropical areas have higher temperatures, which is suitable for Plasmodium to live inside mosquito (at least 20 degrees celsius).
Tropical areas tend to have rainy season, so places there tend to have stagnant water such as puddles, which is essential for mosquito to lay eggs in.

Some timing !!!!