A level Biology: Post your doubts here!

[BSughontha]

hey, im really confused about 9700/13/mj/10 the question bout the electrical activity of the heart.can u help?

 

[dornam]

Can anyone explain me the following point in the syllabus?

"
. (a) explain the need for transport systems in multicellular plants and animals in terms of size and surface area to volume ratios;
"

And also this one:

(j) discuss the difficulties in achieving a balance between preventions and cure with reference to coronary heart disease, coronary by-pass surgery and heart transplant surgery;

 

[aleezay]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s11_qp_12.pdf

In Q28... WHY do we include osmosis?? Xylem is dead, osmosis cant occur in osmosis since theres no partially permaeble membrane in the structure.. :/

 

[Amy Bloom]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_12.pdf

In Q28... WHY do we include osmosis?? Xylem is dead, osmosis cant occur in osmosis since theres no partially permaeble membrane in the structure.. :/

But xylem vessels have pits or pitted walls.

 

[Amy Bloom]

Can anyone explain me the following point in the syllabus?

"
. (a) explain the need for transport systems in multicellular plants and animals in terms of size and surface area to volume ratios;
"

And also this one:

(j) discuss the difficulties in achieving a balance between preventions and cure with reference to coronary heart disease, coronary by-pass surgery and heart transplant surgery;

(a) In unicellular organisms, having small size and large surface area to volume ratio, diffusion is enough to move substances from where they are manufactured to where they are required/are to be eliminated. As organisms get bigger, more complex and have smaller surface area to volume ratio, diffusion is simply a too slow process for movement of substances due to the small surface area. Food and oxygen cannot reach respiring cells on time as well as the waste materials are slow to be discarded. This is why a transport system is required in complex or multicellular organisms.

Hope i helped. good luck

 

[dornam]

Thanks a lot!

do you know anything about the point regarding the preventions and cure of CHD?

 

[Amy Bloom]

Thanks a lot!

do you know anything about the point regarding the preventions and cure of CHD?

This question was from the paper i appeared for. Check the Mark scheme. And welcome here

 

[dornam]

can you tell me the paper, please?

 

[Amy Bloom]

can you tell me the paper, please?

November 2012 paper 22

 

[strangerss]

Hey every one , alsalam allaykom , I'm really confused about question 30 in p1 Oct/Nov 2011 variant 2 . How is the answer related to root pressure? when root pressure involves water moving through the xylem and not sap leaking out :S? And how come vital capacity is defined as the maximum volume of air breathed out after breathing in as deep as possible , but when we want to find the vital capacity on a spirometer graph we add the maximum exhaled air with the maximum inhaled air?!

 

[aleezay]

But xylem vessels have pits or pitted walls.

But that still doesnt mean that osmosis occurs in the xylem :/

 

[abcde]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_12.pdf

In Q28... WHY do we include osmosis?? Xylem is dead, osmosis cant occur in osmosis since theres no partially permaeble membrane in the structure.. :/

I think the answer lies in root pressure. Here, take a look: http://en.wikipedia.org/wiki/Root_pressure

 

[Amy Bloom]

But that still doesnt mean that osmosis occurs in the xylem :/

The pitted walls of the xylem itself act as barrier, like the semi-permeable membrane does.

 

[dornam]

Can someone help me with this?

"Explain the meaning of the term immune response making reference to the terms antigen, self and non-self."

 

[strangerss]

G

Can someone help me with this?

"Explain the meaning of the term immune response making reference to the terms antigen, self and non-self."

Download the biology syllabus , you'll find the definition for an immune response as well as for antigen , non-self and self

 

[dornam]

I downloaded and readed it, but it is far too long

 

[hmlahori]

can anyone upload the november 2011 examiner report for 9700 a level biology? its not here or on freeexampapers.com. please i need it urgently.

 

[Oliveme]

can anyone upload the november 2011 examiner report for 9700 a level biology? its not here or on freeexampapers.com. please i need it urgently.

http://www.mediafire.com/?z342q2qmsvty9j8
I can't upload the file but here's a link where you can download it from.

 

[hmlahori]

http://www.mediafire.com/?z342q2qmsvty9j8
I can't upload the file but here's a link where you can download it from.

Hey thanks a lot!

 

[Yasmeen el-shaarawy]

Hey guys , I have a question regarding paper 41 may/June 2012. Can anyone explain part E in question 4? I tried really hard to understand the mark scheme but I didn't get a thing! :s anyways, any help would be much appreciated. Thanks!