A level Biology: Post your doubts here!

[dornam]

Here is the paper: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf

Can anyone explain me questions 15, 19 and 36?

For question 15, the examiner report states that the cell surface membrane does not allow intracellular transport but intercellular... I don't understand this.

For question 19, doesn't formation of chromosomes occur in prophase? Or is it a matter of terms, and it would be condensation and not formation?

For question 36... examiner report says that malaria is unlikely to be passed on from parent to child directly. But malaria can be transmitted across placenta, so? How can cholera be transmitted directly from parent to child?

Anyone?

 

[Warrior66]

Q30- fungi grows in the xyelm so water transport in xylem will be less efficient. Transport of water through xylem is appoplast pathway so appoplast pathway gets affected
Q27- water transport in xylem depends on the force of cohesion which keeps the water molecules together and maintains a stream or column of water. Interruption in xylem interrupts the cohesive forces

Transport of water through xylem is apoplast pathway?? I never knew that...I mean doesn't the apoplast pathway get disrupted by the casparian strip before entering the xylem? :/ Sorry, but could you please explain this?

 

[saby]

humongous thread.
i need help in ON-07 question 3, b iii) i forgot how to know when result is significant and not due to chance? i understand nulls hypothesis and why it is rejected.but can someone explain me the rest!

 

[Mairaxo]

Transport of water through xylem is apoplast pathway?? I never knew that...I mean doesn't the apoplast pathway get disrupted by the casparian strip before entering the xylem? :/ Sorry, but could you please explain this?

it doesnt get disrupted by the casparian strip. appoplast pathway is pathway of water through non living parts. xylem is non living so it is appoplast pathway. fungi affect the xylem and so the appoplast pathway gets affected

 

[Warrior66]

it doesnt get disrupted by the casparian strip. appoplast pathway is pathway of water through non living parts. xylem is non living so it is appoplast pathway. fungi affect the xylem and so the appoplast pathway gets affected

Okay, will keep that in mind next time! Jazaka'Allahum Khairan!!

 

[Mairaxo]

Anyone?

Q15- intracellular transport is transport within the cell and intercellular is transport between cells.
Q19- chromosome formation is the replicaton of DNA and that happens in interphase not prophase.
Q36- cholera is an infectious disease that can spread without a vector but mosquito is the vector for malaria. also its not very common to pass through placenta.

 

[dornam]

Q15- intracellular transport is transport within the cell and intercellular is transport between cells.
Q19- chromosome formation is the replicaton of DNA and that happens in interphase not prophase.
Q36- cholera is an infectious disease that can spread without a vector but mosquito is the vector for malaria. also its not very common to pass through placenta.

Q19 - don't chromosome also form in prophase?

Q36 - tuberculosis is an infectious disease, and I think that it is more easily transmissible from parent to son than cholera. TB does not have a vector either

 

[Mairaxo]

Q19 - don't chromosome also form in prophase?

Q36 - tuberculosis is an infectious disease, and I think that it is more easily transmissible from parent to son than cholera. TB does not have a vector either

yeah thats why TB is not the answer. It is infectious and doesnt have a vector so it can be transmitted. Question is which is NOT transmitted.
chromosomes just condense and become visible in prophase and crossing over takes place, but the formation takes place in interphase

 

[ahmed abdulla]

thanks

 

[Mustafa Malik]

Hello everyone
I am new to this part of Xtremepapers cuz i hv just finished my O levels n in these vacations i wanna study for A levels .Although i created a thread but there was no reply. Actually i need the name of the best books for Biology A levels that most renown skools follow.

 

[Mairaxo]

Hello everyone
I am new to this part of Xtremepapers cuz i hv just finished my O levels n in these vacations i wanna study for A levels .Although i created a thread but there was no reply. Actually i need the name of the best books for Biology A levels that most renown skools follow.

Cambridge International AS and A Level Biology Coursebook (with CD-ROM) Third edition
Author: Jones, M, Fosbery, R, Gregory, J, and Taylor, D

 

[Mustafa Malik]

Cambridge International AS and A Level Biology Coursebook (with CD-ROM) Third edition
Author: Jones, M, Fosbery, R, Gregory, J, and Taylor, D

thnx here too.
Again any other recommended ??? What abt Core Biology?

 

[Mairaxo]

thnx here too.
Again any other recommended ??? What abt Core Biology?

Again this one is the best one according to me

 

[h4rriet]

just tell me the way plz ...
h4rriet

All you have to do is measure the distance and use the equation I=AM, I being image length (the thing you've measured), A being actual length and M the magnification. And you have to make sure that they're all in the same units.

 

[Noor Ahmad]

how can sodium thiosulphate be used to detect the presence of starch?

 

[h4rriet]

Am I right in that the question 1 papers from a year (let's say 2010 May / June, there are the papers 11, 12, 13), are actually the same ones but with another order of the questions?

There are differences too.

 

[h4rriet]

Here is the paper: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf

Can anyone explain me questions 15, 19 and 36?

For question 15, the examiner report states that the cell surface membrane does not allow intracellular transport but intercellular... I don't understand this.

For question 19, doesn't formation of chromosomes occur in prophase? Or is it a matter of terms, and it would be condensation and not formation?

For question 36... examiner report says that malaria is unlikely to be passed on from parent to child directly. But malaria can be transmitted across placenta, so? How can cholera be transmitted directly from parent to child?

15. Intracellular means within the cell, intercellular means from cell to cell. The membranes inside allow intracellular and the membranes outside allow intercellular.
19. Replication of DNA is the formation of chromosomes. Chromosomes are formed during interphase; they only become visible in prophase.
36. I too thought that the answer was malaria, but for some unfathomable reason CIE has decided it's cholera. I remember reading in an earlier examiner's report that they decided this on the basis that 'the parent will prepare the bottle for the child and in this process the parent's bacteria will be transmitted into the bottle's contents'.

 

[fizzah96]

hey...i have a question.
39
A tree carries out photosynthesis and provides organic compounds for other organisms in a
forest. It takes carbon dioxide from and returns oxygen to the atmosphere. It takes water from the
soil into its roots and its leaves lose water to the atmosphere. Many other organisms live in the
tree.

Which term applies to the description of the tree?
A
ecosystem
B
habitat
C
niche
D
trophic level
this question came twice in the exam in oct nov 2009 and oct nov 2012 but in both cases answer was different.can anyone explain this to me?

 

[Student12]

How to use the C1V1=C2V2 for serial Dilution.. for paper5. Latest 0/n 2012

 

[Noor Ahmad]

What does the rf value say about solubility and the distance travelled?
Is it correct that the greater the rf value the greater the distance travelled?