A level Biology: Post your doubts here!

[My Name]

can u explain.

May be if I revise the topic I can.

 

[Farhad221]

Guys i am starting a revision group for upcoming may june 2o15 exams more details herehttps://www.xtremepapers.com/community/threads/revision-group-on-facebook-or-viber-for-science-subjects-economics-business-studies.37031/

 

[Excellence]

yeah^ why not b?

You know bcos they said that it was sprayed on leaf. Therefore, it would get in phloem and not in xylem bcos xylem comes from roots...

 

[Mimick]

can somebody please explain me this diagram.. its about the nitrogen cycleView attachment 51384

Ok i will give you my notes they are quite simplified... Get on with the other topic in the meantime i upload

xX Love n Good Luck xX

 

[Mimick]

You know bcos they said that it was sprayed on leaf. Therefore, it would get in phloem and not in xylem bcos xylem comes from roots...

You kinda make sense

 

[Mimick]

Ok i will give you my notes they are quite simplified... Get on with the other topic in the meantime i upload

xX Love n Good Luck xX

 

[Mimick]

 

[Mimick]

 

[Mimick]

 

[princess Anu]

You know bcos they said that it was sprayed on leaf. Therefore, it would get in phloem and not in xylem bcos xylem comes from roots...

So what? leaves have xylem vessels as well as phloem sieve tubes, and the spray is dissolved in water so it should go through xylem,no? :/

 

[princess Anu]

Thank you so much

 

[princess Anu]

does Infection ALWAYS result in a disease ?is it that when a person is immunized he might get the infection but not the disease??!?! or is it that disease and infection always go together.?

 

[cool Hassan]

What is the period of diastole in this diagram... I feel its the region "A and C" please tell me whether i'm right or wrong.. explainations will be appreciated .

 

[My Name]

I think I will save theses as well will help later I'm sure. :3

 

[princess Anu]

Q24, why are we adding the last 3 values?

 

[Mahmood Magdy]

What is the period of diastole in this diagram... I feel its the region "A and C" please tell me whether i'm right or wrong.. explainations will be appreciated . View attachment 51423

Well, your question says 'Diastole' , but I will break it up and that will make it a lot easier for you to get it!
First of all, it starts with the atrial systole right? So that is from zero seconds till before 2s, the curve falls down marking that the atrial systole ended, but the curve for the left ventricle rises during A marking the beginning of the ventricular systole therefore A is not diastole. Once the curve starts falling down at B, this marks that the pressure in the left ventricle is decreasing marking that the systole ended and the ventricular diastole started. C and D you have no contraction whatsoever.
Therefore to sum up, Atrial diastole from half of A (0.1) till the end.
Ventricular diastole, 0-0.1 then 0.4-0.8, and so together they make the diastole that is from 0.4-0.8.

 

[cool Hassan]

Well, your question says 'Diastole' , but I will break it up and that will make it a lot easier for you to get it!
First of all, it starts with the atrial systole right? So that is from zero seconds till before 2s, the curve falls down marking that the atrial systole ended, but the curve for the left ventricle rises during A marking the beginning of the ventricular systole therefore A is not diastole. Once the curve starts falling down at B, this marks that the pressure in the left ventricle is decreasing marking that the systole ended and the ventricular diastole started. C and D you have no contraction whatsoever.
Therefore to sum up, Atrial diastole from half of A (0.1) till the end.
Ventricular diastole, 0-0.1 then 0.4-0.8, and so together they make the diastole that is from 0.4-0.8.

Biology revision guide says its region "D"


but then comes the contradiction in the ans of this question
According to the revision guide the answer should be "D" but the ans of this question in mark scheme says the ans is "C'.... so confused about it

 

[Mahmood Magdy]

Dude

Biology revision guide says its region "D"
View attachment 51503
View attachment 51504
but then comes the contradiction in the ans of this question
According to the revision guide the answer should be "D" but the ans of this question in mark scheme says the ans is "C'.... so confused about it

Dude you are confusing yourself, your graph has 2 atrial systoles which is incorrect, you have only one atrial systole per cardiac cycle. The answer C is the correct one. The picture has all the explanation you need to know, May/June 2014 paper 22 last question has the timing thing. With those, I guess you will understand it.
The question says AV valves and SL valves have to be closed, and the total time, which will be from 2-1(arrows on the graph) and from 4-3(on the graph too).

 

[MYLORD]

Dude

Dude you are confusing yourself, your graph has 2 atrial systoles which is incorrect, you have only one atrial systole per cardiac cycle. The answer C is the correct one. The picture has all the explanation you need to know, May/June 2014 paper 22 last question has the timing thing. With those, I guess you will understand it.
The question says AV valves and SL valves have to be closed, and the total time, which will be from 2-1(arrows on the graph) and from 4-3(on the graph too).

can u give more of this chapter notes here ?

 

[Mahmood Magdy]

can u give more of this chapter notes here ?

Here you go!
Sorry for the bad quality though.