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A level Biology: Post your doubts here!

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upload_2015-5-1_15-0-23.png
Answer is C. Because of the fact that when memory cells are persent when second time pathogen enters they are activated and thus more concentration of Antibodies?

Can anyone answer this!
Please and Thank you!
 
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upload_2015-5-1_15-0-54.png
The answer is D.
Why not B? Is it only for the reason that Malaria is mostly transmitted by Female Anopheles mosquito?
 
qwertypoiu

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My Name said:
View attachment 52883
Answer is C. Because of the fact that when memory cells are persent when second time pathogen enters they are activated and thus more concentration of Antibodies?

Can anyone answer this!
Please and Thank you!
Click to expand...
Y is obviously primary, and X secondary, since Y takes longer time to produce antibodies, and makes less of it.
So that limits it to C and D.
During primary response, memory cells were produced by both B-cells and T-cells.
However, for the concentration of antibodies to increase, it's the B-cells that that must have cloned rapidly to develop into plasma cells that produce antibodies. So C.

(Technically, even T-cells could indirectly cause this, since T-helper cells secrete cytokines that stimulate B-cells to develop into plasma cells and produce antibodies, but I guess this is indirect and would take longer time)
 
qwertypoiu

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My Name said:
View attachment 52884
The answer is D.
Why not B? Is it only for the reason that Malaria is mostly transmitted by Female Anopheles mosquito?
Click to expand...
I think you made a mistake in saying the answer is D.
Answer should be A.
B is definitely wrong, HIV cannot be transmitted through airborne droplets.
D is definitely wrong, TB is caused by a bacterium not virus.
Both A and C seem correct to me, however the main method of transmission for malaria is through the vector female Anopheles mosquito, as you said, so A is the best option.
 
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qwertypoiu said:
I think you made a mistake in saying the answer is D.
Answer should be A.
B is definitely wrong, HIV cannot be transmitted through airborne droplets.
D is definitely wrong, TB is caused by a bacterium not virus.
Both A and C seem correct to me, however the main method of transmission for malaria is through the vector female Anopheles mosquito, as you said, so A is the best option.
Click to expand...
Yes,sorry I meant to write A.
Ty :)
 
qwertypoiu

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Wolfgangs said:
Can someone please explain this question?
Click to expand...
On the picture you can see:
40 divisions of eyepiece graticule = 0.1mm
1 division = 0.1mm/40 = 0.0025mm

It is also clear that the radius of vision is 50 divisions:
50 divisions = 0.0025mm x 50 = 0.125mm

Since the answers are in micrometers let's convert it now:
0.125mm = 125 micrometers.

Area = pi*r^2 = 3.14159265358979... x 125 x 125 = 4.9 x 10^4 micrometer squared

C
 
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Aoa
Can someone PLEASEE explain to me the process of semi-conservative replication of DNA through the N14/N15 experiment like I know how replication occurs but Im not able to do the mcqs with this stuff.. I need to know the list of outcomes after each generation so if someone could please list out the results after each generation.. thankss guyss!
 
Farhad221

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fantastic girl said:
isnt it like roots are well growing part so they need more energy ?
23 is D...but y ? :/
Click to expand...
yes as they are growing they require energy for replication of dna and protien synthesis.
23 is D because lingin strengthen the xylem vessels so they wont collapse under hydrostatic pressure which in this case is due to high rate of transpiration.
 
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