A level Biology: Post your doubts here!

[Amy Bloom]

just help me out please!

Well, i tried to do it my way.
First, you measure the length of the scale bar with ur ruler. say x mm.
So, x mm is equivalent to 2 micrometres
Then measure the length of the chloroplast using your ruler. Say y mm.
By proportion, y mm = (2 * y)/x micrometres. Say it is t micrometres
That's the size of the object (actual size)

Then see y mm is equivalent to how many micrometres. Say its z micrometres. This is the size of image
Magnification = size of image/actual size = t/z times

Try it and see if you got the answer.

 

[Student12]

The Cie biology text book chp 8.. The mammalian transport system, How do you do SAQ 8.12 and SAQ 8.13 ??
Can you explain in detail on how and why you get it ?

 

[farhan143]

Well, i tried to do it my way.
First, you measure the length of the scale bar with ur ruler. say x mm.
So, x mm is equivalent to 2 micrometres
Then measure the length of the chloroplast using your ruler. Say y mm.
By proportion, y mm = (2 * y)/x micrometres. Say it is t micrometres
That's the size of the object (actual size)

Then see y mm is equivalent to how many micrometres. Say its z micrometres. This is the size of image
Magnification = size of image/actual size = t/z times

Try it and see if you got the answer.

But isn't (2y/x) going to give me the micrometer value for [y mm]

and isn't z micrometer = t micrometer
?????????????????????????????????????????????????????????

 

[Hazirah Mn]

where did you take this question from? if its from a past year book that has been photocopied, maybe there has been a change that may have occured during the photocopy process.. I think as long as you understand the concept of the formula, it would be okay. My lecturer also told me, it's better to include the units in micrometer inside your calculation, just in case you might have forgotten to change from milli to micro. Correct ne if I'm wrong though ^_^

 

[DANGERBP]

people does anyone have an idea aout question bank for bio or any a level !

 

[Amy Bloom]

But isn't (2y/x) going to give me the micrometer value for [y mm]

and isn't z micrometer = t micrometer
?????????????????????????????????????????????????????????

You're right about (2y/x) will give you the measured length of the chloroplast according to the scale which is what the chloroplast actually measures. but z will never be equal to t.
Can you please post the values you've got for length of chloroplast and length of scale bar please?
Then i'll work it out post my workings. Okay?

 

[farhan143]

You're right about (2y/x) will give you the measured length of the chloroplast according to the scale which is what the chloroplast actually measures. but z will never be equal to t.
Can you please post the values you've got for length of chloroplast and length of scale bar please?
Then i'll work it out post my workings. Okay?

length of scale bar = 23mm = xmm
represented scale bar = 2 microm
length of chloroplast = 94mm = ymm
there for (2y/x) = (2 x 23/94) = 8.1739131043 micrometre = t micrometre

and ymm = z micrometer = same value above!!!!

can u post ur value

 

[smartangel]

why isnt anyone explaining this? pleaseee! i really need help!! november 06 paper 4 Q2!
http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_w06_qp_4.pdf

 

[Amy Bloom]

length of scale bar = 23mm = xmm
represented scale bar = 2 microm
length of chloroplast = 94mm = ymm
there for (2y/x) = (2 x 23/94) = 8.1739131043 micrometre = t micrometre

and ymm = z micrometer = same value above!!!!

can u post ur value

I've missed one part in the explanation i gave u previously. I've worked with the values you gave me. here're my workings:

length of scale bar = 23mm
Therefore, 23 mm is equivalent to 2 micrometres
94 mm will be equivalent to (2*94)/23 = 8.1739 micrometres (Actual size)

from the scale bar, 23 mm is equivalent to 2 micrometres
so will be 23 x 10^3 micrometres
hence 1 micrometre = 2/(23 x 10^3) micrometres = 8.6956 x 10^-5 (the length the scalebar represents)

Magnification = (8.1739/8.6956 x 10^-5) = 94000 times

What do you think?

 

[Dayyanah]

why isnt anyone explaining this? pleaseee! i really need help!! november 06 paper 4 Q2!
http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_w06_qp_4.pdf

b a lil more specific pls... wat part?

 

[smartangel]

part a. i dont get how to calculate the ratios. please help!

 

[rz123]

The Cie biology text book chp 8.. The mammalian transport system, How do you do SAQ 8.12 and SAQ 8.13 ??
Can you explain in detail on how and why you get it ?

hi , 8.12 a) 1 gram of pure haemoglobin combines with 1.3cm^3 oxygen. how much in 1dm^3. we r given in the question dat 1dm cube = 150 g. so simply multiply 1.3cm^3 with 150 grams in order to get the amount of oxygen which can be carried in 1dm^2 which is equal to 150g.


b) see the solubility is 0.025 cm^3 per cm^3 of water. we know that 1dm^3 is equal to 1000cm^3. so multiply 1000 with the solubility which is .025...u will get 25cm^3 as the answer. its basic maths.
8.13) a i) there is graph on the page 109. u can see that on 12 k Pascals, the percentage saturation is about 98 % on the y axis.
ii) 1 gram of fully saturated haemoglobin is combined with 1.3 cm^3 of oxygen, so u know that in lungs the percentage saturation of haemoglobin was about 97%. now simply divide 1.3 with 100 nd multiply with 97% u will get 1.25cm^3.

b i) need to c the graph on page 109 : ) , at 2 kPa u can see the % saturation of haemoglobin is 24%

ii) see we know from a part that at 96 % of hameglobin saturation we got 1.25 cm^3 of oxygen , we can use this to find the unknown x which is amount of oxygen in one gram of heamoglobin in the capillaries of this muscle. so write like this:-
96%---------- 1.25
24%---------- x

cross multiply and u will get the answer to be 0.31 cm^3

 

[hassam]

in describing function of endosperm....ms says it produces cellulose for cell wall production and protien for growth of plant....bt wasnt endosperm just a starch reserve?

 

[saudha]

in describing function of endosperm....ms says it produces cellulose for cell wall production and protien for growth of plant....bt wasnt endosperm just a starch reserve?

as far as i know ... it is mainly known for starch content but also can contain oils and proteins .... used to synthesize cell wall and proteins 4 growth......

 

[farhan143]

I didn't understand this part !!
( the length the scale bar represents )
so ur saying theat 1microm of the scale bar is the needed!!
isn't 23000 representing the length of the scale bAR!

so confused!!

I've missed one part in the explanation i gave u previously. I've worked with the values you gave me. here're my workings:

from the scale bar, 23 mm is equivalent to 2 micrometres
so will be 23 x 10^3 micrometres
hence 1 micrometre = 2/(23 x 10^3) micrometres = 8.6956 x 10^-5 (the length the scalebar represents)

Magnification = (8.1739/8.6956 x 10^-5) = 94000 times

What do you think?

well the book says the answer is ( 100000 times ) bt i gues its the printing fault the size of the page was either too big or too small

yes ur answer is close enough


although there is a sorrection to ur answer

23000 = 2
x = 1
if 23000 micrometers represent 2 micrometer
then x micrometer represents 1 micrometre
that is (23000/2) = 11500 micrometer

if ur were doing the other way around then ur right!
sorry if i gve u a headache!!

 

[rz123]

hi help required in this mcq.
http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_s10_qp_11.pdf
mcq 3

 

[XPFMember]

aoa wr wb!

hi help required in this mcq.
http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_s10_qp_11.pdf
mcq 3

hi..
Area of a circle is pi x r x r...

so you need to find the radius..
Now we can see 40 EPG divisions = 1 division of stage = 0.1 mm
diameter of the field of view is 100 EPG divisions, so radius = 50 EPG divisions ....find out how many mm is that..
50/40 x 0.1 = 0.125 mm = 125 μm

so area = π × 125 x125
so ans. is C

 

[rz123]

aoa wr wb!

hi..
Area of a circle is pi x r x r...

so you need to find the radius..
Now we can see 40 EPG divisions = 1 division of stage = 0.1 mm
diameter of the field of view is 100 EPG divisions, so radius = 50 EPG divisions ....find out how many mm is that..
50/40 x 0.1 = 0.125 mm = 125 μm

so area = π × 125 x125
so ans. is C

thankyou very much

 

[XPFMember]

thankyou very much

any time..

 

[rz123]

http://www.xtremepapers.com/CIE/International A And AS Level/9700 - Biology/9700_s10_qp_11.pdf
14th. how is it A? why not B