A level Biology: Post your doubts here!

[Awesome12]

1- dunno why.

2- coz electron micrographs are colourless and can only show 2D images, so sample cells are supposed to be cut (try to stay attentive in class)

Cutting them won't cause a 3-D structure to appear. The electron microscope will itself display a 2-D structure. (The teacher never told us this. Get your facts straight )

 

[***amd***]

Cutting them won't cause a 3-D structure to appear. The electron microscope will itself display a 2-D structure. (The teacher never told us this. Get your facts straight )

if you cut a football in two halves, only then you can see what is inside it, right? the same way, how can you even look inside a cell when its memberane is covering it?

well, she did

 

[Awesome12]

if you cut a football in two halves, only then you can see what is inside it, right? the same way, how can you even look inside a cell when its memberane is covering it?

well, she did

I will explain it to you tomorrow. Imagining stuff here is difficult.

 

[Awesome12]

How is the answer C??

 

[***amd***]

How is the answer C??

View attachment 47696

we are not given the scale of callibrated smaller divisions. all we know is that the bigger scale shows 0.1 mm in one division. and according to that stage micrometer the radius of the field region is 1.25 divisions = 0.125 mm = 125 micrometers

 

[Al-Anoud]

May/June 2014- Paper-21.
Q3 (e) Acute lymphoblastic leukaemia (ALL) is a cancer of B-lymphocytes. It is very rare in adults but more common in children. A study in 2009 found that exposure to tobacco smoke in the home may put the children at risk of developing ALL.
Suggest how smoking by adults in the home may put their children at risk of cancers, such as ALL. [3]

This is definitely related to passive smoking. But how does leukaemia develop?

 

[♣♠ Magnanimous ♣♠]

May/June 2014- Paper-21.
Q3 (e) Acute lymphoblastic leukaemia (ALL) is a cancer of B-lymphocytes. It is very rare in adults but more common in children. A study in 2009 found that exposure to tobacco smoke in the home may put the children at risk of developing ALL.
Suggest how smoking by adults in the home may put their children at risk of cancers, such as ALL. [3]

This is definitely related to passive smoking. But how does leukaemia develop?

Leukemia is also blood cancer and it develops from the unlimited cell division I mean more than limits so it starts to develop cells which are against the identity and these cells are called cancer cell.. This thing occurs in blood cells which leads to blood cancer

 

[Al-Anoud]

Leukemia is also blood cancer and it develops from the unlimited cell division I mean more than limits so it starts to develop cells which are against the identity and these cells are called cancer cell.. This thing occurs in blood cells which leads to blood cancer

Umm, of course leukemia is blood cancer.
So, the B-cells begin to divide uncontrollably?

 

[♣♠ Magnanimous ♣♠]

Umm, of course leukemia is blood cancer.
So, the B-cells begin to divide uncontrollably?

Yeah
B cells or any white blood cells divide uncontrollably
When leukemia occurs, abnormal white blood cells divide uncontrollably

 

[Heba A.Moety]

hello..
any notes for biology A-level ?!
plz i really need it

 

[sumeru]

October November series are knocking at the door. so if you guys need any kind of help related to biology, feel free to message me. I would be very happy to help you all.

 

[Abeha Malik]

plz tell me how to calculate the answer of mcq no 4
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s07_qp_1.pdf

 

[***amd***]

plz tell me how to calculate the answer of mcq no 4
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_qp_1.pdf

if you see the left most Pollen Grain, it measures 5 divisions b4, and 15 divisions of eye piece graticule after growth.
that means it has grown 10 divisions in 4 hours.

then, from the scale in the upper diagram, we know:
50 divisions of eye piece graticule = 0.1 mm
that makes:
10 * 5 divisions = 0.1 mm
10 divisions = 0.1/5 mm
10 divisions = 0.02 mm

this tells that pollen grains grow 0.02 mm in 4 hours (or simply 0.02 mm / 4h)
we convert mm into micrometer 0.02 mm = 0.02 * 1000 micrometers (=20)

rate = 20 micrometers / 4 h = 5 micrometers / h. (answer = A)

 

[Abeha Malik]

if you see the left most Pollen Grain, it measures 5 divisions b4, and 15 divisions of eye piece graticule after growth.
that means it has grown 10 divisions in 4 hours.

then, from the scale in the upper diagram, we know:
50 divisions of eye piece graticule = 0.1 mm
that makes:
10 * 5 divisions = 0.1 mm
10 divisions = 0.1/5 mm
10 divisions = 0.02 mm

this tells that pollen grains grow 0.02 mm in 4 hours (or simply 0.02 mm / 4h)
we convert mm into micrometer 0.02 mm = 0.02 * 1000 micrometers (=20)

rate = 20 micrometers / 4 h = 5 micrometers / h. (answer = A)

ok thanks alot for the help

 

[RoOkaYya G]

if you see the left most Pollen Grain, it measures 5 divisions b4, and 15 divisions of eye piece graticule after growth. STAGE MICROMETER NOT EYE PIECE GRATICULE!!
that means it has grown 10 divisions in 4 hours.

then, from the scale in the upper diagram, we know:
50 divisions of eye piece graticule = 0.1 mm
that makes:
10 * 5 divisions = 0.1 mm
10 divisions = 0.1/5 mm
10 divisions = 0.02 mm

this tells that pollen grains grow 0.02 mm in 4 hours (or simply 0.02 mm / 4h)
we convert mm into micrometer 0.02 mm = 0.02 * 1000 micrometers (=20)

rate = 20 micrometers / 4 h = 5 micrometers / h. (answer = A)

this is misleading!
this is how we do it :

2 eye piece graticule (EPG) scale= 100 division on stage micrometer
100 div on stage = 2 EPG scale
on fig 1 :
5 div on stage= (2/100) * 5
=0.1 EPG = 0.01 mm = 10micrometer

on fig 2 :
15 div on stage = (2/100) *15
= 0.3 EPG scale =0.03 mm = 30 micrometer

increase in size (growth) = 30 micrometer - 10 micrometer = 20 micrometer

rate of growth = 20/4 = 5 micrometer per hour <---------

u could work out 10 div for growth directly like :

10 div on stage = (2/100)*10 =0.2 EPG scale = 0.02 mm= 20 micrometer
then rate= 20/4 = 5micrometer per hour

 

[♣♠ Magnanimous ♣♠]

this is misleading!
this is how we do it :

2 eye piece graticule (EPG) scale= 100 division on stage micrometer
100 div on stage = 2 EPG scale
on fig 1 :
5 div on stage= (2/100) * 5
=0.1 EPG = 0.01 mm = 10micrometer

on fig 2 :
15 div on stage = (2/100) *15
= 0.3 EPG scale =0.03 mm = 30 micrometer

increase in size (growth) = 30 micrometer - 10 micrometer = 20 micrometer

rate of growth = 20/4 = 5 micrometer per hour <---------

u could work out 10 div for growth directly like :

10 div on stage = (2/100)*10 =0.2 EPG scale = 0.02 mm= 20 micrometer
then rate= 20/4 = 5micrometer per hour

I think your method follows the book examples! So this method is correct

 

[RoOkaYya G]

I think your method follows the book examples! So this method is correct

i highlighted his mistakes in red in my quote.
thts how ive learnt it.
theres worlds difference in stage n eye piece.
if it was paper 2 where u shld show workings....cambridge would deduct marks!

 

[♣♠ Magnanimous ♣♠]

i highlighted his mistakes in red in my quote.
thts how ive learnt it.
theres worlds difference in stage n eye piece.
if it was paper 2 where u shld show workings....cambridge would deduct marks!

Yeah! You're correct but rookayya you showed the mistakes are incorrect coz he used those words are correct on their places.

 

[RoOkaYya G]

Yeah! You're correct but rookayya you showed the mistakes are incorrect coz he used those words are correct on their places.

its correct!
15 div on EPG?? how u do tht? its 15 on stage!
and the 50 divs r on stage not EPG
the mistakes shown is right check again

 

[♣♠ Magnanimous ♣♠]

its correct!
15 div on EPG?? how u do tht? its 15 on stage!
and the 50 divs r on stage not EPG
the mistakes shown is right check again

These 15 divisions and 10 division are 15 and 10 EYEPIECE UNITS!