A level Biology: Post your doubts here!

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_12.pdf

qns 1
qns 4
qns 16 why the ans not c
qns 27 is statement 4 correct?
qns 35

1. Option A is unnecessary because the xylem is measured in millimetres, not micrometres. Option 2 is unnecessary too because 4 tells you that the eyepiece graticule is already calibrated.
4. All you have to do is cross multiply. If 1.5x(10^1) micrometers = 1 cell, then 1x(10^-4) micrometres will = x cells. Take care of the units.
16. DNA replication occurs during interphase, which is not part of nuclear division.
27. Water does move out of cell 3, but it doesn't move out so much as to plasmolyse it. The difference is water potential between cell 3 and the surroundings is very slight.
35. For a person to have absorbed the most O2, he must have had the highest breathing rate, the largest tidal volume and the largest total lung volume. Multiply the 3 columns.

 

[Noor Ahmad]

21) I'm just as confused as you are. I believe the answer should be D as well.

34) You're right. But that's not what the question's asking.
They asked for the disease which is least likely to be passed from parent to child.
A: you already mentioned it
B: HIV can be passed through the placenta (the connection between the mother and the baby in the womb)
C: Malaria must pass through a vector (the female Anopheles mosquito)
D: Sickle-cell anaemia is a genetic disease, so it can definitely pass from parent to child.

OH MY, i din't recognize the least likely part.Thanks alot

 

[ShootingStar]

q40 please
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w12_qp_11.pdf

 

[h4rriet]

q40 please
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w12_qp_11.pdf

GPP=23000. Calculate the energy taken in by the second trophic level and subtract the 10500 from it. Then find out what percentage of the GPP your answer is.

 

[ShootingStar]

and also q34
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w12_qp_12.pdf

 

[Noor Ahmad]

Question 27
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w10_qp_12.pdf

 

[raamish]

in which soil nitrogen fixation bacteria found. Are they found in both boggy(wet soil of denitrifying) and well aerated soil(nitrifying)? can u also confirm if my sentence is correct?

 

[Irfan1995]

and also q34
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w12_qp_12.pdf

100 ml of arterial blood carries 19 ml of oxygen while the same amount of venous blood carries only 12.5 ml of oxygen.
When the blood passes through the lungs, (19 - 12.5) = 6.5 ml of oxygen is absorbed.
In one minute, 5L of blood passes through the lungs. 5L = 5,000 ml.
If 100 ml of blood absorbs 6.5 ml of oxygen, then 5,000 ml (100 x 50) of blood should absorb (6.5 x 50) = 325 ml of oxygen per minute

 

[Irfan1995]

Question 27
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w10_qp_12.pdf

I'll try to prove (or refute) all options:
Option 1: If you have two isotonic solution (with the same water potential) that are separated by a partially permeable membrane, water will definitely move both ways, but the NET water movement is zero. Also, when you have to solutions of different water potentials (separated by a membrane), water will still move both ways, but the rate of water movement outside the solution with higher water potential will be greater than the other rate. This creates a net movement of water down a potential gradient. Conclusion: no matter what case you have, when there are two solutions separated by a membrane, water will always move both ways.

Option 2: Cell 1 has the lowest water potential, so water will move into it.

Option 3: Just like in option 1, there is water movement, but no NET water movement

Option 4: Water does move out of cell 3, but it will not be plasmolysed. Water will continue to move until all three cells have the exact same water potential as the environment (and themselves). Cell 3's water potential will be lower than -4kPa, but higher than -6kPa. Since cell 1 has a lower water potential than that (and it's not mentioned that it's plasmolysed), then you can't assume that cell 3 will plasmolyse.

 

[Irfan1995]

in which soil nitrogen fixation bacteria found. Are they found in both boggy(wet soil of denitrifying) and well aerated soil(nitrifying)? can u also confirm if my sentence is correct?

Nitrogen fixation is a reduction reaction, so no oxygen is required. This means that they can live well in boggy and clogged soils.

As far as I know, diazotrophs are facultative anaerobes. This means that they can grow without oxygen. But they cannot fix nitrogen under aerobic conditions (when oxygen is present). However, diazotrophs can form symbiotic relationships (especially with legumes) that allow them to live in nodules which prevent them from excess oxygen exposure.

 

[raamish]

Nitrogen fixation is a reduction reaction, so no oxygen is required. This means that they can live well in boggy and clogged soils.

As far as I know, diazotrophs are facultative anaerobes. This means that they can grow without oxygen. But they cannot fix nitrogen under aerobic conditions (when oxygen is present). However, diazotrophs can form symbiotic relationships (especially with legumes) that allow them to live in nodules which prevent them from excess oxygen exposure.

can denitrifying bacteria live in boggy soils. they live in wet soils but arent boggy soils the same. And nitrifying present in well aerated soils right?

 

[kingos3111]

The stage micrometer is replaced by a slide of a plant cell.
0 10 20 30 40 50 60 70 80 90 100
What is the width of a chloroplast?
A 5 μm B 10 μm C 50 μm D 100 μm

 

[kingos3111]

help urgent

 

[kingos3111]

now helo

 

[raamish]

now helo

please tell the year and teh question no.

 

[MaxStudentALevel]

Hey can anyone explain ON 2008 p1 Q3???

 

[kingos3111]

oct nov 2006 q1 please

 

[kingos3111]

please tell the year and teh question no.

oct nov 2006 p1

 

[Aries_95]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w11_qp_12.pdf
Q.39 plz!

 

[raamish]

oct nov 2006 q1 please

0.1-40
x-4

the answer will be 10um. 0.1 is the diff between 2 points on stage micrometer.then for those 2 points 40 points for graticule scale. just use the diagram and the formula and calculate the answer.