A level Biology: Post your doubts here!

[dornam]

Can anyone explain me question 40, why are there 6 trophic levels? I chose 5.

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w09_qp_11.pdf

 

[comrade]

Can anyone explain me question 40, why are there 6 trophic levels? I chose 5.

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_11.pdf

I got this wrong too the first time I attempted this question. I also chose 5.

1) herbivorous copepods
2) amphipods and shrimps
3) squid
4) little auk and arctic cod
5) glaucous gull and ringed seal
6) polar bear.

This shows us that there are 6 trophic levels. Squid is a consumer so it is at a different trophic level. You have to count that too.

 

[Capricedcapri]

How to find expected value? Anyone? Chi square test

 

[Just visiting]

when im doing the 8 mark Questions ..... do i have to write like
Independent variable: """"""""
DEPp """""""""""""""""""""""
or just write the points directly?

 

[Dukeofwin]

Could anyone Explain me 10, 14 and 16 from http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w07_qp_1.pdf

 

[aloha]

guys quick ques.............hw do we draw error bars???????

 

[Just visiting]

Alert!
For all ya guys out there freaking about error bars and standard error , imma make it clear once and for all ISA.
You need to knoww that there is a difference between standard deviation and standard error.
standard error is (standard deviation)/(root of no. of sample {root n})
when plotting bars, you need +/- standard deviation
so you need to multiply the standard error with (root n)
this value will be +/- the bar
P.S. the value of n will be the value that is going to be subtracted to find degrees of freedom

 

[strangerss]

hey everyone , alsalum allaykom , can some one help me out in question 38 Maj/June 2004 p1 ? I don;t get how they added the energy used in respiration in photosynthesis and in question 5 I thought that the magnofication of the microscope would be by multiplying 5 with 8 , why is it in correct?

 

[strangerss]

Q16- phosphate and hydrophilic head occupies less space. Hydrocarbon chains are large and have a chain structure.
Q29- xylem is dead. heating will not affect it. only phloem will get affected.
Q30- xylem will be affected 1st. water moves through xylem and its the appoplast pathway. so if fungi grow there it gets affected.
Q 38- photosynthesis is needed for growth and respiration as it provides glucose. so 21500*500*1500=23500
Q7- water potential=solute potential+pressure potential. water and solute potential are equal so pressure is 0

How xylem passes through the apoplast pathway ? Aren't xylem cells dead so there isn't a symplast or apoplast , or because apoplast is between the cell walls which are present?

 

[strangerss]

Q16- phosphate and hydrophilic head occupies less space. Hydrocarbon chains are large and have a chain structure.
Q29- xylem is dead. heating will not affect it. only phloem will get affected.
Q30- xylem will be affected 1st. water moves through xylem and its the appoplast pathway. so if fungi grow there it gets affected.
Q 38- photosynthesis is needed for growth and respiration as it provides glucose. so 21500*500*1500=23500
Q7- water potential=solute potential+pressure potential. water and solute potential are equal so pressure is 0

What would happen if the pressure potential is equal to the water potential? the solute potential in this case would be lower than the water potential or we can't tell?

 

[Kinki Tiffany 12]

Can anyone explain to me about the resolution of the light/electron microscope? 0.5 or 200 nm which of this value has a higher resolution?

 

[ahmed abdulla]

18 Which statement describes a cell that is capable of reproduction and belonging to a haploid
organism?
A It has chromosomes that contain one polynucleotide chain.
B It is capable of carrying out a reduction division to form gametes.
C It possesses two copies of each gene as a result of fertilisation.
D It will undergo cell division by mitosis during asexual reproduction.

ans is D .. but i am pretty sure its B ... from o/n 2009 va'11

 

[sara kamal]

Could anyone Explain me 10, 14 and 16 from http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w07_qp_1.pdf

Q10
if pigment is able to escape,that means phospholipid is broken down and that's only possible if solution is ethanol,where as protein channels are also broken down,cuz HCl denatures the protein 3D shape,.....hence no barrier for the pigment and its able to escape.

Q14
inhibition is independent of substrate and product concentrationsss..as soon as inhibitor is added rate no more increases and and the graph flattens

Q16
facilated diffusion only depends on number of protein channels,if no more empty channels available rate becomes constant.


hope it helped!

 

[Mairaxo]

How xylem passes through the apoplast pathway ? Aren't xylem cells dead so there isn't a symplast or apoplast , or because apoplast is between the cell walls which are present?

dead is appoplast

 

[Mairaxo]

18 Which statement describes a cell that is capable of reproduction and belonging to a haploid
organism?
A It has chromosomes that contain one polynucleotide chain.
B It is capable of carrying out a reduction division to form gametes.
C It possesses two copies of each gene as a result of fertilisation.
D It will undergo cell division by mitosis during asexual reproduction.

ans is D .. but i am pretty sure its B ... from o/n 2009 va'11

its already haploid so it wont undergo reductional division again

 

[Dukeofwin]

Q10
if pigment is able to escape,that means phospholipid is broken down and that's only possible if solution is ethanol,where as protein channels are also broken down,cuz HCl denatures the protein 3D shape,.....hence no barrier for the pigment and its able to escape.

Q14
inhibition is independent of substrate and product concentrationsss..as soon as inhibitor is added rate no more increases and and the graph flattens

Q16
facilated diffusion only depends on number of protein channels,if no more empty channels available rate becomes constant.


hope it helped!

It sure did, Thanks a Bunch

 

[sara kamal]

http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s06_qp_1.pdf
please explain Q24.

 

[Aries_95]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s06_qp_1.pdf
please explain Q24.

since the bases are complementary, they are in the same ratio.Since 20% bases are cytosine, 20% will be guanine (a total of 40%).
the remaining 60% are obviously Adenine and Uracil( since it is mRNA)
Adenine and Uracil are complementary to each other and will be in the same ration i.e 30% each.
therefore 30% uracil molecules will be found in mRNA transcribed form this DNA.

 

[sara kamal]

since the bases are complementary, they are in the same ratio.Since 20% bases are cytosine, 20% will be guanine (a total of 40%).
the remaining 60% are obviously Adenine and Uracil( since it is mRNA)
Adenine and Uracil are complementary to each other and will be in the same ration i.e 30% each.
therefore 30% uracil molecules will be found in mRNA transcribed form this DNA.

Jazak Allah Khairan!

 

[Student12]

Oct/Nov '09:
2) 1 million nanometers = 1 millimeter. You can continue from there.
22) A tRNA molecule can bind to one type of amino acid. After it 'uses up' its amino acid, it goes back to the cytoplasm to bind with another one. After that, it returns to the ribosome to 'use it up' again.
The question tells you that there are only 4 types of amino acids, so you only need 4 different tRNA to translate the polypeptide.
17) Remember that active transport works against a concentration gradient (moving solutes from a region of low concentration to a region of high concentration). So potassium will move inside the cell and sodium moves out.
26) The solute potential is always negative, and the pressure potential is always positive. The water potential is the sum of the other two potentials, so it will be found somewhere in between them.
29) You are looking for the greatest CHANGE. So you're looking for the region where the slope is the highest. That's going to be region B
14) 20) 22) Are you sure you copied the right question paper?

Oct/Nov '08:
4) I think you just have to measure the distance with a ruler and calculate it from the magnification.
24) Actually, D is an adaptation. I'm pretty sure that option B is the right answer.
Water uptake is done through osmosis (a passive process which does not require energy). So mitochondria are not needed as energy is not required.
28) I mean, option C is correct while the others are wrong. Here are the corrections:
A: blood flows into the aorta when the LEFT ventricle contracts
B: blood flows into the left atrium through the pulmonary VEIN ...
D: blood flows into the left ventricle through the AV VALVE...

Oct/Nov '07:
6) Measure it by a ruler and calculate it using the magnification equation
25) Water flows from the roots to the xylem vessels. So the roots must have a higher water potential than the xylem vessels. That makes options C and D wrong. The soil water must contain some salts, so it's impossible to have a water potential of 0. It has to be less than that. So option A is wrong. Option B is the only one left.
28) They're asking for how many oxygen ATOMS are carried. Each oxygen molecule contains two atoms (O2). 4 molecules are carried by one haemoglobin molecule which is equivalent to 8 oxygen atoms.

May/June '07:
1) Simply divide the values to get a ratio of their sizes. Remember to convert 750 nm to 0.75 micrometers (or convert 15 micrometers to 15,000 nanometers)
So 15/0.75 = 20
Or, 15000/750 = 20
You get the same answer both ways.
4) The first figure tells you that 0.1 mm is equivalent to 50 divisions. So each division is 2 micrometers long.
By looking at the horizontal pollen tube, you can see that it grew from the 25th division to the 35th one. So it grew by 10 divisions which is equal to 20 micrometers. But, they also say that it grew 20 micrometers in 4 hours, so in 1 hour, it gre 20/4 = 5 micrometers. So the rate is 5 micrometers per hour.
15) Air contains oxygen, which is required for active transport (it's needed to produce ATP). Nitrogen cannot be used for active transport.
If you bubble air or nitrogen through the solution, the rate of the 3-carbon sugar doesn't change. This tells you that it doesn't involve active transport, which implies that it travels through diffusion.
The rate of the 6-carbon sugar was high when air was bubbled, but it completely stopped when nitrogen was bubbled. This tells you that air (hence oxygen) was necessary for uptake, so it must have been done through active transport.

- I'm still not able to do Q2 can show the working pls. ?
- Yes the paper was may/june http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s09_qp_1.pdf Q 14 A, 20 B, 22C
- For Oct/nov 2008 Q4 From where to where do i hv to measure useing the ruler.. wheres the rbc ? - in the same paper Could u explain Q26 ?