A level Biology: Post your doubts here!

[My Name]

can u mention which chapters should I finish in September

Umm I dont know. Im just a student I can just suggest things.
If I were you Id start from the start.Energy and respiration and Photosynthesis...

One more thing,if you need topic wise past papers then check this thread:
https://www.xtremepapers.com/community/threads/a-level-a2-biology-topical-question-bank.35678/
Oh and this might also help,maybe:
https://www.youtube.com/channel/UCWZtJoFf-INn0A3j07a4MsA

 

[My Name]

The energy trapped by grassland plants is 10 000 kJ m−2 year−1. 2000 kJ m−2 year−1 is used by the plants in respiration.
The energy passed along a food chain based on this grassland is shown, in kJ m−2 year−1.
grassland → herbivore → carnivore 1 → carnivore 2
800 160 32
What percentage of the energy available to the herbivore passes to carnivore 2?
A 0.32%
B 0.40%
C 3.2%
D 4.0%

I have a feeling its simple math but I just dont get it! :/

 

[qwertypoiu]

The energy trapped by grassland plants is 10 000 kJ m−2 year−1. 2000 kJ m−2 year−1 is used by the plants in respiration.
The energy passed along a food chain based on this grassland is shown, in kJ m−2 year−1.
grassland → herbivore → carnivore 1 → carnivore 2
800 160 32
What percentage of the energy available to the herbivore passes to carnivore 2?
A 0.32%
B 0.40%
C 3.2%
D 4.0%

I have a feeling its simple math but I just dont get it! :/

Read the question carefully:
What percentage of the energy available to the herbivore passes to carnivore 2?

Energy AVAILABLE to herbivore = 10,000 the grassland trapped initially - 2000 the grassland used for itself = 8000
Energy passed onto carnivore 2 = 32

So percentage of energy available to the herbivores that got passed onto the carnivore 2 = 32/8000 x 100% = 0.4%

So B then

 

[My Name]

Read the question carefully:
What percentage of the energy available to the herbivore passes to carnivore 2?

Energy AVAILABLE to herbivore = 10,000 the grassland trapped initially - 2000 the grassland used for itself = 8000
Energy passed onto carnivore 2 = 32

So percentage of energy available to the herbivores that got passed onto the carnivore 2 = 32/8000 x 100% = 0.4%

So B then

Ty!

 

[My Name]

I simply wrote To push the blood into the capillary bed.
Im confused,would that get me the mark?

 

[qwertypoiu]

View attachment 55805
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View attachment 55807
I simply wrote To push the blood into the capillary bed.
Im confused,would that get me the mark?

The role of "pushing" blood into the capillary is done by the heart. That's why it keeps pumping! So that blood can flow through all your arteries, capillaries, and veins. It creates pressure, because of which the blood flows.
Now, sometimes, yes we do have muscles surrounding vessels to help push the blood along. This only happens at places of low fluid pressure, which are the veins and the lymph vessels.
So in this case, since the muscles being referred to are surrounding an arteriole, your answer is not correct. The pressure here is still sufficient to ensure good flow.
The role played by the muscles here is control.
They control the flow of blood through this part of the body. They can squeeze and prevent blood from flowing through here into the capillary bed, or relax and allow more blood to enter.
For what reason do we wanna filter? Sometimes the body decides a certain part of our body doesn't need as much oxygen. For example, when exercising, our leg muscles deserve more blood flow (oxygen) than intestines. Or sometimes, the environment is really cold so, through vasoconstriction, the blood flow is reduced.
Hope that makes sense.

 

[My Name]

The role of "pushing" blood into the capillary is done by the heart. That's why it keeps pumping! So that blood can flow through all your arteries, capillaries, and veins. It creates pressure, because of which the blood flows.
Now, sometimes, yes we do have muscles surrounding vessels to help push the blood along. This only happens at places of low fluid pressure, which are the veins and the lymph vessels.
So in this case, since the muscles being referred to are surrounding an arteriole, your answer is not correct. The pressure here is still sufficient to ensure good flow.
The role played by the muscles here is control.
They control the flow of blood through this part of the body. They can squeeze and prevent blood from flowing through here into the capillary bed, or relax and allow more blood to enter.
For what reason do we wanna filter? Sometimes the body decides a certain part of our body doesn't need as much oxygen. For example, when exercising, our leg muscles deserve more blood flow (oxygen) than intestines. Or sometimes, the environment is really cold so, through vasoconstriction, the blood flow is reduced.
Hope that makes sense.

Yes it makes complete sense.I was definitely completely wrong!
Thank you!

 

[My Name]

 

[qwertypoiu]

View attachment 55815
View attachment 55816View attachment 55817

When placed in 0.0% NaCl solution (pure water), 0% of red blood cells remained. As the concentration of NaCl was increased, from 0.2% to 0.5%, the percentage of RBCs that remained steadily increased, so that in 0.5% solution, 10% of RBCs remained. As the concentration of NaCl was increased beyond this point, the percentage of RBCs that remained increased at a great rate, so that in a 0.9% NaCl solution, 100% of the RBCs remained. Increase in concentration beyond here did not affect the number of RBCs remaining, it remained 100% in 1.5% NaCl solution as well.

 

[My Name]

ONE :

 

[iSean97]

Past Paper : May/June 2002.
Which Chapter in the New 2016 Syllabus this question belongs to?
I can't find it :S

 

[princess Anu]

HELP!!

 

[22shimmer22girly]

Past Paper : May/June 2002.
Which Chapter in the New 2016 Syllabus this question belongs to?
I can't find it :S

Hey I think it's a general question ... I solved the really old past papers and found questions like that...when I was doing bio a level

 

[Umna.Asim]

Please send topic wise past papers anyone

 

[My Name]

Please send topic wise past papers anyone

https://www.xtremepapers.com/community/threads/as-level-biology-topical-questions.32984/
https://www.xtremepapers.com/commun...o-phy-chem-maths-with-markschemes-here.36384/
AS ^

https://www.xtremepapers.com/community/threads/a-level-a2-biology-topical-question-bank.35678/
A2^

 

[lemonrsiow]

Hi guys, can anyone explain to me how the collection of mature oocytes work in IVF?
In 2014 summer/43, the collection of mature oocytes:



But in 2007/winter, "outline the techniques of IVF", here they want to stimulate ovulation???


What is HCG/GNRH agonists and why is there no superovulation in the 2014_ms?

Pls helpp!

 

[My Name]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w09_qp_11.pdf
q 23,27,

 

[jason kwon]

how do we know the maximum length of the organelle?
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s12_qp_13.pdf
question_4
plz

 

[SadiaMaryam]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_11.pdf
q 23,27,

23) Answer is C because the main function of DNA polymerase is to copy one molecule of double-stranded DNA into two new double stranded DNA molecules
27) Answer is A because sucrose in phloem is always transported from source to sink, so uploading from source should be 1st step and unload the last one

 

[My Name]

how do we know the maximum length of the organelle?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_qp_13.pdf
question_4
plz

Question 4 says:
What are always present in prokaryote cells? A capsules B flagella C pili D ribosomes