A level Biology: Post your doubts here!

[qwertypoiu]

Yep ik but qwertypoiu told me it isnt
unless i am mixing things up

Nope it isn't....

 

[Jeezan]

http://theallpapers.com/papers/CIE/AS_and_ALevel/Biology (9700)/9700_s13_qp_11.pdf
Q.39 the answer is A
Isn't nitrogen fixation anaerobic ?

qwertypoiu
can u please solve this ?

 

[qwertypoiu]

View attachment 53216
Answer's B
but doesn't it also only occur in A and D?
what else occurs in A and D then? :S

It cannot be A because production of antibodies contains many processes like translation transcription blabla..
B is correct.
C is wrong it's meiosis
D is wrong as well, root hairs are tubular outgrowths, so it's just a part of a cell becoming extended:

 

[qwertypoiu]

View attachment 53217
I thought cholera is food borne too :/
but its D

I think refrigeration perhaps doesn't manage to kill the Vibrio Cholerae

 

[My Name]

PLEASEEEE someone explain this method to me Im not able to do any of these questions please help my exam's tomorrow and also does someone have any notes or tips for A2 P5?

https://www.xtremepapers.com/community/threads/biology-paper-5-tips.27105/

 

[qwertypoiu]

the lug worm lives in a burrow in the sand just above low water mark.it has haemoglobin in its blood. at low tide it retreats to its burrow and shuts itself.....it is cut off from external sources of oxygen until the sea water returns....what dissociation curve for haemoglobin????
closer to % saturation axis or closer to partial pressure of o2 axis??

Well the way i think of this is...
It has overall less partial pressure of oxygen.. So it needs to pick up oxygen at low partial pressure... But also let go of this oxygen at even lower partial pressures. So you just squeeze it towards the y-axis...

 

[qwertypoiu]

Here's the link!

http://www.mrsmbpj.com/IGCSE/pdf/9700_w12_qp_11.pdf

Wow in that case it may be in the syllabus... But here's how you do it:
Gross primary productivity is how much chemical energy a plant has made.
First trophic level in the diagram are the producers, since they're gaining energy from the Sun.
It says they had 23000 energy.
So GPP = 23,000
The third trophic level are the secondary consumers... what they leave behind is what is "available" to the tertiary consumers...
So whats left? Subtract all the losses!
left = 23,000 - 8000 - 10,500 - 4200 = 300 energy
So percentage = 300 / 23,000 x 100% = 1.3%

 

[qwertypoiu]

View attachment 53227
doesnt co2 have higher affinity to o2?
but then its b??? how? :/

Actually haemoglobin has very little affinity for carbon dioxide... Only 10% of carbon dioxide joins with its amide terminal to form carbaminohaemoglobin. Haemoglobin has iron atoms dedicated for bonding with oxygen. However, the problem is that CO has 250 times more affinity, so it bonds usually irreversibly with haemoglobin. Imagine how much fun next year will be learning structure of haem group!

 

[nehaoscar]

Actually haemoglobin has very little affinity for carbon dioxide... Only 10% of carbon dioxide joins with its amide terminal to form carbaminohaemoglobin. Haemoglobin has iron atoms dedicated for bonding with oxygen. However, the problem is that CO has 250 times more affinity, so it bonds usually irreversibly with haemoglobin. Imagine how much fun next year will be learning structure of haem group!

haha okay thanks! i was confuse cause we have the bohr shift and all which shows that hb has more affinity for co2 so o2 is released etc...
Yeah next years gonna be total fun! :/

 

[qwertypoiu]

Can someone explain this question to me?

The answer is C.

Already answered this:
A level Biology: Post your doubts here!

 

[qwertypoiu]

haha okay thanks! i was confuse cause we have the bohr shift and all which shows that hb has more affinity for co2 so o2 is released etc...
Yeah next years gonna be total fun! :/

Bohr shift occurs because of the H+ ions... Not CO2 molecules... H+ ions bind to form HHb, which alters haemoglobin shape... So makes it lose affinity for oxygen.

 

[qwertypoiu]

qwertypoiu
can u please solve this ?

Hmmmm I took a guess at this before:
A level Biology: Post your doubts here!

 

[My Name]

I know its late but anyway here are some questions and answers( sorta notes) for paper 1 Biology. (And like I said before a question may have more answers but I've mentioned the one according to the question)

 

[qwertypoiu]

how to do this ??
https://www.xtremepapers.com/community/attachments/11160221_10204517600243144_750592502_n-jpg.53218/

They tell us the small divisions on stage micrometer is 0.1mm in width.
So:
40 units of eyepiece = 0.1 mm [as seen in the diagram]
1 unit of eyepiece = 0.1 mm /40= 0.0025mm = 2.5 micrometer
I can't see the diagram clearly but it seems like the width of a chloroplast is around 4 eyepiece units...
4 unit of eyepiece = 4 x 2.5 micrometer = 10 micrometer...

 

[My Name]

They tell us the small divisions on stage micrometer is 0.1mm in width.
So:
40 units of eyepiece = 0.1 mm [as seen in the diagram]
1 unit of eyepiece = 0.1 mm /40= 0.0025mm = 2.5 micrometer
I can't see the diagram clearly but it seems like the width of a chloroplast is around 4 eyepiece units...
4 unit of eyepiece = 4 x 2.5 micrometer = 10 micrometer...

You had previously posted a blue picture with some text where is that? I can't find it.
Ty

 

[qwertypoiu]

I know its late but anyway here are some questions and answers( sorta notes) for paper 1 Biology. (And like I said before a question may have more answers but I've mentioned the one according to the question)

It's never too late Thanks.

 

[Laila39]

PLEASEEEE someone explain this method to me Im not able to do any of these questions please help my exam's tomorrow

 

[My Name]

It's never too late Thanks.

^_^ Welcome

 

[My Name]

PLEASEEEE someone explain this method to me Im not able to do any of these questions please help my exam's tomorrow
View attachment 53235

They tell us the small divisions on stage micrometer is 0.1mm in width.
So:
40 units of eyepiece = 0.1 mm [as seen in the diagram]
1 unit of eyepiece = 0.1 mm /40= 0.0025mm = 2.5 micrometer
I can't see the diagram clearly but it seems like the width of a chloroplast is around 4 eyepiece units...
4 unit of eyepiece = 4 x 2.5 micrometer = 10 micrometer...

 

[qwertypoiu]

You had previously posted a blue picture with some text where is that? I can't find it.
Ty

It's here if you're interested:
A level Biology: Post your doubts here!