A level Biology: Post your doubts here!

[mehria]

No I think Ans would Be 25 micro meter( C!!)
It says Nucleus not Cholroplast u misread it Againnnnnnnnnnnnnnnnn!!

:/ it's ok mistakes happen...
atleast she'll get to know how to solve it

 

[Mohammed salik]

first we have to find the value for the smallest division in eyepiece graticule...
for that :_ 0.1/40= 2.5 x 10^-3 mm
cnge mm into micrometer by multiplying 1000 with ur value
(2.5 x 10^-3) x 1000 = 2.5 micrometer <------- ths is the value for the smallest division in eyepiece graticule

frm the second diagram choose any chloroplast , measure its diameter
in the diagram one of the chloroplast's diameter is 3
so:- 3 x 2.5 = 7.5 micrometer
it is closer to 8 then our ans will b B

Look 40 division = 0.1mm=100 Micrometers
Now if u see On Diagram Nucleus is the biggest circle which is almost 10 Units.
Now use Ratio

40 : 100
10 : X
X=1000/40=25 Micrometer ans is C

 

[Mohammed salik]

:/ it's ok mistakes happen...
atleast she'll get to know how to solve it

No Prob.. I know Mistakes do Happen

 

[mehria]

No Prob.. I know Mistakes do Happen

yea u shud knw that...

 

[Mohammed salik]

yea u shud knw that...

Ok Miss.. Aur kuch i need to Know !

 

[mehria]

Ok Miss.. Aur kuch i need to Know !

no...aj k liye itna hi sikho..

 

[Mohammed salik]

no...aj k liye itna hi sikho..

Thank You Miss!

 

[joanna omar]

Someone help me with the dissociation curve n bohr effect I dont underdtand it

dissociation curve --->The affinity of HB for Oxygen is measured experimentally by determining the % saturation of oxygen of samples of blood after exposure to air mixture containing different partial pressure of oxygen ...the results,called an oxygen dissociation curve

Bohr effect (shift) ....> It is when HB has a higher affinity for Co2 and hydrogen ions
Its mainly the presence of high partial pressure of Co2 causes the HB to release more Oxygen than in the absence of Co2 ...the is call bohr effect.

 

[kitkat <3 :P]

dissociation curve --->The affinity of HB for Oxygen is measured experimentally by determining the % saturation of oxygen of samples of blood after exposure to air mixture containing different partial pressure of oxygen ...the results,called an oxygen dissociation curve

Bohr effect (shift) ....> It is when HB has a higher affinity for Co2 and hydrogen ions
Its mainly the presence of high partial pressure of Co2 causes the HB to release more Oxygen than in the absence of Co2 ...the is call bohr effect.

Thanks alot ^_^

 

[joanna omar]

can you help me with this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
and this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_13.pdf q39

 

[joanna omar]

Anyone help me out with .........> Q6 (C)
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s09_qp_2.pdf

 

[thats_me]

can you help me with this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
and this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_13.pdf q39

I had the same doubts they're both the same questions so q39 has to be wrong in the ms

 

[Exo_luhan]

Can any one please help me with the answer of 2013 oct nov V1 last question!!!!i jus need the answer

 

[Snowysangel]

Could someone please describe the effects of nicotine on our bodies? Give at least 4 points.

 

[Snowysangel]

Anyone help me out with .........> Q6 (C)
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s09_qp_2.pdf

A) you can still see remains of the nuclear membrane, the chromosomes/sister chromatids are still lined up at the equator & the sister chromatids haven't separated yet
B) smoke contains a lot of carcinogens which change the sequence of bases is the DNA and hence create mutated genes...and u basically elaborate on thus point by giving examples etc

 

[thats_me]

Could someone please describe the effects of nicotine on our bodies? Give at least 4 points.

It is readily absorbed by blood & travels to the brain, there it imitates as acetyl choline which is a neurotransmitter
it stimulates the nervous system to reduce the diameter of the arterioles & to release the hormone adrenaline which causes smooth muscles to contract so blood pressure & heart rate increases
Due to this there is a decrease in blood supply to extremeties of the body such as hands or feet, reducing their supply of oxygen
It also increases the stickiness of blood platelets so there is an increase in risk of blood clotting

 

[Harsh Poddar]

I've made this site that can help you to quickly access past papers for a few common subjects. Try it out and please leave a feedback here

http://server-poddarh.rhcloud.com/paper.html

 

[Karim Nabil]

Can any one please help me with the answer of 2013 oct nov V1 last question!!!!i jus need the answer

EFFICIENCY=(total energy absorbed by sea urchins/total energy availabe in kelps)*100

 

[Snowysangel]

Could someone list down the reasons why Africans are so susceptible to diseases such as aids and cholera?

 

[princeali97]

can you help me with this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w13_qp_12.pdf q40
and this http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_13.pdf q39

q40-statementA is valid since in ecosystem Y the dominant producer is large and woody, so would not be easily consumed. StatementB is valid since there is a smaller fluctuation of temperature in marine aquatic ecosystems and also there is less oxygen. Statement C is also valid, since with lower energy losses between trophic levels the ecosystem X can support more trophiclevels. Therefore the answer is statement D.
Q39-same.So it will be B.