A level Biology: Post your doubts here!

[Noor Ahmad]

like i said, google it...I'm sorry, i'm in A2 and that's the max i can do for u guys

It's alright! Thank youu!

 

[biba]

can someone explain me the vertical and horizontal transmissions ?

 

[Noor Ahmad]

can someone explain me the vertical and horizontal transmissions ?

Vertical transmission,is the transmission of genetic material,from parents to offsprings.
Horizontal transmission is the transfer of genetic material (DNA) from one bacterium to another.

 

[knowitall10]

Not really

Ok...
C1= concentration provided
C2= concentration you want to make
V1= volume of the original solution u must use
V2= total volume of the solution (which you must keep constant)

C1V1=C2V2
According to the question, the total volume being kept constant is 10cm3
Your C1= o.1
V1= x
C2= 0.05
V2= 10
Now apply the formula.
0.1x= 0.05 x 10
x= 5
so you're taking out 5cm3 of the original solution and diluting it with (10-5 =5) 5cm3 water.
Now, try the table yourself. I explained what they did in the question. Tell me if u still don't get it.
You should make your own concentrations, a minimum of 5.

 

[knowitall10]

Vertical transmission,is the inheritance of genetic material,from parents to offsprings.
Horizontal transmission is the transfer of genetic material (Plasmids) from one bacterium to another.

Yes. But both of them can be the transfer of plasmids.

 

[knowitall10]

Thank you so much. But i've got a question.
do we use the ruler to calibrate the eye piece graticule or do we directly measure the specimen using the ruler?

i don't get ur question...

 

[biba]

Vertical transmission,is the transmission of genetic material,from parents to offsprings.
Horizontal transmission is the transfer of genetic material (DNA) from one bacterium to another.

jazakALLAH!

 

[Noor Ahmad]

i don't get ur question...

I meant how is the ruler exactly used.how do we position it?
I remember i was once trying to place the ruler above the microscope slide and it just covers the specimen. :/

 

[Noor Ahmad]

Question 2c (i) how do we use a hand lens http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Biology%20(9700)/9700_y07_sp_31.pdf

 

[knowitall10]

I don't really know man...practicals was never really my thing...
I'm sorry i can't help.....i'm having a very bad day.............................

 

[strangerss]

Yeah... nothing really seems to be wrong with it...

Really thanks a lot but I'm confused if they give me a slide should my drawing be proportional to it??

 

[strangerss]

It isn't percentage error i guess.
Im not quite sure but is it 50% of the smallest division?

YES it's half the smallest division on the instrument used for measuring

 

[strangerss]

Can you help me with this one? If I have 6.25 cm^3 of 10% solution, and I mix it with 3.75 cm^3 of water, what will be the concentration of the solution?

Use this formula:volume of solute =(required concentration/initial concentration )* the total volume of solution . In your case the required concentration is missing , so if we put all the values given in the formula then solve it , we get the required concentration with a value of 6.25% . Please correct me if I'm wrong.

 

[Freaked out]

hey does anyone know when is the P41 and P43 biology chem and physics paper

 

[Noor Ahmad]

YES it's half the smallest division on the instrument used for measuring

Thank you so much!

 

[Noor Ahmad]

Can you help me with this one? If I have 6.25 cm^3 of 10% solution, and I mix it with 3.75 cm^3 of water, what will be the concentration of the solution?

C1V1=C2V2
Where the total volume is 6.25+3.75=10
6.25x10 = 10 x C2
C2 = 6.25

 

[Noor Ahmad]

CAN ANYONE TELL ME HOW IS THIS DONE ? Q2A (ii)
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w08_qp_32.pdf

 

[Irfan1995]

CAN ANYONE TELL ME HOW IS THIS DONE ? Q2A (ii)
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w08_qp_32.pdf

Just draw the three layers. Ignore the details outside the artery. It must be large and proportional (it must be like an oval, not a circle).
The mark scheme provides a good example of a drawing.

 

[Noor Ahmad]

Just draw the three layers. Ignore the details outside the artery. It must be large and proportional (it must be like an oval, not a circle).
The mark scheme provides a good example of a drawing.

No no i meant the question below that,about the eye piece graticule and the stage micrometer?

 

[strangerss]

C1V1=C2V2
Where the total volume is 6.25+3.75=10
6.25x10 = 10 x C2
C2 = 6.25

It's the percentage concentration right?